From 78cc8cdc54008f54b79711fc027afc3564588a04 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Thu, 25 Feb 2021 17:16:22 -0800 Subject: mm,thp,shm: limit gfp mask to no more than specified Matthew Wilcox pointed out that the i915 driver opportunistically allocates tmpfs memory, but will happily reclaim some of its pool if no memory is available. Make sure the gfp mask used to opportunistically allocate a THP is always at least as restrictive as the original gfp mask. Link: https://lkml.kernel.org/r/20201124194925.623931-3-riel@surriel.com Signed-off-by: Rik van Riel Suggested-by: Matthew Wilcox Cc: Andrea Arcangeli Cc: Hugh Dickins Cc: Mel Gorman Cc: Michal Hocko Cc: Vlastimil Babka Cc: Xu Yu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/mm/shmem.c b/mm/shmem.c index 596009a44431..06c771d23127 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1505,6 +1505,26 @@ static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp, return page; } +/* + * Make sure huge_gfp is always more limited than limit_gfp. + * Some of the flags set permissions, while others set limitations. + */ +static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp) +{ + gfp_t allowflags = __GFP_IO | __GFP_FS | __GFP_RECLAIM; + gfp_t denyflags = __GFP_NOWARN | __GFP_NORETRY; + gfp_t result = huge_gfp & ~allowflags; + + /* + * Minimize the result gfp by taking the union with the deny flags, + * and the intersection of the allow flags. + */ + result |= (limit_gfp & denyflags); + result |= (huge_gfp & limit_gfp) & allowflags; + + return result; +} + static struct page *shmem_alloc_hugepage(gfp_t gfp, struct shmem_inode_info *info, pgoff_t index) { @@ -1864,6 +1884,7 @@ repeat: alloc_huge: huge_gfp = vma_thp_gfp_mask(vma); + huge_gfp = limit_gfp_mask(huge_gfp, gfp); page = shmem_alloc_and_acct_page(huge_gfp, inode, index, true); if (IS_ERR(page)) { alloc_nohuge: -- cgit v1.2.3-58-ga151