* [PATCH v3 0/3] fix hugepage coredump
@ 2013-04-03 18:35 Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
` (2 more replies)
0 siblings, 3 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-03 18:35 UTC (permalink / raw)
To: Andrew Morton
Cc: Mel Gorman, Hugh Dickins, Rik van Riel, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel, Naoya Horiguchi
Hi,
Here is 3nd version of hugepage coredump fix.
I added some minor changes based on Hatayama-san's and Michal's comments.
Thank you very much.
Naoya Horiguchi
^ permalink raw reply [flat|nested] 18+ messages in thread
* [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB)
2013-04-03 18:35 [PATCH v3 0/3] fix hugepage coredump Naoya Horiguchi
@ 2013-04-03 18:35 ` Naoya Horiguchi
2013-04-03 19:20 ` Rik van Riel
2013-04-05 18:32 ` KOSAKI Motohiro
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() Naoya Horiguchi
2 siblings, 2 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-03 18:35 UTC (permalink / raw)
To: Andrew Morton
Cc: Mel Gorman, Hugh Dickins, Rik van Riel, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel, Naoya Horiguchi
Currently we fail to include any data on hugepages into coredump,
because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
mm->reserved_vm counter". This looks to me a serious regression,
so let's fix it.
ChangeLog v3:
- move 'return 0' into a separate patch
ChangeLog v2:
- add 'return 0' in hugepage memory check
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: stable@vger.kernel.org
---
fs/hugetlbfs/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git v3.9-rc3.orig/fs/hugetlbfs/inode.c v3.9-rc3/fs/hugetlbfs/inode.c
index 84e3d85..523464e 100644
--- v3.9-rc3.orig/fs/hugetlbfs/inode.c
+++ v3.9-rc3/fs/hugetlbfs/inode.c
@@ -110,7 +110,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
* way when do_mmap_pgoff unwinds (may be important on powerpc
* and ia64).
*/
- vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND | VM_DONTDUMP;
+ vma->vm_flags |= VM_HUGETLB | VM_DONTEXPAND;
vma->vm_ops = &hugetlb_vm_ops;
if (vma->vm_pgoff & (~huge_page_mask(h) >> PAGE_SHIFT))
--
1.7.11.7
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size()
2013-04-03 18:35 [PATCH v3 0/3] fix hugepage coredump Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
@ 2013-04-03 18:35 ` Naoya Horiguchi
2013-04-03 19:22 ` Rik van Riel
` (3 more replies)
2013-04-03 18:35 ` [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() Naoya Horiguchi
2 siblings, 4 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-03 18:35 UTC (permalink / raw)
To: Andrew Morton
Cc: Mel Gorman, Hugh Dickins, Rik van Riel, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel, Naoya Horiguchi
Documentation/filesystems/proc.txt says about coredump_filter bitmask,
Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
effected by bit 5-6.
However current code can go into the subsequent flag checks of bit 0-4
for vma(VM_HUGETLB). So this patch inserts 'return' and makes it work
as written in the document.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: stable@vger.kernel.org
---
fs/binfmt_elf.c | 1 +
1 file changed, 1 insertion(+)
diff --git v3.9-rc3.orig/fs/binfmt_elf.c v3.9-rc3/fs/binfmt_elf.c
index 3939829..86af964 100644
--- v3.9-rc3.orig/fs/binfmt_elf.c
+++ v3.9-rc3/fs/binfmt_elf.c
@@ -1137,6 +1137,7 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
goto whole;
if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
goto whole;
+ return 0;
}
/* Do not dump I/O mapped devices or special mappings */
--
1.7.11.7
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-03 18:35 [PATCH v3 0/3] fix hugepage coredump Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
@ 2013-04-03 18:35 ` Naoya Horiguchi
2013-04-03 20:01 ` Rik van Riel
2013-04-05 18:59 ` KOSAKI Motohiro
2 siblings, 2 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-03 18:35 UTC (permalink / raw)
To: Andrew Morton
Cc: Mel Gorman, Hugh Dickins, Rik van Riel, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel, Naoya Horiguchi
With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
error happens on a hugepage and the affected processes try to access
the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0)
in get_page().
The reason for this bug is that coredump-related code doesn't recognise
"hugepage hwpoison entry" with which a pmd entry is replaced when a memory
error occurs on a hugepage.
In other words, physical address information is stored in different bit layout
between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page()
which is called in get_dump_page() returns a wrong page from a given address.
We need to filter out only hwpoison hugepages to have data on healthy
hugepages in coredump. So this patch makes follow_hugetlb_page() avoid
trying to get page when a pmd is in swap entry like format.
ChangeLog v3:
- add comment about using is_swap_pte()
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: stable@vger.kernel.org
---
mm/hugetlb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c
index 0d1705b..3bc20bd 100644
--- v3.9-rc3.orig/mm/hugetlb.c
+++ v3.9-rc3/mm/hugetlb.c
@@ -2966,9 +2966,15 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
* Some archs (sparc64, sh*) have multiple pte_ts to
* each hugepage. We have to make sure we get the
* first, for the page indexing below to work.
+ *
+ * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
+ * and hugepages under migration in which case
+ * hugetlb_fault waits for the migration and bails out
+ * properly for HWPosined pages.
*/
pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
- absent = !pte || huge_pte_none(huge_ptep_get(pte));
+ absent = !pte || huge_pte_none(huge_ptep_get(pte)) ||
+ is_swap_pte(huge_ptep_get(pte));
/*
* When coredumping, it suits get_dump_page if we just return
--
1.7.11.7
^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB)
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
@ 2013-04-03 19:20 ` Rik van Riel
2013-04-05 18:32 ` KOSAKI Motohiro
1 sibling, 0 replies; 18+ messages in thread
From: Rik van Riel @ 2013-04-03 19:20 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel
On 04/03/2013 02:35 PM, Naoya Horiguchi wrote:
> Currently we fail to include any data on hugepages into coredump,
> because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
> introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
> mm->reserved_vm counter". This looks to me a serious regression,
> so let's fix it.
>
> ChangeLog v3:
> - move 'return 0' into a separate patch
>
> ChangeLog v2:
> - add 'return 0' in hugepage memory check
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Acked-by: Michal Hocko <mhocko@suse.cz>
> Cc: stable@vger.kernel.org
Reviewed-by: Rik van Riel <riel@redhat.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size()
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
@ 2013-04-03 19:22 ` Rik van Riel
2013-04-03 21:14 ` Michal Hocko
` (2 subsequent siblings)
3 siblings, 0 replies; 18+ messages in thread
From: Rik van Riel @ 2013-04-03 19:22 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel
On 04/03/2013 02:35 PM, Naoya Horiguchi wrote:
> Documentation/filesystems/proc.txt says about coredump_filter bitmask,
>
> Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
> effected by bit 5-6.
>
> However current code can go into the subsequent flag checks of bit 0-4
> for vma(VM_HUGETLB). So this patch inserts 'return' and makes it work
> as written in the document.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: stable@vger.kernel.org
Reviewed-by: Rik van Riel <riel@redhat.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-03 18:35 ` [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() Naoya Horiguchi
@ 2013-04-03 20:01 ` Rik van Riel
2013-04-05 18:59 ` KOSAKI Motohiro
1 sibling, 0 replies; 18+ messages in thread
From: Rik van Riel @ 2013-04-03 20:01 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, KOSAKI Motohiro,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
linux-kernel
On 04/03/2013 02:35 PM, Naoya Horiguchi wrote:
> With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
> initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
> error happens on a hugepage and the affected processes try to access
> the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0)
> in get_page().
>
> The reason for this bug is that coredump-related code doesn't recognise
> "hugepage hwpoison entry" with which a pmd entry is replaced when a memory
> error occurs on a hugepage.
> In other words, physical address information is stored in different bit layout
> between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page()
> which is called in get_dump_page() returns a wrong page from a given address.
>
> We need to filter out only hwpoison hugepages to have data on healthy
> hugepages in coredump. So this patch makes follow_hugetlb_page() avoid
> trying to get page when a pmd is in swap entry like format.
>
> ChangeLog v3:
> - add comment about using is_swap_pte()
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Reviewed-by: Michal Hocko <mhocko@suse.cz>
> Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Cc: stable@vger.kernel.org
Reviewed-by: Rik van Riel <riel@redhat.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size()
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
2013-04-03 19:22 ` Rik van Riel
@ 2013-04-03 21:14 ` Michal Hocko
2013-04-04 0:42 ` HATAYAMA Daisuke
2013-04-05 18:33 ` KOSAKI Motohiro
3 siblings, 0 replies; 18+ messages in thread
From: Michal Hocko @ 2013-04-03 21:14 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, HATAYAMA Daisuke,
linux-mm, linux-kernel
On Wed 03-04-13 14:35:37, Naoya Horiguchi wrote:
> Documentation/filesystems/proc.txt says about coredump_filter bitmask,
>
> Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
> effected by bit 5-6.
>
> However current code can go into the subsequent flag checks of bit 0-4
> for vma(VM_HUGETLB). So this patch inserts 'return' and makes it work
> as written in the document.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: stable@vger.kernel.org
Just for the record. It should be stable for 3.7+ since (314e51b98)
becuase then have lost VM_RESERVED check which used to stop hugetlb
mappings.
Acked-by: Michal Hocko <mhocko@suse.cz>
> ---
> fs/binfmt_elf.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git v3.9-rc3.orig/fs/binfmt_elf.c v3.9-rc3/fs/binfmt_elf.c
> index 3939829..86af964 100644
> --- v3.9-rc3.orig/fs/binfmt_elf.c
> +++ v3.9-rc3/fs/binfmt_elf.c
> @@ -1137,6 +1137,7 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
> goto whole;
> if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
> goto whole;
> + return 0;
> }
>
> /* Do not dump I/O mapped devices or special mappings */
> --
> 1.7.11.7
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size()
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
2013-04-03 19:22 ` Rik van Riel
2013-04-03 21:14 ` Michal Hocko
@ 2013-04-04 0:42 ` HATAYAMA Daisuke
2013-04-05 18:33 ` KOSAKI Motohiro
3 siblings, 0 replies; 18+ messages in thread
From: HATAYAMA Daisuke @ 2013-04-04 0:42 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko, linux-mm,
linux-kernel
(2013/04/04 3:35), Naoya Horiguchi wrote:
> Documentation/filesystems/proc.txt says about coredump_filter bitmask,
>
> Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
> effected by bit 5-6.
>
> However current code can go into the subsequent flag checks of bit 0-4
> for vma(VM_HUGETLB). So this patch inserts 'return' and makes it work
> as written in the document.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: stable@vger.kernel.org
> ---
> fs/binfmt_elf.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git v3.9-rc3.orig/fs/binfmt_elf.c v3.9-rc3/fs/binfmt_elf.c
> index 3939829..86af964 100644
> --- v3.9-rc3.orig/fs/binfmt_elf.c
> +++ v3.9-rc3/fs/binfmt_elf.c
> @@ -1137,6 +1137,7 @@ static unsigned long vma_dump_size(struct vm_area_struct *vma,
> goto whole;
> if (!(vma->vm_flags & VM_SHARED) && FILTER(HUGETLB_PRIVATE))
> goto whole;
> + return 0;
> }
>
> /* Do not dump I/O mapped devices or special mappings */
>
Thanks for splitting this fix. Now it's easier to keep track of this fix.
Reviewed-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Thanks.
HATAYAMA, Daisuke
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB)
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
2013-04-03 19:20 ` Rik van Riel
@ 2013-04-05 18:32 ` KOSAKI Motohiro
2013-04-05 18:40 ` Naoya Horiguchi
1 sibling, 1 reply; 18+ messages in thread
From: KOSAKI Motohiro @ 2013-04-05 18:32 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko,
HATAYAMA Daisuke, linux-mm, linux-kernel, kosaki.motohiro
(4/3/13 2:35 PM), Naoya Horiguchi wrote:
> Currently we fail to include any data on hugepages into coredump,
> because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
> introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
> mm->reserved_vm counter". This looks to me a serious regression,
> so let's fix it.
I don't think this is enough explanations. Let's explain the code meaning
time to time order.
First, we had no madvice(DONTDUMP) nor coredump_filter(HUGETLB). then hugetlb
pages were never dumped.
Second, I added coredump_filter(HUGETLB). and then vm_dump_size became..
vm_dump_size()
{
/* Hugetlb memory check */
if (vma->vm_flags & VM_HUGETLB) {
..
goto whole;
}
if (vma->vm_flags & VM_RESERVED)
return 0;
The point is, hugetlb was checked before VM_RESERVED. i.e. hugetlb core dump ignored
VM_RESERVED. At this time, "if (vma->vm_flags & VM_HUGETLB)" statement don't need
return 0 because VM_RESERVED prevented to go into the subsequent flag checks.
Third, Jason added madvise(DONTDUMP). then vm_dump_size became...
vm_dump_size()
{
if (vma->vm_flags & VM_NODUMP)
return 0;
/* Hugetlb memory check */
if (vma->vm_flags & VM_HUGETLB) {
..
goto whole;
}
if (vma->vm_flags & VM_RESERVED)
return 0;
Look, VM_NODUMP and VM_RESERVED had similar and different meanings at this time.
Finally, Konstantin removed VM_RESERVED and hugetlb coredump behavior
has been changed.
Thus, patch [1/3] and [2/3] should be marked [stable for v3.6 or later].
Anyway, this patch is correct. Thank you!
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size()
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
` (2 preceding siblings ...)
2013-04-04 0:42 ` HATAYAMA Daisuke
@ 2013-04-05 18:33 ` KOSAKI Motohiro
3 siblings, 0 replies; 18+ messages in thread
From: KOSAKI Motohiro @ 2013-04-05 18:33 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko,
HATAYAMA Daisuke, linux-mm, linux-kernel, kosaki.motohiro
(4/3/13 2:35 PM), Naoya Horiguchi wrote:
> Documentation/filesystems/proc.txt says about coredump_filter bitmask,
>
> Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
> effected by bit 5-6.
>
> However current code can go into the subsequent flag checks of bit 0-4
> for vma(VM_HUGETLB). So this patch inserts 'return' and makes it work
> as written in the document.
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: stable@vger.kernel.org
If I were you, I merge this patch into [1/3] because both patches treat the same
regression. but it is no big matter.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB)
2013-04-05 18:32 ` KOSAKI Motohiro
@ 2013-04-05 18:40 ` Naoya Horiguchi
0 siblings, 0 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-05 18:40 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko,
HATAYAMA Daisuke, linux-mm, linux-kernel
On Fri, Apr 05, 2013 at 02:32:08PM -0400, KOSAKI Motohiro wrote:
> (4/3/13 2:35 PM), Naoya Horiguchi wrote:
> > Currently we fail to include any data on hugepages into coredump,
> > because VM_DONTDUMP is set on hugetlbfs's vma. This behavior was recently
> > introduced by commit 314e51b98 "mm: kill vma flag VM_RESERVED and
> > mm->reserved_vm counter". This looks to me a serious regression,
> > so let's fix it.
>
> I don't think this is enough explanations. Let's explain the code meaning
> time to time order.
>
> First, we had no madvice(DONTDUMP) nor coredump_filter(HUGETLB). then hugetlb
> pages were never dumped.
>
> Second, I added coredump_filter(HUGETLB). and then vm_dump_size became..
>
> vm_dump_size()
> {
> /* Hugetlb memory check */
> if (vma->vm_flags & VM_HUGETLB) {
> ..
> goto whole;
> }
> if (vma->vm_flags & VM_RESERVED)
> return 0;
>
> The point is, hugetlb was checked before VM_RESERVED. i.e. hugetlb core dump ignored
> VM_RESERVED. At this time, "if (vma->vm_flags & VM_HUGETLB)" statement don't need
> return 0 because VM_RESERVED prevented to go into the subsequent flag checks.
>
> Third, Jason added madvise(DONTDUMP). then vm_dump_size became...
>
> vm_dump_size()
> {
> if (vma->vm_flags & VM_NODUMP)
> return 0;
>
> /* Hugetlb memory check */
> if (vma->vm_flags & VM_HUGETLB) {
> ..
> goto whole;
> }
> if (vma->vm_flags & VM_RESERVED)
> return 0;
>
> Look, VM_NODUMP and VM_RESERVED had similar and different meanings at this time.
>
> Finally, Konstantin removed VM_RESERVED and hugetlb coredump behavior
> has been changed.
Things were/are quite complicated, and this is a wonderful step-by-step explanation.
Thank you very much.
Naoya
> Thus, patch [1/3] and [2/3] should be marked [stable for v3.6 or later].
>
> Anyway, this patch is correct. Thank you!
>
> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-03 18:35 ` [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() Naoya Horiguchi
2013-04-03 20:01 ` Rik van Riel
@ 2013-04-05 18:59 ` KOSAKI Motohiro
2013-04-08 19:27 ` Naoya Horiguchi
1 sibling, 1 reply; 18+ messages in thread
From: KOSAKI Motohiro @ 2013-04-05 18:59 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko,
HATAYAMA Daisuke, linux-mm, linux-kernel, kosaki.motohiro
(4/3/13 2:35 PM), Naoya Horiguchi wrote:
> With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
> initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
> error happens on a hugepage and the affected processes try to access
> the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0)
> in get_page().
>
> The reason for this bug is that coredump-related code doesn't recognise
> "hugepage hwpoison entry" with which a pmd entry is replaced when a memory
> error occurs on a hugepage.
> In other words, physical address information is stored in different bit layout
> between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page()
> which is called in get_dump_page() returns a wrong page from a given address.
>
> We need to filter out only hwpoison hugepages to have data on healthy
> hugepages in coredump. So this patch makes follow_hugetlb_page() avoid
> trying to get page when a pmd is in swap entry like format.
>
> ChangeLog v3:
> - add comment about using is_swap_pte()
>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Reviewed-by: Michal Hocko <mhocko@suse.cz>
> Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Cc: stable@vger.kernel.org
> ---
> mm/hugetlb.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c
> index 0d1705b..3bc20bd 100644
> --- v3.9-rc3.orig/mm/hugetlb.c
> +++ v3.9-rc3/mm/hugetlb.c
> @@ -2966,9 +2966,15 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
> * Some archs (sparc64, sh*) have multiple pte_ts to
> * each hugepage. We have to make sure we get the
> * first, for the page indexing below to work.
> + *
> + * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
> + * and hugepages under migration in which case
> + * hugetlb_fault waits for the migration and bails out
> + * properly for HWPosined pages.
> */
> pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
> - absent = !pte || huge_pte_none(huge_ptep_get(pte));
> + absent = !pte || huge_pte_none(huge_ptep_get(pte)) ||
> + is_swap_pte(huge_ptep_get(pte));
Hmmm...
Now absent has two meanings. 1) skip hugetlb_fault() and return immediately if FOLL_DUMP is used.
2) call hugetlb_fault() if to be need page population or cow.
The description of this patch only explain about (2). and I'm not convinced why we don't need to
dump pages under migraion.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-05 18:59 ` KOSAKI Motohiro
@ 2013-04-08 19:27 ` Naoya Horiguchi
2013-04-08 20:57 ` KOSAKI Motohiro
0 siblings, 1 reply; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-08 19:27 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
KOSAKI Motohiro, Konstantin Khlebnikov, Michal Hocko,
HATAYAMA Daisuke, linux-mm, linux-kernel
On Fri, Apr 05, 2013 at 02:59:43PM -0400, KOSAKI Motohiro wrote:
> (4/3/13 2:35 PM), Naoya Horiguchi wrote:
> > With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
> > initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
> > error happens on a hugepage and the affected processes try to access
> > the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0)
> > in get_page().
> >
> > The reason for this bug is that coredump-related code doesn't recognise
> > "hugepage hwpoison entry" with which a pmd entry is replaced when a memory
> > error occurs on a hugepage.
> > In other words, physical address information is stored in different bit layout
> > between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page()
> > which is called in get_dump_page() returns a wrong page from a given address.
> >
> > We need to filter out only hwpoison hugepages to have data on healthy
> > hugepages in coredump. So this patch makes follow_hugetlb_page() avoid
> > trying to get page when a pmd is in swap entry like format.
> >
> > ChangeLog v3:
> > - add comment about using is_swap_pte()
> >
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > Reviewed-by: Michal Hocko <mhocko@suse.cz>
> > Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
> > Cc: stable@vger.kernel.org
> > ---
> > mm/hugetlb.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git v3.9-rc3.orig/mm/hugetlb.c v3.9-rc3/mm/hugetlb.c
> > index 0d1705b..3bc20bd 100644
> > --- v3.9-rc3.orig/mm/hugetlb.c
> > +++ v3.9-rc3/mm/hugetlb.c
> > @@ -2966,9 +2966,15 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
> > * Some archs (sparc64, sh*) have multiple pte_ts to
> > * each hugepage. We have to make sure we get the
> > * first, for the page indexing below to work.
> > + *
> > + * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
> > + * and hugepages under migration in which case
> > + * hugetlb_fault waits for the migration and bails out
> > + * properly for HWPosined pages.
> > */
> > pte = huge_pte_offset(mm, vaddr & huge_page_mask(h));
> > - absent = !pte || huge_pte_none(huge_ptep_get(pte));
> > + absent = !pte || huge_pte_none(huge_ptep_get(pte)) ||
> > + is_swap_pte(huge_ptep_get(pte));
>
> Hmmm...
>
> Now absent has two meanings. 1) skip hugetlb_fault() and return immediately if FOLL_DUMP is used.
> 2) call hugetlb_fault() if to be need page population or cow.
>
> The description of this patch only explain about (2). and I'm not convinced why we don't need to
> dump pages under migraion.
We can/should dump hugepages under migration, and to do that we have to
put is_swap_pte() in the check of the hugetlb_falut block.
I updated this patch like below.
# I suspended Reviewed and Acked given for the previous version, because
# it has a non-minor change. If you want to restore it, please let me know.
Thanks,
Naoya
------------------------------------------------------------------------
From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Date: Thu, 28 Mar 2013 10:17:38 -0400
Subject: [PATCH v4] hugetlbfs: add swap entry check in follow_hugetlb_page()
With applying the previous patch "hugetlbfs: stop setting VM_DONTDUMP in
initializing vma(VM_HUGETLB)" to reenable hugepage coredump, if a memory
error happens on a hugepage and the affected processes try to access
the error hugepage, we hit VM_BUG_ON(atomic_read(&page->_count) <= 0)
in get_page().
The reason for this bug is that coredump-related code doesn't recognise
"hugepage hwpoison entry" with which a pmd entry is replaced when a memory
error occurs on a hugepage.
In other words, physical address information is stored in different bit layout
between hugepage hwpoison entry and pmd entry, so follow_hugetlb_page()
which is called in get_dump_page() returns a wrong page from a given address.
The expected behavior is like this:
absent is_swap_pte FOLL_DUMP Expected behavior
---------------------------------------------------------------------
true false false hugetlb_fault
false true false hugetlb_fault
false false false return page
true false true skip page (to avoid allocation)
false true true hugetlb_fault
false false true return page
With this patch, we can call hugetlb_fault() and take proper actions
(we can wait for migration entries, fail with VM_FAULT_HWPOISON_LARGE for
hwpoisoned entries,) and as the result we can dump all hugepages except
for hwpoisoned ones.
ChangeLog v4:
- move is_swap_page() to right place.
ChangeLog v3:
- add comment about using is_swap_pte()
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: stable@vger.kernel.org
---
mm/hugetlb.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0d1705b..f155e59 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2983,7 +2983,13 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
break;
}
- if (absent ||
+ /*
+ * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
+ * and hugepages under migration in which case
+ * hugetlb_fault waits for the migration and bails out
+ * properly for HWPosined pages.
+ */
+ if (absent || is_swap_pte(huge_ptep_get(pte)) ||
((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
int ret;
--
1.7.11.7
^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-08 19:27 ` Naoya Horiguchi
@ 2013-04-08 20:57 ` KOSAKI Motohiro
2013-04-09 22:00 ` Naoya Horiguchi
0 siblings, 1 reply; 18+ messages in thread
From: KOSAKI Motohiro @ 2013-04-08 20:57 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
LKML
> - if (absent ||
> + /*
> + * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
> + * and hugepages under migration in which case
> + * hugetlb_fault waits for the migration and bails out
> + * properly for HWPosined pages.
> + */
> + if (absent || is_swap_pte(huge_ptep_get(pte)) ||
> ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
> int ret;
Your comment describe what the code is. However we want the comment describe
why. In migration case, calling hugetlb_fault() is natural. but in
hwpoison case, it is
needed more explanation. Why can't we call is_hugetlb_hwpoisoned() directly?
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-08 20:57 ` KOSAKI Motohiro
@ 2013-04-09 22:00 ` Naoya Horiguchi
2013-04-10 1:53 ` KOSAKI Motohiro
2013-04-10 8:07 ` Michal Hocko
0 siblings, 2 replies; 18+ messages in thread
From: Naoya Horiguchi @ 2013-04-09 22:00 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
LKML
On Mon, Apr 08, 2013 at 04:57:44PM -0400, KOSAKI Motohiro wrote:
> > - if (absent ||
> > + /*
> > + * is_swap_pte test covers both is_hugetlb_entry_hwpoisoned
> > + * and hugepages under migration in which case
> > + * hugetlb_fault waits for the migration and bails out
> > + * properly for HWPosined pages.
> > + */
> > + if (absent || is_swap_pte(huge_ptep_get(pte)) ||
> > ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
> > int ret;
>
> Your comment describe what the code is. However we want the comment describe
> why. In migration case, calling hugetlb_fault() is natural. but in
> hwpoison case, it is
> needed more explanation.
We should call hugetlb_fault() when we encounter any kind of swap
type entry. It's consistent with handling of normal pages.
> Why can't we call is_hugetlb_hwpoisoned() directly?
We can use it, but I like to make code simple.
I rewrite the comment here, how about this?
- if (absent ||
+ /*
+ * We need call hugetlb_fault for both hugepages under migration
+ * (in which case hugetlb_fault waits for the migration,) and
+ * hwpoisoned hugepages (in which case we need to prevent the
+ * caller from accessing to them.) In order to do this, we use
+ * here is_swap_pte instead of is_hugetlb_entry_migration and
+ * is_hugetlb_entry_hwpoisoned. This is because it simply covers
+ * both cases, and because we can't follow correct pages directly
+ * from any kind of swap entries.
+ */
+ if (absent || is_swap_pte(huge_ptep_get(pte)) ||
((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
int ret;
Thanks,
Naoya
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-09 22:00 ` Naoya Horiguchi
@ 2013-04-10 1:53 ` KOSAKI Motohiro
2013-04-10 8:07 ` Michal Hocko
1 sibling, 0 replies; 18+ messages in thread
From: KOSAKI Motohiro @ 2013-04-10 1:53 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: Andrew Morton, Mel Gorman, Hugh Dickins, Rik van Riel,
Konstantin Khlebnikov, Michal Hocko, HATAYAMA Daisuke, linux-mm,
LKML
> I rewrite the comment here, how about this?
>
> - if (absent ||
> + /*
> + * We need call hugetlb_fault for both hugepages under migration
> + * (in which case hugetlb_fault waits for the migration,) and
> + * hwpoisoned hugepages (in which case we need to prevent the
> + * caller from accessing to them.) In order to do this, we use
> + * here is_swap_pte instead of is_hugetlb_entry_migration and
> + * is_hugetlb_entry_hwpoisoned. This is because it simply covers
> + * both cases, and because we can't follow correct pages directly
> + * from any kind of swap entries.
> + */
> + if (absent || is_swap_pte(huge_ptep_get(pte)) ||
> ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
> int ret;
Looks ok to me.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page()
2013-04-09 22:00 ` Naoya Horiguchi
2013-04-10 1:53 ` KOSAKI Motohiro
@ 2013-04-10 8:07 ` Michal Hocko
1 sibling, 0 replies; 18+ messages in thread
From: Michal Hocko @ 2013-04-10 8:07 UTC (permalink / raw)
To: Naoya Horiguchi
Cc: KOSAKI Motohiro, Andrew Morton, Mel Gorman, Hugh Dickins,
Rik van Riel, Konstantin Khlebnikov, HATAYAMA Daisuke, linux-mm,
LKML
On Tue 09-04-13 18:00:34, Naoya Horiguchi wrote:
[...]
> I rewrite the comment here, how about this?
>
> - if (absent ||
> + /*
> + * We need call hugetlb_fault for both hugepages under migration
> + * (in which case hugetlb_fault waits for the migration,) and
> + * hwpoisoned hugepages (in which case we need to prevent the
> + * caller from accessing to them.) In order to do this, we use
> + * here is_swap_pte instead of is_hugetlb_entry_migration and
> + * is_hugetlb_entry_hwpoisoned. This is because it simply covers
> + * both cases, and because we can't follow correct pages directly
> + * from any kind of swap entries.
> + */
> + if (absent || is_swap_pte(huge_ptep_get(pte)) ||
> ((flags & FOLL_WRITE) && !pte_write(huge_ptep_get(pte)))) {
> int ret;
OK, thanks!
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 18+ messages in thread
end of thread, other threads:[~2013-04-10 8:07 UTC | newest]
Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-04-03 18:35 [PATCH v3 0/3] fix hugepage coredump Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 1/3] hugetlbfs: stop setting VM_DONTDUMP in initializing vma(VM_HUGETLB) Naoya Horiguchi
2013-04-03 19:20 ` Rik van Riel
2013-04-05 18:32 ` KOSAKI Motohiro
2013-04-05 18:40 ` Naoya Horiguchi
2013-04-03 18:35 ` [PATCH v3 2/3] fix hugetlb memory check in vma_dump_size() Naoya Horiguchi
2013-04-03 19:22 ` Rik van Riel
2013-04-03 21:14 ` Michal Hocko
2013-04-04 0:42 ` HATAYAMA Daisuke
2013-04-05 18:33 ` KOSAKI Motohiro
2013-04-03 18:35 ` [PATCH v3 3/3] hugetlbfs: add swap entry check in follow_hugetlb_page() Naoya Horiguchi
2013-04-03 20:01 ` Rik van Riel
2013-04-05 18:59 ` KOSAKI Motohiro
2013-04-08 19:27 ` Naoya Horiguchi
2013-04-08 20:57 ` KOSAKI Motohiro
2013-04-09 22:00 ` Naoya Horiguchi
2013-04-10 1:53 ` KOSAKI Motohiro
2013-04-10 8:07 ` Michal Hocko
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