On Thu, Jun 04, 2020 at 05:45:55PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@xxxxxxxxxx>
>
> Inode reclaim will still throttle direct reclaim on the per-ag
> reclaim locks. This is no longer necessary as reclaim can run
> non-blocking now. Hence we can remove these locks so that we don't
> arbitrarily block reclaimers just because there are more direct
> reclaimers than there are AGs.
>
> This can result in multiple reclaimers working on the same range of
> an AG, but this doesn't cause any apparent issues. Optimising the
> spread of concurrent reclaimers for best efficiency can be done in a
> future patchset.
>
> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
> Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_icache.c | 31 ++++++++++++-------------------
> fs/xfs/xfs_mount.c | 4 ----
> fs/xfs/xfs_mount.h | 1 -
> 3 files changed, 12 insertions(+), 24 deletions(-)
>
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 74032316ce5cc..c4ba8d7bc45bc 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
...
> @@ -1298,11 +1293,9 @@ xfs_reclaim_inodes_ag(
>
> } while (nr_found && !done && *nr_to_scan > 0);
>
> - if (trylock && !done)
> - pag->pag_ici_reclaim_cursor = first_index;
> - else
> - pag->pag_ici_reclaim_cursor = 0;
> - mutex_unlock(&pag->pag_ici_reclaim_lock);
> + if (done)
> + first_index = 0;
> + WRITE_ONCE(pag->pag_ici_reclaim_cursor, first_index);
I thought the [READ|WRITE]_ONCE() macros had to do with ordering, not
necessarily atomicity. Is this write safe if we're running a 32-bit
kernel, for example? Outside of that the broader functional change seems
reasonable.
Brian
> xfs_perag_put(pag);
> }
> return skipped;
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index d5dcf98698600..03158b42a1943 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -148,7 +148,6 @@ xfs_free_perag(
> ASSERT(atomic_read(&pag->pag_ref) == 0);
> xfs_iunlink_destroy(pag);
> xfs_buf_hash_destroy(pag);
> - mutex_destroy(&pag->pag_ici_reclaim_lock);
> call_rcu(&pag->rcu_head, __xfs_free_perag);
> }
> }
> @@ -200,7 +199,6 @@ xfs_initialize_perag(
> pag->pag_agno = index;
> pag->pag_mount = mp;
> spin_lock_init(&pag->pag_ici_lock);
> - mutex_init(&pag->pag_ici_reclaim_lock);
> INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
> if (xfs_buf_hash_init(pag))
> goto out_free_pag;
> @@ -242,7 +240,6 @@ xfs_initialize_perag(
> out_hash_destroy:
> xfs_buf_hash_destroy(pag);
> out_free_pag:
> - mutex_destroy(&pag->pag_ici_reclaim_lock);
> kmem_free(pag);
> out_unwind_new_pags:
> /* unwind any prior newly initialized pags */
> @@ -252,7 +249,6 @@ xfs_initialize_perag(
> break;
> xfs_buf_hash_destroy(pag);
> xfs_iunlink_destroy(pag);
> - mutex_destroy(&pag->pag_ici_reclaim_lock);
> kmem_free(pag);
> }
> return error;
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index 3725d25ad97e8..a72cfcaa4ad12 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -354,7 +354,6 @@ typedef struct xfs_perag {
> spinlock_t pag_ici_lock; /* incore inode cache lock */
> struct radix_tree_root pag_ici_root; /* incore inode cache root */
> int pag_ici_reclaimable; /* reclaimable inodes */
> - struct mutex pag_ici_reclaim_lock; /* serialisation point */
> unsigned long pag_ici_reclaim_cursor; /* reclaim restart point */
>
> /* buffer cache index */
> --
> 2.26.2.761.g0e0b3e54be
>
