From: Marek Szyprowski m.szyprowski@samsung.com
[ Upstream commit 1ca7554d05ac038c98271f8968ed821266ecaa9c ]
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: 09d91cda0e82 ("mm,thp: avoid writes to file with THP in pagecache") Fixes: 06d3eff62d9d ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- mm/huge_memory.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index afff3ac87067..163c2da2a654 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2724,12 +2724,14 @@ 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);