This is a note to let you know that I've just added the patch titled mm, thp: lock filemap when truncating page cache to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-thp-lock-filemap-when-truncating-page-cache.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 55fc0d91746759c71bc165bba62a2db64ac98e35 Mon Sep 17 00:00:00 2001 From: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> Date: Fri, 5 Nov 2021 13:43:41 -0700 Subject: mm, thp: lock filemap when truncating page cache From: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> commit 55fc0d91746759c71bc165bba62a2db64ac98e35 upstream. Patch series "fix two bugs for file THP". This patch (of 2): Transparent huge page has supported read-only non-shmem files. The file- backed THP is collapsed by khugepaged and truncated when written (for shared libraries). However, there is a race when multiple writers truncate the same page cache concurrently. In that case, subpage(s) of file THP can be revealed by find_get_entry in truncate_inode_pages_range, which will trigger PageTail BUG_ON in truncate_inode_page, as follows: page:000000009e420ff2 refcount:1 mapcount:0 mapping:0000000000000000 index:0x7ff pfn:0x50c3ff head:0000000075ff816d order:9 compound_mapcount:0 compound_pincount:0 flags: 0x37fffe0000010815(locked|uptodate|lru|arch_1|head) raw: 37fffe0000000000 fffffe0013108001 dead000000000122 dead000000000400 raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000 head: 37fffe0000010815 fffffe001066bd48 ffff000404183c20 0000000000000000 head: 0000000000000600 0000000000000000 00000001ffffffff ffff000c0345a000 page dumped because: VM_BUG_ON_PAGE(PageTail(page)) ------------[ cut here ]------------ kernel BUG at mm/truncate.c:213! Internal error: Oops - BUG: 0 [#1] SMP Modules linked in: xfs(E) libcrc32c(E) rfkill(E) ... CPU: 14 PID: 11394 Comm: check_madvise_d Kdump: ... Hardware name: ECS, BIOS 0.0.0 02/06/2015 pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) Call trace: truncate_inode_page+0x64/0x70 truncate_inode_pages_range+0x550/0x7e4 truncate_pagecache+0x58/0x80 do_dentry_open+0x1e4/0x3c0 vfs_open+0x38/0x44 do_open+0x1f0/0x310 path_openat+0x114/0x1dc do_filp_open+0x84/0x134 do_sys_openat2+0xbc/0x164 __arm64_sys_openat+0x74/0xc0 el0_svc_common.constprop.0+0x88/0x220 do_el0_svc+0x30/0xa0 el0_svc+0x20/0x30 el0_sync_handler+0x1a4/0x1b0 el0_sync+0x180/0x1c0 Code: aa0103e0 900061e1 910ec021 9400d300 (d4210000) This patch mainly to lock filemap when one enter truncate_pagecache(), avoiding truncating the same page cache concurrently. Link: https://lkml.kernel.org/r/20211025092134.18562-1-rongwei.wang@xxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20211025092134.18562-2-rongwei.wang@xxxxxxxxxxxxxxxxx Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") Signed-off-by: Xu Yu <xuyu@xxxxxxxxxxxxxxxxx> Signed-off-by: Rongwei Wang <rongwei.wang@xxxxxxxxxxxxxxxxx> Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Tested-by: Song Liu <song@xxxxxxxxxx> Cc: Collin Fijalkovich <cfijalkovich@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Yang Shi <shy828301@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/open.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/fs/open.c +++ b/fs/open.c @@ -856,8 +856,11 @@ static int do_dentry_open(struct file *f * of THPs into the page cache will fail. */ smp_mb(); - if (filemap_nr_thps(inode->i_mapping)) + if (filemap_nr_thps(inode->i_mapping)) { + filemap_invalidate_lock(inode->i_mapping); truncate_pagecache(inode, 0); + filemap_invalidate_unlock(inode->i_mapping); + } } return 0; Patches currently in stable-queue which might be from rongwei.wang@xxxxxxxxxxxxxxxxx are queue-5.15/mm-thp-fix-incorrect-unmap-behavior-for-private-pages.patch queue-5.15/mm-thp-lock-filemap-when-truncating-page-cache.patch