Squashfs: optimise squashfs_cache_get entry search

squashfs_cache_get() iterates over all entries to search for
 block its looking for. Often get() / put() are called for
 same block.

If we cache the current entry index, then we can optimise the
subsequent *_get() calls.

Signed-off-by: Ajeet Yadav <ajeet.yadav.77@gmail.com>
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index ea6e798e548b..af0b73802592 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -70,11 +70,15 @@ struct squashfs_cache_entry *squashfs_cache_get(struct super_block *sb,
         spin_lock(&cache->lock);
 
         while (1) {
-                for (i = 0; i < cache->entries; i++)
-                        if (cache->entry[i].block == block)
+                for (i = cache->curr_blk, n = 0; n < cache->entries; n++) {
+                        if (cache->entry[i].block == block) {
+                                cache->curr_blk = i;
                                 break;
+                        }
+                        i = (i + 1) % cache->entries;
+                }
 
-                if (i == cache->entries) {
+                if (n == cache->entries) {
                         /*
                          * Block not in cache, if all cache entries are used
                          * go to sleep waiting for one to become available.
@@ -245,6 +249,7 @@ struct squashfs_cache *squashfs_cache_init(char *name, int entries,
                 goto cleanup;
         }
 
+        cache->curr_blk = 0;
         cache->next_blk = 0;
         cache->unused = entries;
         cache->entries = entries;