http://bugzilla.suse.com/show_bug.cgi?id=1025053 Bug ID: 1025053 Summary: Btrfs: fix shrinking truncate when the no_holes feature is enabled Classification: openSUSE Product: openSUSE Distribution Version: Leap 42.1 Hardware: Other OS: Other Status: NEW Severity: Normal Priority: P5 - None Component: Kernel Assignee: jeffm@suse.com Reporter: jeffm@suse.com QA Contact: qa-bugs@suse.de Found By: --- Blocker: --- From: Filipe Manana Date: Sat, 20 Jun 2015 18:20:09 +0100 Subject: Btrfs: fix shrinking truncate when the no_holes feature is enabled Git-commit: c1aa45759e90b4204ab8bce027a925fc7c87d00a Patch-mainline: v4.2-rc6 References: revisit If the no_holes feature is enabled, we attempt to shrink a file to a size that ends up in the middle of a hole and we don't have any file extent items in the fs/subvol tree that go beyond the new file size (or any ordered extents that will insert such file extent items), we end up not updating the inode's disk_i_size, we only update the inode's i_size. This means that after unmounting and mounting the filesystem, or after the inode is evicted and reloaded, its i_size ends up being incorrect (an inode's i_size is set to the disk_i_size field when an inode is loaded). This happens when btrfs_truncate_inode_items() doesn't find any file extent items to drop - in this case it never makes a call to btrfs_ordered_update_i_size() in order to update the inode's disk_i_size. Example reproducer: $ mkfs.btrfs -O no-holes -f /dev/sdd $ mount /dev/sdd /mnt # Create our test file with some data and durably persist it. $ xfs_io -f -c "pwrite -S 0xaa 0 128K" /mnt/foo $ sync # Append some data to the file, increasing its size, and leave a hole # between the old size and the start offset if the following write. So # our file gets a hole in the range [128Kb, 256Kb[. $ xfs_io -c "truncate 160K" /mnt/foo # We expect to see our file with a size of 160Kb, with the first 128Kb # of data all having the value 0xaa and the remaining 32Kb of data all # having the value 0x00. $ od -t x1 /mnt/foo 0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa * 0400000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 * 0500000 # Now cleanly unmount and mount again the filesystem. $ umount /mnt $ mount /dev/sdd /mnt # We expect to get the same result as before, a file with a size of # 160Kb, with the first 128Kb of data all having the value 0xaa and the # remaining 32Kb of data all having the value 0x00. $ od -t x1 /mnt/foo 0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa * 0400000 In the example above the file size/data do not match what they were before the remount. Fix this by always calling btrfs_ordered_update_i_size() with a size matching the size the file was truncated to if btrfs_truncate_inode_items() is not called for a log tree and no file extent items were dropped. This ensures the same behaviour as when the no_holes feature is not enabled. A test case for fstests follows soon. Signed-off-by: Filipe Manana Acked-by: Jeff Mahoney --- fs/btrfs/inode.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) -- You are receiving this mail because: You are on the CC list for the bug.