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Btrfs: fix sync fs to actually wait for all data to be persisted
Currently the fs sync function (super.c:btrfs_sync_fs()) doesn't wait for delayed work to finish before returning success to the caller. This change fixes this, ensuring that there's no data loss if a power failure happens right after fs sync returns success to the caller and before the next commit happens. Steps to reproduce the data loss issue: $ mkfs.btrfs -f /dev/sdb3 $ mount /dev/sdb3 /mnt/btrfs $ perl -e '$d = ("\x41" x 6001); open($f,">","/mnt/btrfs/foobar"); print $f $d; close($f);' && btrfs fi sync /mnt/btrfs Right after the btrfs fi sync command (a second or 2 for example), power off the machine and reboot it. The file will be empty, as it can be verified after mounting the filesystem and through btrfs-debug-tree: $ btrfs-debug-tree /dev/sdb3 | egrep '\(257 INODE_ITEM 0\) itemoff' -B 3 -A 8 item 3 key (256 DIR_INDEX 2) itemoff 3751 itemsize 36 location key (257 INODE_ITEM 0) type FILE namelen 6 datalen 0 name: foobar item 4 key (257 INODE_ITEM 0) itemoff 3591 itemsize 160 inode generation 7 transid 7 size 0 block group 0 mode 100644 links 1 item 5 key (257 INODE_REF 256) itemoff 3575 itemsize 16 inode ref index 2 namelen 6 name: foobar checksum tree key (CSUM_TREE ROOT_ITEM 0) leaf 29429760 items 0 free space 3995 generation 7 owner 7 fs uuid 6192815c-af2a-4b75-b3db-a959ffb6166e chunk uuid b529c44b-938c-4d3d-910a-013b4700bcae uuid tree key (UUID_TREE ROOT_ITEM 0) After this patch, the data loss no longer happens after a power failure and btrfs-debug-tree shows: $ btrfs-debug-tree /dev/sdb3 | egrep '\(257 INODE_ITEM 0\) itemoff' -B 3 -A 8 item 3 key (256 DIR_INDEX 2) itemoff 3751 itemsize 36 location key (257 INODE_ITEM 0) type FILE namelen 6 datalen 0 name: foobar item 4 key (257 INODE_ITEM 0) itemoff 3591 itemsize 160 inode generation 6 transid 6 size 6001 block group 0 mode 100644 links 1 item 5 key (257 INODE_REF 256) itemoff 3575 itemsize 16 inode ref index 2 namelen 6 name: foobar item 6 key (257 EXTENT_DATA 0) itemoff 3522 itemsize 53 extent data disk byte 12845056 nr 8192 extent data offset 0 nr 8192 ram 8192 extent compression 0 checksum tree key (CSUM_TREE ROOT_ITEM 0) Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Josef Bacik <jbacik@fusionio.com> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
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@ -4557,9 +4557,15 @@ long btrfs_ioctl(struct file *file, unsigned int
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return btrfs_ioctl_logical_to_ino(root, argp);
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return btrfs_ioctl_logical_to_ino(root, argp);
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case BTRFS_IOC_SPACE_INFO:
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case BTRFS_IOC_SPACE_INFO:
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return btrfs_ioctl_space_info(root, argp);
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return btrfs_ioctl_space_info(root, argp);
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case BTRFS_IOC_SYNC:
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case BTRFS_IOC_SYNC: {
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btrfs_sync_fs(file->f_dentry->d_sb, 1);
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int ret;
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return 0;
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ret = btrfs_start_all_delalloc_inodes(root->fs_info, 0);
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if (ret)
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return ret;
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ret = btrfs_sync_fs(file->f_dentry->d_sb, 1);
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return ret;
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}
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case BTRFS_IOC_START_SYNC:
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case BTRFS_IOC_START_SYNC:
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return btrfs_ioctl_start_sync(root, argp);
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return btrfs_ioctl_start_sync(root, argp);
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case BTRFS_IOC_WAIT_SYNC:
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case BTRFS_IOC_WAIT_SYNC:
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