From: Mikulas Patocka <mpatocka@redhat.com> To: Linus Torvalds <torvalds@linux-foundation.org>, Jan Kara <jack@suse.cz>, "Darrick J. Wong" <darrick.wong@oracle.com>, Dave Chinner <dchinner@redhat.com> Cc: Jann Horn <jannh@google.com>, Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>, Kirill Shutemov <kirill@shutemov.name>, Theodore Ts'o <tytso@mit.edu>, Andrea Arcangeli <aarcange@redhat.com>, Matthew Wilcox <willy@infradead.org>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org Subject: [PATCH 2/2] xfs: don't update mtime on COW faults Date: Sat, 5 Sep 2020 08:13:02 -0400 (EDT) [thread overview] Message-ID: <alpine.LRH.2.02.2009050812060.12419@file01.intranet.prod.int.rdu2.redhat.com> (raw) In-Reply-To: <alpine.LRH.2.02.2009050805250.12419@file01.intranet.prod.int.rdu2.redhat.com> When running in a dax mode, if the user maps a page with MAP_PRIVATE and PROT_WRITE, the xfs filesystem would incorrectly update ctime and mtime when the user hits a COW fault. This breaks building of the Linux kernel. How to reproduce: 1. extract the Linux kernel tree on dax-mounted xfs filesystem 2. run make clean 3. run make -j12 4. run make -j12 - at step 4, make would incorrectly rebuild the whole kernel (although it was already built in step 3). The reason for the breakage is that almost all object files depend on objtool. When we run objtool, it takes COW page fault on its .data section, and these faults will incorrectly update the timestamp of the objtool binary. The updated timestamp causes make to rebuild the whole tree. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org --- fs/xfs/xfs_file.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) Index: linux-2.6/fs/xfs/xfs_file.c =================================================================== --- linux-2.6.orig/fs/xfs/xfs_file.c 2020-09-05 10:01:42.000000000 +0200 +++ linux-2.6/fs/xfs/xfs_file.c 2020-09-05 13:59:12.000000000 +0200 @@ -1223,6 +1223,13 @@ __xfs_filemap_fault( return ret; } +static bool +xfs_is_write_fault( + struct vm_fault *vmf) +{ + return vmf->flags & FAULT_FLAG_WRITE && vmf->vma->vm_flags & VM_SHARED; +} + static vm_fault_t xfs_filemap_fault( struct vm_fault *vmf) @@ -1230,7 +1237,7 @@ xfs_filemap_fault( /* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, PE_SIZE_PTE, IS_DAX(file_inode(vmf->vma->vm_file)) && - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); } static vm_fault_t @@ -1243,7 +1250,7 @@ xfs_filemap_huge_fault( /* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, pe_size, - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); } static vm_fault_t _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
WARNING: multiple messages have this Message-ID (diff)
From: Mikulas Patocka <mpatocka@redhat.com> To: Linus Torvalds <torvalds@linux-foundation.org>, Jan Kara <jack@suse.cz>, "Darrick J. Wong" <darrick.wong@oracle.com>, Dave Chinner <dchinner@redhat.com> Cc: Jann Horn <jannh@google.com>, Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>, Kirill Shutemov <kirill@shutemov.name>, "Theodore Ts'o" <tytso@mit.edu>, Andrea Arcangeli <aarcange@redhat.com>, Matthew Wilcox <willy@infradead.org>, Andrew Morton <akpm@linux-foundation.org>, Dan Williams <dan.j.williams@intel.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org Subject: [PATCH 2/2] xfs: don't update mtime on COW faults Date: Sat, 5 Sep 2020 08:13:02 -0400 (EDT) [thread overview] Message-ID: <alpine.LRH.2.02.2009050812060.12419@file01.intranet.prod.int.rdu2.redhat.com> (raw) In-Reply-To: <alpine.LRH.2.02.2009050805250.12419@file01.intranet.prod.int.rdu2.redhat.com> When running in a dax mode, if the user maps a page with MAP_PRIVATE and PROT_WRITE, the xfs filesystem would incorrectly update ctime and mtime when the user hits a COW fault. This breaks building of the Linux kernel. How to reproduce: 1. extract the Linux kernel tree on dax-mounted xfs filesystem 2. run make clean 3. run make -j12 4. run make -j12 - at step 4, make would incorrectly rebuild the whole kernel (although it was already built in step 3). The reason for the breakage is that almost all object files depend on objtool. When we run objtool, it takes COW page fault on its .data section, and these faults will incorrectly update the timestamp of the objtool binary. The updated timestamp causes make to rebuild the whole tree. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org --- fs/xfs/xfs_file.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) Index: linux-2.6/fs/xfs/xfs_file.c =================================================================== --- linux-2.6.orig/fs/xfs/xfs_file.c 2020-09-05 10:01:42.000000000 +0200 +++ linux-2.6/fs/xfs/xfs_file.c 2020-09-05 13:59:12.000000000 +0200 @@ -1223,6 +1223,13 @@ __xfs_filemap_fault( return ret; } +static bool +xfs_is_write_fault( + struct vm_fault *vmf) +{ + return vmf->flags & FAULT_FLAG_WRITE && vmf->vma->vm_flags & VM_SHARED; +} + static vm_fault_t xfs_filemap_fault( struct vm_fault *vmf) @@ -1230,7 +1237,7 @@ xfs_filemap_fault( /* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, PE_SIZE_PTE, IS_DAX(file_inode(vmf->vma->vm_file)) && - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); } static vm_fault_t @@ -1243,7 +1250,7 @@ xfs_filemap_huge_fault( /* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, pe_size, - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); } static vm_fault_t
next prev parent reply other threads:[~2020-09-05 12:13 UTC|newest] Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-03 19:24 a crash when running strace from persistent memory Mikulas Patocka 2020-09-03 19:24 ` Mikulas Patocka 2020-09-03 19:55 ` Linus Torvalds 2020-09-03 19:55 ` Linus Torvalds 2020-09-03 19:55 ` Linus Torvalds 2020-09-04 8:08 ` Mikulas Patocka 2020-09-04 8:08 ` Mikulas Patocka 2020-09-04 17:11 ` Linus Torvalds 2020-09-04 17:11 ` Linus Torvalds 2020-09-04 17:11 ` Linus Torvalds 2020-09-04 16:21 ` make misbehavior on ext2 in dax mode (was: a crash when running strace from persistent memory) Mikulas Patocka 2020-09-04 16:21 ` Mikulas Patocka 2020-09-05 12:11 ` Mikulas Patocka 2020-09-05 12:11 ` Mikulas Patocka 2020-09-05 12:12 ` [PATCH 1/2] ext2: don't update mtime on COW faults Mikulas Patocka 2020-09-05 12:12 ` Mikulas Patocka 2020-09-07 9:00 ` Jan Kara 2020-09-07 9:00 ` Jan Kara 2020-09-07 15:03 ` Sasha Levin 2020-09-05 12:13 ` Mikulas Patocka [this message] 2020-09-05 12:13 ` [PATCH 2/2] xfs: " Mikulas Patocka 2020-09-05 15:36 ` Darrick J. Wong 2020-09-05 15:36 ` Darrick J. Wong 2020-09-05 17:02 ` Mikulas Patocka 2020-09-05 17:02 ` Mikulas Patocka 2020-09-10 6:06 ` Darrick J. Wong 2020-09-10 6:06 ` Darrick J. Wong 2020-09-11 16:41 ` Mikulas Patocka 2020-09-11 16:41 ` Mikulas Patocka 2020-09-05 16:47 ` Linus Torvalds 2020-09-05 16:47 ` Linus Torvalds 2020-09-05 16:47 ` Linus Torvalds 2020-09-05 17:03 ` Linus Torvalds 2020-09-05 17:03 ` Linus Torvalds 2020-09-05 17:03 ` Linus Torvalds 2020-09-07 8:59 ` Jan Kara 2020-09-07 8:59 ` Jan Kara 2020-09-05 17:04 ` [PATCH 2/2 v2] " Mikulas Patocka 2020-09-05 17:04 ` Mikulas Patocka 2020-09-07 6:47 ` [PATCH 2/2] " Christoph Hellwig 2020-09-07 6:47 ` Christoph Hellwig
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