btrfs: fix missing file extent item for hole after ranged fsync
When doing a fast fsync for a range that starts at an offset greater than zero, we can end up with a log that when replayed causes the respective inode miss a file extent item representing a hole if we are not using the NO_HOLES feature. This is because for fast fsyncs we don't log any extents that cover a range different from the one requested in the fsync. Example scenario to trigger it: $ mkfs.btrfs -O ^no-holes -f /dev/sdd $ mount /dev/sdd /mnt # Create a file with a single 256K and fsync it to clear to full sync # bit in the inode - we want the msync below to trigger a fast fsync. $ xfs_io -f -c "pwrite -S 0xab 0 256K" -c "fsync" /mnt/foo # Force a transaction commit and wipe out the log tree. $ sync # Dirty 768K of data, increasing the file size to 1Mb, and flush only # the range from 256K to 512K without updating the log tree # (sync_file_range() does not trigger fsync, it only starts writeback # and waits for it to finish). $ xfs_io -c "pwrite -S 0xcd 256K 768K" /mnt/foo $ xfs_io -c "sync_range -abw 256K 256K" /mnt/foo # Now dirty the range from 768K to 1M again and sync that range. $ xfs_io -c "mmap -w 768K 256K" \ -c "mwrite -S 0xef 768K 256K" \ -c "msync -s 768K 256K" \ -c "munmap" \ /mnt/foo <power fail> # Mount to replay the log. $ mount /dev/sdd /mnt $ umount /mnt $ btrfs check /dev/sdd Opening filesystem to check... Checking filesystem on /dev/sdd UUID: 482fb574-b288-478e-a190-a9c44a78fca6 [1/7] checking root items [2/7] checking extents [3/7] checking free space cache [4/7] checking fs roots root 5 inode 257 errors 100, file extent discount Found file extent holes: start: 262144, len: 524288 ERROR: errors found in fs roots found 720896 bytes used, error(s) found total csum bytes: 512 total tree bytes: 131072 total fs tree bytes: 32768 total extent tree bytes: 16384 btree space waste bytes: 123514 file data blocks allocated: 589824 referenced 589824 Fix this issue by setting the range to full (0 to LLONG_MAX) when the NO_HOLES feature is not enabled. This results in extra work being done but it gives the guarantee we don't end up with missing holes after replaying the log. CC: stable@vger.kernel.org # 4.19+ Reviewed-by: NJosef Bacik <josef@toxicpanda.com> Signed-off-by: NFilipe Manana <fdmanana@suse.com> Signed-off-by: NDavid Sterba <dsterba@suse.com>
Showing
想要评论请 注册 或 登录