jffs2: Dynamically choose inocache hash size

When JFFS2 is used for large volumes, the mount times are quite long.
Increasing the hash size provides a significant speed boost on the OLPC
XO-1 laptop.

Add logic that dynamically selects a hash size based on the size of
the medium. A 64mb medium will result in a hash size of 128, and a 512mb
medium will result in a hash size of 1024.

Signed-off-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

5 files changed, 29 insertions, 7 deletions

diff --git a/fs/jffs2/build.c b/fs/jffs2/build.c
index a906f538d11c..85c6be2db02f 100644
--- a/fs/jffs2/build.c
+++ b/fs/jffs2/build.c
@@ -23,7 +23,7 @@ static void jffs2_build_remove_unlinked_inode(struct jffs2_sb_info *,
 static inline struct jffs2_inode_cache *
 first_inode_chain(int *i, struct jffs2_sb_info *c)
 {
-        for (; *i < INOCACHE_HASHSIZE; (*i)++) {
+        for (; *i < c->inocache_hashsize; (*i)++) {
                 if (c->inocache_list[*i])
                         return c->inocache_list[*i];
         }
diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index 6b2964a19850..2701b372da78 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -478,6 +478,25 @@ struct inode *jffs2_new_inode (struct inode *dir_i, int mode, struct jffs2_raw_i
         return inode;
 }
 
+static int calculate_inocache_hashsize(uint32_t flash_size)
+{
+        /*
+         * Pick a inocache hash size based on the size of the medium.
+         * Count how many megabytes we're dealing with, apply a hashsize twice
+         * that size, but rounding down to the usual big powers of 2. And keep
+         * to sensible bounds.
+         */
+
+        int size_mb = flash_size / 1024 / 1024;
+        int hashsize = (size_mb * 2) & ~0x3f;
+
+        if (hashsize < INOCACHE_HASHSIZE_MIN)
+                return INOCACHE_HASHSIZE_MIN;
+        if (hashsize > INOCACHE_HASHSIZE_MAX)
+                return INOCACHE_HASHSIZE_MAX;
+
+        return hashsize;
+}
 
 int jffs2_do_fill_super(struct super_block *sb, void *data, int silent)
 {
@@ -524,7 +543,8 @@ int jffs2_do_fill_super(struct super_block *sb, void *data, int silent)
         if (ret)
                 return ret;
 
-        c->inocache_list = kcalloc(INOCACHE_HASHSIZE, sizeof(struct jffs2_inode_cache *), GFP_KERNEL);
+        c->inocache_hashsize = calculate_inocache_hashsize(c->flash_size);
+        c->inocache_list = kcalloc(c->inocache_hashsize, sizeof(struct jffs2_inode_cache *), GFP_KERNEL);
         if (!c->inocache_list) {
                 ret = -ENOMEM;
                 goto out_wbuf;
diff --git a/fs/jffs2/jffs2_fs_sb.h b/fs/jffs2/jffs2_fs_sb.h
index 6784bc89add1..f864005de64c 100644
--- a/fs/jffs2/jffs2_fs_sb.h
+++ b/fs/jffs2/jffs2_fs_sb.h
@@ -100,6 +100,7 @@ struct jffs2_sb_info {
         wait_queue_head_t erase_wait;           /* For waiting for erases to complete */
 
         wait_queue_head_t inocache_wq;
+        int inocache_hashsize;
         struct jffs2_inode_cache **inocache_list;
         spinlock_t inocache_lock;
 
diff --git a/fs/jffs2/nodelist.c b/fs/jffs2/nodelist.c
index af02bd138469..5e03233c2363 100644
--- a/fs/jffs2/nodelist.c
+++ b/fs/jffs2/nodelist.c
@@ -420,7 +420,7 @@ struct jffs2_inode_cache *jffs2_get_ino_cache(struct jffs2_sb_info *c, uint32_t
 {
         struct jffs2_inode_cache *ret;
 
-        ret = c->inocache_list[ino % INOCACHE_HASHSIZE];
+        ret = c->inocache_list[ino % c->inocache_hashsize];
         while (ret && ret->ino < ino) {
                 ret = ret->next;
         }
@@ -441,7 +441,7 @@ void jffs2_add_ino_cache (struct jffs2_sb_info *c, struct jffs2_inode_cache *new
 
         dbg_inocache("add %p (ino #%u)\n", new, new->ino);
 
-        prev = &c->inocache_list[new->ino % INOCACHE_HASHSIZE];
+        prev = &c->inocache_list[new->ino % c->inocache_hashsize];
 
         while ((*prev) && (*prev)->ino < new->ino) {
                 prev = &(*prev)->next;
@@ -462,7 +462,7 @@ void jffs2_del_ino_cache(struct jffs2_sb_info *c, struct jffs2_inode_cache *old)
         dbg_inocache("del %p (ino #%u)\n", old, old->ino);
         spin_lock(&c->inocache_lock);
 
-        prev = &c->inocache_list[old->ino % INOCACHE_HASHSIZE];
+        prev = &c->inocache_list[old->ino % c->inocache_hashsize];
 
         while ((*prev) && (*prev)->ino < old->ino) {
                 prev = &(*prev)->next;
@@ -487,7 +487,7 @@ void jffs2_free_ino_caches(struct jffs2_sb_info *c)
         int i;
         struct jffs2_inode_cache *this, *next;
 
-        for (i=0; i<INOCACHE_HASHSIZE; i++) {
+        for (i=0; i < c->inocache_hashsize; i++) {
                 this = c->inocache_list[i];
                 while (this) {
                         next = this->next;
diff --git a/fs/jffs2/nodelist.h b/fs/jffs2/nodelist.h
index 523a91691052..5a53d9bdb2b5 100644
--- a/fs/jffs2/nodelist.h
+++ b/fs/jffs2/nodelist.h
@@ -199,7 +199,8 @@ struct jffs2_inode_cache {
 #define RAWNODE_CLASS_XATTR_DATUM       1
 #define RAWNODE_CLASS_XATTR_REF         2
 
-#define INOCACHE_HASHSIZE 128
+#define INOCACHE_HASHSIZE_MIN 128
+#define INOCACHE_HASHSIZE_MAX 1024
 
 #define write_ofs(c) ((c)->nextblock->offset + (c)->sector_size - (c)->nextblock->free_size)