The patch titled
Subject: mm: shmem: make stat.st_blksize return huge page size if THP is on
has been added to the -mm tree. Its filename is
mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on.patch
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------------------------------------------------------
From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Subject: mm: shmem: make stat.st_blksize return huge page size if THP is on
Since tmpfs THP was supported in 4.8, hugetlbfs is not the only filesystem
with huge page support anymore. tmpfs can use huge page via THP when
mounting by "huge=" mount option.
When applications use huge page on hugetlbfs, it just need check the
filesystem magic number, but it is not enough for tmpfs. Make
stat.st_blksize return huge page size if it is mounted by appropriate
"huge=" option to give applications a hint to optimize the behavior with
THP.
Some applications may not do wisely with THP. For example, QEMU may mmap
file on non huge page aligned hint address with MAP_FIXED, which results
in no pages are PMD mapped even though THP is used. Some applications may
mmap file with non huge page aligned offset. Both behaviors make THP
pointless.
statfs.f_bsize still returns 4KB for tmpfs since THP could be split, and
it also may fallback to 4KB page silently if there is not enough huge
page. Furthermore, different f_bsize makes max_blocks and free_blocks
calculation harder but without too much benefit. Returning huge page size
via stat.st_blksize sounds good enough.
Since PUD size huge page for THP has not been supported, now it just
returns HPAGE_PMD_SIZE.
Link: http://lkml.kernel.org/r/1524665633-83806-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff -puN mm/shmem.c~mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on mm/shmem.c
--- a/mm/shmem.c~mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on
+++ a/mm/shmem.c
@@ -571,6 +571,16 @@ static unsigned long shmem_unused_huge_s
}
#endif /* CONFIG_TRANSPARENT_HUGE_PAGECACHE */
+static inline bool is_huge_enabled(struct shmem_sb_info *sbinfo)
+{
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE) &&
+ (shmem_huge == SHMEM_HUGE_FORCE || sbinfo->huge) &&
+ shmem_huge != SHMEM_HUGE_DENY)
+ return true;
+ else
+ return false;
+}
+
/*
* Like add_to_page_cache_locked, but error if expected item has gone.
*/
@@ -988,6 +998,7 @@ static int shmem_getattr(const struct pa
{
struct inode *inode = path->dentry->d_inode;
struct shmem_inode_info *info = SHMEM_I(inode);
+ struct shmem_sb_info *sb_info = SHMEM_SB(inode->i_sb);
if (info->alloced - info->swapped != inode->i_mapping->nrpages) {
spin_lock_irq(&info->lock);
@@ -995,6 +1006,10 @@ static int shmem_getattr(const struct pa
spin_unlock_irq(&info->lock);
}
generic_fillattr(inode, stat);
+
+ if (is_huge_enabled(sb_info))
+ stat->blksize = HPAGE_PMD_SIZE;
+
return 0;
}
_
Patches currently in -mm which might be from yang.shi@xxxxxxxxxxxxxxxxx are
mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct.patch
mm-introduce-arg_lock-to-protect-arg_startend-and-env_startend-in-mm_struct-fix.patch
mm-shmem-make-statst_blksize-return-huge-page-size-if-thp-is-on.patch
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