xfs: per-filesystem dquot LRU lists

Replace the global dquot lru lists with a per-filesystem one.

Note that the shrinker isn't wire up to the per-superblock VFS shrinker
infrastructure as would have problems summing up and splitting the counts
for inodes and dquots.  I don't think this is a major problem as the quota
cache isn't as interwinded with the inode cache as the dentry cache is,
because an inode that is dropped from the cache will generally release
a dquot reference, but most of the time it won't be the last one.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --git a/fs/xfs/xfs_dquot.h b/fs/xfs/xfs_dquot.h
index 60b0d72..f291c25 100644
--- a/fs/xfs/xfs_dquot.h
+++ b/fs/xfs/xfs_dquot.h
@@ -47,7 +47,7 @@
  */
 typedef struct xfs_dquot {
 	uint		 dq_flags;	/* various flags (XFS_DQ_*) */
-	struct list_head q_freelist;	/* global free list of dquots */
+	struct list_head q_lru;		/* global free list of dquots */
 	struct list_head q_mplist;	/* mount's list of dquots */
 	struct list_head q_hashlist;	/* gloabl hash list of dquots */
 	xfs_dqhash_t	*q_hash;	/* the hashchain header */