xfs: when replaying bmap operations, don't let unlinked inodes get reaped

Log recovery will iget an inode to replay BUI items and iput the inode
when it's done.  Unfortunately, if the inode was unlinked, the iput
will see that i_nlink == 0 and decide to truncate & free the inode,
which prevents us from replaying subsequent BUIs.  We can't skip the
BUIs because we have to replay all the redo items to ensure that
atomic operations complete.

Since unlinked inode recovery will reap the inode anyway, we can
safely introduce a new inode flag to indicate that an inode is in this
'unlinked recovery' state and should not be auto-reaped in the
drop_inode path.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 9697e94..9b3d7c7 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -4969,6 +4969,7 @@
 	if (error)
 		goto fail_iput;
 
+	xfs_iflags_clear(ip, XFS_IRECOVERY);
 	ASSERT(VFS_I(ip)->i_nlink == 0);
 	ASSERT(VFS_I(ip)->i_mode != 0);