1. 16 Apr, 2010 1 commit
    • Dave Chinner's avatar
      xfs: ensure that sync updates the log tail correctly · b6f8dd49
      Dave Chinner authored
      Updates to the VFS layer removed an extra ->sync_fs call into the
      filesystem during the sync process (from the quota code).
      Unfortunately the sync code was unknowingly relying on this call to
      make sure metadata buffers were flushed via a xfs_buftarg_flush()
      call to move the tail of the log forward in memory before the final
      transactions of the sync process were issued.
      
      As a result, the old code would write a very recent log tail value
      to the log by the end of the sync process, and so a subsequent crash
      would leave nothing for log recovery to do. Hence in qa test 182,
      log recovery only replayed a small handle for inode fsync
      transactions in this case.
      
      However, with the removal of the extra ->sync_fs call, the log tail
      was now not moved forward with the inode fsync transactions near the
      end of the sync procese the first (and only) buftarg flush occurred
      after these transactions went to disk. The result is that log
      recovery now sees a large number of transactions for metadata that
      is already on disk.
      
      This usually isn't a problem, but when the transactions include
      inode chunk allocation, the inode create transactions and all
      subsequent changes are replayed as we cannt rely on what is on disk
      is valid. As a result, if the inode was written and contains
      unlogged changes, the unlogged changes are lost, thereby violating
      sync semantics.
      
      The fix is to always issue a transaction after the buftarg flush
      occurs is the log iѕ not idle or covered. This results in a dummy
      transaction being written that contains the up-to-date log tail
      value, which will be very recent. Indeed, it will be at least as
      recent as the old code would have left on disk, so log recovery
      will behave exactly as it used to in this situation.
      Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
      Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
      Signed-off-by: default avatarAlex Elder <aelder@sgi.com>
      b6f8dd49
  2. 15 Apr, 2010 10 commits
  3. 14 Apr, 2010 15 commits
  4. 13 Apr, 2010 14 commits