ext4: Use an rbtree for tracking blocks freed during transaction.

With this patch we track the block freed during a transaction using
red-black tree.  We also make sure contiguous blocks freed are collected
in one node in the tree.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

2 files changed, 133 insertions, 77 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 154f8dec97ea..bd9b011941a2 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2300,6 +2300,7 @@ int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
         }
 
         INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);
+        meta_group_info[i]->bb_free_root.rb_node = NULL;;
 
 #ifdef DOUBLE_CHECK
         {
@@ -2647,13 +2648,11 @@ int ext4_mb_release(struct super_block *sb)
 static noinline_for_stack void
 ext4_mb_free_committed_blocks(struct super_block *sb)
 {
-        struct ext4_sb_info *sbi = EXT4_SB(sb);
-        int err;
-        int i;
-        int count = 0;
-        int count2 = 0;
-        struct ext4_free_metadata *md;
         struct ext4_buddy e4b;
+        struct ext4_group_info *db;
+        struct ext4_sb_info *sbi = EXT4_SB(sb);
+        int err, count = 0, count2 = 0;
+        struct ext4_free_data *entry;
 
         if (list_empty(&sbi->s_committed_transaction))
                 return;
@@ -2661,44 +2660,46 @@ ext4_mb_free_committed_blocks(struct super_block *sb)
         /* there is committed blocks to be freed yet */
         do {
                 /* get next array of blocks */
-                md = NULL;
+                entry = NULL;
                 spin_lock(&sbi->s_md_lock);
                 if (!list_empty(&sbi->s_committed_transaction)) {
-                        md = list_entry(sbi->s_committed_transaction.next,
-                                        struct ext4_free_metadata, list);
-                        list_del(&md->list);
+                        entry = list_entry(sbi->s_committed_transaction.next,
+                                        struct ext4_free_data, list);
+                        list_del(&entry->list);
                 }
                 spin_unlock(&sbi->s_md_lock);
 
-                if (md == NULL)
+                if (entry == NULL)
                         break;
 
                 mb_debug("gonna free %u blocks in group %lu (0x%p):",
-                                md->num, md->group, md);
+                                entry->count, entry->group, entry);
 
-                err = ext4_mb_load_buddy(sb, md->group, &e4b);
+                err = ext4_mb_load_buddy(sb, entry->group, &e4b);
                 /* we expect to find existing buddy because it's pinned */
                 BUG_ON(err != 0);
 
+                db = e4b.bd_info;
                 /* there are blocks to put in buddy to make them really free */
-                count += md->num;
+                count += entry->count;
                 count2++;
-                ext4_lock_group(sb, md->group);
-                for (i = 0; i < md->num; i++) {
-                        mb_debug(" %u", md->blocks[i]);
-                        mb_free_blocks(NULL, &e4b, md->blocks[i], 1);
+                ext4_lock_group(sb, entry->group);
+                /* Take it out of per group rb tree */
+                rb_erase(&entry->node, &(db->bb_free_root));
+                mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);
+
+                if (!db->bb_free_root.rb_node) {
+                        /* No more items in the per group rb tree
+                         * balance refcounts from ext4_mb_free_metadata()
+                         */
+                        page_cache_release(e4b.bd_buddy_page);
+                        page_cache_release(e4b.bd_bitmap_page);
                 }
-                mb_debug("\n");
-                ext4_unlock_group(sb, md->group);
-
-                /* balance refcounts from ext4_mb_free_metadata() */
-                page_cache_release(e4b.bd_buddy_page);
-                page_cache_release(e4b.bd_bitmap_page);
+                ext4_unlock_group(sb, entry->group);
 
-                kfree(md);
+                kmem_cache_free(ext4_free_ext_cachep, entry);
                 ext4_mb_release_desc(&e4b);
-
-        } while (md);
+        } while (1);
 
         mb_debug("freed %u blocks in %u structures\n", count, count2);
 }
@@ -2771,6 +2772,16 @@ int __init init_ext4_mballoc(void)
                 kmem_cache_destroy(ext4_pspace_cachep);
                 return -ENOMEM;
         }
+
+        ext4_free_ext_cachep =
+                kmem_cache_create("ext4_free_block_extents",
+                                     sizeof(struct ext4_free_data),
+                                     0, SLAB_RECLAIM_ACCOUNT, NULL);
+        if (ext4_free_ext_cachep == NULL) {
+                kmem_cache_destroy(ext4_pspace_cachep);
+                kmem_cache_destroy(ext4_ac_cachep);
+                return -ENOMEM;
+        }
         return 0;
 }
 
@@ -2779,6 +2790,7 @@ void exit_ext4_mballoc(void)
         /* XXX: synchronize_rcu(); */
         kmem_cache_destroy(ext4_pspace_cachep);
         kmem_cache_destroy(ext4_ac_cachep);
+        kmem_cache_destroy(ext4_free_ext_cachep);
 }
 
 
@@ -4415,6 +4427,21 @@ static void ext4_mb_poll_new_transaction(struct super_block *sb,
         ext4_mb_free_committed_blocks(sb);
 }
 
+/*
+ * We can merge two free data extents only if the physical blocks
+ * are contiguous, AND the extents were freed by the same transaction,
+ * AND the blocks are associated with the same group.
+ */
+static int can_merge(struct ext4_free_data *entry1,
+                        struct ext4_free_data *entry2)
+{
+        if ((entry1->t_tid == entry2->t_tid) &&
+            (entry1->group == entry2->group) &&
+            ((entry1->start_blk + entry1->count) == entry2->start_blk))
+                return 1;
+        return 0;
+}
+
 static noinline_for_stack int
 ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
                           ext4_group_t group, ext4_grpblk_t block, int count)
@@ -4422,57 +4449,80 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,
         struct ext4_group_info *db = e4b->bd_info;
         struct super_block *sb = e4b->bd_sb;
         struct ext4_sb_info *sbi = EXT4_SB(sb);
-        struct ext4_free_metadata *md;
-        int i;
+        struct ext4_free_data *entry, *new_entry;
+        struct rb_node **n = &db->bb_free_root.rb_node, *node;
+        struct rb_node *parent = NULL, *new_node;
+
 
         BUG_ON(e4b->bd_bitmap_page == NULL);
         BUG_ON(e4b->bd_buddy_page == NULL);
 
+        new_entry  = kmem_cache_alloc(ext4_free_ext_cachep, GFP_NOFS);
+        new_entry->start_blk = block;
+        new_entry->group  = group;
+        new_entry->count = count;
+        new_entry->t_tid = handle->h_transaction->t_tid;
+        new_node = &new_entry->node;
+
         ext4_lock_group(sb, group);
-        for (i = 0; i < count; i++) {
-                md = db->bb_md_cur;
-                if (md && db->bb_tid != handle->h_transaction->t_tid) {
-                        db->bb_md_cur = NULL;
-                        md = NULL;
+        if (!*n) {
+                /* first free block exent. We need to
+                   protect buddy cache from being freed,
+                 * otherwise we'll refresh it from
+                 * on-disk bitmap and lose not-yet-available
+                 * blocks */
+                page_cache_get(e4b->bd_buddy_page);
+                page_cache_get(e4b->bd_bitmap_page);
+        }
+        while (*n) {
+                parent = *n;
+                entry = rb_entry(parent, struct ext4_free_data, node);
+                if (block < entry->start_blk)
+                        n = &(*n)->rb_left;
+                else if (block >= (entry->start_blk + entry->count))
+                        n = &(*n)->rb_right;
+                else {
+                        ext4_error(sb, __func__,
+                            "Double free of blocks %d (%d %d)\n",
+                            block, entry->start_blk, entry->count);
+                        return 0;
                 }
+        }
 
-                if (md == NULL) {
-                        ext4_unlock_group(sb, group);
-                        md = kmalloc(sizeof(*md), GFP_NOFS);
-                        if (md == NULL)
-                                return -ENOMEM;
-                        md->num = 0;
-                        md->group = group;
-
-                        ext4_lock_group(sb, group);
-                        if (db->bb_md_cur == NULL) {
-                                spin_lock(&sbi->s_md_lock);
-                                list_add(&md->list, &sbi->s_active_transaction);
-                                spin_unlock(&sbi->s_md_lock);
-                                /* protect buddy cache from being freed,
-                                 * otherwise we'll refresh it from
-                                 * on-disk bitmap and lose not-yet-available
-                                 * blocks */
-                                page_cache_get(e4b->bd_buddy_page);
-                                page_cache_get(e4b->bd_bitmap_page);
-                                db->bb_md_cur = md;
-                                db->bb_tid = handle->h_transaction->t_tid;
-                                mb_debug("new md 0x%p for group %lu\n",
-                                                md, md->group);
-                        } else {
-                                kfree(md);
-                                md = db->bb_md_cur;
-                        }
+        rb_link_node(new_node, parent, n);
+        rb_insert_color(new_node, &db->bb_free_root);
+
+        /* Now try to see the extent can be merged to left and right */
+        node = rb_prev(new_node);
+        if (node) {
+                entry = rb_entry(node, struct ext4_free_data, node);
+                if (can_merge(entry, new_entry)) {
+                        new_entry->start_blk = entry->start_blk;
+                        new_entry->count += entry->count;
+                        rb_erase(node, &(db->bb_free_root));
+                        spin_lock(&sbi->s_md_lock);
+                        list_del(&entry->list);
+                        spin_unlock(&sbi->s_md_lock);
+                        kmem_cache_free(ext4_free_ext_cachep, entry);
                 }
+        }
 
-                BUG_ON(md->num >= EXT4_BB_MAX_BLOCKS);
-                md->blocks[md->num] = block + i;
-                md->num++;
-                if (md->num == EXT4_BB_MAX_BLOCKS) {
-                        /* no more space, put full container on a sb's list */
-                        db->bb_md_cur = NULL;
+        node = rb_next(new_node);
+        if (node) {
+                entry = rb_entry(node, struct ext4_free_data, node);
+                if (can_merge(new_entry, entry)) {
+                        new_entry->count += entry->count;
+                        rb_erase(node, &(db->bb_free_root));
+                        spin_lock(&sbi->s_md_lock);
+                        list_del(&entry->list);
+                        spin_unlock(&sbi->s_md_lock);
+                        kmem_cache_free(ext4_free_ext_cachep, entry);
                 }
         }
+        /* Add the extent to active_transaction list */
+        spin_lock(&sbi->s_md_lock);
+        list_add(&new_entry->list, &sbi->s_active_transaction);
+        spin_unlock(&sbi->s_md_lock);
         ext4_unlock_group(sb, group);
         return 0;
 }
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index b3b4828f8b89..9e815c4e37df 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -98,23 +98,29 @@
 
 static struct kmem_cache *ext4_pspace_cachep;
 static struct kmem_cache *ext4_ac_cachep;
+static struct kmem_cache *ext4_free_ext_cachep;
 
-#ifdef EXT4_BB_MAX_BLOCKS
-#undef EXT4_BB_MAX_BLOCKS
-#endif
-#define EXT4_BB_MAX_BLOCKS      30
+struct ext4_free_data {
+        /* this links the free block information from group_info */
+        struct rb_node node;
 
-struct ext4_free_metadata {
-        ext4_group_t group;
-        unsigned short num;
-        ext4_grpblk_t  blocks[EXT4_BB_MAX_BLOCKS];
+        /* this links the free block information from ext4_sb_info */
         struct list_head list;
+
+        /* group which free block extent belongs */
+        ext4_group_t group;
+
+        /* free block extent */
+        ext4_grpblk_t start_blk;
+        ext4_grpblk_t count;
+
+        /* transaction which freed this extent */
+        tid_t   t_tid;
 };
 
 struct ext4_group_info {
         unsigned long   bb_state;
-        unsigned long   bb_tid;
-        struct ext4_free_metadata *bb_md_cur;
+        struct rb_root  bb_free_root;
         unsigned short  bb_first_free;
         unsigned short  bb_free;
         unsigned short  bb_fragments;