• David Chinner's avatar
    [XFS] Account for allocated blocks when expanding directories · a7444053
    David Chinner authored
    When we create a directory, we reserve a number of blocks for the maximum
    possible expansion of of the directory due to various btree splits,
    freespace allocation, etc. Unfortunately, each allocation is not reflected
    in the total number of blocks still available to the transaction, so the
    maximal reservation is used over and over again.
    
    This leads to problems where an allocation group has only enough blocks
    for *some* of the allocations required for the directory modification.
    After the first N allocations, the remaining blocks in the allocation
    group drops below the total reservation, and subsequent allocations fail
    because the allocator will not allow the allocation to proceed if the AG
    does not have the enough blocks available for the entire allocation total.
    
    This results in an ENOSPC occurring after an allocation has already
    occurred. This results in aborting the directory operation (leaving the
    directory in an inconsistent state) and cancelling a dirty transaction,
    which results in a filesystem shutdown.
    
    Avoid the problem by reflecting the number of blocks allocated in any
    directory expansion in the total number of blocks available to the
    modification in progress. This prevents a directory modification from
    being aborted part way through with an ENOSPC.
    
    SGI-PV: 988144
    
    SGI-Modid: xfs-linux-melb:xfs-kern:32340a
    Signed-off-by: default avatarDavid Chinner <david@fromorbit.com>
    Signed-off-by: default avatarLachlan McIlroy <lachlan@sgi.com>
    a7444053
xfs_da_btree.c 66.2 KB