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Btrfs: part 2, fix incremental send's decision to delay a dir move/rename
For an incremental send, fix the process of determining whether the directory
inode we're currently processing needs to have its move/rename operation delayed.
We were ignoring the fact that if the inode's new immediate ancestor has a higher
inode number than ours but wasn't renamed/moved, we might still need to delay our
move/rename, because some other ancestor directory higher in the hierarchy might
have an inode number higher than ours *and* was renamed/moved too - in this case
we have to wait for rename/move of that ancestor to happen before our current
directory's rename/move operation.
Simple steps to reproduce this issue:
$ mkfs.btrfs -f /dev/sdd
$ mount /dev/sdd /mnt
$ mkdir -p /mnt/a/x1/x2
$ mkdir /mnt/a/Z
$ mkdir -p /mnt/a/x1/x2/x3/x4/x5
$ btrfs subvolume snapshot -r /mnt /mnt/snap1
$ btrfs send /mnt/snap1 -f /tmp/base.send
$ mv /mnt/a/x1/x2/x3 /mnt/a/Z/X33
$ mv /mnt/a/x1/x2 /mnt/a/Z/X33/x4/x5/X22
$ btrfs subvolume snapshot -r /mnt /mnt/snap2
$ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send
The incremental send caused the kernel code to enter an infinite loop when
building the path string for directory Z after its references are processed.
A more complex scenario:
$ mkfs.btrfs -f /dev/sdd
$ mount /dev/sdd /mnt
$ mkdir -p /mnt/a/b/c/d
$ mkdir /mnt/a/b/c/d/e
$ mkdir /mnt/a/b/c/d/f
$ mv /mnt/a/b/c/d/e /mnt/a/b/c/d/f/E2
$ mkdir /mmt/a/b/c/g
$ mv /mnt/a/b/c/d /mnt/a/b/D2
$ btrfs subvolume snapshot -r /mnt /mnt/snap1
$ btrfs send /mnt/snap1 -f /tmp/base.send
$ mkdir /mnt/a/o
$ mv /mnt/a/b/c/g /mnt/a/b/D2/f/G2
$ mv /mnt/a/b/D2 /mnt/a/b/dd
$ mv /mnt/a/b/c /mnt/a/C2
$ mv /mnt/a/b/dd/f /mnt/a/o/FF
$ mv /mnt/a/b /mnt/a/o/FF/E2/BB
$ btrfs subvolume snapshot -r /mnt /mnt/snap2
$ btrfs send -p /mnt/snap1 /mnt/snap2 -f /tmp/incremental.send
A test case for xfstests follows.
Signed-off-by: 
Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>