[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>
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 3a0ba1d..d3da000 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -136,6 +136,40 @@
}
/*
+ * 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 @@
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 @@
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_ihash_t *ih;
xfs_inode_t *ip;
+ ulong version;
ih = XFS_IHASH(mp, ino);
read_lock(&ih->ih_lock);
@@ -554,11 +598,15 @@
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 @@
iq->i_prevp = ip->i_prevp;
}
*ip->i_prevp = iq;
+ ih->ih_version++;
write_unlock(&ih->ih_lock);
/*