| From e6f839944d0e2345e93b0afeeb2e51a847f362f1 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Mon, 18 Oct 2021 15:16:19 -0700 |
| Subject: mm/thp: decrease nr_thps in file's mapping on THP split |
| |
| 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); |
| -- |
| 2.33.0 |
| |
