| Message ID | 20211011022241.97072-2-rongwei.wang@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm, thp: fix file-backed THP race in collapse_file and truncate pagecache | expand |
Hello I see this patch has not been replied by all. I'm not sure whether this patch has passed review or the status needs to be modified. Thanks! On 10/11/21 10:22 AM, Rongwei Wang wrote: > 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=--) > pc : truncate_inode_page+0x64/0x70 > lr : truncate_inode_page+0x64/0x70 > sp : ffff80001b60b900 > x29: ffff80001b60b900 x28: 00000000000007ff > x27: ffff80001b60b9a0 x26: 0000000000000000 > x25: 000000000000000f x24: ffff80001b60b9a0 > x23: ffff80001b60ba18 x22: ffff0001e0999ea8 > x21: ffff0000c21db300 x20: ffffffffffffffff > x19: fffffe001310ffc0 x18: 0000000000000020 > x17: 0000000000000000 x16: 0000000000000000 > x15: ffff0000c21db960 x14: 3030306666666620 > x13: 6666666666666666 x12: 3130303030303030 > x11: ffff8000117b69b8 x10: 00000000ffff8000 > x9 : ffff80001012690c x8 : 0000000000000000 > x7 : ffff8000114f69b8 x6 : 0000000000017ffd > x5 : ffff0007fffbcbc8 x4 : ffff80001b60b5c0 > x3 : 0000000000000001 x2 : 0000000000000000 > x1 : 0000000000000000 x0 : 0000000000000000 > 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) > ---[ end trace f70cdb42cb7c2d42 ]--- > Kernel panic - not syncing: Oops - BUG: Fatal exception > > This patch mainly to lock filemap when one enter truncate_pagecache(), > avoiding truncating the same page cache concurrently. > > Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") > Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org> > Tested-by: Song Liu <song@kernel.org> > Signed-off-by: Xu Yu <xuyu@linux.alibaba.com> > Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com> > --- > fs/open.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/fs/open.c b/fs/open.c > index daa324606a41..9ec3cfca3b1a 100644 > --- 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; >
diff --git a/fs/open.c b/fs/open.c index daa324606a41..9ec3cfca3b1a 100644 --- 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;
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=--) pc : truncate_inode_page+0x64/0x70 lr : truncate_inode_page+0x64/0x70 sp : ffff80001b60b900 x29: ffff80001b60b900 x28: 00000000000007ff x27: ffff80001b60b9a0 x26: 0000000000000000 x25: 000000000000000f x24: ffff80001b60b9a0 x23: ffff80001b60ba18 x22: ffff0001e0999ea8 x21: ffff0000c21db300 x20: ffffffffffffffff x19: fffffe001310ffc0 x18: 0000000000000020 x17: 0000000000000000 x16: 0000000000000000 x15: ffff0000c21db960 x14: 3030306666666620 x13: 6666666666666666 x12: 3130303030303030 x11: ffff8000117b69b8 x10: 00000000ffff8000 x9 : ffff80001012690c x8 : 0000000000000000 x7 : ffff8000114f69b8 x6 : 0000000000017ffd x5 : ffff0007fffbcbc8 x4 : ffff80001b60b5c0 x3 : 0000000000000001 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000 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) ---[ end trace f70cdb42cb7c2d42 ]--- Kernel panic - not syncing: Oops - BUG: Fatal exception This patch mainly to lock filemap when one enter truncate_pagecache(), avoiding truncating the same page cache concurrently. Fixes: eb6ecbed0aa2 ("mm, thp: relax the VM_DENYWRITE constraint on file-backed THPs") Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org> Tested-by: Song Liu <song@kernel.org> Signed-off-by: Xu Yu <xuyu@linux.alibaba.com> Signed-off-by: Rongwei Wang <rongwei.wang@linux.alibaba.com> --- fs/open.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)