diff options
| author | Hugh Dickins <hughd@google.com> | 2021-09-02 14:54:21 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-03 09:58:11 -0700 |
| commit | d144bf6205342a4b5fed5d204ae18849a4de741b (patch) | |
| tree | 3e015dccb761d5958ba455c8ef4ab796b88aa9d9 /mm/shmem.c | |
| parent | 050dcb5c85bb47f8151175ca5833aa882cc7fe0c (diff) | |
huge tmpfs: fix split_huge_page() after FALLOC_FL_KEEP_SIZE
A successful shmem_fallocate() guarantees that the extent has been
reserved, even beyond i_size when the FALLOC_FL_KEEP_SIZE flag was used.
But that guarantee is broken by shmem_unused_huge_shrink()'s attempts to
split huge pages and free their excess beyond i_size; and by other uses of
split_huge_page() near i_size.
It's sad to add a shmem inode field just for this, but I did not find a
better way to keep the guarantee. A flag to say KEEP_SIZE has been used
would be cheaper, but I'm averse to unclearable flags. The fallocend
field is not perfect either (many disjoint ranges might be fallocated),
but good enough; and gains another use later on.
Link: https://lkml.kernel.org/r/ca9a146-3a59-6cd3-7f28-e9a044bb1052@google.com
Fixes: 779750d20b93 ("shmem: split huge pages beyond i_size under memory pressure")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 15 |
1 files changed, 14 insertions, 1 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 9ef579f6cab3..e391325dfc21 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -902,6 +902,9 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend, if (lend == -1) end = -1; /* unsigned, so actually very big */ + if (info->fallocend > start && info->fallocend <= end && !unfalloc) + info->fallocend = start; + pagevec_init(&pvec); index = start; while (index < end && find_lock_entries(mapping, index, end - 1, @@ -2650,7 +2653,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb); struct shmem_inode_info *info = SHMEM_I(inode); struct shmem_falloc shmem_falloc; - pgoff_t start, index, end; + pgoff_t start, index, end, undo_fallocend; int error; if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) @@ -2719,6 +2722,15 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, inode->i_private = &shmem_falloc; spin_unlock(&inode->i_lock); + /* + * info->fallocend is only relevant when huge pages might be + * involved: to prevent split_huge_page() freeing fallocated + * pages when FALLOC_FL_KEEP_SIZE committed beyond i_size. + */ + undo_fallocend = info->fallocend; + if (info->fallocend < end) + info->fallocend = end; + for (index = start; index < end; ) { struct page *page; @@ -2733,6 +2745,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, else error = shmem_getpage(inode, index, &page, SGP_FALLOC); if (error) { + info->fallocend = undo_fallocend; /* Remove the !PageUptodate pages we added */ if (index > start) { shmem_undo_range(inode, |