Re: [PATCH 11/16] xfs: split inode AG walking into separate code for reclaim

Alex Elder
2010-09-23T16:44:58Z

On Wed, 2010-09-22 at 16:44 +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> The reclaim walk requires different locking and has a slightly
> different walk algorithm, so separate it out so that it can be
> optimised separately.

You assert this above xfs_reclaim_inodes_ag():
Walk the AGs and reclaim the inodes in them. Even if the filesystem is
corrupted, we still want to try to reclaim all the inodes.

I don't refute that statement, but if I'm not mistaken
this is new handling. I just felt it should not slip in
without being mentioned. I also suggest a short sentence
along with that comment to justify it might be in order.

I have one other minor comment below, but otherwise this
looks good.

Reviewed-by: Alex Elder <aelder@sgi.com>

> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/linux-2.6/xfs_sync.c | 200 ++++++++++++++++++----------------------
> fs/xfs/linux-2.6/xfs_sync.h | 2 +-
> fs/xfs/linux-2.6/xfs_trace.h | 2 +-
> fs/xfs/quota/xfs_qm_syscalls.c | 3 +-
> fs/xfs/xfs_mount.c | 26 +++++
> fs/xfs/xfs_mount.h | 2 +
> 6 files changed, 120 insertions(+), 115 deletions(-)
>
> diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
> index ddeaff9..7737a13 100644
> --- a/fs/xfs/linux-2.6/xfs_sync.c
> +++ b/fs/xfs/linux-2.6/xfs_sync.c

. . .

> @@ -859,13 +781,70 @@ reclaim:
>
> }
>
> +/*
> + * Walk the AGs and reclaim the inodes in them. Even if the filesystem is
> + * corrupted, we still want to try to reclaim all the inodes.
> + */
> +int
> +xfs_reclaim_inodes_ag(
> + struct xfs_mount *mp,
> + int flags,
> + int *nr_to_scan)
> +{
> + struct xfs_perag *pag;
> + int error = 0;
> + int last_error = 0;
> + xfs_agnumber_t ag;
> +
> + ag = 0;
> + while ((pag = xfs_perag_get_tag(mp, ag, XFS_ICI_RECLAIM_TAG))) {
> + unsigned long first_index = 0;
> + int done = 0;
> +
> + ag = pag->pag_agno + 1;
> +
> + do {
> + struct xfs_inode *ip;
> + int nr_found;
> +
> + write_lock(&pag->pag_ici_lock);
> + nr_found = radix_tree_gang_lookup_tag(&pag->pag_ici_root,
> + (void **)&ip, first_index, 1,
> + XFS_ICI_RECLAIM_TAG);
> + if (!nr_found) {
> + write_unlock(&pag->pag_ici_lock);
> + break;
> + }
> +
> + /*
> + * Update the index for the next lookup. Catch overflows
> + * into the next AG range which can occur if we have inodes
> + * in the last block of the AG and we are currently
> + * pointing to the last inode.
> + */
> + first_index = XFS_INO_TO_AGINO(mp, ip->i_ino + 1);
> + if (first_index < XFS_INO_TO_AGINO(mp, ip->i_ino))
> + done = 1;
> +
> + error = xfs_reclaim_inode(ip, pag, flags);
> + if (error && last_error != EFSCORRUPTED)
> + last_error = error;
> +
> + } while (!done && (*nr_to_scan)--);

I know you guys disagreed with me before on this point.
But since there is no reason anybody outside this function
has a need to see the intermediate values of *nr_to_scan,
you should use a local variable to keep track of it instead,
and then assign its final value to *nr_to_scan before returning.
It allows registers to be used rather than updating real
memory at each iteration.

> +
> + xfs_perag_put(pag);
> + }
> + return XFS_ERROR(last_error);
> +}
> +
> int
> xfs_reclaim_inodes(
> xfs_mount_t *mp,
> int mode)
> {

. . .