Re: [PATCH 08/14] xfs: remote attribute allocation may be contiguous

Brian Foster
2013-05-20T18:59:39Z

On 05/19/2013 07:51 PM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> When CRCs are enabled, there may be multiple allocations made if the
> headers cause a length overflow. This, however, does not mean that
> the number of headers required increases, as the second and
> subsequent extents may be contiguous with the previous extent. Hence
> when we map the extents to write the attribute data, we may end up
> with less extents than allocations made. Hence the assertion that we
> consume th enumber of headers we calculated in the allocation loop
> is incorrect and needs to be removed.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_attr_remote.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_attr_remote.c b/fs/xfs/xfs_attr_remote.c
> index dee8446..aad95b0 100644
> --- a/fs/xfs/xfs_attr_remote.c
> +++ b/fs/xfs/xfs_attr_remote.c
> @@ -359,6 +359,11 @@ xfs_attr_rmtval_set(
> * into requiring more blocks. e.g. for 512 byte blocks, we'll
> * spill for another block every 9 headers we require in this
> * loop.
> + *
> + * Note that this can result in contiguous allocation of blocks,
> + * so we don't use all the space we allocate for headers as we
> + * have one less header for each contiguous allocation that
> + * occurs in the map/write loop below.
> */
> if (crcs && blkcnt == 0) {
> int total_len;
> @@ -439,7 +444,6 @@ xfs_attr_rmtval_set(
> lblkno += map.br_blockcount;
> }
> ASSERT(valuelen == 0);
> - ASSERT(hdrcnt == 0);

I can't say I grok the context enough atm to send a Reviewed-by, but if
we're removing this, why not just remove the hdrcnt-- a few lines up as
well? It doesn't appear to be used after the first loop at this point.

Brian

> return 0;
> }