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

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/[email protected]
Signed-off-by: Marek Szyprowski <[email protected]>
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) <[email protected]>
Reviewed-by: Yang Shi <[email protected]>
Cc: <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: William Kucharski <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions