1 files changed, 39 insertions, 25 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 3d73c8d93bbb..c571734d5e5a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -32,10 +32,8 @@
 
 static noinline void put_transaction(struct btrfs_transaction *transaction)
 {
-        WARN_ON(transaction->use_count == 0);
-        transaction->use_count--;
-        if (transaction->use_count == 0) {
-                list_del_init(&transaction->list);
+        WARN_ON(atomic_read(&transaction->use_count) == 0);
+        if (atomic_dec_and_test(&transaction->use_count)) {
                 memset(transaction, 0, sizeof(*transaction));
                 kmem_cache_free(btrfs_transaction_cachep, transaction);
         }
@@ -57,16 +55,17 @@ static noinline int join_transaction(struct btrfs_root *root)
         if (!cur_trans) {
                 cur_trans = kmem_cache_alloc(btrfs_transaction_cachep,
                                              GFP_NOFS);
-                BUG_ON(!cur_trans);
+                if (!cur_trans)
+                        return -ENOMEM;
                 root->fs_info->generation++;
-                cur_trans->num_writers = 1;
+                atomic_set(&cur_trans->num_writers, 1);
                 cur_trans->num_joined = 0;
                 cur_trans->transid = root->fs_info->generation;
                 init_waitqueue_head(&cur_trans->writer_wait);
                 init_waitqueue_head(&cur_trans->commit_wait);
                 cur_trans->in_commit = 0;
                 cur_trans->blocked = 0;
-                cur_trans->use_count = 1;
+                atomic_set(&cur_trans->use_count, 1);
                 cur_trans->commit_done = 0;
                 cur_trans->start_time = get_seconds();
 
@@ -87,7 +86,7 @@ static noinline int join_transaction(struct btrfs_root *root)
                 root->fs_info->running_transaction = cur_trans;
                 spin_unlock(&root->fs_info->new_trans_lock);
         } else {
-                cur_trans->num_writers++;
+                atomic_inc(&cur_trans->num_writers);
                 cur_trans->num_joined++;
         }
 
@@ -144,7 +143,7 @@ static void wait_current_trans(struct btrfs_root *root)
         cur_trans = root->fs_info->running_transaction;
         if (cur_trans && cur_trans->blocked) {
                 DEFINE_WAIT(wait);
-                cur_trans->use_count++;
+                atomic_inc(&cur_trans->use_count);
                 while (1) {
                         prepare_to_wait(&root->fs_info->transaction_wait, &wait,
                                         TASK_UNINTERRUPTIBLE);
@@ -180,6 +179,7 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
 {
         struct btrfs_trans_handle *h;
         struct btrfs_transaction *cur_trans;
+        int retries = 0;
         int ret;
 
         if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
@@ -195,10 +195,15 @@ again:
                 wait_current_trans(root);
 
         ret = join_transaction(root);
-        BUG_ON(ret);
+        if (ret < 0) {
+                kmem_cache_free(btrfs_trans_handle_cachep, h);
+                if (type != TRANS_JOIN_NOLOCK)
+                        mutex_unlock(&root->fs_info->trans_mutex);
+                return ERR_PTR(ret);
+        }
 
         cur_trans = root->fs_info->running_transaction;
-        cur_trans->use_count++;
+        atomic_inc(&cur_trans->use_count);
         if (type != TRANS_JOIN_NOLOCK)
                 mutex_unlock(&root->fs_info->trans_mutex);
 
@@ -218,10 +223,18 @@ again:
 
         if (num_items > 0) {
                 ret = btrfs_trans_reserve_metadata(h, root, num_items);
-                if (ret == -EAGAIN) {
+                if (ret == -EAGAIN && !retries) {
+                        retries++;
                         btrfs_commit_transaction(h, root);
                         goto again;
+                } else if (ret == -EAGAIN) {
+                        /*
+                         * We have already retried and got EAGAIN, so really we
+                         * don't have space, so set ret to -ENOSPC.
+                         */
+                        ret = -ENOSPC;
                 }
+
                 if (ret < 0) {
                         btrfs_end_transaction(h, root);
                         return ERR_PTR(ret);
@@ -321,7 +334,7 @@ int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid)
                         goto out_unlock;  /* nothing committing|committed */
         }
 
-        cur_trans->use_count++;
+        atomic_inc(&cur_trans->use_count);
         mutex_unlock(&root->fs_info->trans_mutex);
 
         wait_for_commit(root, cur_trans);
@@ -451,18 +464,14 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
                         wake_up_process(info->transaction_kthread);
         }
 
-        if (lock)
-                mutex_lock(&info->trans_mutex);
         WARN_ON(cur_trans != info->running_transaction);
-        WARN_ON(cur_trans->num_writers < 1);
-        cur_trans->num_writers--;
+        WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
+        atomic_dec(&cur_trans->num_writers);
 
         smp_mb();
         if (waitqueue_active(&cur_trans->writer_wait))
                 wake_up(&cur_trans->writer_wait);
         put_transaction(cur_trans);
-        if (lock)
-                mutex_unlock(&info->trans_mutex);
 
         if (current->journal_info == trans)
                 current->journal_info = NULL;
@@ -970,6 +979,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         record_root_in_trans(trans, root);
         btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
+        btrfs_check_and_init_root_item(new_root_item);
 
         root_flags = btrfs_root_flags(new_root_item);
         if (pending->readonly)
@@ -1156,7 +1166,8 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
         struct btrfs_transaction *cur_trans;
 
         ac = kmalloc(sizeof(*ac), GFP_NOFS);
-        BUG_ON(!ac);
+        if (!ac)
+                return -ENOMEM;
 
         INIT_DELAYED_WORK(&ac->work, do_async_commit);
         ac->root = root;
@@ -1170,7 +1181,7 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
         /* take transaction reference */
         mutex_lock(&root->fs_info->trans_mutex);
         cur_trans = trans->transaction;
-        cur_trans->use_count++;
+        atomic_inc(&cur_trans->use_count);
         mutex_unlock(&root->fs_info->trans_mutex);
 
         btrfs_end_transaction(trans, root);
@@ -1229,7 +1240,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
         mutex_lock(&root->fs_info->trans_mutex);
         if (cur_trans->in_commit) {
-                cur_trans->use_count++;
+                atomic_inc(&cur_trans->use_count);
                 mutex_unlock(&root->fs_info->trans_mutex);
                 btrfs_end_transaction(trans, root);
 
@@ -1251,7 +1262,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                 prev_trans = list_entry(cur_trans->list.prev,
                                         struct btrfs_transaction, list);
                 if (!prev_trans->commit_done) {
-                        prev_trans->use_count++;
+                        atomic_inc(&prev_trans->use_count);
                         mutex_unlock(&root->fs_info->trans_mutex);
 
                         wait_for_commit(root, prev_trans);
@@ -1292,14 +1303,14 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                                 TASK_UNINTERRUPTIBLE);
 
                 smp_mb();
-                if (cur_trans->num_writers > 1)
+                if (atomic_read(&cur_trans->num_writers) > 1)
                         schedule_timeout(MAX_SCHEDULE_TIMEOUT);
                 else if (should_grow)
                         schedule_timeout(1);
 
                 mutex_lock(&root->fs_info->trans_mutex);
                 finish_wait(&cur_trans->writer_wait, &wait);
-        } while (cur_trans->num_writers > 1 ||
+        } while (atomic_read(&cur_trans->num_writers) > 1 ||
                  (should_grow && cur_trans->num_joined != joined));
 
         ret = create_pending_snapshots(trans, root->fs_info);
@@ -1386,9 +1397,12 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 
         wake_up(&cur_trans->commit_wait);
 
+        list_del_init(&cur_trans->list);
         put_transaction(cur_trans);
         put_transaction(cur_trans);
 
+        trace_btrfs_transaction_commit(root);
+
         mutex_unlock(&root->fs_info->trans_mutex);
 
         if (current->journal_info == trans)