From: Ross Zwisler <ross.zwisler@linux.intel.com>
To: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Theodore Ts'o <tytso@mit.edu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Christoph Hellwig <hch@lst.de>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Ingo Molnar <mingo@redhat.com>, Jan Kara <jack@suse.cz>,
Jonathan Corbet <corbet@lwn.net>,
Matthew Wilcox <mawilcox@microsoft.com>,
Steven Rostedt <rostedt@goodmis.org>,
linux-doc@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-nvdimm@lists.01.org, linux-xfs@vger.kernel.org
Subject: [PATCH v3 1/5] mm: add vm_insert_mixed_mkwrite()
Date: Wed, 28 Jun 2017 16:01:48 -0600 [thread overview]
Message-ID: <20170628220152.28161-2-ross.zwisler@linux.intel.com> (raw)
In-Reply-To: <20170628220152.28161-1-ross.zwisler@linux.intel.com>
To be able to use the common 4k zero page in DAX we need to have our PTE
fault path look more like our PMD fault path where a PTE entry can be
marked as dirty and writeable as it is first inserted, rather than waiting
for a follow-up dax_pfn_mkwrite() => finish_mkwrite_fault() call.
Right now we can rely on having a dax_pfn_mkwrite() call because we can
distinguish between these two cases in do_wp_page():
case 1: 4k zero page => writable DAX storage
case 2: read-only DAX storage => writeable DAX storage
This distinction is made by via vm_normal_page(). vm_normal_page() returns
false for the common 4k zero page, though, just as it does for DAX ptes.
Instead of special casing the DAX + 4k zero page case, we will simplify our
DAX PTE page fault sequence so that it matches our DAX PMD sequence, and
get rid of dax_pfn_mkwrite() completely.
This means that insert_pfn() needs to follow the lead of insert_pfn_pmd()
and allow us to pass in a 'mkwrite' flag. If 'mkwrite' is set insert_pfn()
will do the work that was previously done by wp_page_reuse() as part of the
dax_pfn_mkwrite() call path.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
---
include/linux/mm.h | 2 ++
mm/memory.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++-----
2 files changed, 54 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 6f543a4..096052f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2293,6 +2293,8 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
unsigned long pfn, pgprot_t pgprot);
int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
pfn_t pfn);
+int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr,
+ pfn_t pfn);
int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len);
diff --git a/mm/memory.c b/mm/memory.c
index bb11c47..de4aa71 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1646,7 +1646,7 @@ int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
EXPORT_SYMBOL(vm_insert_page);
static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
- pfn_t pfn, pgprot_t prot)
+ pfn_t pfn, pgprot_t prot, bool mkwrite)
{
struct mm_struct *mm = vma->vm_mm;
int retval;
@@ -1658,14 +1658,26 @@ static int insert_pfn(struct vm_area_struct *vma, unsigned long addr,
if (!pte)
goto out;
retval = -EBUSY;
- if (!pte_none(*pte))
- goto out_unlock;
+ if (!pte_none(*pte)) {
+ if (mkwrite) {
+ entry = *pte;
+ goto out_mkwrite;
+ } else
+ goto out_unlock;
+ }
/* Ok, finally just insert the thing.. */
if (pfn_t_devmap(pfn))
entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
else
entry = pte_mkspecial(pfn_t_pte(pfn, prot));
+
+out_mkwrite:
+ if (mkwrite) {
+ entry = pte_mkyoung(entry);
+ entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ }
+
set_pte_at(mm, addr, pte, entry);
update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
@@ -1736,7 +1748,8 @@ int vm_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));
- ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot);
+ ret = insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
+ false);
return ret;
}
@@ -1772,10 +1785,44 @@ int vm_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
page = pfn_to_page(pfn_t_to_pfn(pfn));
return insert_page(vma, addr, page, pgprot);
}
- return insert_pfn(vma, addr, pfn, pgprot);
+ return insert_pfn(vma, addr, pfn, pgprot, false);
}
EXPORT_SYMBOL(vm_insert_mixed);
+int vm_insert_mixed_mkwrite(struct vm_area_struct *vma, unsigned long addr,
+ pfn_t pfn)
+{
+ pgprot_t pgprot = vma->vm_page_prot;
+
+ BUG_ON(!(vma->vm_flags & VM_MIXEDMAP));
+
+ if (addr < vma->vm_start || addr >= vma->vm_end)
+ return -EFAULT;
+
+ track_pfn_insert(vma, &pgprot, pfn);
+
+ /*
+ * If we don't have pte special, then we have to use the pfn_valid()
+ * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
+ * refcount the page if pfn_valid is true (hence insert_page rather
+ * than insert_pfn). If a zero_pfn were inserted into a VM_MIXEDMAP
+ * without pte special, it would there be refcounted as a normal page.
+ */
+ if (!HAVE_PTE_SPECIAL && !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
+ struct page *page;
+
+ /*
+ * At this point we are committed to insert_page()
+ * regardless of whether the caller specified flags that
+ * result in pfn_t_has_page() == false.
+ */
+ page = pfn_to_page(pfn_t_to_pfn(pfn));
+ return insert_page(vma, addr, page, pgprot);
+ }
+ return insert_pfn(vma, addr, pfn, pgprot, true);
+}
+EXPORT_SYMBOL(vm_insert_mixed_mkwrite);
+
/*
* maps a range of physical memory into the requested pages. the old
* mappings are removed. any references to nonexistent pages results
--
2.9.4
--
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next prev parent reply other threads:[~2017-06-28 22:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-28 22:01 [PATCH v3 0/5] DAX common 4k zero page Ross Zwisler
2017-06-28 22:01 ` Ross Zwisler [this message]
2017-07-19 14:16 ` [PATCH v3 1/5] mm: add vm_insert_mixed_mkwrite() Jan Kara
2017-07-19 17:51 ` Ross Zwisler
2017-07-19 21:58 ` Ross Zwisler
2017-07-21 17:44 ` Ross Zwisler
2017-07-24 11:20 ` Jan Kara
2017-07-20 15:26 ` Vivek Goyal
2017-07-20 15:59 ` Ross Zwisler
2017-07-21 18:02 ` Ross Zwisler
2017-06-28 22:01 ` [PATCH v3 2/5] dax: relocate some dax functions Ross Zwisler
2017-06-28 22:01 ` [PATCH v3 3/5] dax: use common 4k zero page for dax mmap reads Ross Zwisler
2017-07-19 15:33 ` Jan Kara
2017-07-19 16:26 ` Ross Zwisler
2017-07-20 10:27 ` Jan Kara
2017-07-20 14:28 ` Ross Zwisler
2017-06-28 22:01 ` [PATCH v3 4/5] dax: remove DAX code from page_cache_tree_insert() Ross Zwisler
2017-06-28 22:01 ` [PATCH v3 5/5] dax: move all DAX radix tree defs to fs/dax.c Ross Zwisler
2017-06-30 19:05 ` [PATCH v3 0/5] DAX common 4k zero page Ross Zwisler
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