[XFS] Move the XFS inode to the front of its hash list on a cache hit

SGI Modid: xfs-linux:xfs-kern:21915a

Signed-off-by: Nathan Scott <nathans@sgi.com>
Signed-off-by: Christoph Hellwig <hch@sgi.com>

1 files changed, 50 insertions, 1 deletions

diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 3a0ba1dfd0e8..d3da00045f26 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -136,6 +136,40 @@ xfs_chash_free(xfs_mount_t *mp)
 }
 
 /*
+ * Try to move an inode to the front of its hash list if possible
+ * (and if its not there already).  Called right after obtaining
+ * the list version number and then dropping the read_lock on the
+ * hash list in question (which is done right after looking up the
+ * inode in question...).
+ */
+STATIC void
+xfs_ihash_promote(
+        xfs_ihash_t     *ih,
+        xfs_inode_t     *ip,
+        ulong           version)
+{
+        xfs_inode_t     *iq;
+
+        if ((ip->i_prevp != &ih->ih_next) && write_trylock(&ih->ih_lock)) {
+                if (likely(version == ih->ih_version)) {
+                        /* remove from list */
+                        if ((iq = ip->i_next)) {
+                                iq->i_prevp = ip->i_prevp;
+                        }
+                        *ip->i_prevp = iq;
+
+                        /* insert at list head */
+                        iq = ih->ih_next;
+                        iq->i_prevp = &ip->i_next;
+                        ip->i_next = iq;
+                        ip->i_prevp = &ih->ih_next;
+                        ih->ih_next = ip;
+                }
+                write_unlock(&ih->ih_lock);
+        }
+}
+
+/*
  * Look up an inode by number in the given file system.
  * The inode is looked up in the hash table for the file system
  * represented by the mount point parameter mp.  Each bucket of
@@ -229,7 +263,9 @@ again:
                                 XFS_STATS_INC(xs_ig_found);
 
                                 ip->i_flags &= ~XFS_IRECLAIMABLE;
+                                version = ih->ih_version;
                                 read_unlock(&ih->ih_lock);
+                                xfs_ihash_promote(ih, ip, version);
 
                                 XFS_MOUNT_ILOCK(mp);
                                 list_del_init(&ip->i_reclaim);
@@ -259,8 +295,15 @@ again:
                                                 inode_vp, vp);
                         }
 
+                        /*
+                         * Inode cache hit: if ip is not at the front of
+                         * its hash chain, move it there now.
+                         * Do this with the lock held for update, but
+                         * do statistics after releasing the lock.
+                         */
+                        version = ih->ih_version;
                         read_unlock(&ih->ih_lock);
-
+                        xfs_ihash_promote(ih, ip, version);
                         XFS_STATS_INC(xs_ig_found);
 
 finish_inode:
@@ -547,6 +590,7 @@ xfs_inode_incore(xfs_mount_t	*mp,
 {
         xfs_ihash_t     *ih;
         xfs_inode_t     *ip;
+        ulong           version;
 
         ih = XFS_IHASH(mp, ino);
         read_lock(&ih->ih_lock);
@@ -554,11 +598,15 @@ xfs_inode_incore(xfs_mount_t	*mp,
                 if (ip->i_ino == ino) {
                         /*
                          * If we find it and tp matches, return it.
+                         * Also move it to the front of the hash list
+                         * if we find it and it is not already there.
                          * Otherwise break from the loop and return
                          * NULL.
                          */
                         if (ip->i_transp == tp) {
+                                version = ih->ih_version;
                                 read_unlock(&ih->ih_lock);
+                                xfs_ihash_promote(ih, ip, version);
                                 return (ip);
                         }
                         break;
@@ -685,6 +733,7 @@ xfs_iextract(
                 iq->i_prevp = ip->i_prevp;
         }
         *ip->i_prevp = iq;
+        ih->ih_version++;
         write_unlock(&ih->ih_lock);
 
         /*