[T][SRU][PATCH 1/1] Btrfs: send, don't send rmdir for same target multiple times

[Po-Hsu Lin]

From: Filipe Manana <fdmanana at gmail.com>

BugLink: https://bugs.launchpad.net/bugs/1809868

When doing an incremental send, if we delete a directory that has N > 1
hardlinks for the same file and that file has the highest inode number
inside the directory contents, an incremental send would send N times an
rmdir operation against the directory. This made the btrfs receive command
fail on the second rmdir instruction, as the target directory didn't exist
anymore.

Steps to reproduce the issue:

    $ mkfs.btrfs -f /dev/sdb3
    $ mount /dev/sdb3 /mnt/btrfs
    $ mkdir -p /mnt/btrfs/a/b/c
    $ echo 'ola mundo' > /mnt/btrfs/a/b/c/foo.txt
    $ ln /mnt/btrfs/a/b/c/foo.txt /mnt/btrfs/a/b/c/bar.txt
    $ btrfs subvolume snapshot -r /mnt/btrfs /mnt/btrfs/snap1
    $ btrfs send /mnt/btrfs/snap1 -f /tmp/base.send
    $ rm -f /mnt/btrfs/a/b/c/foo.txt
    $ rm -f /mnt/btrfs/a/b/c/bar.txt
    $ rmdir /mnt/btrfs/a/b/c
    $ btrfs subvolume snapshot -r /mnt/btrfs /mnt/btrfs/snap2
    $ btrfs send -p /mnt/btrfs/snap1 /mnt/btrfs/snap2 -f /tmp/incremental.send

    $ umount /mnt/btrfs
    $ mkfs.btrfs -f /dev/sdb3
    $ mount /dev/sdb3 /mnt/btrfs
    $ btrfs receive /mnt/btrfs -f /tmp/base.send
    $ btrfs receive /mnt/btrfs -f /tmp/incremental.send

The second btrfs receive command failed with:

    ERROR: rmdir o259-6-0 failed. No such file or directory

A test case for xfstests follows.

Signed-off-by: Filipe David Borba Manana <fdmanana at gmail.com>
Signed-off-by: Josef Bacik <jbacik at fb.com>
(backported from commit 29d6d30f5c8aa58b04f40a58442df3bcaae5a1d5)
Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 fs/btrfs/send.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index d553752..9cc2ef0 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2686,6 +2686,7 @@ static int process_recorded_refs(struct send_ctx *sctx)
 	u64 ow_gen;
 	int did_overwrite = 0;
 	int is_orphan = 0;
+	u64 last_dir_ino_rm = 0;
 
 verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
 
@@ -2941,7 +2942,8 @@ verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
 			ret = send_utimes(sctx, cur->dir, cur->dir_gen);
 			if (ret < 0)
 				goto out;
-		} else if (ret == inode_state_did_delete) {
+		} else if (ret == inode_state_did_delete &&
+			   cur->dir != last_dir_ino_rm) {
 			ret = can_rmdir(sctx, cur->dir, sctx->cur_ino);
 			if (ret < 0)
 				goto out;
@@ -2953,6 +2955,7 @@ verbose_printk("btrfs: process_recorded_refs %llu\n", sctx->cur_ino);
 				ret = send_rmdir(sctx, valid_path);
 				if (ret < 0)
 					goto out;
+				last_dir_ino_rm = cur->dir;
 			}
 		}
 	}
-- 
2.7.4