diff mbox series

[v4,2/6] dax: fix cache flush on PMD-mapped pages

Message ID 20220302082718.32268-3-songmuchun@bytedance.com (mailing list archive)
State New, archived
Headers show
Series Fix some bugs related to ramp and dax | expand

Commit Message

Muchun Song March 2, 2022, 8:27 a.m. UTC
The flush_cache_page() only remove a PAGE_SIZE sized range from the cache.
However, it does not cover the full pages in a THP except a head page.
Replace it with flush_cache_range() to fix this issue.

Fixes: f729c8c9b24f ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 fs/dax.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Dan Williams March 10, 2022, 12:06 a.m. UTC | #1
On Wed, Mar 2, 2022 at 12:29 AM Muchun Song <songmuchun@bytedance.com> wrote:
>
> The flush_cache_page() only remove a PAGE_SIZE sized range from the cache.
> However, it does not cover the full pages in a THP except a head page.
> Replace it with flush_cache_range() to fix this issue.

This needs to clarify that this is just a documentation issue with the
respect to properly documenting the expected usage of cache flushing
before modifying the pmd. However, in practice this is not a problem
due to the fact that DAX is not available on architectures with
virtually indexed caches per:

d92576f1167c dax: does not work correctly with virtual aliasing caches

Otherwise, you can add:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Muchun Song March 10, 2022, 1:48 p.m. UTC | #2
On Thu, Mar 10, 2022 at 8:06 AM Dan Williams <dan.j.williams@intel.com> wrote:
>
> On Wed, Mar 2, 2022 at 12:29 AM Muchun Song <songmuchun@bytedance.com> wrote:
> >
> > The flush_cache_page() only remove a PAGE_SIZE sized range from the cache.
> > However, it does not cover the full pages in a THP except a head page.
> > Replace it with flush_cache_range() to fix this issue.
>
> This needs to clarify that this is just a documentation issue with the
> respect to properly documenting the expected usage of cache flushing
> before modifying the pmd. However, in practice this is not a problem
> due to the fact that DAX is not available on architectures with
> virtually indexed caches per:

Right. I'll add this into the commit log.

>
> d92576f1167c dax: does not work correctly with virtual aliasing caches
>
> Otherwise, you can add:
>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Thanks.
diff mbox series

Patch

diff --git a/fs/dax.c b/fs/dax.c
index 67a08a32fccb..a372304c9695 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -845,7 +845,8 @@  static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 			if (!pmd_dirty(*pmdp) && !pmd_write(*pmdp))
 				goto unlock_pmd;
 
-			flush_cache_page(vma, address, pfn);
+			flush_cache_range(vma, address,
+					  address + HPAGE_PMD_SIZE);
 			pmd = pmdp_invalidate(vma, address, pmdp);
 			pmd = pmd_wrprotect(pmd);
 			pmd = pmd_mkclean(pmd);