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mm/thp: decrease nr_thps in file's mapping on THP split

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Decrease nr_thps counter in file's mapping to ensure that the page cache
won't be dropped excessively on file write access if page has been
already split.

I've tried a test scenario running a big binary, kernel remaps it with
THPs, then force a THP split with /sys/kernel/debug/split_huge_pages.
During any further open of that binary with O_RDWR or O_WRITEONLY kernel
drops page cache for it, because of non-zero thps counter.

Link: https://lkml.kernel.org/r/20211012120237.2600-1-m.szyprowski@samsung.com
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Fixes: 09d91cda0e ("mm,thp: avoid writes to file with THP in pagecache")
Fixes: 06d3eff62d ("mm/thp: fix node page state in split_huge_page_to_list()")
Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: <sfoon.kim@samsung.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Marek Szyprowski 2021-10-18 15:16:19 -07:00 committed by Linus Torvalds
parent 79f9bc5843
commit 1ca7554d05
1 changed files with 4 additions and 2 deletions
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6
mm/huge_memory.c
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@ -2700,12 +2700,14 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
if (mapping) {
int nr = thp_nr_pages(head);
if (PageSwapBacked(head))
if (PageSwapBacked(head)) {
__mod_lruvec_page_state(head, NR_SHMEM_THPS,
-nr);
else
} else {
__mod_lruvec_page_state(head, NR_FILE_THPS,
-nr);
filemap_nr_thps_dec(mapping);
}
}
__split_huge_page(page, list, end);