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    xfs: ensure btree root split sets blkno correctly · 088c9f67
    Dave Chinner 提交于
    For CRC enabled filesystems, the BMBT is rooted in an inode, so it
    passes through a different code path on root splits than the
    freespace and inode btrees. This is much less traversed by xfstests
    than the other trees. When testing on a 1k block size filesystem,
    I've been seeing ASSERT failures in generic/234 like:
    
    XFS: Assertion failed: cur->bc_btnum != XFS_BTNUM_BMAP || cur->bc_private.b.allocated == 0, file: fs/xfs/xfs_btree.c, line: 317
    
    which are generally preceded by a lblock check failure. I noticed
    this in the bmbt stats:
    
    $ pminfo -f xfs.btree.block_map
    
    xfs.btree.block_map.lookup
        value 39135
    
    xfs.btree.block_map.compare
        value 268432
    
    xfs.btree.block_map.insrec
        value 15786
    
    xfs.btree.block_map.delrec
        value 13884
    
    xfs.btree.block_map.newroot
        value 2
    
    xfs.btree.block_map.killroot
        value 0
    .....
    
    Very little coverage of root splits and merges. Indeed, on a 4k
    filesystem, block_map.newroot and block_map.killroot are both zero.
    i.e. the code is not exercised at all, and it's the only generic
    btree infrastructure operation that is not exercised by a default run
    of xfstests.
    
    Turns out that on a 1k filesystem, generic/234 accounts for one of
    those two root splits, and that is somewhat of a smoking gun. In
    fact, it's the same problem we saw in the directory/attr code where
    headers are memcpy()d from one block to another without updating the
    self describing metadata.
    
    Simple fix - when copying the header out of the root block, make
    sure the block number is updated correctly.
    Signed-off-by: NDave Chinner <dchinner@redhat.com>
    Reviewed-by: NBen Myers <bpm@sgi.com>
    Signed-off-by: NBen Myers <bpm@sgi.com>
    
    (cherry picked from commit ade1335a)
    088c9f67
xfs_btree.c 99.7 KB