xfs: teach buftargs to maintain their own buffer hashtable

Currently, cached buffers are indexed by per-AG hashtables.  This works
great for the data device, but won't work for in-memory btrees.  To
handle that use case, buftargs will need to be able to index buffers
independently of other data structures.

We accomplish this by hoisting the rhashtable and its lock into a
separate xfs_buf_cache structure, make the buftarg point to the
_buf_cache structure, and rework various functions to use it.  This
will enable the in-memory buftarg to come up with its own _buf_cache.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 1 insertions, 3 deletions

diff --git a/fs/xfs/libxfs/xfs_ag.h b/fs/xfs/libxfs/xfs_ag.h
index 19eddba09894..29bfa6273dec 100644
--- a/fs/xfs/libxfs/xfs_ag.h
+++ b/fs/xfs/libxfs/xfs_ag.h
@@ -106,9 +106,7 @@ struct xfs_perag {
 	int		pag_ici_reclaimable;	/* reclaimable inodes */
 	unsigned long	pag_ici_reclaim_cursor;	/* reclaim restart point */
 
-	/* buffer cache index */
-	spinlock_t	pag_buf_lock;	/* lock for pag_buf_hash */
-	struct rhashtable pag_buf_hash;
+	struct xfs_buf_cache	pag_bcache;
 
 	/* background prealloc block trimming */
 	struct delayed_work	pag_blockgc_work;