Btrfs: Introduce global metadata reservation

Reserve metadata space for extent tree, checksum tree and root tree

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

8 files changed, 241 insertions, 76 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index d4744192eada..504d5daf2f1c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -683,21 +683,15 @@ struct btrfs_space_info {
         u64 bytes_reserved;     /* total bytes the allocator has reserved for
                                    current allocations */
         u64 bytes_readonly;     /* total bytes that are read only */
-        u64 bytes_super;        /* total bytes reserved for the super blocks */
-        u64 bytes_root;         /* the number of bytes needed to commit a
-                                   transaction */
+
         u64 bytes_may_use;      /* number of bytes that may be used for
                                    delalloc/allocations */
-        u64 bytes_delalloc;     /* number of bytes currently reserved for
-                                   delayed allocation */
         u64 disk_used;          /* total bytes used on disk */
 
         int full;               /* indicates that we cannot allocate any more
                                    chunks for this space */
         int force_alloc;        /* set if we need to force a chunk alloc for
                                    this space */
-        int force_delalloc;     /* make people start doing filemap_flush until
-                                   we're under a threshold */
 
         struct list_head list;
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 054b4475c757..309d8c08a640 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1463,10 +1463,6 @@ static int cleaner_kthread(void *arg)
         struct btrfs_root *root = arg;
 
         do {
-                smp_mb();
-                if (root->fs_info->closing)
-                        break;
-
                 vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
 
                 if (!(root->fs_info->sb->s_flags & MS_RDONLY) &&
@@ -1479,11 +1475,9 @@ static int cleaner_kthread(void *arg)
                 if (freezing(current)) {
                         refrigerator();
                 } else {
-                        smp_mb();
-                        if (root->fs_info->closing)
-                                break;
                         set_current_state(TASK_INTERRUPTIBLE);
-                        schedule();
+                        if (!kthread_should_stop())
+                                schedule();
                         __set_current_state(TASK_RUNNING);
                 }
         } while (!kthread_should_stop());
@@ -1495,36 +1489,40 @@ static int transaction_kthread(void *arg)
         struct btrfs_root *root = arg;
         struct btrfs_trans_handle *trans;
         struct btrfs_transaction *cur;
+        u64 transid;
         unsigned long now;
         unsigned long delay;
         int ret;
 
         do {
-                smp_mb();
-                if (root->fs_info->closing)
-                        break;
-
                 delay = HZ * 30;
                 vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
                 mutex_lock(&root->fs_info->transaction_kthread_mutex);
 
-                mutex_lock(&root->fs_info->trans_mutex);
+                spin_lock(&root->fs_info->new_trans_lock);
                 cur = root->fs_info->running_transaction;
                 if (!cur) {
-                        mutex_unlock(&root->fs_info->trans_mutex);
+                        spin_unlock(&root->fs_info->new_trans_lock);
                         goto sleep;
                 }
 
                 now = get_seconds();
-                if (now < cur->start_time || now - cur->start_time < 30) {
-                        mutex_unlock(&root->fs_info->trans_mutex);
+                if (!cur->blocked &&
+                    (now < cur->start_time || now - cur->start_time < 30)) {
+                        spin_unlock(&root->fs_info->new_trans_lock);
                         delay = HZ * 5;
                         goto sleep;
                 }
-                mutex_unlock(&root->fs_info->trans_mutex);
-                trans = btrfs_join_transaction(root, 1);
-                ret = btrfs_commit_transaction(trans, root);
+                transid = cur->transid;
+                spin_unlock(&root->fs_info->new_trans_lock);
 
+                trans = btrfs_join_transaction(root, 1);
+                if (transid == trans->transid) {
+                        ret = btrfs_commit_transaction(trans, root);
+                        BUG_ON(ret);
+                } else {
+                        btrfs_end_transaction(trans, root);
+                }
 sleep:
                 wake_up_process(root->fs_info->cleaner_kthread);
                 mutex_unlock(&root->fs_info->transaction_kthread_mutex);
@@ -1532,10 +1530,10 @@ sleep:
                 if (freezing(current)) {
                         refrigerator();
                 } else {
-                        if (root->fs_info->closing)
-                                break;
                         set_current_state(TASK_INTERRUPTIBLE);
-                        schedule_timeout(delay);
+                        if (!kthread_should_stop() &&
+                            !btrfs_transaction_blocked(root->fs_info))
+                                schedule_timeout(delay);
                         __set_current_state(TASK_RUNNING);
                 }
         } while (!kthread_should_stop());
@@ -1917,17 +1915,18 @@ struct btrfs_root *open_ctree(struct super_block *sb,
 
         csum_root->track_dirty = 1;
 
+        fs_info->generation = generation;
+        fs_info->last_trans_committed = generation;
+        fs_info->data_alloc_profile = (u64)-1;
+        fs_info->metadata_alloc_profile = (u64)-1;
+        fs_info->system_alloc_profile = fs_info->metadata_alloc_profile;
+
         ret = btrfs_read_block_groups(extent_root);
         if (ret) {
                 printk(KERN_ERR "Failed to read block groups: %d\n", ret);
                 goto fail_block_groups;
         }
 
-        fs_info->generation = generation;
-        fs_info->last_trans_committed = generation;
-        fs_info->data_alloc_profile = (u64)-1;
-        fs_info->metadata_alloc_profile = (u64)-1;
-        fs_info->system_alloc_profile = fs_info->metadata_alloc_profile;
         fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
                                                "btrfs-cleaner");
         if (IS_ERR(fs_info->cleaner_kthread))
@@ -2430,15 +2429,15 @@ int close_ctree(struct btrfs_root *root)
         fs_info->closing = 1;
         smp_mb();
 
-        kthread_stop(root->fs_info->transaction_kthread);
-        kthread_stop(root->fs_info->cleaner_kthread);
-
         if (!(fs_info->sb->s_flags & MS_RDONLY)) {
                 ret =  btrfs_commit_super(root);
                 if (ret)
                         printk(KERN_ERR "btrfs: commit super ret %d\n", ret);
         }
 
+        kthread_stop(root->fs_info->transaction_kthread);
+        kthread_stop(root->fs_info->cleaner_kthread);
+
         fs_info->closing = 2;
         smp_mb();
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index b1822e752b4a..cb814a71800d 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2895,10 +2895,9 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes)
 again:
         /* make sure we have enough space to handle the data first */
         spin_lock(&data_sinfo->lock);
-        used = data_sinfo->bytes_used + data_sinfo->bytes_delalloc +
-                data_sinfo->bytes_reserved + data_sinfo->bytes_pinned +
-                data_sinfo->bytes_readonly + data_sinfo->bytes_may_use +
-                data_sinfo->bytes_super;
+        used = data_sinfo->bytes_used + data_sinfo->bytes_reserved +
+                data_sinfo->bytes_pinned + data_sinfo->bytes_readonly +
+                data_sinfo->bytes_may_use;
 
         if (used + bytes > data_sinfo->total_bytes) {
                 struct btrfs_trans_handle *trans;
@@ -2922,7 +2921,7 @@ alloc:
                                              bytes + 2 * 1024 * 1024,
                                              alloc_target, 0);
                         btrfs_end_transaction(trans, root);
-                        if (ret)
+                        if (ret < 0)
                                 return ret;
 
                         if (!data_sinfo) {
@@ -2945,11 +2944,10 @@ alloc:
                         goto again;
                 }
 
-                printk(KERN_ERR "no space left, need %llu, %llu delalloc bytes"
-                       ", %llu bytes_used, %llu bytes_reserved, "
-                       "%llu bytes_pinned, %llu bytes_readonly, %llu may use "
-                       "%llu total\n", (unsigned long long)bytes,
-                       (unsigned long long)data_sinfo->bytes_delalloc,
+                printk(KERN_ERR "no space left, need %llu, %llu bytes_used, "
+                       "%llu bytes_reserved, " "%llu bytes_pinned, "
+                       "%llu bytes_readonly, %llu may use %llu total\n",
+                       (unsigned long long)bytes,
                        (unsigned long long)data_sinfo->bytes_used,
                        (unsigned long long)data_sinfo->bytes_reserved,
                        (unsigned long long)data_sinfo->bytes_pinned,
@@ -3464,6 +3462,91 @@ void btrfs_block_rsv_release(struct btrfs_root *root,
         block_rsv_release_bytes(block_rsv, global_rsv, num_bytes);
 }
 
+/*
+ * helper to calculate size of global block reservation.
+ * the desired value is sum of space used by extent tree,
+ * checksum tree and root tree
+ */
+static u64 calc_global_metadata_size(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_space_info *sinfo;
+        u64 num_bytes;
+        u64 meta_used;
+        u64 data_used;
+        int csum_size = btrfs_super_csum_size(&fs_info->super_copy);
+#if 0
+        /*
+         * per tree used space accounting can be inaccuracy, so we
+         * can't rely on it.
+         */
+        spin_lock(&fs_info->extent_root->accounting_lock);
+        num_bytes = btrfs_root_used(&fs_info->extent_root->root_item);
+        spin_unlock(&fs_info->extent_root->accounting_lock);
+
+        spin_lock(&fs_info->csum_root->accounting_lock);
+        num_bytes += btrfs_root_used(&fs_info->csum_root->root_item);
+        spin_unlock(&fs_info->csum_root->accounting_lock);
+
+        spin_lock(&fs_info->tree_root->accounting_lock);
+        num_bytes += btrfs_root_used(&fs_info->tree_root->root_item);
+        spin_unlock(&fs_info->tree_root->accounting_lock);
+#endif
+        sinfo = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_DATA);
+        spin_lock(&sinfo->lock);
+        data_used = sinfo->bytes_used;
+        spin_unlock(&sinfo->lock);
+
+        sinfo = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
+        spin_lock(&sinfo->lock);
+        meta_used = sinfo->bytes_used;
+        spin_unlock(&sinfo->lock);
+
+        num_bytes = (data_used >> fs_info->sb->s_blocksize_bits) *
+                    csum_size * 2;
+        num_bytes += div64_u64(data_used + meta_used, 50);
+
+        if (num_bytes * 3 > meta_used)
+                num_bytes = div64_u64(meta_used, 3);
+
+        return ALIGN(num_bytes, fs_info->extent_root->leafsize << 10);
+}
+
+static void update_global_block_rsv(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_block_rsv *block_rsv = &fs_info->global_block_rsv;
+        struct btrfs_space_info *sinfo = block_rsv->space_info;
+        u64 num_bytes;
+
+        num_bytes = calc_global_metadata_size(fs_info);
+
+        spin_lock(&block_rsv->lock);
+        spin_lock(&sinfo->lock);
+
+        block_rsv->size = num_bytes;
+
+        num_bytes = sinfo->bytes_used + sinfo->bytes_pinned +
+                    sinfo->bytes_reserved + sinfo->bytes_readonly;
+
+        if (sinfo->total_bytes > num_bytes) {
+                num_bytes = sinfo->total_bytes - num_bytes;
+                block_rsv->reserved += num_bytes;
+                sinfo->bytes_reserved += num_bytes;
+        }
+
+        if (block_rsv->reserved >= block_rsv->size) {
+                num_bytes = block_rsv->reserved - block_rsv->size;
+                sinfo->bytes_reserved -= num_bytes;
+                block_rsv->reserved = block_rsv->size;
+                block_rsv->full = 1;
+        }
+#if 0
+        printk(KERN_INFO"global block rsv size %llu reserved %llu\n",
+                block_rsv->size, block_rsv->reserved);
+#endif
+        spin_unlock(&sinfo->lock);
+        spin_unlock(&block_rsv->lock);
+}
+
 static void init_global_block_rsv(struct btrfs_fs_info *fs_info)
 {
         struct btrfs_space_info *space_info;
@@ -3473,11 +3556,36 @@ static void init_global_block_rsv(struct btrfs_fs_info *fs_info)
         fs_info->chunk_block_rsv.priority = 10;
 
         space_info = __find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
+        fs_info->global_block_rsv.space_info = space_info;
+        fs_info->global_block_rsv.priority = 10;
+        fs_info->global_block_rsv.refill_used = 1;
+        fs_info->delalloc_block_rsv.space_info = space_info;
         fs_info->trans_block_rsv.space_info = space_info;
         fs_info->empty_block_rsv.space_info = space_info;
         fs_info->empty_block_rsv.priority = 10;
 
+        fs_info->extent_root->block_rsv = &fs_info->global_block_rsv;
+        fs_info->csum_root->block_rsv = &fs_info->global_block_rsv;
+        fs_info->dev_root->block_rsv = &fs_info->global_block_rsv;
+        fs_info->tree_root->block_rsv = &fs_info->global_block_rsv;
         fs_info->chunk_root->block_rsv = &fs_info->chunk_block_rsv;
+
+        btrfs_add_durable_block_rsv(fs_info, &fs_info->global_block_rsv);
+
+        btrfs_add_durable_block_rsv(fs_info, &fs_info->delalloc_block_rsv);
+
+        update_global_block_rsv(fs_info);
+}
+
+static void release_global_block_rsv(struct btrfs_fs_info *fs_info)
+{
+        block_rsv_release_bytes(&fs_info->global_block_rsv, NULL, (u64)-1);
+        WARN_ON(fs_info->delalloc_block_rsv.size > 0);
+        WARN_ON(fs_info->delalloc_block_rsv.reserved > 0);
+        WARN_ON(fs_info->trans_block_rsv.size > 0);
+        WARN_ON(fs_info->trans_block_rsv.reserved > 0);
+        WARN_ON(fs_info->chunk_block_rsv.size > 0);
+        WARN_ON(fs_info->chunk_block_rsv.reserved > 0);
 }
 
 static u64 calc_trans_metadata_size(struct btrfs_root *root, int num_items)
@@ -3826,6 +3934,8 @@ int btrfs_prepare_extent_commit(struct btrfs_trans_handle *trans,
                 fs_info->pinned_extents = &fs_info->freed_extents[0];
 
         up_write(&fs_info->extent_commit_sem);
+
+        update_global_block_rsv(fs_info);
         return 0;
 }
 
@@ -4818,19 +4928,16 @@ static void dump_space_info(struct btrfs_space_info *info, u64 bytes,
         printk(KERN_INFO "space_info has %llu free, is %sfull\n",
                (unsigned long long)(info->total_bytes - info->bytes_used -
                                     info->bytes_pinned - info->bytes_reserved -
-                                    info->bytes_super),
+                                    info->bytes_readonly),
                (info->full) ? "" : "not ");
-        printk(KERN_INFO "space_info total=%llu, pinned=%llu, delalloc=%llu,"
-               " may_use=%llu, used=%llu, root=%llu, super=%llu, reserved=%llu"
-               "\n",
+        printk(KERN_INFO "space_info total=%llu, used=%llu, pinned=%llu, "
+               "reserved=%llu, may_use=%llu, readonly=%llu\n",
                (unsigned long long)info->total_bytes,
+               (unsigned long long)info->bytes_used,
                (unsigned long long)info->bytes_pinned,
-               (unsigned long long)info->bytes_delalloc,
+               (unsigned long long)info->bytes_reserved,
                (unsigned long long)info->bytes_may_use,
-               (unsigned long long)info->bytes_used,
-               (unsigned long long)info->bytes_root,
-               (unsigned long long)info->bytes_super,
-               (unsigned long long)info->bytes_reserved);
+               (unsigned long long)info->bytes_readonly);
         spin_unlock(&info->lock);
 
         if (!dump_block_groups)
@@ -7727,6 +7834,8 @@ int btrfs_free_block_groups(struct btrfs_fs_info *info)
          */
         synchronize_rcu();
 
+        release_global_block_rsv(info);
+
         while(!list_empty(&info->space_info)) {
                 space_info = list_entry(info->space_info.next,
                                         struct btrfs_space_info,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6e54665d37f7..f9c40b839452 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4060,7 +4060,7 @@ int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
         struct btrfs_trans_handle *trans;
         int ret = 0;
 
-        if (root->fs_info->btree_inode == inode)
+        if (BTRFS_I(inode)->dummy_inode)
                 return 0;
 
         if (wbc->sync_mode == WB_SYNC_ALL) {
@@ -4081,10 +4081,19 @@ void btrfs_dirty_inode(struct inode *inode)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_trans_handle *trans;
+        int ret;
+
+        if (BTRFS_I(inode)->dummy_inode)
+                return;
 
         trans = btrfs_join_transaction(root, 1);
         btrfs_set_trans_block_group(trans, inode);
-        btrfs_update_inode(trans, root, inode);
+
+        ret = btrfs_update_inode(trans, root, inode);
+        if (ret)
+                printk(KERN_ERR"btrfs: fail to dirty inode %lu error %d\n",
+                        inode->i_ino, ret);
+
         btrfs_end_transaction(trans, root);
 }
 
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 6a706e691377..a0686658a3f6 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1341,8 +1341,10 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
                         ret = -EPERM;
                         goto out;
                 }
-                btrfs_defrag_root(root, 0);
-                btrfs_defrag_root(root->fs_info->extent_root, 0);
+                ret = btrfs_defrag_root(root, 0);
+                if (ret)
+                        goto out;
+                ret = btrfs_defrag_root(root->fs_info->extent_root, 0);
                 break;
         case S_IFREG:
                 if (!(file->f_mode & FMODE_WRITE)) {
@@ -1372,9 +1374,11 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
                         /* the rest are all set to zero by kzalloc */
                         range->len = (u64)-1;
                 }
-                btrfs_defrag_file(file, range);
+                ret = btrfs_defrag_file(file, range);
                 kfree(range);
                 break;
+        default:
+                ret = -EINVAL;
         }
 out:
         mnt_drop_write(file->f_path.mnt);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 2616491a5c5b..6217bb6d516a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -321,10 +321,36 @@ void btrfs_throttle(struct btrfs_root *root)
         mutex_unlock(&root->fs_info->trans_mutex);
 }
 
+static int should_end_transaction(struct btrfs_trans_handle *trans,
+                                  struct btrfs_root *root)
+{
+        int ret;
+        ret = btrfs_block_rsv_check(trans, root,
+                                    &root->fs_info->global_block_rsv, 0, 5);
+        return ret ? 1 : 0;
+}
+
+int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root)
+{
+        struct btrfs_transaction *cur_trans = trans->transaction;
+        int updates;
+
+        if (cur_trans->blocked || cur_trans->delayed_refs.flushing)
+                return 1;
+
+        updates = trans->delayed_ref_updates;
+        trans->delayed_ref_updates = 0;
+        if (updates)
+                btrfs_run_delayed_refs(trans, root, updates);
+
+        return should_end_transaction(trans, root);
+}
+
 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root, int throttle)
 {
-        struct btrfs_transaction *cur_trans;
+        struct btrfs_transaction *cur_trans = trans->transaction;
         struct btrfs_fs_info *info = root->fs_info;
         int count = 0;
 
@@ -350,9 +376,19 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 
         btrfs_trans_release_metadata(trans, root);
 
+        if (!root->fs_info->open_ioctl_trans &&
+            should_end_transaction(trans, root))
+                trans->transaction->blocked = 1;
+
+        if (cur_trans->blocked && !cur_trans->in_commit) {
+                if (throttle)
+                        return btrfs_commit_transaction(trans, root);
+                else
+                        wake_up_process(info->transaction_kthread);
+        }
+
         mutex_lock(&info->trans_mutex);
-        cur_trans = info->running_transaction;
-        WARN_ON(cur_trans != trans->transaction);
+        WARN_ON(cur_trans != info->running_transaction);
         WARN_ON(cur_trans->num_writers < 1);
         cur_trans->num_writers--;
 
@@ -664,30 +700,30 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans,
 int btrfs_defrag_root(struct btrfs_root *root, int cacheonly)
 {
         struct btrfs_fs_info *info = root->fs_info;
-        int ret;
         struct btrfs_trans_handle *trans;
+        int ret;
         unsigned long nr;
 
-        smp_mb();
-        if (root->defrag_running)
+        if (xchg(&root->defrag_running, 1))
                 return 0;
-        trans = btrfs_start_transaction(root, 1);
+
         while (1) {
-                root->defrag_running = 1;
+                trans = btrfs_start_transaction(root, 0);
+                if (IS_ERR(trans))
+                        return PTR_ERR(trans);
+
                 ret = btrfs_defrag_leaves(trans, root, cacheonly);
+
                 nr = trans->blocks_used;
                 btrfs_end_transaction(trans, root);
                 btrfs_btree_balance_dirty(info->tree_root, nr);
                 cond_resched();
 
-                trans = btrfs_start_transaction(root, 1);
                 if (root->fs_info->closing || ret != -EAGAIN)
                         break;
         }
         root->defrag_running = 0;
-        smp_mb();
-        btrfs_end_transaction(trans, root);
-        return 0;
+        return ret;
 }
 
 #if 0
@@ -924,6 +960,16 @@ int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
         return ret;
 }
 
+int btrfs_transaction_blocked(struct btrfs_fs_info *info)
+{
+        int ret = 0;
+        spin_lock(&info->new_trans_lock);
+        if (info->running_transaction)
+                ret = info->running_transaction->blocked;
+        spin_unlock(&info->new_trans_lock);
+        return ret;
+}
+
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root)
 {
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 14b3841b75d5..e104986d0bfd 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -106,6 +106,8 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root);
 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root);
+int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root);
 void btrfs_throttle(struct btrfs_root *root);
 int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root);
@@ -115,5 +117,6 @@ int btrfs_write_marked_extents(struct btrfs_root *root,
                                 struct extent_io_tree *dirty_pages, int mark);
 int btrfs_wait_marked_extents(struct btrfs_root *root,
                                 struct extent_io_tree *dirty_pages, int mark);
+int btrfs_transaction_blocked(struct btrfs_fs_info *info);
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
 #endif
diff --git a/fs/btrfs/tree-defrag.c b/fs/btrfs/tree-defrag.c
index b10eacdb1620..f7ac8e013ed7 100644
--- a/fs/btrfs/tree-defrag.c
+++ b/fs/btrfs/tree-defrag.c
@@ -117,13 +117,14 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
                                  path->nodes[1], 0,
                                  cache_only, &last_ret,
                                  &root->defrag_progress);
-        WARN_ON(ret && ret != -EAGAIN);
+        if (ret) {
+                WARN_ON(ret == -EAGAIN);
+                goto out;
+        }
         if (next_key_ret == 0) {
                 memcpy(&root->defrag_progress, &key, sizeof(key));
                 ret = -EAGAIN;
         }
-
-        btrfs_release_path(root, path);
 out:
         if (path)
                 btrfs_free_path(path);