This looks OK by me. Reviewed-by: Phil White <pwhite@xxxxxxx> On Thu, Oct 25, 2012 at 05:33:51PM +1100, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > When we free a block from the alloc btree tree, we move it to the > freelist held in the AGFL and mark it busy in the busy extent tree. > This typically happens when we merge btree blocks. > > Once the transaction is committed and checkpointed, the block can > remain on the free list for an indefinite amount of time. Now, this > isn't the end of the world at this point - if the free list is > shortened, the buffer is invalidated in the transaction that moves > it back to free space. If the buffer is allocated as metadata from > the free list, then all the modifications getted logged, and we have > no issues, either. And if it gets allocated as userdata direct from > the freelist, it gets invalidated and so will never get written. > > However, during the time it sits on the free list, pressure on the > log can cause the AIL to be pushed and the buffer that covers the > block gets pushed for write. IOWs, we end up writing a freed > metadata block to disk. Again, this isn't the end of the world > because we know from the above we are only writing to free space. > > The problem, however, is for validation callbacks. If the block was > on old btree root block, then the level of the block is going to be > higher than the current tree root, and so will fail validation. > There may be other inconsistencies in the block as well, and > currently we don't care because the block is in free space. Shutting > down the filesystem because a freed block doesn't pass write > validation, OTOH, is rather unfriendly. > > So, make sure we always invalidate buffers as they move from the > free space trees to the free list so that we guarantee they never > get written to disk while on the free list. > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > --- > fs/xfs/xfs_alloc_btree.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/xfs/xfs_alloc_btree.c b/fs/xfs/xfs_alloc_btree.c > index f1647ca..f7876c6 100644 > --- a/fs/xfs/xfs_alloc_btree.c > +++ b/fs/xfs/xfs_alloc_btree.c > @@ -121,6 +121,8 @@ xfs_allocbt_free_block( > xfs_extent_busy_insert(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1, > XFS_EXTENT_BUSY_SKIP_DISCARD); > xfs_trans_agbtree_delta(cur->bc_tp, -1); > + > + xfs_trans_binval(cur->bc_tp, bp); > return 0; > } > > -- > 1.7.10 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
