* [PATCH v10 0/3] Memory poison recovery in khugepaged collapsing
@ 2023-03-05 6:51 Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
` (2 more replies)
0 siblings, 3 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-05 6:51 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck, akpm
Cc: naoya.horiguchi, linmiaohe, jiaqiyan, linux-mm, osalvador,
wangkefeng.wang
Problem
=======
Memory DIMMs are subject to multi-bit flips, i.e. memory errors.
As memory size and density increase, the chances of and number of
memory errors increase. The increasing size and density of server
RAM in the data center and cloud have shown increased uncorrectable
memory errors. There are already mechanisms in the kernel to recover
from uncorrectable memory errors. This series of patches provides
the recovery mechanism for the particular kernel agent khugepaged
when it collapses memory pages.
Impact
======
The main reason we chose to make khugepaged collapsing tolerant of
memory failures was its high possibility of accessing poisoned memory
while performing functionally optional compaction actions.
Standard applications typically don't have strict requirements on
the size of its pages. So they are given 4K pages by the kernel.
The kernel is able to improve application performance by either
1) giving applications 2M pages to begin with, or
2) collapsing 4K pages into 2M pages when possible.
This collapsing operation is done by khugepaged, a kernel agent that
is constantly scanning memory. When collapsing 4K pages into a 2M page,
it must copy the data from the 4K pages into a physically contiguous
2M page. Therefore, as long as there exists one poisoned cache line in
collapsible 4K pages, khugepaged will eventually access it. The current
impact to users is a machine check exception triggered kernel panic.
However, khugepaged’s compaction operations are not functionally required
kernel actions. Therefore making khugepaged tolerant to poisoned memory
will greatly improve user experience.
This patch series is for cases where khugepaged is the first guy
that detects the memory errors on the poisoned pages. IOW, the pages
are not known to have memory errors when khugepaged collapsing gets to
them. In our observation, this happens frequently when the huge page
ratio of the system is relatively low, which is fairly common in
virtual machines running on cloud.
Solution
========
As stated before, it is less desirable to crash the system only because
khugepaged accesses poisoned pages while it is collapsing 4K pages.
The high level idea of this patch series is to skip the group of pages
(usually 512 4K-size pages) once khugepaged finds one of them is poisoned,
as these pages have become ineligible to be collapsed.
We are also careful to unwind operations khuagepaged has performed before
it detects memory failures. For example, before copying and collapsing
a group of anonymous pages into a huge page, the source pages will be
isolated and their page table is unlinked from their PMD. These operations
need to be undone in order to ensure these pages are not changed/lost from
the perspective of other threads (both user and kernel space). As for
file backed memory pages, there already exists a rollback case. This
patch just extends it so that khugepaged also correctly rolls back when
it fails to copy poisoned 4K pages.
Changelog
=========
v10 changes
- Incorporate feedbacks from Kirill A. Shutemov
<kirill.shutemov@linux.intel.com>
- Refactor the 2nd loop (after the loop for copying memory) into 2 helper
functions, one for actions to take when copying succeeded, one for when
copying failed due to #MC.
- Use copy_mc_user_highpage for anonymous memory.
- Introduce copy_mc_highpage and use it for file-backed memory.
- Rename the original PMD from `rollback` to `orig_pmd`.
- Some minor changes in comments, e.g. `normal page` to `raw page`.
- This revision is rebased to mm-unstable at commit df3ae4347aff9
("dma-buf: system_heap: avoid reclaim for order 4")
v9 changes
- Incorporate feedback from Andrew Morton <akpm@linux-foundation.org>
- Move copy_mc_highpage into khugepage.c as a static out-of-line
function copy_mc_page.
v8 changes
- Incorporate feedbacks from Tony Luck <tony.luck@intel.com>
- Rename copy_highpage_mc to copy_mc_highpage.
- Update copy_mc_highpage with kmsan changes.
- Code style changes:
1) copy_mc_highpage returns int as "copy" is an action and is consistent
with copy_mc_user_highpage.
2) __collapse_huge_page_copy returns scan_result(int) and is consistent
with __collapse_huge_page_isolate/swapin.
3) variables are declared in separate lines in collapse_file.
v7 changes
- Fix a bug "KASAN: stack-out-of-bounds Read in collapse_file". After copying
all pages into the huge page, clear_highpage should use index instead of
page->index.
v6 changes
- Address comments from Kirill Shutemov <kirill@shutemov.name>
- Rewrite __collapse_huge_page_copy to make rollback operations more
clear to its reader.
- Add detailed test steps in each commit message.
v5 changes
- Rebase patches to mm-unstable at
commit ffb39098bf87 ("Merge tag 'linux-kselftest-kunit-6.1-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest").
- Resolves conflicts with:
commit 2f55f070e5b8 ("mm/khugepaged: minor cleanup for collapse_file")
commit 1baec203b77c ("mm/khugepaged: try to free transhuge swapcache
when possible")
v4 changes
- Incorporate feedbacks from Yang Shi <shy828301@gmail.com>
- Remove tracepoint for __collapse_huge_page_copy, just keep SCAN_COPY_MC
and let trace_mm_collapse_huge_page it
- Remove unnecessary comments
v3 changes
- Incorporate feedbacks from Yang Shi <shy828301@gmail.com>
- Add tracepoint for __collapse_huge_page_copy
- Restore PMD in collapse_huge_page
- Correct comment about mmap_read_lock
v2 changes
- Incorporate feedbacks from Yang Shi <shy828301@gmail.com>
- Only keep copy_highpage_mc
- Adding new scan_result SCAN_COPY_MC
- Defer NR_FILE_THPS update until copying succeeded
Jiaqi Yan (3):
mm/khugepaged: recover from poisoned anonymous memory
mm/hwpoison: introduce copy_mc_highpage
mm/khugepaged: recover from poisoned file-backed memory
include/linux/highmem.h | 54 +++++--
include/trace/events/huge_memory.h | 3 +-
mm/khugepaged.c | 226 ++++++++++++++++++++++-------
3 files changed, 217 insertions(+), 66 deletions(-)
--
2.40.0.rc0.216.gc4246ad0f0-goog
^ permalink raw reply [flat|nested] 17+ messages in thread
* [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-05 6:51 [PATCH v10 0/3] Memory poison recovery in khugepaged collapsing Jiaqi Yan
@ 2023-03-05 6:51 ` Jiaqi Yan
2023-03-20 14:42 ` Jiaqi Yan
2023-03-23 21:37 ` Yang Shi
2023-03-05 6:51 ` [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory Jiaqi Yan
2 siblings, 2 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-05 6:51 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck, akpm
Cc: naoya.horiguchi, linmiaohe, jiaqiyan, linux-mm, osalvador,
wangkefeng.wang
Make __collapse_huge_page_copy return whether copying anonymous pages
succeeded, and make collapse_huge_page handle the return status.
Break existing PTE scan loop into two for-loops. The first loop copies
source pages into target huge page, and can fail gracefully when running
into memory errors in source pages. If copying all pages succeeds, the
second loop releases and clears up these normal pages. Otherwise, the
second loop rolls back the page table and page states by:
- re-establishing the original PTEs-to-PMD connection.
- releasing source pages back to their LRU list.
Tested manually:
0. Enable khugepaged on system under test.
1. Start a two-thread application. Each thread allocates a chunk of
non-huge anonymous memory buffer.
2. Pick 4 random buffer locations (2 in each thread) and inject
uncorrectable memory errors at corresponding physical addresses.
3. Signal both threads to make their memory buffer collapsible, i.e.
calling madvise(MADV_HUGEPAGE).
4. Wait and check kernel log: khugepaged is able to recover from poisoned
pages and skips collapsing them.
5. Signal both threads to inspect their buffer contents and make sure no
data corruption.
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
---
include/trace/events/huge_memory.h | 3 +-
mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
2 files changed, 128 insertions(+), 23 deletions(-)
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
index 3e6fb05852f9a..46cce509957ba 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/huge_memory.h
@@ -36,7 +36,8 @@
EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
EM( SCAN_TRUNCATED, "truncated") \
- EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
+ EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
+ EMe(SCAN_COPY_MC, "copy_poisoned_page") \
#undef EM
#undef EMe
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 27956d4404134..c3c217f6ebc6e 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -19,6 +19,7 @@
#include <linux/page_table_check.h>
#include <linux/swapops.h>
#include <linux/shmem_fs.h>
+#include <linux/kmsan.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
@@ -55,6 +56,7 @@ enum scan_result {
SCAN_CGROUP_CHARGE_FAIL,
SCAN_TRUNCATED,
SCAN_PAGE_HAS_PRIVATE,
+ SCAN_COPY_MC,
};
#define CREATE_TRACE_POINTS
@@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
return result;
}
-static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
- struct vm_area_struct *vma,
- unsigned long address,
- spinlock_t *ptl,
- struct list_head *compound_pagelist)
+static void __collapse_huge_page_copy_succeeded(pte_t *pte,
+ pmd_t *pmd,
+ struct vm_area_struct *vma,
+ unsigned long address,
+ spinlock_t *pte_ptl,
+ struct list_head *compound_pagelist)
{
struct page *src_page, *tmp;
pte_t *_pte;
- for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
- _pte++, page++, address += PAGE_SIZE) {
- pte_t pteval = *_pte;
+ pte_t pteval;
+ unsigned long _address;
+ for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
+ _pte++, _address += PAGE_SIZE) {
+ pteval = *_pte;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
- clear_user_highpage(page, address);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
if (is_zero_pfn(pte_pfn(pteval))) {
/*
- * ptl mostly unnecessary.
+ * pte_ptl mostly unnecessary.
*/
- spin_lock(ptl);
- ptep_clear(vma->vm_mm, address, _pte);
- spin_unlock(ptl);
+ spin_lock(pte_ptl);
+ pte_clear(vma->vm_mm, _address, _pte);
+ spin_unlock(pte_ptl);
}
} else {
src_page = pte_page(pteval);
- copy_user_highpage(page, src_page, address, vma);
if (!PageCompound(src_page))
release_pte_page(src_page);
/*
- * ptl mostly unnecessary, but preempt has to
- * be disabled to update the per-cpu stats
+ * pte_ptl mostly unnecessary, but preempt has
+ * to be disabled to update the per-cpu stats
* inside page_remove_rmap().
*/
- spin_lock(ptl);
- ptep_clear(vma->vm_mm, address, _pte);
+ spin_lock(pte_ptl);
+ ptep_clear(vma->vm_mm, _address, _pte);
page_remove_rmap(src_page, vma, false);
- spin_unlock(ptl);
+ spin_unlock(pte_ptl);
free_page_and_swap_cache(src_page);
}
}
-
list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
list_del(&src_page->lru);
mod_node_page_state(page_pgdat(src_page),
@@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
}
}
+static void __collapse_huge_page_copy_failed(pte_t *pte,
+ pmd_t *pmd,
+ pmd_t orig_pmd,
+ struct vm_area_struct *vma,
+ unsigned long address,
+ struct list_head *compound_pagelist)
+{
+ struct page *src_page, *tmp;
+ pte_t *_pte;
+ pte_t pteval;
+ unsigned long _address;
+ spinlock_t *pmd_ptl;
+
+ /*
+ * Re-establish the PMD to point to the original page table
+ * entry. Restoring PMD needs to be done prior to releasing
+ * pages. Since pages are still isolated and locked here,
+ * acquiring anon_vma_lock_write is unnecessary.
+ */
+ pmd_ptl = pmd_lock(vma->vm_mm, pmd);
+ pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
+ spin_unlock(pmd_ptl);
+ /*
+ * Release both raw and compound pages isolated
+ * in __collapse_huge_page_isolate.
+ */
+ for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
+ _pte++, _address += PAGE_SIZE) {
+ pteval = *_pte;
+ if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
+ continue;
+ src_page = pte_page(pteval);
+ if (!PageCompound(src_page))
+ release_pte_page(src_page);
+ }
+ list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
+ list_del(&src_page->lru);
+ release_pte_page(src_page);
+ }
+}
+
+/*
+ * __collapse_huge_page_copy - attempts to copy memory contents from raw
+ * pages to a hugepage. Cleans up the raw pages if copying succeeds;
+ * otherwise restores the original page table and releases isolated raw pages.
+ * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
+ *
+ * @pte: starting of the PTEs to copy from
+ * @page: the new hugepage to copy contents to
+ * @pmd: pointer to the new hugepage's PMD
+ * @orig_pmd: the original raw pages' PMD
+ * @vma: the original raw pages' virtual memory area
+ * @address: starting address to copy
+ * @pte_ptl: lock on raw pages' PTEs
+ * @compound_pagelist: list that stores compound pages
+ */
+static int __collapse_huge_page_copy(pte_t *pte,
+ struct page *page,
+ pmd_t *pmd,
+ pmd_t orig_pmd,
+ struct vm_area_struct *vma,
+ unsigned long address,
+ spinlock_t *pte_ptl,
+ struct list_head *compound_pagelist)
+{
+ struct page *src_page;
+ pte_t *_pte;
+ pte_t pteval;
+ unsigned long _address;
+ int result = SCAN_SUCCEED;
+
+ /*
+ * Copying pages' contents is subject to memory poison at any iteration.
+ */
+ for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
+ _pte++, page++, _address += PAGE_SIZE) {
+ pteval = *_pte;
+ if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
+ clear_user_highpage(page, _address);
+ continue;
+ }
+ src_page = pte_page(pteval);
+ if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
+ result = SCAN_COPY_MC;
+ break;
+ }
+ }
+
+ if (likely(result == SCAN_SUCCEED))
+ __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
+ pte_ptl, compound_pagelist);
+ else
+ __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
+ address, compound_pagelist);
+
+ return result;
+}
+
static void khugepaged_alloc_sleep(void)
{
DEFINE_WAIT(wait);
@@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
*/
anon_vma_unlock_write(vma->anon_vma);
- __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
- &compound_pagelist);
+ result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
+ vma, address, pte_ptl,
+ &compound_pagelist);
pte_unmap(pte);
+ if (unlikely(result != SCAN_SUCCEED))
+ goto out_up_write;
+
/*
* spin_lock() below is not the equivalent of smp_wmb(), but
* the smp_wmb() inside __SetPageUptodate() can be reused to
--
2.40.0.rc0.216.gc4246ad0f0-goog
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage
2023-03-05 6:51 [PATCH v10 0/3] Memory poison recovery in khugepaged collapsing Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
@ 2023-03-05 6:51 ` Jiaqi Yan
2023-03-05 6:56 ` Jiaqi Yan
2023-03-24 20:24 ` Yang Shi
2023-03-05 6:51 ` [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory Jiaqi Yan
2 siblings, 2 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-05 6:51 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck, akpm
Cc: naoya.horiguchi, linmiaohe, jiaqiyan, linux-mm, osalvador,
wangkefeng.wang
Similar to how copy_mc_user_highpage is implemented for
copy_user_highpage on #MC supported architecture, introduce
the #MC handled version of copy_highpage.
This helper has immediate usage when khugepaged wants to copy
file-backed memory pages and tolerate #MC.
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
---
include/linux/highmem.h | 54 +++++++++++++++++++++++++++++++----------
1 file changed, 41 insertions(+), 13 deletions(-)
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 1128b7114931f..7cbecae39b3eb 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -315,7 +315,29 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
#endif
+#ifndef __HAVE_ARCH_COPY_HIGHPAGE
+
+static inline void copy_highpage(struct page *to, struct page *from)
+{
+ char *vfrom, *vto;
+
+ vfrom = kmap_local_page(from);
+ vto = kmap_local_page(to);
+ copy_page(vto, vfrom);
+ kmsan_copy_page_meta(to, from);
+ kunmap_local(vto);
+ kunmap_local(vfrom);
+}
+
+#endif
+
#ifdef copy_mc_to_kernel
+/*
+ * If architecture supports machine check exception handling, define the
+ * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
+ * page with #MC in source page (@from) handled, and return the number
+ * of bytes not copied if there was a #MC, otherwise 0 for success.
+ */
static inline int copy_mc_user_highpage(struct page *to, struct page *from,
unsigned long vaddr, struct vm_area_struct *vma)
{
@@ -332,29 +354,35 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
return ret;
}
-#else
-static inline int copy_mc_user_highpage(struct page *to, struct page *from,
- unsigned long vaddr, struct vm_area_struct *vma)
-{
- copy_user_highpage(to, from, vaddr, vma);
- return 0;
-}
-#endif
-#ifndef __HAVE_ARCH_COPY_HIGHPAGE
-
-static inline void copy_highpage(struct page *to, struct page *from)
+static inline int copy_mc_highpage(struct page *to, struct page *from)
{
+ unsigned long ret;
char *vfrom, *vto;
vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
- copy_page(vto, vfrom);
- kmsan_copy_page_meta(to, from);
+ ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
+ if (!ret)
+ kmsan_copy_page_meta(to, from);
kunmap_local(vto);
kunmap_local(vfrom);
+
+ return ret;
+}
+#else
+static inline int copy_mc_user_highpage(struct page *to, struct page *from,
+ unsigned long vaddr, struct vm_area_struct *vma)
+{
+ copy_user_highpage(to, from, vaddr, vma);
+ return 0;
}
+static inline int copy_mc_highpage(struct page *to, struct page *from)
+{
+ copy_highpage(to, from);
+ return 0;
+}
#endif
static inline void memcpy_page(struct page *dst_page, size_t dst_off,
--
2.40.0.rc0.216.gc4246ad0f0-goog
^ permalink raw reply related [flat|nested] 17+ messages in thread
* [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory
2023-03-05 6:51 [PATCH v10 0/3] Memory poison recovery in khugepaged collapsing Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage Jiaqi Yan
@ 2023-03-05 6:51 ` Jiaqi Yan
2023-03-24 21:15 ` Yang Shi
2 siblings, 1 reply; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-05 6:51 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck, akpm
Cc: naoya.horiguchi, linmiaohe, jiaqiyan, linux-mm, osalvador,
wangkefeng.wang
Make collapse_file roll back when copying pages failed. More concretely:
- extract copying operations into a separate loop
- postpone the updates for nr_none until both scanning and copying
succeeded
- postpone joining small xarray entries until both scanning and copying
succeeded
- postpone the update operations to NR_XXX_THPS until both scanning and
copying succeeded
- for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
copying failed
Tested manually:
0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
1. Start a two-thread application. Each thread allocates a chunk of
non-huge memory buffer from /mnt/ramdisk.
2. Pick 4 random buffer address (2 in each thread) and inject
uncorrectable memory errors at physical addresses.
3. Signal both threads to make their memory buffer collapsible, i.e.
calling madvise(MADV_HUGEPAGE).
4. Wait and then check kernel log: khugepaged is able to recover from
poisoned pages by skipping them.
5. Signal both threads to inspect their buffer contents and make sure no
data corruption.
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
---
mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++-------------------
1 file changed, 48 insertions(+), 30 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c3c217f6ebc6e..3ea2aa55c2c52 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1890,6 +1890,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
{
struct address_space *mapping = file->f_mapping;
struct page *hpage;
+ struct page *page;
+ struct page *tmp;
+ struct folio *folio;
pgoff_t index = 0, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
@@ -1934,8 +1937,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_set(&xas, start);
for (index = start; index < end; index++) {
- struct page *page = xas_next(&xas);
- struct folio *folio;
+ page = xas_next(&xas);
VM_BUG_ON(index != xas.xa_index);
if (is_shmem) {
@@ -2117,10 +2119,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
}
nr = thp_nr_pages(hpage);
- if (is_shmem)
- __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
- else {
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
+ if (!is_shmem) {
filemap_nr_thps_inc(mapping);
/*
* Paired with smp_mb() in do_dentry_open() to ensure
@@ -2131,21 +2130,10 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
smp_mb();
if (inode_is_open_for_write(mapping->host)) {
result = SCAN_FAIL;
- __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
filemap_nr_thps_dec(mapping);
goto xa_locked;
}
}
-
- if (nr_none) {
- __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
- /* nr_none is always 0 for non-shmem. */
- __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
- }
-
- /* Join all the small entries into a single multi-index entry */
- xas_set_order(&xas, start, HPAGE_PMD_ORDER);
- xas_store(&xas, hpage);
xa_locked:
xas_unlock_irq(&xas);
xa_unlocked:
@@ -2158,21 +2146,35 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
try_to_unmap_flush();
if (result == SCAN_SUCCEED) {
- struct page *page, *tmp;
- struct folio *folio;
-
/*
* Replacing old pages with new one has succeeded, now we
- * need to copy the content and free the old pages.
+ * attempt to copy the contents.
*/
index = start;
- list_for_each_entry_safe(page, tmp, &pagelist, lru) {
+ list_for_each_entry(page, &pagelist, lru) {
while (index < page->index) {
clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
- copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
- page);
+ if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR),
+ page) > 0) {
+ result = SCAN_COPY_MC;
+ break;
+ }
+ index++;
+ }
+ while (result == SCAN_SUCCEED && index < end) {
+ clear_highpage(hpage + (index % HPAGE_PMD_NR));
+ index++;
+ }
+ }
+
+ if (result == SCAN_SUCCEED) {
+ /*
+ * Copying old pages to huge one has succeeded, now we
+ * need to free the old pages.
+ */
+ list_for_each_entry_safe(page, tmp, &pagelist, lru) {
list_del(&page->lru);
page->mapping = NULL;
page_ref_unfreeze(page, 1);
@@ -2180,12 +2182,23 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
ClearPageUnevictable(page);
unlock_page(page);
put_page(page);
- index++;
}
- while (index < end) {
- clear_highpage(hpage + (index % HPAGE_PMD_NR));
- index++;
+
+ xas_lock_irq(&xas);
+ if (is_shmem)
+ __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
+ else
+ __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
+
+ if (nr_none) {
+ __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
+ /* nr_none is always 0 for non-shmem. */
+ __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
}
+ /* Join all the small entries into a single multi-index entry. */
+ xas_set_order(&xas, start, HPAGE_PMD_ORDER);
+ xas_store(&xas, hpage);
+ xas_unlock_irq(&xas);
folio = page_folio(hpage);
folio_mark_uptodate(folio);
@@ -2203,8 +2216,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
unlock_page(hpage);
hpage = NULL;
} else {
- struct page *page;
-
/* Something went wrong: roll back page cache changes */
xas_lock_irq(&xas);
if (nr_none) {
@@ -2238,6 +2249,13 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_lock_irq(&xas);
}
VM_BUG_ON(nr_none);
+ /*
+ * Undo the updates of filemap_nr_thps_inc for non-SHMEM file only.
+ * This undo is not needed unless failure is due to SCAN_COPY_MC.
+ */
+ if (!is_shmem && result == SCAN_COPY_MC)
+ filemap_nr_thps_dec(mapping);
+
xas_unlock_irq(&xas);
hpage->mapping = NULL;
--
2.40.0.rc0.216.gc4246ad0f0-goog
^ permalink raw reply related [flat|nested] 17+ messages in thread
* Re: [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage
2023-03-05 6:51 ` [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage Jiaqi Yan
@ 2023-03-05 6:56 ` Jiaqi Yan
2023-03-24 20:24 ` Yang Shi
1 sibling, 0 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-05 6:56 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck, akpm
Cc: naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> Similar to how copy_mc_user_highpage is implemented for
> copy_user_highpage on #MC supported architecture, introduce
> the #MC handled version of copy_highpage.
>
> This helper has immediate usage when khugepaged wants to copy
> file-backed memory pages and tolerate #MC.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> ---
> include/linux/highmem.h | 54 +++++++++++++++++++++++++++++++----------
> 1 file changed, 41 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 1128b7114931f..7cbecae39b3eb 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -315,7 +315,29 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
>
> #endif
>
> +#ifndef __HAVE_ARCH_COPY_HIGHPAGE
> +
> +static inline void copy_highpage(struct page *to, struct page *from)
> +{
> + char *vfrom, *vto;
> +
> + vfrom = kmap_local_page(from);
> + vto = kmap_local_page(to);
> + copy_page(vto, vfrom);
> + kmsan_copy_page_meta(to, from);
> + kunmap_local(vto);
> + kunmap_local(vfrom);
> +}
> +
> +#endif
> +
> #ifdef copy_mc_to_kernel
> +/*
> + * If architecture supports machine check exception handling, define the
> + * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
> + * page with #MC in source page (@from) handled, and return the number
> + * of bytes not copied if there was a #MC, otherwise 0 for success.
> + */
I know that back in v8, Andrew said copy_mc_* should not be inline,
but I am still putting them here as inline functions because to me
they blend in this file well. However, if you have strong opinions,
let me know and I will move copy_mc_user_highpage + copy_mc_highpage
to a .c file (maybe highmem.c?).
> static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> unsigned long vaddr, struct vm_area_struct *vma)
> {
> @@ -332,29 +354,35 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
>
> return ret;
> }
> -#else
> -static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> - unsigned long vaddr, struct vm_area_struct *vma)
> -{
> - copy_user_highpage(to, from, vaddr, vma);
> - return 0;
> -}
> -#endif
>
> -#ifndef __HAVE_ARCH_COPY_HIGHPAGE
> -
> -static inline void copy_highpage(struct page *to, struct page *from)
> +static inline int copy_mc_highpage(struct page *to, struct page *from)
> {
> + unsigned long ret;
> char *vfrom, *vto;
>
> vfrom = kmap_local_page(from);
> vto = kmap_local_page(to);
> - copy_page(vto, vfrom);
> - kmsan_copy_page_meta(to, from);
> + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
> + if (!ret)
> + kmsan_copy_page_meta(to, from);
> kunmap_local(vto);
> kunmap_local(vfrom);
> +
> + return ret;
> +}
> +#else
> +static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> + unsigned long vaddr, struct vm_area_struct *vma)
> +{
> + copy_user_highpage(to, from, vaddr, vma);
> + return 0;
> }
>
> +static inline int copy_mc_highpage(struct page *to, struct page *from)
> +{
> + copy_highpage(to, from);
> + return 0;
> +}
> #endif
>
> static inline void memcpy_page(struct page *dst_page, size_t dst_off,
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
@ 2023-03-20 14:42 ` Jiaqi Yan
2023-03-21 0:12 ` Yang Shi
2023-03-23 21:37 ` Yang Shi
1 sibling, 1 reply; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-20 14:42 UTC (permalink / raw)
To: kirill.shutemov, kirill, shy828301, tongtiangen, tony.luck
Cc: naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang, akpm
ping for review :)
On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> Make __collapse_huge_page_copy return whether copying anonymous pages
> succeeded, and make collapse_huge_page handle the return status.
>
> Break existing PTE scan loop into two for-loops. The first loop copies
> source pages into target huge page, and can fail gracefully when running
> into memory errors in source pages. If copying all pages succeeds, the
> second loop releases and clears up these normal pages. Otherwise, the
> second loop rolls back the page table and page states by:
> - re-establishing the original PTEs-to-PMD connection.
> - releasing source pages back to their LRU list.
>
> Tested manually:
> 0. Enable khugepaged on system under test.
> 1. Start a two-thread application. Each thread allocates a chunk of
> non-huge anonymous memory buffer.
> 2. Pick 4 random buffer locations (2 in each thread) and inject
> uncorrectable memory errors at corresponding physical addresses.
> 3. Signal both threads to make their memory buffer collapsible, i.e.
> calling madvise(MADV_HUGEPAGE).
> 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> pages and skips collapsing them.
> 5. Signal both threads to inspect their buffer contents and make sure no
> data corruption.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> ---
> include/trace/events/huge_memory.h | 3 +-
> mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> 2 files changed, 128 insertions(+), 23 deletions(-)
>
> diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> index 3e6fb05852f9a..46cce509957ba 100644
> --- a/include/trace/events/huge_memory.h
> +++ b/include/trace/events/huge_memory.h
> @@ -36,7 +36,8 @@
> EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> EM( SCAN_TRUNCATED, "truncated") \
> - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
>
> #undef EM
> #undef EMe
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 27956d4404134..c3c217f6ebc6e 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -19,6 +19,7 @@
> #include <linux/page_table_check.h>
> #include <linux/swapops.h>
> #include <linux/shmem_fs.h>
> +#include <linux/kmsan.h>
>
> #include <asm/tlb.h>
> #include <asm/pgalloc.h>
> @@ -55,6 +56,7 @@ enum scan_result {
> SCAN_CGROUP_CHARGE_FAIL,
> SCAN_TRUNCATED,
> SCAN_PAGE_HAS_PRIVATE,
> + SCAN_COPY_MC,
> };
>
> #define CREATE_TRACE_POINTS
> @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> return result;
> }
>
> -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> - struct vm_area_struct *vma,
> - unsigned long address,
> - spinlock_t *ptl,
> - struct list_head *compound_pagelist)
> +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> + pmd_t *pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + spinlock_t *pte_ptl,
> + struct list_head *compound_pagelist)
> {
> struct page *src_page, *tmp;
> pte_t *_pte;
> - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> - _pte++, page++, address += PAGE_SIZE) {
> - pte_t pteval = *_pte;
> + pte_t pteval;
> + unsigned long _address;
>
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> - clear_user_highpage(page, address);
> add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> if (is_zero_pfn(pte_pfn(pteval))) {
> /*
> - * ptl mostly unnecessary.
> + * pte_ptl mostly unnecessary.
> */
> - spin_lock(ptl);
> - ptep_clear(vma->vm_mm, address, _pte);
> - spin_unlock(ptl);
> + spin_lock(pte_ptl);
> + pte_clear(vma->vm_mm, _address, _pte);
> + spin_unlock(pte_ptl);
> }
> } else {
> src_page = pte_page(pteval);
> - copy_user_highpage(page, src_page, address, vma);
> if (!PageCompound(src_page))
> release_pte_page(src_page);
> /*
> - * ptl mostly unnecessary, but preempt has to
> - * be disabled to update the per-cpu stats
> + * pte_ptl mostly unnecessary, but preempt has
> + * to be disabled to update the per-cpu stats
> * inside page_remove_rmap().
> */
> - spin_lock(ptl);
> - ptep_clear(vma->vm_mm, address, _pte);
> + spin_lock(pte_ptl);
> + ptep_clear(vma->vm_mm, _address, _pte);
> page_remove_rmap(src_page, vma, false);
> - spin_unlock(ptl);
> + spin_unlock(pte_ptl);
> free_page_and_swap_cache(src_page);
> }
> }
> -
> list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> list_del(&src_page->lru);
> mod_node_page_state(page_pgdat(src_page),
> @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> }
> }
>
> +static void __collapse_huge_page_copy_failed(pte_t *pte,
> + pmd_t *pmd,
> + pmd_t orig_pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + struct list_head *compound_pagelist)
> +{
> + struct page *src_page, *tmp;
> + pte_t *_pte;
> + pte_t pteval;
> + unsigned long _address;
> + spinlock_t *pmd_ptl;
> +
> + /*
> + * Re-establish the PMD to point to the original page table
> + * entry. Restoring PMD needs to be done prior to releasing
> + * pages. Since pages are still isolated and locked here,
> + * acquiring anon_vma_lock_write is unnecessary.
> + */
> + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> + spin_unlock(pmd_ptl);
> + /*
> + * Release both raw and compound pages isolated
> + * in __collapse_huge_page_isolate.
> + */
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> + continue;
> + src_page = pte_page(pteval);
> + if (!PageCompound(src_page))
> + release_pte_page(src_page);
> + }
> + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> + list_del(&src_page->lru);
> + release_pte_page(src_page);
> + }
> +}
> +
> +/*
> + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> + * otherwise restores the original page table and releases isolated raw pages.
> + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> + *
> + * @pte: starting of the PTEs to copy from
> + * @page: the new hugepage to copy contents to
> + * @pmd: pointer to the new hugepage's PMD
> + * @orig_pmd: the original raw pages' PMD
> + * @vma: the original raw pages' virtual memory area
> + * @address: starting address to copy
> + * @pte_ptl: lock on raw pages' PTEs
> + * @compound_pagelist: list that stores compound pages
> + */
> +static int __collapse_huge_page_copy(pte_t *pte,
> + struct page *page,
> + pmd_t *pmd,
> + pmd_t orig_pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + spinlock_t *pte_ptl,
> + struct list_head *compound_pagelist)
> +{
> + struct page *src_page;
> + pte_t *_pte;
> + pte_t pteval;
> + unsigned long _address;
> + int result = SCAN_SUCCEED;
> +
> + /*
> + * Copying pages' contents is subject to memory poison at any iteration.
> + */
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, page++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> + clear_user_highpage(page, _address);
> + continue;
> + }
> + src_page = pte_page(pteval);
> + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> + result = SCAN_COPY_MC;
> + break;
> + }
> + }
> +
> + if (likely(result == SCAN_SUCCEED))
> + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> + pte_ptl, compound_pagelist);
> + else
> + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> + address, compound_pagelist);
> +
> + return result;
> +}
> +
> static void khugepaged_alloc_sleep(void)
> {
> DEFINE_WAIT(wait);
> @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> */
> anon_vma_unlock_write(vma->anon_vma);
>
> - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> - &compound_pagelist);
> + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> + vma, address, pte_ptl,
> + &compound_pagelist);
> pte_unmap(pte);
> + if (unlikely(result != SCAN_SUCCEED))
> + goto out_up_write;
> +
> /*
> * spin_lock() below is not the equivalent of smp_wmb(), but
> * the smp_wmb() inside __SetPageUptodate() can be reused to
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-20 14:42 ` Jiaqi Yan
@ 2023-03-21 0:12 ` Yang Shi
0 siblings, 0 replies; 17+ messages in thread
From: Yang Shi @ 2023-03-21 0:12 UTC (permalink / raw)
To: Jiaqi Yan
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, naoya.horiguchi,
linmiaohe, linux-mm, osalvador, wangkefeng.wang, akpm
On Mon, Mar 20, 2023 at 7:42 AM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> ping for review :)
Quite busy recently so I didn't spend too much time on the recent
revisions. Hopefully I can find some time this week.
>
> On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> >
> > Make __collapse_huge_page_copy return whether copying anonymous pages
> > succeeded, and make collapse_huge_page handle the return status.
> >
> > Break existing PTE scan loop into two for-loops. The first loop copies
> > source pages into target huge page, and can fail gracefully when running
> > into memory errors in source pages. If copying all pages succeeds, the
> > second loop releases and clears up these normal pages. Otherwise, the
> > second loop rolls back the page table and page states by:
> > - re-establishing the original PTEs-to-PMD connection.
> > - releasing source pages back to their LRU list.
> >
> > Tested manually:
> > 0. Enable khugepaged on system under test.
> > 1. Start a two-thread application. Each thread allocates a chunk of
> > non-huge anonymous memory buffer.
> > 2. Pick 4 random buffer locations (2 in each thread) and inject
> > uncorrectable memory errors at corresponding physical addresses.
> > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > calling madvise(MADV_HUGEPAGE).
> > 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> > pages and skips collapsing them.
> > 5. Signal both threads to inspect their buffer contents and make sure no
> > data corruption.
> >
> > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > ---
> > include/trace/events/huge_memory.h | 3 +-
> > mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> > 2 files changed, 128 insertions(+), 23 deletions(-)
> >
> > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > index 3e6fb05852f9a..46cce509957ba 100644
> > --- a/include/trace/events/huge_memory.h
> > +++ b/include/trace/events/huge_memory.h
> > @@ -36,7 +36,8 @@
> > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> > EM( SCAN_TRUNCATED, "truncated") \
> > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
> >
> > #undef EM
> > #undef EMe
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 27956d4404134..c3c217f6ebc6e 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -19,6 +19,7 @@
> > #include <linux/page_table_check.h>
> > #include <linux/swapops.h>
> > #include <linux/shmem_fs.h>
> > +#include <linux/kmsan.h>
> >
> > #include <asm/tlb.h>
> > #include <asm/pgalloc.h>
> > @@ -55,6 +56,7 @@ enum scan_result {
> > SCAN_CGROUP_CHARGE_FAIL,
> > SCAN_TRUNCATED,
> > SCAN_PAGE_HAS_PRIVATE,
> > + SCAN_COPY_MC,
> > };
> >
> > #define CREATE_TRACE_POINTS
> > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > return result;
> > }
> >
> > -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > - struct vm_area_struct *vma,
> > - unsigned long address,
> > - spinlock_t *ptl,
> > - struct list_head *compound_pagelist)
> > +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> > + pmd_t *pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + spinlock_t *pte_ptl,
> > + struct list_head *compound_pagelist)
> > {
> > struct page *src_page, *tmp;
> > pte_t *_pte;
> > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> > - _pte++, page++, address += PAGE_SIZE) {
> > - pte_t pteval = *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> >
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > - clear_user_highpage(page, address);
> > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> > if (is_zero_pfn(pte_pfn(pteval))) {
> > /*
> > - * ptl mostly unnecessary.
> > + * pte_ptl mostly unnecessary.
> > */
> > - spin_lock(ptl);
> > - ptep_clear(vma->vm_mm, address, _pte);
> > - spin_unlock(ptl);
> > + spin_lock(pte_ptl);
> > + pte_clear(vma->vm_mm, _address, _pte);
> > + spin_unlock(pte_ptl);
> > }
> > } else {
> > src_page = pte_page(pteval);
> > - copy_user_highpage(page, src_page, address, vma);
> > if (!PageCompound(src_page))
> > release_pte_page(src_page);
> > /*
> > - * ptl mostly unnecessary, but preempt has to
> > - * be disabled to update the per-cpu stats
> > + * pte_ptl mostly unnecessary, but preempt has
> > + * to be disabled to update the per-cpu stats
> > * inside page_remove_rmap().
> > */
> > - spin_lock(ptl);
> > - ptep_clear(vma->vm_mm, address, _pte);
> > + spin_lock(pte_ptl);
> > + ptep_clear(vma->vm_mm, _address, _pte);
> > page_remove_rmap(src_page, vma, false);
> > - spin_unlock(ptl);
> > + spin_unlock(pte_ptl);
> > free_page_and_swap_cache(src_page);
> > }
> > }
> > -
> > list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > list_del(&src_page->lru);
> > mod_node_page_state(page_pgdat(src_page),
> > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > }
> > }
> >
> > +static void __collapse_huge_page_copy_failed(pte_t *pte,
> > + pmd_t *pmd,
> > + pmd_t orig_pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + struct list_head *compound_pagelist)
> > +{
> > + struct page *src_page, *tmp;
> > + pte_t *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> > + spinlock_t *pmd_ptl;
> > +
> > + /*
> > + * Re-establish the PMD to point to the original page table
> > + * entry. Restoring PMD needs to be done prior to releasing
> > + * pages. Since pages are still isolated and locked here,
> > + * acquiring anon_vma_lock_write is unnecessary.
> > + */
> > + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> > + spin_unlock(pmd_ptl);
> > + /*
> > + * Release both raw and compound pages isolated
> > + * in __collapse_huge_page_isolate.
> > + */
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> > + continue;
> > + src_page = pte_page(pteval);
> > + if (!PageCompound(src_page))
> > + release_pte_page(src_page);
> > + }
> > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > + list_del(&src_page->lru);
> > + release_pte_page(src_page);
> > + }
> > +}
> > +
> > +/*
> > + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> > + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> > + * otherwise restores the original page table and releases isolated raw pages.
> > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> > + *
> > + * @pte: starting of the PTEs to copy from
> > + * @page: the new hugepage to copy contents to
> > + * @pmd: pointer to the new hugepage's PMD
> > + * @orig_pmd: the original raw pages' PMD
> > + * @vma: the original raw pages' virtual memory area
> > + * @address: starting address to copy
> > + * @pte_ptl: lock on raw pages' PTEs
> > + * @compound_pagelist: list that stores compound pages
> > + */
> > +static int __collapse_huge_page_copy(pte_t *pte,
> > + struct page *page,
> > + pmd_t *pmd,
> > + pmd_t orig_pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + spinlock_t *pte_ptl,
> > + struct list_head *compound_pagelist)
> > +{
> > + struct page *src_page;
> > + pte_t *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> > + int result = SCAN_SUCCEED;
> > +
> > + /*
> > + * Copying pages' contents is subject to memory poison at any iteration.
> > + */
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, page++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > + clear_user_highpage(page, _address);
> > + continue;
> > + }
> > + src_page = pte_page(pteval);
> > + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> > + result = SCAN_COPY_MC;
> > + break;
> > + }
> > + }
> > +
> > + if (likely(result == SCAN_SUCCEED))
> > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> > + pte_ptl, compound_pagelist);
> > + else
> > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> > + address, compound_pagelist);
> > +
> > + return result;
> > +}
> > +
> > static void khugepaged_alloc_sleep(void)
> > {
> > DEFINE_WAIT(wait);
> > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > */
> > anon_vma_unlock_write(vma->anon_vma);
> >
> > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > - &compound_pagelist);
> > + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> > + vma, address, pte_ptl,
> > + &compound_pagelist);
> > pte_unmap(pte);
> > + if (unlikely(result != SCAN_SUCCEED))
> > + goto out_up_write;
> > +
> > /*
> > * spin_lock() below is not the equivalent of smp_wmb(), but
> > * the smp_wmb() inside __SetPageUptodate() can be reused to
> > --
> > 2.40.0.rc0.216.gc4246ad0f0-goog
> >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
2023-03-20 14:42 ` Jiaqi Yan
@ 2023-03-23 21:37 ` Yang Shi
2023-03-24 15:34 ` Jiaqi Yan
1 sibling, 1 reply; 17+ messages in thread
From: Yang Shi @ 2023-03-23 21:37 UTC (permalink / raw)
To: Jiaqi Yan
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> Make __collapse_huge_page_copy return whether copying anonymous pages
> succeeded, and make collapse_huge_page handle the return status.
>
> Break existing PTE scan loop into two for-loops. The first loop copies
> source pages into target huge page, and can fail gracefully when running
> into memory errors in source pages. If copying all pages succeeds, the
> second loop releases and clears up these normal pages. Otherwise, the
> second loop rolls back the page table and page states by:
> - re-establishing the original PTEs-to-PMD connection.
> - releasing source pages back to their LRU list.
>
> Tested manually:
> 0. Enable khugepaged on system under test.
> 1. Start a two-thread application. Each thread allocates a chunk of
> non-huge anonymous memory buffer.
> 2. Pick 4 random buffer locations (2 in each thread) and inject
> uncorrectable memory errors at corresponding physical addresses.
> 3. Signal both threads to make their memory buffer collapsible, i.e.
> calling madvise(MADV_HUGEPAGE).
> 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> pages and skips collapsing them.
> 5. Signal both threads to inspect their buffer contents and make sure no
> data corruption.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> ---
> include/trace/events/huge_memory.h | 3 +-
> mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> 2 files changed, 128 insertions(+), 23 deletions(-)
>
> diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> index 3e6fb05852f9a..46cce509957ba 100644
> --- a/include/trace/events/huge_memory.h
> +++ b/include/trace/events/huge_memory.h
> @@ -36,7 +36,8 @@
> EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> EM( SCAN_TRUNCATED, "truncated") \
> - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
>
> #undef EM
> #undef EMe
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 27956d4404134..c3c217f6ebc6e 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -19,6 +19,7 @@
> #include <linux/page_table_check.h>
> #include <linux/swapops.h>
> #include <linux/shmem_fs.h>
> +#include <linux/kmsan.h>
>
> #include <asm/tlb.h>
> #include <asm/pgalloc.h>
> @@ -55,6 +56,7 @@ enum scan_result {
> SCAN_CGROUP_CHARGE_FAIL,
> SCAN_TRUNCATED,
> SCAN_PAGE_HAS_PRIVATE,
> + SCAN_COPY_MC,
> };
>
> #define CREATE_TRACE_POINTS
> @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> return result;
> }
>
> -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> - struct vm_area_struct *vma,
> - unsigned long address,
> - spinlock_t *ptl,
> - struct list_head *compound_pagelist)
> +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> + pmd_t *pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + spinlock_t *pte_ptl,
> + struct list_head *compound_pagelist)
> {
> struct page *src_page, *tmp;
> pte_t *_pte;
> - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> - _pte++, page++, address += PAGE_SIZE) {
> - pte_t pteval = *_pte;
> + pte_t pteval;
> + unsigned long _address;
>
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> - clear_user_highpage(page, address);
> add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> if (is_zero_pfn(pte_pfn(pteval))) {
> /*
> - * ptl mostly unnecessary.
> + * pte_ptl mostly unnecessary.
> */
> - spin_lock(ptl);
> - ptep_clear(vma->vm_mm, address, _pte);
> - spin_unlock(ptl);
> + spin_lock(pte_ptl);
Why did you have to rename ptl to pte_ptl? It seems unnecessary.
> + pte_clear(vma->vm_mm, _address, _pte);
> + spin_unlock(pte_ptl);
> }
> } else {
> src_page = pte_page(pteval);
> - copy_user_highpage(page, src_page, address, vma);
> if (!PageCompound(src_page))
> release_pte_page(src_page);
> /*
> - * ptl mostly unnecessary, but preempt has to
> - * be disabled to update the per-cpu stats
> + * pte_ptl mostly unnecessary, but preempt has
> + * to be disabled to update the per-cpu stats
> * inside page_remove_rmap().
> */
> - spin_lock(ptl);
> - ptep_clear(vma->vm_mm, address, _pte);
> + spin_lock(pte_ptl);
> + ptep_clear(vma->vm_mm, _address, _pte);
> page_remove_rmap(src_page, vma, false);
> - spin_unlock(ptl);
> + spin_unlock(pte_ptl);
> free_page_and_swap_cache(src_page);
> }
> }
> -
> list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> list_del(&src_page->lru);
> mod_node_page_state(page_pgdat(src_page),
> @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> }
> }
>
> +static void __collapse_huge_page_copy_failed(pte_t *pte,
> + pmd_t *pmd,
> + pmd_t orig_pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + struct list_head *compound_pagelist)
> +{
> + struct page *src_page, *tmp;
> + pte_t *_pte;
> + pte_t pteval;
> + unsigned long _address;
> + spinlock_t *pmd_ptl;
> +
> + /*
> + * Re-establish the PMD to point to the original page table
> + * entry. Restoring PMD needs to be done prior to releasing
> + * pages. Since pages are still isolated and locked here,
> + * acquiring anon_vma_lock_write is unnecessary.
> + */
> + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> + spin_unlock(pmd_ptl);
> + /*
> + * Release both raw and compound pages isolated
> + * in __collapse_huge_page_isolate.
> + */
It looks like the below code could be replaced by release_pte_pages()
with advancing _pte to (pte + HPAGE_PMD_NR - 1).
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> + continue;
> + src_page = pte_page(pteval);
> + if (!PageCompound(src_page))
> + release_pte_page(src_page);
> + }
> + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> + list_del(&src_page->lru);
> + release_pte_page(src_page);
> + }
> +}
> +
> +/*
> + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> + * otherwise restores the original page table and releases isolated raw pages.
> + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> + *
> + * @pte: starting of the PTEs to copy from
> + * @page: the new hugepage to copy contents to
> + * @pmd: pointer to the new hugepage's PMD
> + * @orig_pmd: the original raw pages' PMD
> + * @vma: the original raw pages' virtual memory area
> + * @address: starting address to copy
> + * @pte_ptl: lock on raw pages' PTEs
> + * @compound_pagelist: list that stores compound pages
> + */
> +static int __collapse_huge_page_copy(pte_t *pte,
> + struct page *page,
> + pmd_t *pmd,
> + pmd_t orig_pmd,
> + struct vm_area_struct *vma,
> + unsigned long address,
> + spinlock_t *pte_ptl,
> + struct list_head *compound_pagelist)
> +{
> + struct page *src_page;
> + pte_t *_pte;
> + pte_t pteval;
> + unsigned long _address;
> + int result = SCAN_SUCCEED;
> +
> + /*
> + * Copying pages' contents is subject to memory poison at any iteration.
> + */
> + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> + _pte++, page++, _address += PAGE_SIZE) {
> + pteval = *_pte;
> + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> + clear_user_highpage(page, _address);
> + continue;
> + }
> + src_page = pte_page(pteval);
> + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> + result = SCAN_COPY_MC;
> + break;
> + }
> + }
> +
> + if (likely(result == SCAN_SUCCEED))
> + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> + pte_ptl, compound_pagelist);
> + else
> + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> + address, compound_pagelist);
> +
> + return result;
> +}
> +
> static void khugepaged_alloc_sleep(void)
> {
> DEFINE_WAIT(wait);
> @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> */
> anon_vma_unlock_write(vma->anon_vma);
>
> - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> - &compound_pagelist);
> + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> + vma, address, pte_ptl,
> + &compound_pagelist);
> pte_unmap(pte);
> + if (unlikely(result != SCAN_SUCCEED))
> + goto out_up_write;
> +
> /*
> * spin_lock() below is not the equivalent of smp_wmb(), but
> * the smp_wmb() inside __SetPageUptodate() can be reused to
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-23 21:37 ` Yang Shi
@ 2023-03-24 15:34 ` Jiaqi Yan
2023-03-24 20:11 ` Yang Shi
0 siblings, 1 reply; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-24 15:34 UTC (permalink / raw)
To: Yang Shi
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Thu, Mar 23, 2023 at 2:38 PM Yang Shi <shy828301@gmail.com> wrote:
>
> On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> >
> > Make __collapse_huge_page_copy return whether copying anonymous pages
> > succeeded, and make collapse_huge_page handle the return status.
> >
> > Break existing PTE scan loop into two for-loops. The first loop copies
> > source pages into target huge page, and can fail gracefully when running
> > into memory errors in source pages. If copying all pages succeeds, the
> > second loop releases and clears up these normal pages. Otherwise, the
> > second loop rolls back the page table and page states by:
> > - re-establishing the original PTEs-to-PMD connection.
> > - releasing source pages back to their LRU list.
> >
> > Tested manually:
> > 0. Enable khugepaged on system under test.
> > 1. Start a two-thread application. Each thread allocates a chunk of
> > non-huge anonymous memory buffer.
> > 2. Pick 4 random buffer locations (2 in each thread) and inject
> > uncorrectable memory errors at corresponding physical addresses.
> > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > calling madvise(MADV_HUGEPAGE).
> > 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> > pages and skips collapsing them.
> > 5. Signal both threads to inspect their buffer contents and make sure no
> > data corruption.
> >
> > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > ---
> > include/trace/events/huge_memory.h | 3 +-
> > mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> > 2 files changed, 128 insertions(+), 23 deletions(-)
> >
> > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > index 3e6fb05852f9a..46cce509957ba 100644
> > --- a/include/trace/events/huge_memory.h
> > +++ b/include/trace/events/huge_memory.h
> > @@ -36,7 +36,8 @@
> > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> > EM( SCAN_TRUNCATED, "truncated") \
> > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
> >
> > #undef EM
> > #undef EMe
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 27956d4404134..c3c217f6ebc6e 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -19,6 +19,7 @@
> > #include <linux/page_table_check.h>
> > #include <linux/swapops.h>
> > #include <linux/shmem_fs.h>
> > +#include <linux/kmsan.h>
> >
> > #include <asm/tlb.h>
> > #include <asm/pgalloc.h>
> > @@ -55,6 +56,7 @@ enum scan_result {
> > SCAN_CGROUP_CHARGE_FAIL,
> > SCAN_TRUNCATED,
> > SCAN_PAGE_HAS_PRIVATE,
> > + SCAN_COPY_MC,
> > };
> >
> > #define CREATE_TRACE_POINTS
> > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > return result;
> > }
> >
> > -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > - struct vm_area_struct *vma,
> > - unsigned long address,
> > - spinlock_t *ptl,
> > - struct list_head *compound_pagelist)
> > +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> > + pmd_t *pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + spinlock_t *pte_ptl,
> > + struct list_head *compound_pagelist)
> > {
> > struct page *src_page, *tmp;
> > pte_t *_pte;
> > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> > - _pte++, page++, address += PAGE_SIZE) {
> > - pte_t pteval = *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> >
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > - clear_user_highpage(page, address);
> > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> > if (is_zero_pfn(pte_pfn(pteval))) {
> > /*
> > - * ptl mostly unnecessary.
> > + * pte_ptl mostly unnecessary.
> > */
> > - spin_lock(ptl);
> > - ptep_clear(vma->vm_mm, address, _pte);
> > - spin_unlock(ptl);
> > + spin_lock(pte_ptl);
>
> Why did you have to rename ptl to pte_ptl? It seems unnecessary.
Thanks, I will use `ptl` in the next version.
>
> > + pte_clear(vma->vm_mm, _address, _pte);
> > + spin_unlock(pte_ptl);
> > }
> > } else {
> > src_page = pte_page(pteval);
> > - copy_user_highpage(page, src_page, address, vma);
> > if (!PageCompound(src_page))
> > release_pte_page(src_page);
> > /*
> > - * ptl mostly unnecessary, but preempt has to
> > - * be disabled to update the per-cpu stats
> > + * pte_ptl mostly unnecessary, but preempt has
> > + * to be disabled to update the per-cpu stats
> > * inside page_remove_rmap().
> > */
> > - spin_lock(ptl);
> > - ptep_clear(vma->vm_mm, address, _pte);
> > + spin_lock(pte_ptl);
> > + ptep_clear(vma->vm_mm, _address, _pte);
> > page_remove_rmap(src_page, vma, false);
> > - spin_unlock(ptl);
> > + spin_unlock(pte_ptl);
> > free_page_and_swap_cache(src_page);
> > }
> > }
> > -
> > list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > list_del(&src_page->lru);
> > mod_node_page_state(page_pgdat(src_page),
> > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > }
> > }
> >
> > +static void __collapse_huge_page_copy_failed(pte_t *pte,
> > + pmd_t *pmd,
> > + pmd_t orig_pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + struct list_head *compound_pagelist)
> > +{
> > + struct page *src_page, *tmp;
> > + pte_t *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> > + spinlock_t *pmd_ptl;
> > +
> > + /*
> > + * Re-establish the PMD to point to the original page table
> > + * entry. Restoring PMD needs to be done prior to releasing
> > + * pages. Since pages are still isolated and locked here,
> > + * acquiring anon_vma_lock_write is unnecessary.
> > + */
> > + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> > + spin_unlock(pmd_ptl);
> > + /*
> > + * Release both raw and compound pages isolated
> > + * in __collapse_huge_page_isolate.
> > + */
>
> It looks like the below code could be replaced by release_pte_pages()
> with advancing _pte to (pte + HPAGE_PMD_NR - 1).
>
Yeah, but I think _pte should be (pte + HPAGE_PMR_NR) because _pte is
decremented before comparison in release_pte_pages(pte, _pte,
compound_pagelist):
while (--_pte >= pte) {...}
Advancing _pte to (pte + HPAGE_PMD_NR - 1) may leave the last page not released.
>
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> > + continue;
> > + src_page = pte_page(pteval);
> > + if (!PageCompound(src_page))
> > + release_pte_page(src_page);
> > + }
> > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > + list_del(&src_page->lru);
> > + release_pte_page(src_page);
> > + }
> > +}
> > +
> > +/*
> > + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> > + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> > + * otherwise restores the original page table and releases isolated raw pages.
> > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> > + *
> > + * @pte: starting of the PTEs to copy from
> > + * @page: the new hugepage to copy contents to
> > + * @pmd: pointer to the new hugepage's PMD
> > + * @orig_pmd: the original raw pages' PMD
> > + * @vma: the original raw pages' virtual memory area
> > + * @address: starting address to copy
> > + * @pte_ptl: lock on raw pages' PTEs
> > + * @compound_pagelist: list that stores compound pages
> > + */
> > +static int __collapse_huge_page_copy(pte_t *pte,
> > + struct page *page,
> > + pmd_t *pmd,
> > + pmd_t orig_pmd,
> > + struct vm_area_struct *vma,
> > + unsigned long address,
> > + spinlock_t *pte_ptl,
> > + struct list_head *compound_pagelist)
> > +{
> > + struct page *src_page;
> > + pte_t *_pte;
> > + pte_t pteval;
> > + unsigned long _address;
> > + int result = SCAN_SUCCEED;
> > +
> > + /*
> > + * Copying pages' contents is subject to memory poison at any iteration.
> > + */
> > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > + _pte++, page++, _address += PAGE_SIZE) {
> > + pteval = *_pte;
> > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > + clear_user_highpage(page, _address);
> > + continue;
> > + }
> > + src_page = pte_page(pteval);
> > + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> > + result = SCAN_COPY_MC;
> > + break;
> > + }
> > + }
> > +
> > + if (likely(result == SCAN_SUCCEED))
> > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> > + pte_ptl, compound_pagelist);
> > + else
> > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> > + address, compound_pagelist);
> > +
> > + return result;
> > +}
> > +
> > static void khugepaged_alloc_sleep(void)
> > {
> > DEFINE_WAIT(wait);
> > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > */
> > anon_vma_unlock_write(vma->anon_vma);
> >
> > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > - &compound_pagelist);
> > + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> > + vma, address, pte_ptl,
> > + &compound_pagelist);
> > pte_unmap(pte);
> > + if (unlikely(result != SCAN_SUCCEED))
> > + goto out_up_write;
> > +
> > /*
> > * spin_lock() below is not the equivalent of smp_wmb(), but
> > * the smp_wmb() inside __SetPageUptodate() can be reused to
> > --
> > 2.40.0.rc0.216.gc4246ad0f0-goog
> >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-24 15:34 ` Jiaqi Yan
@ 2023-03-24 20:11 ` Yang Shi
2023-03-24 22:31 ` Jiaqi Yan
0 siblings, 1 reply; 17+ messages in thread
From: Yang Shi @ 2023-03-24 20:11 UTC (permalink / raw)
To: Jiaqi Yan
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Fri, Mar 24, 2023 at 8:34 AM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> On Thu, Mar 23, 2023 at 2:38 PM Yang Shi <shy828301@gmail.com> wrote:
> >
> > On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > >
> > > Make __collapse_huge_page_copy return whether copying anonymous pages
> > > succeeded, and make collapse_huge_page handle the return status.
> > >
> > > Break existing PTE scan loop into two for-loops. The first loop copies
> > > source pages into target huge page, and can fail gracefully when running
> > > into memory errors in source pages. If copying all pages succeeds, the
> > > second loop releases and clears up these normal pages. Otherwise, the
> > > second loop rolls back the page table and page states by:
> > > - re-establishing the original PTEs-to-PMD connection.
> > > - releasing source pages back to their LRU list.
> > >
> > > Tested manually:
> > > 0. Enable khugepaged on system under test.
> > > 1. Start a two-thread application. Each thread allocates a chunk of
> > > non-huge anonymous memory buffer.
> > > 2. Pick 4 random buffer locations (2 in each thread) and inject
> > > uncorrectable memory errors at corresponding physical addresses.
> > > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > > calling madvise(MADV_HUGEPAGE).
> > > 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> > > pages and skips collapsing them.
> > > 5. Signal both threads to inspect their buffer contents and make sure no
> > > data corruption.
> > >
> > > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > > ---
> > > include/trace/events/huge_memory.h | 3 +-
> > > mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> > > 2 files changed, 128 insertions(+), 23 deletions(-)
> > >
> > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > > index 3e6fb05852f9a..46cce509957ba 100644
> > > --- a/include/trace/events/huge_memory.h
> > > +++ b/include/trace/events/huge_memory.h
> > > @@ -36,7 +36,8 @@
> > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> > > EM( SCAN_TRUNCATED, "truncated") \
> > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
> > >
> > > #undef EM
> > > #undef EMe
> > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > index 27956d4404134..c3c217f6ebc6e 100644
> > > --- a/mm/khugepaged.c
> > > +++ b/mm/khugepaged.c
> > > @@ -19,6 +19,7 @@
> > > #include <linux/page_table_check.h>
> > > #include <linux/swapops.h>
> > > #include <linux/shmem_fs.h>
> > > +#include <linux/kmsan.h>
> > >
> > > #include <asm/tlb.h>
> > > #include <asm/pgalloc.h>
> > > @@ -55,6 +56,7 @@ enum scan_result {
> > > SCAN_CGROUP_CHARGE_FAIL,
> > > SCAN_TRUNCATED,
> > > SCAN_PAGE_HAS_PRIVATE,
> > > + SCAN_COPY_MC,
> > > };
> > >
> > > #define CREATE_TRACE_POINTS
> > > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > > return result;
> > > }
> > >
> > > -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > - struct vm_area_struct *vma,
> > > - unsigned long address,
> > > - spinlock_t *ptl,
> > > - struct list_head *compound_pagelist)
> > > +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> > > + pmd_t *pmd,
> > > + struct vm_area_struct *vma,
> > > + unsigned long address,
> > > + spinlock_t *pte_ptl,
> > > + struct list_head *compound_pagelist)
> > > {
> > > struct page *src_page, *tmp;
> > > pte_t *_pte;
> > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> > > - _pte++, page++, address += PAGE_SIZE) {
> > > - pte_t pteval = *_pte;
> > > + pte_t pteval;
> > > + unsigned long _address;
> > >
> > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > + _pte++, _address += PAGE_SIZE) {
> > > + pteval = *_pte;
> > > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > - clear_user_highpage(page, address);
> > > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> > > if (is_zero_pfn(pte_pfn(pteval))) {
> > > /*
> > > - * ptl mostly unnecessary.
> > > + * pte_ptl mostly unnecessary.
> > > */
> > > - spin_lock(ptl);
> > > - ptep_clear(vma->vm_mm, address, _pte);
> > > - spin_unlock(ptl);
> > > + spin_lock(pte_ptl);
> >
> > Why did you have to rename ptl to pte_ptl? It seems unnecessary.
>
> Thanks, I will use `ptl` in the next version.
>
> >
> > > + pte_clear(vma->vm_mm, _address, _pte);
> > > + spin_unlock(pte_ptl);
> > > }
> > > } else {
> > > src_page = pte_page(pteval);
> > > - copy_user_highpage(page, src_page, address, vma);
> > > if (!PageCompound(src_page))
> > > release_pte_page(src_page);
> > > /*
> > > - * ptl mostly unnecessary, but preempt has to
> > > - * be disabled to update the per-cpu stats
> > > + * pte_ptl mostly unnecessary, but preempt has
> > > + * to be disabled to update the per-cpu stats
> > > * inside page_remove_rmap().
> > > */
> > > - spin_lock(ptl);
> > > - ptep_clear(vma->vm_mm, address, _pte);
> > > + spin_lock(pte_ptl);
> > > + ptep_clear(vma->vm_mm, _address, _pte);
> > > page_remove_rmap(src_page, vma, false);
> > > - spin_unlock(ptl);
> > > + spin_unlock(pte_ptl);
> > > free_page_and_swap_cache(src_page);
> > > }
> > > }
> > > -
> > > list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > list_del(&src_page->lru);
> > > mod_node_page_state(page_pgdat(src_page),
> > > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > }
> > > }
> > >
> > > +static void __collapse_huge_page_copy_failed(pte_t *pte,
> > > + pmd_t *pmd,
> > > + pmd_t orig_pmd,
> > > + struct vm_area_struct *vma,
> > > + unsigned long address,
> > > + struct list_head *compound_pagelist)
> > > +{
> > > + struct page *src_page, *tmp;
> > > + pte_t *_pte;
> > > + pte_t pteval;
> > > + unsigned long _address;
> > > + spinlock_t *pmd_ptl;
> > > +
> > > + /*
> > > + * Re-establish the PMD to point to the original page table
> > > + * entry. Restoring PMD needs to be done prior to releasing
> > > + * pages. Since pages are still isolated and locked here,
> > > + * acquiring anon_vma_lock_write is unnecessary.
> > > + */
> > > + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> > > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> > > + spin_unlock(pmd_ptl);
> > > + /*
> > > + * Release both raw and compound pages isolated
> > > + * in __collapse_huge_page_isolate.
> > > + */
> >
> > It looks like the below code could be replaced by release_pte_pages()
> > with advancing _pte to (pte + HPAGE_PMD_NR - 1).
> >
>
> Yeah, but I think _pte should be (pte + HPAGE_PMR_NR) because _pte is
> decremented before comparison in release_pte_pages(pte, _pte,
> compound_pagelist):
>
> while (--_pte >= pte) {...}
>
> Advancing _pte to (pte + HPAGE_PMD_NR - 1) may leave the last page not released.
Yeah, good catch. I think it is because the only user of
release_pte_pages() is __collapse_huge_page_isolate(). Once the loop
in it is done _pte is pte + HPAGE_PMD_NR.
>
> >
> > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > + _pte++, _address += PAGE_SIZE) {
> > > + pteval = *_pte;
> > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> > > + continue;
> > > + src_page = pte_page(pteval);
> > > + if (!PageCompound(src_page))
> > > + release_pte_page(src_page);
> > > + }
> > > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > + list_del(&src_page->lru);
> > > + release_pte_page(src_page);
> > > + }
> > > +}
> > > +
> > > +/*
> > > + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> > > + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> > > + * otherwise restores the original page table and releases isolated raw pages.
> > > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> > > + *
> > > + * @pte: starting of the PTEs to copy from
> > > + * @page: the new hugepage to copy contents to
> > > + * @pmd: pointer to the new hugepage's PMD
> > > + * @orig_pmd: the original raw pages' PMD
> > > + * @vma: the original raw pages' virtual memory area
> > > + * @address: starting address to copy
> > > + * @pte_ptl: lock on raw pages' PTEs
> > > + * @compound_pagelist: list that stores compound pages
> > > + */
> > > +static int __collapse_huge_page_copy(pte_t *pte,
> > > + struct page *page,
> > > + pmd_t *pmd,
> > > + pmd_t orig_pmd,
> > > + struct vm_area_struct *vma,
> > > + unsigned long address,
> > > + spinlock_t *pte_ptl,
> > > + struct list_head *compound_pagelist)
> > > +{
> > > + struct page *src_page;
> > > + pte_t *_pte;
> > > + pte_t pteval;
> > > + unsigned long _address;
> > > + int result = SCAN_SUCCEED;
> > > +
> > > + /*
> > > + * Copying pages' contents is subject to memory poison at any iteration.
> > > + */
> > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > + _pte++, page++, _address += PAGE_SIZE) {
> > > + pteval = *_pte;
> > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > + clear_user_highpage(page, _address);
> > > + continue;
> > > + }
> > > + src_page = pte_page(pteval);
> > > + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> > > + result = SCAN_COPY_MC;
> > > + break;
> > > + }
> > > + }
> > > +
> > > + if (likely(result == SCAN_SUCCEED))
> > > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> > > + pte_ptl, compound_pagelist);
> > > + else
> > > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> > > + address, compound_pagelist);
> > > +
> > > + return result;
> > > +}
> > > +
> > > static void khugepaged_alloc_sleep(void)
> > > {
> > > DEFINE_WAIT(wait);
> > > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > > */
> > > anon_vma_unlock_write(vma->anon_vma);
> > >
> > > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > > - &compound_pagelist);
> > > + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> > > + vma, address, pte_ptl,
> > > + &compound_pagelist);
> > > pte_unmap(pte);
> > > + if (unlikely(result != SCAN_SUCCEED))
> > > + goto out_up_write;
> > > +
> > > /*
> > > * spin_lock() below is not the equivalent of smp_wmb(), but
> > > * the smp_wmb() inside __SetPageUptodate() can be reused to
> > > --
> > > 2.40.0.rc0.216.gc4246ad0f0-goog
> > >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage
2023-03-05 6:51 ` [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage Jiaqi Yan
2023-03-05 6:56 ` Jiaqi Yan
@ 2023-03-24 20:24 ` Yang Shi
1 sibling, 0 replies; 17+ messages in thread
From: Yang Shi @ 2023-03-24 20:24 UTC (permalink / raw)
To: Jiaqi Yan
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> Similar to how copy_mc_user_highpage is implemented for
> copy_user_highpage on #MC supported architecture, introduce
> the #MC handled version of copy_highpage.
>
> This helper has immediate usage when khugepaged wants to copy
> file-backed memory pages and tolerate #MC.
I don't have a strong opinion on non-inline or inline. Putting
copy_mc_highpage() together with copy_mc_user_highpage() makes sense
to me.
Reviewed-by: Yang Shi <shy828301@gmail.com>
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> ---
> include/linux/highmem.h | 54 +++++++++++++++++++++++++++++++----------
> 1 file changed, 41 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 1128b7114931f..7cbecae39b3eb 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -315,7 +315,29 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
>
> #endif
>
> +#ifndef __HAVE_ARCH_COPY_HIGHPAGE
> +
> +static inline void copy_highpage(struct page *to, struct page *from)
> +{
> + char *vfrom, *vto;
> +
> + vfrom = kmap_local_page(from);
> + vto = kmap_local_page(to);
> + copy_page(vto, vfrom);
> + kmsan_copy_page_meta(to, from);
> + kunmap_local(vto);
> + kunmap_local(vfrom);
> +}
> +
> +#endif
> +
> #ifdef copy_mc_to_kernel
> +/*
> + * If architecture supports machine check exception handling, define the
> + * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
> + * page with #MC in source page (@from) handled, and return the number
> + * of bytes not copied if there was a #MC, otherwise 0 for success.
> + */
> static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> unsigned long vaddr, struct vm_area_struct *vma)
> {
> @@ -332,29 +354,35 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
>
> return ret;
> }
> -#else
> -static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> - unsigned long vaddr, struct vm_area_struct *vma)
> -{
> - copy_user_highpage(to, from, vaddr, vma);
> - return 0;
> -}
> -#endif
>
> -#ifndef __HAVE_ARCH_COPY_HIGHPAGE
> -
> -static inline void copy_highpage(struct page *to, struct page *from)
> +static inline int copy_mc_highpage(struct page *to, struct page *from)
> {
> + unsigned long ret;
> char *vfrom, *vto;
>
> vfrom = kmap_local_page(from);
> vto = kmap_local_page(to);
> - copy_page(vto, vfrom);
> - kmsan_copy_page_meta(to, from);
> + ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
> + if (!ret)
> + kmsan_copy_page_meta(to, from);
> kunmap_local(vto);
> kunmap_local(vfrom);
> +
> + return ret;
> +}
> +#else
> +static inline int copy_mc_user_highpage(struct page *to, struct page *from,
> + unsigned long vaddr, struct vm_area_struct *vma)
> +{
> + copy_user_highpage(to, from, vaddr, vma);
> + return 0;
> }
>
> +static inline int copy_mc_highpage(struct page *to, struct page *from)
> +{
> + copy_highpage(to, from);
> + return 0;
> +}
> #endif
>
> static inline void memcpy_page(struct page *dst_page, size_t dst_off,
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory
2023-03-05 6:51 ` [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory Jiaqi Yan
@ 2023-03-24 21:15 ` Yang Shi
2023-03-24 22:54 ` Jiaqi Yan
0 siblings, 1 reply; 17+ messages in thread
From: Yang Shi @ 2023-03-24 21:15 UTC (permalink / raw)
To: Jiaqi Yan
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> Make collapse_file roll back when copying pages failed. More concretely:
> - extract copying operations into a separate loop
> - postpone the updates for nr_none until both scanning and copying
> succeeded
> - postpone joining small xarray entries until both scanning and copying
> succeeded
> - postpone the update operations to NR_XXX_THPS until both scanning and
> copying succeeded
> - for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
> copying failed
>
> Tested manually:
> 0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
> 1. Start a two-thread application. Each thread allocates a chunk of
> non-huge memory buffer from /mnt/ramdisk.
> 2. Pick 4 random buffer address (2 in each thread) and inject
> uncorrectable memory errors at physical addresses.
> 3. Signal both threads to make their memory buffer collapsible, i.e.
> calling madvise(MADV_HUGEPAGE).
> 4. Wait and then check kernel log: khugepaged is able to recover from
> poisoned pages by skipping them.
> 5. Signal both threads to inspect their buffer contents and make sure no
> data corruption.
>
> Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Just a nit below:
> ---
> mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++-------------------
> 1 file changed, 48 insertions(+), 30 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index c3c217f6ebc6e..3ea2aa55c2c52 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1890,6 +1890,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> {
> struct address_space *mapping = file->f_mapping;
> struct page *hpage;
> + struct page *page;
> + struct page *tmp;
> + struct folio *folio;
> pgoff_t index = 0, end = start + HPAGE_PMD_NR;
> LIST_HEAD(pagelist);
> XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> @@ -1934,8 +1937,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
>
> xas_set(&xas, start);
> for (index = start; index < end; index++) {
> - struct page *page = xas_next(&xas);
> - struct folio *folio;
> + page = xas_next(&xas);
>
> VM_BUG_ON(index != xas.xa_index);
> if (is_shmem) {
> @@ -2117,10 +2119,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> }
> nr = thp_nr_pages(hpage);
>
> - if (is_shmem)
> - __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> - else {
> - __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> + if (!is_shmem) {
> filemap_nr_thps_inc(mapping);
> /*
> * Paired with smp_mb() in do_dentry_open() to ensure
> @@ -2131,21 +2130,10 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> smp_mb();
> if (inode_is_open_for_write(mapping->host)) {
> result = SCAN_FAIL;
> - __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
> filemap_nr_thps_dec(mapping);
> goto xa_locked;
> }
> }
> -
> - if (nr_none) {
> - __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
> - /* nr_none is always 0 for non-shmem. */
> - __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
> - }
> -
> - /* Join all the small entries into a single multi-index entry */
> - xas_set_order(&xas, start, HPAGE_PMD_ORDER);
> - xas_store(&xas, hpage);
> xa_locked:
> xas_unlock_irq(&xas);
> xa_unlocked:
> @@ -2158,21 +2146,35 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> try_to_unmap_flush();
>
> if (result == SCAN_SUCCEED) {
> - struct page *page, *tmp;
> - struct folio *folio;
> -
> /*
> * Replacing old pages with new one has succeeded, now we
> - * need to copy the content and free the old pages.
> + * attempt to copy the contents.
> */
> index = start;
> - list_for_each_entry_safe(page, tmp, &pagelist, lru) {
> + list_for_each_entry(page, &pagelist, lru) {
> while (index < page->index) {
> clear_highpage(hpage + (index % HPAGE_PMD_NR));
> index++;
> }
> - copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
> - page);
> + if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR),
> + page) > 0) {
> + result = SCAN_COPY_MC;
> + break;
> + }
> + index++;
> + }
> + while (result == SCAN_SUCCEED && index < end) {
> + clear_highpage(hpage + (index % HPAGE_PMD_NR));
> + index++;
> + }
> + }
> +
> + if (result == SCAN_SUCCEED) {
> + /*
> + * Copying old pages to huge one has succeeded, now we
> + * need to free the old pages.
> + */
> + list_for_each_entry_safe(page, tmp, &pagelist, lru) {
> list_del(&page->lru);
> page->mapping = NULL;
> page_ref_unfreeze(page, 1);
> @@ -2180,12 +2182,23 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> ClearPageUnevictable(page);
> unlock_page(page);
> put_page(page);
> - index++;
> }
> - while (index < end) {
> - clear_highpage(hpage + (index % HPAGE_PMD_NR));
> - index++;
> +
> + xas_lock_irq(&xas);
> + if (is_shmem)
> + __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> + else
> + __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> +
> + if (nr_none) {
> + __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
> + /* nr_none is always 0 for non-shmem. */
> + __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
> }
> + /* Join all the small entries into a single multi-index entry. */
> + xas_set_order(&xas, start, HPAGE_PMD_ORDER);
> + xas_store(&xas, hpage);
> + xas_unlock_irq(&xas);
>
> folio = page_folio(hpage);
> folio_mark_uptodate(folio);
> @@ -2203,8 +2216,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> unlock_page(hpage);
> hpage = NULL;
> } else {
> - struct page *page;
> -
> /* Something went wrong: roll back page cache changes */
> xas_lock_irq(&xas);
> if (nr_none) {
> @@ -2238,6 +2249,13 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> xas_lock_irq(&xas);
> }
> VM_BUG_ON(nr_none);
> + /*
> + * Undo the updates of filemap_nr_thps_inc for non-SHMEM file only.
> + * This undo is not needed unless failure is due to SCAN_COPY_MC.
> + */
> + if (!is_shmem && result == SCAN_COPY_MC)
> + filemap_nr_thps_dec(mapping);
We may need a memory barrier here. But missing the memory barrier is
not a fatal issue either, the worst case is unnecessary truncate from
open path if it sees obsolete nr_thps counter. And it may be better to
handle it in a follow up patch by moving smp_mb() into
filemap_nr_thp_xxx functions.
> +
> xas_unlock_irq(&xas);
>
> hpage->mapping = NULL;
> --
> 2.40.0.rc0.216.gc4246ad0f0-goog
>
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-24 20:11 ` Yang Shi
@ 2023-03-24 22:31 ` Jiaqi Yan
2023-03-27 20:46 ` Jiaqi Yan
0 siblings, 1 reply; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-24 22:31 UTC (permalink / raw)
To: Yang Shi
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Fri, Mar 24, 2023 at 1:11 PM Yang Shi <shy828301@gmail.com> wrote:
>
> On Fri, Mar 24, 2023 at 8:34 AM Jiaqi Yan <jiaqiyan@google.com> wrote:
> >
> > On Thu, Mar 23, 2023 at 2:38 PM Yang Shi <shy828301@gmail.com> wrote:
> > >
> > > On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > > >
> > > > Make __collapse_huge_page_copy return whether copying anonymous pages
> > > > succeeded, and make collapse_huge_page handle the return status.
> > > >
> > > > Break existing PTE scan loop into two for-loops. The first loop copies
> > > > source pages into target huge page, and can fail gracefully when running
> > > > into memory errors in source pages. If copying all pages succeeds, the
> > > > second loop releases and clears up these normal pages. Otherwise, the
> > > > second loop rolls back the page table and page states by:
> > > > - re-establishing the original PTEs-to-PMD connection.
> > > > - releasing source pages back to their LRU list.
> > > >
> > > > Tested manually:
> > > > 0. Enable khugepaged on system under test.
> > > > 1. Start a two-thread application. Each thread allocates a chunk of
> > > > non-huge anonymous memory buffer.
> > > > 2. Pick 4 random buffer locations (2 in each thread) and inject
> > > > uncorrectable memory errors at corresponding physical addresses.
> > > > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > > > calling madvise(MADV_HUGEPAGE).
> > > > 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> > > > pages and skips collapsing them.
> > > > 5. Signal both threads to inspect their buffer contents and make sure no
> > > > data corruption.
> > > >
> > > > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > > > ---
> > > > include/trace/events/huge_memory.h | 3 +-
> > > > mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> > > > 2 files changed, 128 insertions(+), 23 deletions(-)
> > > >
> > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > > > index 3e6fb05852f9a..46cce509957ba 100644
> > > > --- a/include/trace/events/huge_memory.h
> > > > +++ b/include/trace/events/huge_memory.h
> > > > @@ -36,7 +36,8 @@
> > > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> > > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> > > > EM( SCAN_TRUNCATED, "truncated") \
> > > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
> > > >
> > > > #undef EM
> > > > #undef EMe
> > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > > index 27956d4404134..c3c217f6ebc6e 100644
> > > > --- a/mm/khugepaged.c
> > > > +++ b/mm/khugepaged.c
> > > > @@ -19,6 +19,7 @@
> > > > #include <linux/page_table_check.h>
> > > > #include <linux/swapops.h>
> > > > #include <linux/shmem_fs.h>
> > > > +#include <linux/kmsan.h>
> > > >
> > > > #include <asm/tlb.h>
> > > > #include <asm/pgalloc.h>
> > > > @@ -55,6 +56,7 @@ enum scan_result {
> > > > SCAN_CGROUP_CHARGE_FAIL,
> > > > SCAN_TRUNCATED,
> > > > SCAN_PAGE_HAS_PRIVATE,
> > > > + SCAN_COPY_MC,
> > > > };
> > > >
> > > > #define CREATE_TRACE_POINTS
> > > > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > > > return result;
> > > > }
> > > >
> > > > -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > > - struct vm_area_struct *vma,
> > > > - unsigned long address,
> > > > - spinlock_t *ptl,
> > > > - struct list_head *compound_pagelist)
> > > > +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> > > > + pmd_t *pmd,
> > > > + struct vm_area_struct *vma,
> > > > + unsigned long address,
> > > > + spinlock_t *pte_ptl,
> > > > + struct list_head *compound_pagelist)
> > > > {
> > > > struct page *src_page, *tmp;
> > > > pte_t *_pte;
> > > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> > > > - _pte++, page++, address += PAGE_SIZE) {
> > > > - pte_t pteval = *_pte;
> > > > + pte_t pteval;
> > > > + unsigned long _address;
> > > >
> > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > + _pte++, _address += PAGE_SIZE) {
> > > > + pteval = *_pte;
> > > > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > > - clear_user_highpage(page, address);
> > > > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> > > > if (is_zero_pfn(pte_pfn(pteval))) {
> > > > /*
> > > > - * ptl mostly unnecessary.
> > > > + * pte_ptl mostly unnecessary.
> > > > */
> > > > - spin_lock(ptl);
> > > > - ptep_clear(vma->vm_mm, address, _pte);
> > > > - spin_unlock(ptl);
> > > > + spin_lock(pte_ptl);
> > >
> > > Why did you have to rename ptl to pte_ptl? It seems unnecessary.
> >
> > Thanks, I will use `ptl` in the next version.
> >
> > >
> > > > + pte_clear(vma->vm_mm, _address, _pte);
> > > > + spin_unlock(pte_ptl);
> > > > }
> > > > } else {
> > > > src_page = pte_page(pteval);
> > > > - copy_user_highpage(page, src_page, address, vma);
> > > > if (!PageCompound(src_page))
> > > > release_pte_page(src_page);
> > > > /*
> > > > - * ptl mostly unnecessary, but preempt has to
> > > > - * be disabled to update the per-cpu stats
> > > > + * pte_ptl mostly unnecessary, but preempt has
> > > > + * to be disabled to update the per-cpu stats
> > > > * inside page_remove_rmap().
> > > > */
> > > > - spin_lock(ptl);
> > > > - ptep_clear(vma->vm_mm, address, _pte);
> > > > + spin_lock(pte_ptl);
> > > > + ptep_clear(vma->vm_mm, _address, _pte);
> > > > page_remove_rmap(src_page, vma, false);
> > > > - spin_unlock(ptl);
> > > > + spin_unlock(pte_ptl);
> > > > free_page_and_swap_cache(src_page);
> > > > }
> > > > }
> > > > -
> > > > list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > > list_del(&src_page->lru);
> > > > mod_node_page_state(page_pgdat(src_page),
> > > > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > > }
> > > > }
> > > >
> > > > +static void __collapse_huge_page_copy_failed(pte_t *pte,
> > > > + pmd_t *pmd,
> > > > + pmd_t orig_pmd,
> > > > + struct vm_area_struct *vma,
> > > > + unsigned long address,
> > > > + struct list_head *compound_pagelist)
> > > > +{
> > > > + struct page *src_page, *tmp;
> > > > + pte_t *_pte;
> > > > + pte_t pteval;
> > > > + unsigned long _address;
> > > > + spinlock_t *pmd_ptl;
> > > > +
> > > > + /*
> > > > + * Re-establish the PMD to point to the original page table
> > > > + * entry. Restoring PMD needs to be done prior to releasing
> > > > + * pages. Since pages are still isolated and locked here,
> > > > + * acquiring anon_vma_lock_write is unnecessary.
> > > > + */
> > > > + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> > > > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> > > > + spin_unlock(pmd_ptl);
> > > > + /*
> > > > + * Release both raw and compound pages isolated
> > > > + * in __collapse_huge_page_isolate.
> > > > + */
> > >
> > > It looks like the below code could be replaced by release_pte_pages()
> > > with advancing _pte to (pte + HPAGE_PMD_NR - 1).
> > >
> >
> > Yeah, but I think _pte should be (pte + HPAGE_PMR_NR) because _pte is
> > decremented before comparison in release_pte_pages(pte, _pte,
> > compound_pagelist):
> >
> > while (--_pte >= pte) {...}
> >
> > Advancing _pte to (pte + HPAGE_PMD_NR - 1) may leave the last page not released.
>
> Yeah, good catch. I think it is because the only user of
> release_pte_pages() is __collapse_huge_page_isolate(). Once the loop
> in it is done _pte is pte + HPAGE_PMD_NR.
>
Thanks for confirming ;)
Since you have reviewed other 2 commits, I will soon send out V11 for
your comments on this commit.
> >
> > >
> > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > + _pte++, _address += PAGE_SIZE) {
> > > > + pteval = *_pte;
> > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> > > > + continue;
> > > > + src_page = pte_page(pteval);
> > > > + if (!PageCompound(src_page))
> > > > + release_pte_page(src_page);
> > > > + }
> > > > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > > + list_del(&src_page->lru);
> > > > + release_pte_page(src_page);
> > > > + }
> > > > +}
> > > > +
> > > > +/*
> > > > + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> > > > + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> > > > + * otherwise restores the original page table and releases isolated raw pages.
> > > > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> > > > + *
> > > > + * @pte: starting of the PTEs to copy from
> > > > + * @page: the new hugepage to copy contents to
> > > > + * @pmd: pointer to the new hugepage's PMD
> > > > + * @orig_pmd: the original raw pages' PMD
> > > > + * @vma: the original raw pages' virtual memory area
> > > > + * @address: starting address to copy
> > > > + * @pte_ptl: lock on raw pages' PTEs
> > > > + * @compound_pagelist: list that stores compound pages
> > > > + */
> > > > +static int __collapse_huge_page_copy(pte_t *pte,
> > > > + struct page *page,
> > > > + pmd_t *pmd,
> > > > + pmd_t orig_pmd,
> > > > + struct vm_area_struct *vma,
> > > > + unsigned long address,
> > > > + spinlock_t *pte_ptl,
> > > > + struct list_head *compound_pagelist)
> > > > +{
> > > > + struct page *src_page;
> > > > + pte_t *_pte;
> > > > + pte_t pteval;
> > > > + unsigned long _address;
> > > > + int result = SCAN_SUCCEED;
> > > > +
> > > > + /*
> > > > + * Copying pages' contents is subject to memory poison at any iteration.
> > > > + */
> > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > + _pte++, page++, _address += PAGE_SIZE) {
> > > > + pteval = *_pte;
> > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > > + clear_user_highpage(page, _address);
> > > > + continue;
> > > > + }
> > > > + src_page = pte_page(pteval);
> > > > + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> > > > + result = SCAN_COPY_MC;
> > > > + break;
> > > > + }
> > > > + }
> > > > +
> > > > + if (likely(result == SCAN_SUCCEED))
> > > > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> > > > + pte_ptl, compound_pagelist);
> > > > + else
> > > > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> > > > + address, compound_pagelist);
> > > > +
> > > > + return result;
> > > > +}
> > > > +
> > > > static void khugepaged_alloc_sleep(void)
> > > > {
> > > > DEFINE_WAIT(wait);
> > > > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > > > */
> > > > anon_vma_unlock_write(vma->anon_vma);
> > > >
> > > > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > > > - &compound_pagelist);
> > > > + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> > > > + vma, address, pte_ptl,
> > > > + &compound_pagelist);
> > > > pte_unmap(pte);
> > > > + if (unlikely(result != SCAN_SUCCEED))
> > > > + goto out_up_write;
> > > > +
> > > > /*
> > > > * spin_lock() below is not the equivalent of smp_wmb(), but
> > > > * the smp_wmb() inside __SetPageUptodate() can be reused to
> > > > --
> > > > 2.40.0.rc0.216.gc4246ad0f0-goog
> > > >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory
2023-03-24 21:15 ` Yang Shi
@ 2023-03-24 22:54 ` Jiaqi Yan
2023-03-25 0:39 ` Hugh Dickins
0 siblings, 1 reply; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-24 22:54 UTC (permalink / raw)
To: Yang Shi
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Fri, Mar 24, 2023 at 2:15 PM Yang Shi <shy828301@gmail.com> wrote:
>
> On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> >
> > Make collapse_file roll back when copying pages failed. More concretely:
> > - extract copying operations into a separate loop
> > - postpone the updates for nr_none until both scanning and copying
> > succeeded
> > - postpone joining small xarray entries until both scanning and copying
> > succeeded
> > - postpone the update operations to NR_XXX_THPS until both scanning and
> > copying succeeded
> > - for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
> > copying failed
> >
> > Tested manually:
> > 0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
> > 1. Start a two-thread application. Each thread allocates a chunk of
> > non-huge memory buffer from /mnt/ramdisk.
> > 2. Pick 4 random buffer address (2 in each thread) and inject
> > uncorrectable memory errors at physical addresses.
> > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > calling madvise(MADV_HUGEPAGE).
> > 4. Wait and then check kernel log: khugepaged is able to recover from
> > poisoned pages by skipping them.
> > 5. Signal both threads to inspect their buffer contents and make sure no
> > data corruption.
> >
> > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
>
> Reviewed-by: Yang Shi <shy828301@gmail.com>
>
> Just a nit below:
>
> > ---
> > mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++-------------------
> > 1 file changed, 48 insertions(+), 30 deletions(-)
> >
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index c3c217f6ebc6e..3ea2aa55c2c52 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -1890,6 +1890,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > {
> > struct address_space *mapping = file->f_mapping;
> > struct page *hpage;
> > + struct page *page;
> > + struct page *tmp;
> > + struct folio *folio;
> > pgoff_t index = 0, end = start + HPAGE_PMD_NR;
> > LIST_HEAD(pagelist);
> > XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> > @@ -1934,8 +1937,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> >
> > xas_set(&xas, start);
> > for (index = start; index < end; index++) {
> > - struct page *page = xas_next(&xas);
> > - struct folio *folio;
> > + page = xas_next(&xas);
> >
> > VM_BUG_ON(index != xas.xa_index);
> > if (is_shmem) {
> > @@ -2117,10 +2119,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > }
> > nr = thp_nr_pages(hpage);
> >
> > - if (is_shmem)
> > - __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> > - else {
> > - __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> > + if (!is_shmem) {
> > filemap_nr_thps_inc(mapping);
> > /*
> > * Paired with smp_mb() in do_dentry_open() to ensure
> > @@ -2131,21 +2130,10 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > smp_mb();
> > if (inode_is_open_for_write(mapping->host)) {
> > result = SCAN_FAIL;
> > - __mod_lruvec_page_state(hpage, NR_FILE_THPS, -nr);
> > filemap_nr_thps_dec(mapping);
> > goto xa_locked;
I notice the "goto xa_locked" statement can be removed now that the
code between here and xa_locked are all gone.
> > }
> > }
> > -
> > - if (nr_none) {
> > - __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
> > - /* nr_none is always 0 for non-shmem. */
> > - __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
> > - }
> > -
> > - /* Join all the small entries into a single multi-index entry */
> > - xas_set_order(&xas, start, HPAGE_PMD_ORDER);
> > - xas_store(&xas, hpage);
> > xa_locked:
> > xas_unlock_irq(&xas);
> > xa_unlocked:
> > @@ -2158,21 +2146,35 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > try_to_unmap_flush();
> >
> > if (result == SCAN_SUCCEED) {
> > - struct page *page, *tmp;
> > - struct folio *folio;
> > -
> > /*
> > * Replacing old pages with new one has succeeded, now we
> > - * need to copy the content and free the old pages.
> > + * attempt to copy the contents.
> > */
> > index = start;
> > - list_for_each_entry_safe(page, tmp, &pagelist, lru) {
> > + list_for_each_entry(page, &pagelist, lru) {
> > while (index < page->index) {
> > clear_highpage(hpage + (index % HPAGE_PMD_NR));
> > index++;
> > }
> > - copy_highpage(hpage + (page->index % HPAGE_PMD_NR),
> > - page);
> > + if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR),
> > + page) > 0) {
> > + result = SCAN_COPY_MC;
> > + break;
> > + }
> > + index++;
> > + }
> > + while (result == SCAN_SUCCEED && index < end) {
> > + clear_highpage(hpage + (index % HPAGE_PMD_NR));
> > + index++;
> > + }
> > + }
> > +
> > + if (result == SCAN_SUCCEED) {
> > + /*
> > + * Copying old pages to huge one has succeeded, now we
> > + * need to free the old pages.
> > + */
> > + list_for_each_entry_safe(page, tmp, &pagelist, lru) {
> > list_del(&page->lru);
> > page->mapping = NULL;
> > page_ref_unfreeze(page, 1);
> > @@ -2180,12 +2182,23 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > ClearPageUnevictable(page);
> > unlock_page(page);
> > put_page(page);
> > - index++;
> > }
> > - while (index < end) {
> > - clear_highpage(hpage + (index % HPAGE_PMD_NR));
> > - index++;
> > +
> > + xas_lock_irq(&xas);
> > + if (is_shmem)
> > + __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> > + else
> > + __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> > +
> > + if (nr_none) {
> > + __mod_lruvec_page_state(hpage, NR_FILE_PAGES, nr_none);
> > + /* nr_none is always 0 for non-shmem. */
> > + __mod_lruvec_page_state(hpage, NR_SHMEM, nr_none);
> > }
> > + /* Join all the small entries into a single multi-index entry. */
> > + xas_set_order(&xas, start, HPAGE_PMD_ORDER);
> > + xas_store(&xas, hpage);
> > + xas_unlock_irq(&xas);
> >
> > folio = page_folio(hpage);
> > folio_mark_uptodate(folio);
> > @@ -2203,8 +2216,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > unlock_page(hpage);
> > hpage = NULL;
> > } else {
> > - struct page *page;
> > -
> > /* Something went wrong: roll back page cache changes */
> > xas_lock_irq(&xas);
> > if (nr_none) {
> > @@ -2238,6 +2249,13 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > xas_lock_irq(&xas);
> > }
> > VM_BUG_ON(nr_none);
> > + /*
> > + * Undo the updates of filemap_nr_thps_inc for non-SHMEM file only.
> > + * This undo is not needed unless failure is due to SCAN_COPY_MC.
> > + */
> > + if (!is_shmem && result == SCAN_COPY_MC)
> > + filemap_nr_thps_dec(mapping);
>
> We may need a memory barrier here. But missing the memory barrier is
> not a fatal issue either, the worst case is unnecessary truncate from
> open path if it sees obsolete nr_thps counter. And it may be better to
> handle it in a follow up patch by moving smp_mb() into
> filemap_nr_thp_xxx functions.
Ah, for the same reason as the comment above: "Paired with smp_mb() in
do_dentry_open() to ensure i_writecount is up to date and the update
to nr_thps is visible."?
In that case, let me add the smp_mb() like this:
smp_mb();
if (!is_shmem && result == SCAN_COPY_MC) {...}
>
> > +
> > xas_unlock_irq(&xas);
> >
> > hpage->mapping = NULL;
> > --
> > 2.40.0.rc0.216.gc4246ad0f0-goog
> >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory
2023-03-24 22:54 ` Jiaqi Yan
@ 2023-03-25 0:39 ` Hugh Dickins
2023-03-27 21:15 ` Jiaqi Yan
0 siblings, 1 reply; 17+ messages in thread
From: Hugh Dickins @ 2023-03-25 0:39 UTC (permalink / raw)
To: Jiaqi Yan
Cc: Yang Shi, kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
[-- Attachment #1: Type: text/plain, Size: 3879 bytes --]
On Fri, 24 Mar 2023, Jiaqi Yan wrote:
> On Fri, Mar 24, 2023 at 2:15 PM Yang Shi <shy828301@gmail.com> wrote:
> > On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > >
> > > Make collapse_file roll back when copying pages failed. More concretely:
> > > - extract copying operations into a separate loop
> > > - postpone the updates for nr_none until both scanning and copying
> > > succeeded
> > > - postpone joining small xarray entries until both scanning and copying
> > > succeeded
> > > - postpone the update operations to NR_XXX_THPS until both scanning and
> > > copying succeeded
> > > - for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
> > > copying failed
> > >
> > > Tested manually:
> > > 0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
> > > 1. Start a two-thread application. Each thread allocates a chunk of
> > > non-huge memory buffer from /mnt/ramdisk.
> > > 2. Pick 4 random buffer address (2 in each thread) and inject
> > > uncorrectable memory errors at physical addresses.
> > > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > > calling madvise(MADV_HUGEPAGE).
> > > 4. Wait and then check kernel log: khugepaged is able to recover from
> > > poisoned pages by skipping them.
> > > 5. Signal both threads to inspect their buffer contents and make sure no
> > > data corruption.
> > >
> > > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> >
> > Reviewed-by: Yang Shi <shy828301@gmail.com>
> >
> > Just a nit below:
Acked-by: Hugh Dickins <hughd@google.com>
with a little nit from me below, if you are respinning:
> >
> > > ---
> > > mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++-------------------
> > > 1 file changed, 48 insertions(+), 30 deletions(-)
> > >
> > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > index c3c217f6ebc6e..3ea2aa55c2c52 100644
> > > --- a/mm/khugepaged.c
> > > +++ b/mm/khugepaged.c
> > > @@ -1890,6 +1890,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > > {
> > > struct address_space *mapping = file->f_mapping;
> > > struct page *hpage;
> > > + struct page *page;
> > > + struct page *tmp;
> > > + struct folio *folio;
> > > pgoff_t index = 0, end = start + HPAGE_PMD_NR;
> > > LIST_HEAD(pagelist);
> > > XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> > > @@ -1934,8 +1937,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > >
> > > xas_set(&xas, start);
> > > for (index = start; index < end; index++) {
> > > - struct page *page = xas_next(&xas);
> > > - struct folio *folio;
> > > + page = xas_next(&xas);
> > >
> > > VM_BUG_ON(index != xas.xa_index);
> > > if (is_shmem) {
> > > @@ -2117,10 +2119,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > > }
> > > nr = thp_nr_pages(hpage);
> > >
> > > - if (is_shmem)
> > > - __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> > > - else {
> > > - __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> > > + if (!is_shmem) {
> > > filemap_nr_thps_inc(mapping);
> > > /*
> > > * Paired with smp_mb() in do_dentry_open() to ensure
That "nr = thp_nr_pages(hpage);" above becomes stranded a long way away
from where "nr" is actually used for updating those statistics: please
move it down with them. (I see "nr" is also reported in the tracepoint
at the end, FWIW, so maybe that will show "0" in more failure cases than
it used to, but that's okay - it has been decently initialized.)
Thanks,
Hugh
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory
2023-03-24 22:31 ` Jiaqi Yan
@ 2023-03-27 20:46 ` Jiaqi Yan
0 siblings, 0 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-27 20:46 UTC (permalink / raw)
To: Yang Shi
Cc: kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Fri, Mar 24, 2023 at 3:31 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
>
> On Fri, Mar 24, 2023 at 1:11 PM Yang Shi <shy828301@gmail.com> wrote:
> >
> > On Fri, Mar 24, 2023 at 8:34 AM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > >
> > > On Thu, Mar 23, 2023 at 2:38 PM Yang Shi <shy828301@gmail.com> wrote:
> > > >
> > > > On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > > > >
> > > > > Make __collapse_huge_page_copy return whether copying anonymous pages
> > > > > succeeded, and make collapse_huge_page handle the return status.
> > > > >
> > > > > Break existing PTE scan loop into two for-loops. The first loop copies
> > > > > source pages into target huge page, and can fail gracefully when running
> > > > > into memory errors in source pages. If copying all pages succeeds, the
> > > > > second loop releases and clears up these normal pages. Otherwise, the
> > > > > second loop rolls back the page table and page states by:
> > > > > - re-establishing the original PTEs-to-PMD connection.
> > > > > - releasing source pages back to their LRU list.
> > > > >
> > > > > Tested manually:
> > > > > 0. Enable khugepaged on system under test.
> > > > > 1. Start a two-thread application. Each thread allocates a chunk of
> > > > > non-huge anonymous memory buffer.
> > > > > 2. Pick 4 random buffer locations (2 in each thread) and inject
> > > > > uncorrectable memory errors at corresponding physical addresses.
> > > > > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > > > > calling madvise(MADV_HUGEPAGE).
> > > > > 4. Wait and check kernel log: khugepaged is able to recover from poisoned
> > > > > pages and skips collapsing them.
> > > > > 5. Signal both threads to inspect their buffer contents and make sure no
> > > > > data corruption.
> > > > >
> > > > > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > > > > ---
> > > > > include/trace/events/huge_memory.h | 3 +-
> > > > > mm/khugepaged.c | 148 ++++++++++++++++++++++++-----
> > > > > 2 files changed, 128 insertions(+), 23 deletions(-)
> > > > >
> > > > > diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h
> > > > > index 3e6fb05852f9a..46cce509957ba 100644
> > > > > --- a/include/trace/events/huge_memory.h
> > > > > +++ b/include/trace/events/huge_memory.h
> > > > > @@ -36,7 +36,8 @@
> > > > > EM( SCAN_ALLOC_HUGE_PAGE_FAIL, "alloc_huge_page_failed") \
> > > > > EM( SCAN_CGROUP_CHARGE_FAIL, "ccgroup_charge_failed") \
> > > > > EM( SCAN_TRUNCATED, "truncated") \
> > > > > - EMe(SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > > > + EM( SCAN_PAGE_HAS_PRIVATE, "page_has_private") \
> > > > > + EMe(SCAN_COPY_MC, "copy_poisoned_page") \
> > > > >
> > > > > #undef EM
> > > > > #undef EMe
> > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > > > index 27956d4404134..c3c217f6ebc6e 100644
> > > > > --- a/mm/khugepaged.c
> > > > > +++ b/mm/khugepaged.c
> > > > > @@ -19,6 +19,7 @@
> > > > > #include <linux/page_table_check.h>
> > > > > #include <linux/swapops.h>
> > > > > #include <linux/shmem_fs.h>
> > > > > +#include <linux/kmsan.h>
> > > > >
> > > > > #include <asm/tlb.h>
> > > > > #include <asm/pgalloc.h>
> > > > > @@ -55,6 +56,7 @@ enum scan_result {
> > > > > SCAN_CGROUP_CHARGE_FAIL,
> > > > > SCAN_TRUNCATED,
> > > > > SCAN_PAGE_HAS_PRIVATE,
> > > > > + SCAN_COPY_MC,
> > > > > };
> > > > >
> > > > > #define CREATE_TRACE_POINTS
> > > > > @@ -681,47 +683,47 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> > > > > return result;
> > > > > }
> > > > >
> > > > > -static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > > > - struct vm_area_struct *vma,
> > > > > - unsigned long address,
> > > > > - spinlock_t *ptl,
> > > > > - struct list_head *compound_pagelist)
> > > > > +static void __collapse_huge_page_copy_succeeded(pte_t *pte,
> > > > > + pmd_t *pmd,
> > > > > + struct vm_area_struct *vma,
> > > > > + unsigned long address,
> > > > > + spinlock_t *pte_ptl,
> > > > > + struct list_head *compound_pagelist)
> > > > > {
> > > > > struct page *src_page, *tmp;
> > > > > pte_t *_pte;
> > > > > - for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
> > > > > - _pte++, page++, address += PAGE_SIZE) {
> > > > > - pte_t pteval = *_pte;
> > > > > + pte_t pteval;
> > > > > + unsigned long _address;
> > > > >
> > > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > > + _pte++, _address += PAGE_SIZE) {
> > > > > + pteval = *_pte;
> > > > > if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > > > - clear_user_highpage(page, address);
> > > > > add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
> > > > > if (is_zero_pfn(pte_pfn(pteval))) {
> > > > > /*
> > > > > - * ptl mostly unnecessary.
> > > > > + * pte_ptl mostly unnecessary.
> > > > > */
> > > > > - spin_lock(ptl);
> > > > > - ptep_clear(vma->vm_mm, address, _pte);
> > > > > - spin_unlock(ptl);
> > > > > + spin_lock(pte_ptl);
> > > >
> > > > Why did you have to rename ptl to pte_ptl? It seems unnecessary.
> > >
> > > Thanks, I will use `ptl` in the next version.
> > >
> > > >
> > > > > + pte_clear(vma->vm_mm, _address, _pte);
A bug here: calling pte_clear is wrong; we should use ptep_clear. V11
will make sure it is fixed.
BTW, __collapse_huge_page_copy_succeeded can drop _address and use
address directly.
> > > > > + spin_unlock(pte_ptl);
> > > > > }
> > > > > } else {
> > > > > src_page = pte_page(pteval);
> > > > > - copy_user_highpage(page, src_page, address, vma);
> > > > > if (!PageCompound(src_page))
> > > > > release_pte_page(src_page);
> > > > > /*
> > > > > - * ptl mostly unnecessary, but preempt has to
> > > > > - * be disabled to update the per-cpu stats
> > > > > + * pte_ptl mostly unnecessary, but preempt has
> > > > > + * to be disabled to update the per-cpu stats
> > > > > * inside page_remove_rmap().
> > > > > */
> > > > > - spin_lock(ptl);
> > > > > - ptep_clear(vma->vm_mm, address, _pte);
> > > > > + spin_lock(pte_ptl);
> > > > > + ptep_clear(vma->vm_mm, _address, _pte);
> > > > > page_remove_rmap(src_page, vma, false);
> > > > > - spin_unlock(ptl);
> > > > > + spin_unlock(pte_ptl);
> > > > > free_page_and_swap_cache(src_page);
> > > > > }
> > > > > }
> > > > > -
> > > > > list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > > > list_del(&src_page->lru);
> > > > > mod_node_page_state(page_pgdat(src_page),
> > > > > @@ -733,6 +735,104 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> > > > > }
> > > > > }
> > > > >
> > > > > +static void __collapse_huge_page_copy_failed(pte_t *pte,
> > > > > + pmd_t *pmd,
> > > > > + pmd_t orig_pmd,
> > > > > + struct vm_area_struct *vma,
> > > > > + unsigned long address,
> > > > > + struct list_head *compound_pagelist)
> > > > > +{
> > > > > + struct page *src_page, *tmp;
> > > > > + pte_t *_pte;
> > > > > + pte_t pteval;
> > > > > + unsigned long _address;
> > > > > + spinlock_t *pmd_ptl;
> > > > > +
> > > > > + /*
> > > > > + * Re-establish the PMD to point to the original page table
> > > > > + * entry. Restoring PMD needs to be done prior to releasing
> > > > > + * pages. Since pages are still isolated and locked here,
> > > > > + * acquiring anon_vma_lock_write is unnecessary.
> > > > > + */
> > > > > + pmd_ptl = pmd_lock(vma->vm_mm, pmd);
> > > > > + pmd_populate(vma->vm_mm, pmd, pmd_pgtable(orig_pmd));
> > > > > + spin_unlock(pmd_ptl);
> > > > > + /*
> > > > > + * Release both raw and compound pages isolated
> > > > > + * in __collapse_huge_page_isolate.
> > > > > + */
> > > >
> > > > It looks like the below code could be replaced by release_pte_pages()
> > > > with advancing _pte to (pte + HPAGE_PMD_NR - 1).
> > > >
> > >
> > > Yeah, but I think _pte should be (pte + HPAGE_PMR_NR) because _pte is
> > > decremented before comparison in release_pte_pages(pte, _pte,
> > > compound_pagelist):
> > >
> > > while (--_pte >= pte) {...}
> > >
> > > Advancing _pte to (pte + HPAGE_PMD_NR - 1) may leave the last page not released.
> >
> > Yeah, good catch. I think it is because the only user of
> > release_pte_pages() is __collapse_huge_page_isolate(). Once the loop
> > in it is done _pte is pte + HPAGE_PMD_NR.
> >
>
> Thanks for confirming ;)
> Since you have reviewed other 2 commits, I will soon send out V11 for
> your comments on this commit.
>
>
> > >
> > > >
> > > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > > + _pte++, _address += PAGE_SIZE) {
> > > > > + pteval = *_pte;
> > > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval)))
> > > > > + continue;
> > > > > + src_page = pte_page(pteval);
> > > > > + if (!PageCompound(src_page))
> > > > > + release_pte_page(src_page);
> > > > > + }
> > > > > + list_for_each_entry_safe(src_page, tmp, compound_pagelist, lru) {
> > > > > + list_del(&src_page->lru);
> > > > > + release_pte_page(src_page);
> > > > > + }
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * __collapse_huge_page_copy - attempts to copy memory contents from raw
> > > > > + * pages to a hugepage. Cleans up the raw pages if copying succeeds;
> > > > > + * otherwise restores the original page table and releases isolated raw pages.
> > > > > + * Returns SCAN_SUCCEED if copying succeeds, otherwise returns SCAN_COPY_MC.
> > > > > + *
> > > > > + * @pte: starting of the PTEs to copy from
> > > > > + * @page: the new hugepage to copy contents to
> > > > > + * @pmd: pointer to the new hugepage's PMD
> > > > > + * @orig_pmd: the original raw pages' PMD
> > > > > + * @vma: the original raw pages' virtual memory area
> > > > > + * @address: starting address to copy
> > > > > + * @pte_ptl: lock on raw pages' PTEs
> > > > > + * @compound_pagelist: list that stores compound pages
> > > > > + */
> > > > > +static int __collapse_huge_page_copy(pte_t *pte,
> > > > > + struct page *page,
> > > > > + pmd_t *pmd,
> > > > > + pmd_t orig_pmd,
> > > > > + struct vm_area_struct *vma,
> > > > > + unsigned long address,
> > > > > + spinlock_t *pte_ptl,
> > > > > + struct list_head *compound_pagelist)
> > > > > +{
> > > > > + struct page *src_page;
> > > > > + pte_t *_pte;
> > > > > + pte_t pteval;
> > > > > + unsigned long _address;
> > > > > + int result = SCAN_SUCCEED;
> > > > > +
> > > > > + /*
> > > > > + * Copying pages' contents is subject to memory poison at any iteration.
> > > > > + */
> > > > > + for (_pte = pte, _address = address; _pte < pte + HPAGE_PMD_NR;
> > > > > + _pte++, page++, _address += PAGE_SIZE) {
> > > > > + pteval = *_pte;
> > > > > + if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
> > > > > + clear_user_highpage(page, _address);
> > > > > + continue;
> > > > > + }
> > > > > + src_page = pte_page(pteval);
> > > > > + if (copy_mc_user_highpage(page, src_page, _address, vma) > 0) {
> > > > > + result = SCAN_COPY_MC;
> > > > > + break;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + if (likely(result == SCAN_SUCCEED))
> > > > > + __collapse_huge_page_copy_succeeded(pte, pmd, vma, address,
> > > > > + pte_ptl, compound_pagelist);
> > > > > + else
> > > > > + __collapse_huge_page_copy_failed(pte, pmd, orig_pmd, vma,
> > > > > + address, compound_pagelist);
> > > > > +
> > > > > + return result;
> > > > > +}
> > > > > +
> > > > > static void khugepaged_alloc_sleep(void)
> > > > > {
> > > > > DEFINE_WAIT(wait);
> > > > > @@ -1106,9 +1206,13 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
> > > > > */
> > > > > anon_vma_unlock_write(vma->anon_vma);
> > > > >
> > > > > - __collapse_huge_page_copy(pte, hpage, vma, address, pte_ptl,
> > > > > - &compound_pagelist);
> > > > > + result = __collapse_huge_page_copy(pte, hpage, pmd, _pmd,
> > > > > + vma, address, pte_ptl,
> > > > > + &compound_pagelist);
> > > > > pte_unmap(pte);
> > > > > + if (unlikely(result != SCAN_SUCCEED))
> > > > > + goto out_up_write;
> > > > > +
> > > > > /*
> > > > > * spin_lock() below is not the equivalent of smp_wmb(), but
> > > > > * the smp_wmb() inside __SetPageUptodate() can be reused to
> > > > > --
> > > > > 2.40.0.rc0.216.gc4246ad0f0-goog
> > > > >
^ permalink raw reply [flat|nested] 17+ messages in thread
* Re: [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory
2023-03-25 0:39 ` Hugh Dickins
@ 2023-03-27 21:15 ` Jiaqi Yan
0 siblings, 0 replies; 17+ messages in thread
From: Jiaqi Yan @ 2023-03-27 21:15 UTC (permalink / raw)
To: Hugh Dickins
Cc: Yang Shi, kirill.shutemov, kirill, tongtiangen, tony.luck, akpm,
naoya.horiguchi, linmiaohe, linux-mm, osalvador, wangkefeng.wang
On Fri, Mar 24, 2023 at 5:39 PM Hugh Dickins <hughd@google.com> wrote:
>
> On Fri, 24 Mar 2023, Jiaqi Yan wrote:
> > On Fri, Mar 24, 2023 at 2:15 PM Yang Shi <shy828301@gmail.com> wrote:
> > > On Sat, Mar 4, 2023 at 10:51 PM Jiaqi Yan <jiaqiyan@google.com> wrote:
> > > >
> > > > Make collapse_file roll back when copying pages failed. More concretely:
> > > > - extract copying operations into a separate loop
> > > > - postpone the updates for nr_none until both scanning and copying
> > > > succeeded
> > > > - postpone joining small xarray entries until both scanning and copying
> > > > succeeded
> > > > - postpone the update operations to NR_XXX_THPS until both scanning and
> > > > copying succeeded
> > > > - for non-SHMEM file, roll back filemap_nr_thps_inc if scan succeeded but
> > > > copying failed
> > > >
> > > > Tested manually:
> > > > 0. Enable khugepaged on system under test. Mount tmpfs at /mnt/ramdisk.
> > > > 1. Start a two-thread application. Each thread allocates a chunk of
> > > > non-huge memory buffer from /mnt/ramdisk.
> > > > 2. Pick 4 random buffer address (2 in each thread) and inject
> > > > uncorrectable memory errors at physical addresses.
> > > > 3. Signal both threads to make their memory buffer collapsible, i.e.
> > > > calling madvise(MADV_HUGEPAGE).
> > > > 4. Wait and then check kernel log: khugepaged is able to recover from
> > > > poisoned pages by skipping them.
> > > > 5. Signal both threads to inspect their buffer contents and make sure no
> > > > data corruption.
> > > >
> > > > Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
> > >
> > > Reviewed-by: Yang Shi <shy828301@gmail.com>
> > >
> > > Just a nit below:
>
> Acked-by: Hugh Dickins <hughd@google.com>
>
> with a little nit from me below, if you are respinning:
>
> > >
> > > > ---
> > > > mm/khugepaged.c | 78 ++++++++++++++++++++++++++++++-------------------
> > > > 1 file changed, 48 insertions(+), 30 deletions(-)
> > > >
> > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > > > index c3c217f6ebc6e..3ea2aa55c2c52 100644
> > > > --- a/mm/khugepaged.c
> > > > +++ b/mm/khugepaged.c
> > > > @@ -1890,6 +1890,9 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > > > {
> > > > struct address_space *mapping = file->f_mapping;
> > > > struct page *hpage;
> > > > + struct page *page;
> > > > + struct page *tmp;
> > > > + struct folio *folio;
> > > > pgoff_t index = 0, end = start + HPAGE_PMD_NR;
> > > > LIST_HEAD(pagelist);
> > > > XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER);
> > > > @@ -1934,8 +1937,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > > >
> > > > xas_set(&xas, start);
> > > > for (index = start; index < end; index++) {
> > > > - struct page *page = xas_next(&xas);
> > > > - struct folio *folio;
> > > > + page = xas_next(&xas);
> > > >
> > > > VM_BUG_ON(index != xas.xa_index);
> > > > if (is_shmem) {
> > > > @@ -2117,10 +2119,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
> > > > }
> > > > nr = thp_nr_pages(hpage);
> > > >
> > > > - if (is_shmem)
> > > > - __mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
> > > > - else {
> > > > - __mod_lruvec_page_state(hpage, NR_FILE_THPS, nr);
> > > > + if (!is_shmem) {
> > > > filemap_nr_thps_inc(mapping);
> > > > /*
> > > > * Paired with smp_mb() in do_dentry_open() to ensure
>
> That "nr = thp_nr_pages(hpage);" above becomes stranded a long way away
> from where "nr" is actually used for updating those statistics: please
> move it down with them. (I see "nr" is also reported in the tracepoint
> at the end, FWIW, so maybe that will show "0" in more failure cases than
> it used to, but that's okay - it has been decently initialized.)
>
Thanks Hugh! I will make sure V11 moves "nr" closer to the place it is used.
> Thanks,
> Hugh
^ permalink raw reply [flat|nested] 17+ messages in thread
end of thread, other threads:[~2023-03-27 21:15 UTC | newest]
Thread overview: 17+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-03-05 6:51 [PATCH v10 0/3] Memory poison recovery in khugepaged collapsing Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 1/3] mm/khugepaged: recover from poisoned anonymous memory Jiaqi Yan
2023-03-20 14:42 ` Jiaqi Yan
2023-03-21 0:12 ` Yang Shi
2023-03-23 21:37 ` Yang Shi
2023-03-24 15:34 ` Jiaqi Yan
2023-03-24 20:11 ` Yang Shi
2023-03-24 22:31 ` Jiaqi Yan
2023-03-27 20:46 ` Jiaqi Yan
2023-03-05 6:51 ` [PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage Jiaqi Yan
2023-03-05 6:56 ` Jiaqi Yan
2023-03-24 20:24 ` Yang Shi
2023-03-05 6:51 ` [PATCH v10 3/3] mm/khugepaged: recover from poisoned file-backed memory Jiaqi Yan
2023-03-24 21:15 ` Yang Shi
2023-03-24 22:54 ` Jiaqi Yan
2023-03-25 0:39 ` Hugh Dickins
2023-03-27 21:15 ` Jiaqi Yan
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.