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| 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/huge_memory.c | |
| parent | 050dcb5c85bb47f8151175ca5833aa882cc7fe0c (diff) | |
| download | linux-d144bf6205342a4b5fed5d204ae18849a4de741b.tar.gz linux-d144bf6205342a4b5fed5d204ae18849a4de741b.tar.bz2 linux-d144bf6205342a4b5fed5d204ae18849a4de741b.zip | |
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/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index afff3ac87067..890fb73ac89b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2454,11 +2454,11 @@ static void __split_huge_page(struct page *page, struct list_head *list, for (i = nr - 1; i >= 1; i--) { __split_huge_page_tail(head, i, lruvec, list); - /* Some pages can be beyond i_size: drop them from page cache */ + /* Some pages can be beyond EOF: drop them from page cache */ if (head[i].index >= end) { ClearPageDirty(head + i); __delete_from_page_cache(head + i, NULL); - if (IS_ENABLED(CONFIG_SHMEM) && PageSwapBacked(head)) + if (shmem_mapping(head->mapping)) shmem_uncharge(head->mapping->host, 1); put_page(head + i); } else if (!PageAnon(page)) { @@ -2686,6 +2686,8 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) * head page lock is good enough to serialize the trimming. */ end = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE); + if (shmem_mapping(mapping)) + end = shmem_fallocend(mapping->host, end); } /* |