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btrfs: send: fix invalid commands for inodes with changed type but sa…
…me gen When doing a send, if a new inode has the same number as an inode in the parent subvolume it will only be detected as to be recreated when the genrations differ. But with inodes in the same generation the emitted commands will cause the receiver to fail. This case does not happen when doing incremental sends with snapshots that are kept read-only by the user all the time, but it may happen if - a snapshot was modified after it was created - the subvol used as parent was created independently from the sent subvol Example reproducers: # case 1: same ino at same path btrfs subvolume create subvol1 btrfs subvolume create subvol2 mkdir subvol1/a touch subvol2/a btrfs property set subvol1 ro true btrfs property set subvol2 ro true btrfs send -p subvol1 subvol2 | btrfs receive --dump The produced tree state here is: |-- subvol1 | `-- a/ (ino 257) | `-- subvol2 `-- a (ino 257) Where subvol1/a/ is a directory and subvol2/a is a file with the same inode number and same generation. Example output of the receive command: At subvol subvol2 snapshot ./subvol2 uuid=19d2be0a-5af1-fa44-9b3f-f21815178d00 transid=9 parent_uuid=1bac8b12-ddb2-6441-8551-700456991785 parent_transid=9 utimes ./subvol2/ atime=2021-01-11T13:41:36+0000 mtime=2021-01-11T13:41:36+0000 ctime=2021-01-11T13:41:36+0000 link ./subvol2/a dest=a unlink ./subvol2/a utimes ./subvol2/ atime=2021-01-11T13:41:36+0000 mtime=2021-01-11T13:41:36+0000 ctime=2021-01-11T13:41:36+0000 chmod ./subvol2/a mode=644 utimes ./subvol2/a atime=2021-01-11T13:41:36+0000 mtime=2021-01-11T13:41:36+0000 ctime=2021-01-11T13:41:36+0000 => the `link` command causes the receiver to fail with: ERROR: link a -> a failed: File exists Second example: # case 2: same ino at different path btrfs subvolume create subvol1 btrfs subvolume create subvol2 mkdir subvol1/a touch subvol2/b btrfs property set subvol1 ro true btrfs property set subvol2 ro true btrfs send -p subvol1 subvol2 | btrfs receive --dump The produced tree state here is: |-- subvol1 | `-- a/ (ino 257) | `-- subvol2 `-- b (ino 257) Where subvol1/a/ is a directory and subvol2/b is a file with the same inode number and same generation. Example output of the receive command: At subvol subvol2 snapshot ./subvol2 uuid=ea93c47a-5f47-724f-8a43-e15ce745aef0 transid=20 parent_uuid=f03578ef-5bca-1445-a480-3df63677fddf parent_transid=20 utimes ./subvol2/ atime=2021-01-11T13:58:00+0000 mtime=2021-01-11T13:58:00+0000 ctime=2021-01-11T13:58:00+0000 link ./subvol2/b dest=a unlink ./subvol2/a utimes ./subvol2/ atime=2021-01-11T13:58:00+0000 mtime=2021-01-11T13:58:00+0000 ctime=2021-01-11T13:58:00+0000 chmod ./subvol2/b mode=644 utimes ./subvol2/b atime=2021-01-11T13:58:00+0000 mtime=2021-01-11T13:58:00+0000 ctime=2021-01-11T13:58:00+0000 => the `link` command causes the receiver to fail with: ERROR: link b -> a failed: Operation not permitted Signed-off-by: Roman Anasal <roman.anasal@bdsu.de>
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