Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[linux-2.6-block.git] / drivers / md / dm-zoned-metadata.c

diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
index 969954915566f2cf1a15b684eb5b3d33dca58160..fa68336560c34dab4acdc2bd9f2dd207ce1d2f5e 100644 (file)
--- a/drivers/md/dm-zoned-metadata.c
+++ b/drivers/md/dm-zoned-metadata.c
@@ -99,7 +99,7 @@ struct dmz_mblock {
        struct rb_node          node;
        struct list_head        link;
        sector_t                no;
-       atomic_t                ref;
+       unsigned int            ref;
        unsigned long           state;
        struct page             *page;
        void                    *data;
@@ -296,7 +296,7 @@ static struct dmz_mblock *dmz_alloc_mblock(struct dmz_metadata *zmd,
 
        RB_CLEAR_NODE(&mblk->node);
        INIT_LIST_HEAD(&mblk->link);
-       atomic_set(&mblk->ref, 0);
+       mblk->ref = 0;
        mblk->state = 0;
        mblk->no = mblk_no;
        mblk->data = page_address(mblk->page);
@@ -339,10 +339,11 @@ static void dmz_insert_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk)
 }
 
 /*
- * Lookup a metadata block in the rbtree.
+ * Lookup a metadata block in the rbtree. If the block is found, increment
+ * its reference count.
  */
-static struct dmz_mblock *dmz_lookup_mblock(struct dmz_metadata *zmd,
-                                           sector_t mblk_no)
+static struct dmz_mblock *dmz_get_mblock_fast(struct dmz_metadata *zmd,
+                                             sector_t mblk_no)
 {
        struct rb_root *root = &zmd->mblk_rbtree;
        struct rb_node *node = root->rb_node;
@@ -350,8 +351,17 @@ static struct dmz_mblock *dmz_lookup_mblock(struct dmz_metadata *zmd,
 
        while (node) {
                mblk = container_of(node, struct dmz_mblock, node);
-               if (mblk->no == mblk_no)
+               if (mblk->no == mblk_no) {
+                       /*
+                        * If this is the first reference to the block,
+                        * remove it from the LRU list.
+                        */
+                       mblk->ref++;
+                       if (mblk->ref == 1 &&
+                           !test_bit(DMZ_META_DIRTY, &mblk->state))
+                               list_del_init(&mblk->link);
                        return mblk;
+               }
                node = (mblk->no < mblk_no) ? node->rb_left : node->rb_right;
        }
 
@@ -382,32 +392,47 @@ static void dmz_mblock_bio_end_io(struct bio *bio)
 }
 
 /*
- * Read a metadata block from disk.
+ * Read an uncached metadata block from disk and add it to the cache.
  */
-static struct dmz_mblock *dmz_fetch_mblock(struct dmz_metadata *zmd,
-                                          sector_t mblk_no)
+static struct dmz_mblock *dmz_get_mblock_slow(struct dmz_metadata *zmd,
+                                             sector_t mblk_no)
 {
-       struct dmz_mblock *mblk;
+       struct dmz_mblock *mblk, *m;
        sector_t block = zmd->sb[zmd->mblk_primary].block + mblk_no;
        struct bio *bio;
 
-       /* Get block and insert it */
+       /* Get a new block and a BIO to read it */
        mblk = dmz_alloc_mblock(zmd, mblk_no);
        if (!mblk)
                return NULL;
 
-       spin_lock(&zmd->mblk_lock);
-       atomic_inc(&mblk->ref);
-       set_bit(DMZ_META_READING, &mblk->state);
-       dmz_insert_mblock(zmd, mblk);
-       spin_unlock(&zmd->mblk_lock);
-
        bio = bio_alloc(GFP_NOIO, 1);
        if (!bio) {
                dmz_free_mblock(zmd, mblk);
                return NULL;
        }
 
+       spin_lock(&zmd->mblk_lock);
+
+       /*
+        * Make sure that another context did not start reading
+        * the block already.
+        */
+       m = dmz_get_mblock_fast(zmd, mblk_no);
+       if (m) {
+               spin_unlock(&zmd->mblk_lock);
+               dmz_free_mblock(zmd, mblk);
+               bio_put(bio);
+               return m;
+       }
+
+       mblk->ref++;
+       set_bit(DMZ_META_READING, &mblk->state);
+       dmz_insert_mblock(zmd, mblk);
+
+       spin_unlock(&zmd->mblk_lock);
+
+       /* Submit read BIO */
        bio->bi_iter.bi_sector = dmz_blk2sect(block);
        bio_set_dev(bio, zmd->dev->bdev);
        bio->bi_private = mblk;
@@ -484,7 +509,8 @@ static void dmz_release_mblock(struct dmz_metadata *zmd,
 
        spin_lock(&zmd->mblk_lock);
 
-       if (atomic_dec_and_test(&mblk->ref)) {
+       mblk->ref--;
+       if (mblk->ref == 0) {
                if (test_bit(DMZ_META_ERROR, &mblk->state)) {
                        rb_erase(&mblk->node, &zmd->mblk_rbtree);
                        dmz_free_mblock(zmd, mblk);
@@ -508,18 +534,12 @@ static struct dmz_mblock *dmz_get_mblock(struct dmz_metadata *zmd,
 
        /* Check rbtree */
        spin_lock(&zmd->mblk_lock);
-       mblk = dmz_lookup_mblock(zmd, mblk_no);
-       if (mblk) {
-               /* Cache hit: remove block from LRU list */
-               if (atomic_inc_return(&mblk->ref) == 1 &&
-                   !test_bit(DMZ_META_DIRTY, &mblk->state))
-                       list_del_init(&mblk->link);
-       }
+       mblk = dmz_get_mblock_fast(zmd, mblk_no);
        spin_unlock(&zmd->mblk_lock);
 
        if (!mblk) {
                /* Cache miss: read the block from disk */
-               mblk = dmz_fetch_mblock(zmd, mblk_no);
+               mblk = dmz_get_mblock_slow(zmd, mblk_no);
                if (!mblk)
                        return ERR_PTR(-ENOMEM);
        }
@@ -753,7 +773,7 @@ int dmz_flush_metadata(struct dmz_metadata *zmd)
 
                spin_lock(&zmd->mblk_lock);
                clear_bit(DMZ_META_DIRTY, &mblk->state);
-               if (atomic_read(&mblk->ref) == 0)
+               if (mblk->ref == 0)
                        list_add_tail(&mblk->link, &zmd->mblk_lru_list);
                spin_unlock(&zmd->mblk_lock);
        }
@@ -2308,7 +2328,7 @@ static void dmz_cleanup_metadata(struct dmz_metadata *zmd)
                mblk = list_first_entry(&zmd->mblk_dirty_list,
                                        struct dmz_mblock, link);
                dmz_dev_warn(zmd->dev, "mblock %llu still in dirty list (ref %u)",
-                            (u64)mblk->no, atomic_read(&mblk->ref));
+                            (u64)mblk->no, mblk->ref);
                list_del_init(&mblk->link);
                rb_erase(&mblk->node, &zmd->mblk_rbtree);
                dmz_free_mblock(zmd, mblk);
@@ -2326,8 +2346,8 @@ static void dmz_cleanup_metadata(struct dmz_metadata *zmd)
        root = &zmd->mblk_rbtree;
        rbtree_postorder_for_each_entry_safe(mblk, next, root, node) {
                dmz_dev_warn(zmd->dev, "mblock %llu ref %u still in rbtree",
-                            (u64)mblk->no, atomic_read(&mblk->ref));
-               atomic_set(&mblk->ref, 0);
+                            (u64)mblk->no, mblk->ref);
+               mblk->ref = 0;
                dmz_free_mblock(zmd, mblk);
        }