From 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Mon, 23 Sep 2019 15:38:00 -0700 Subject: mm,thp: add read-only THP support for (non-shmem) FS This patch is (hopefully) the first step to enable THP for non-shmem filesystems. This patch enables an application to put part of its text sections to THP via madvise, for example: madvise((void *)0x600000, 0x200000, MADV_HUGEPAGE); We tried to reuse the logic for THP on tmpfs. Currently, write is not supported for non-shmem THP. khugepaged will only process vma with VM_DENYWRITE. sys_mmap() ignores VM_DENYWRITE requests (see ksys_mmap_pgoff). The only way to create vma with VM_DENYWRITE is execve(). This requirement limits non-shmem THP to text sections. The next patch will handle writes, which would only happen when the all the vmas with VM_DENYWRITE are unmapped. An EXPERIMENTAL config, READ_ONLY_THP_FOR_FS, is added to gate this feature. [songliubraving@fb.com: fix build without CONFIG_SHMEM] Link: http://lkml.kernel.org/r/F53407FB-96CC-42E8-9862-105C92CC2B98@fb.com [songliubraving@fb.com: fix double unlock in collapse_file()] Link: http://lkml.kernel.org/r/B960CBFA-8EFC-4DA4-ABC5-1977FFF2CA57@fb.com Link: http://lkml.kernel.org/r/20190801184244.3169074-7-songliubraving@fb.com Signed-off-by: Song Liu Acked-by: Rik van Riel Acked-by: Kirill A. Shutemov Acked-by: Johannes Weiner Cc: Stephen Rothwell Cc: Dan Carpenter Cc: Hillf Danton Cc: Hugh Dickins Cc: William Kucharski Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/filemap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/filemap.c') diff --git a/mm/filemap.c b/mm/filemap.c index f4d2971abd7c..91fe3a08ca4a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -203,8 +203,8 @@ static void unaccount_page_cache_page(struct address_space *mapping, __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); if (PageTransHuge(page)) __dec_node_page_state(page, NR_SHMEM_THPS); - } else { - VM_BUG_ON_PAGE(PageTransHuge(page), page); + } else if (PageTransHuge(page)) { + __dec_node_page_state(page, NR_FILE_THPS); } /* -- cgit v1.2.3