btrfs: fix return value check of btrfs_join_transaction()

The error check of btrfs_join_transaction()/btrfs_join_transaction_nolock()
is added, and the mistake of the error check in several places is
corrected.

For more stable Btrfs, I think that we should reduce BUG_ON().
But, I think that long time is necessary for this.
So, I propose this patch as a short-term solution.

With this patch:
 - To more stable Btrfs, the part that should be corrected is clarified.
 - The panic isn't done by the NULL pointer reference etc. (even if
   BUG_ON() is increased temporarily)
 - The error code is returned in the place where the error can be easily
   returned.

As a long-term plan:
 - BUG_ON() is reduced by using the forced-readonly framework, etc.

Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

6 files changed, 51 insertions, 13 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 2887b8be6fdd..b36eeef19194 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1550,6 +1550,7 @@ static int transaction_kthread(void *arg)
                 spin_unlock(&root->fs_info->new_trans_lock);
 
                 trans = btrfs_join_transaction(root, 1);
+                BUG_ON(IS_ERR(trans));
                 if (transid == trans->transid) {
                         ret = btrfs_commit_transaction(trans, root);
                         BUG_ON(ret);
@@ -2464,10 +2465,14 @@ int btrfs_commit_super(struct btrfs_root *root)
         up_write(&root->fs_info->cleanup_work_sem);
 
         trans = btrfs_join_transaction(root, 1);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
         ret = btrfs_commit_transaction(trans, root);
         BUG_ON(ret);
         /* run commit again to drop the original snapshot */
         trans = btrfs_join_transaction(root, 1);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
         btrfs_commit_transaction(trans, root);
         ret = btrfs_write_and_wait_transaction(NULL, root);
         BUG_ON(ret);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index bcf303204f7f..98ee139885cc 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -7478,7 +7478,7 @@ int btrfs_drop_dead_reloc_roots(struct btrfs_root *root)
                 BUG_ON(reloc_root->commit_root != NULL);
                 while (1) {
                         trans = btrfs_join_transaction(root, 1);
-                        BUG_ON(!trans);
+                        BUG_ON(IS_ERR(trans));
 
                         mutex_lock(&root->fs_info->drop_mutex);
                         ret = btrfs_drop_snapshot(trans, reloc_root);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 2b7d251d6ad1..40fee137dd11 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -416,7 +416,7 @@ again:
         }
         if (start == 0) {
                 trans = btrfs_join_transaction(root, 1);
-                BUG_ON(!trans);
+                BUG_ON(IS_ERR(trans));
                 btrfs_set_trans_block_group(trans, inode);
                 trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
@@ -612,6 +612,7 @@ retry:
                             GFP_NOFS);
 
                 trans = btrfs_join_transaction(root, 1);
+                BUG_ON(IS_ERR(trans));
                 ret = btrfs_reserve_extent(trans, root,
                                            async_extent->compressed_size,
                                            async_extent->compressed_size,
@@ -771,7 +772,7 @@ static noinline int cow_file_range(struct inode *inode,
 
         BUG_ON(root == root->fs_info->tree_root);
         trans = btrfs_join_transaction(root, 1);
-        BUG_ON(!trans);
+        BUG_ON(IS_ERR(trans));
         btrfs_set_trans_block_group(trans, inode);
         trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
@@ -1049,7 +1050,7 @@ static noinline int run_delalloc_nocow(struct inode *inode,
         } else {
                 trans = btrfs_join_transaction(root, 1);
         }
-        BUG_ON(!trans);
+        BUG_ON(IS_ERR(trans));
 
         cow_start = (u64)-1;
         cur_offset = start;
@@ -1704,7 +1705,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
                                 trans = btrfs_join_transaction_nolock(root, 1);
                         else
                                 trans = btrfs_join_transaction(root, 1);
-                        BUG_ON(!trans);
+                        BUG_ON(IS_ERR(trans));
                         btrfs_set_trans_block_group(trans, inode);
                         trans->block_rsv = &root->fs_info->delalloc_block_rsv;
                         ret = btrfs_update_inode(trans, root, inode);
@@ -1721,6 +1722,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
                 trans = btrfs_join_transaction_nolock(root, 1);
         else
                 trans = btrfs_join_transaction(root, 1);
+        BUG_ON(IS_ERR(trans));
         btrfs_set_trans_block_group(trans, inode);
         trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
@@ -2382,6 +2384,7 @@ void btrfs_orphan_cleanup(struct btrfs_root *root)
 
         if (root->orphan_block_rsv || root->orphan_item_inserted) {
                 trans = btrfs_join_transaction(root, 1);
+                BUG_ON(IS_ERR(trans));
                 btrfs_end_transaction(trans, root);
         }
 
@@ -4350,6 +4353,8 @@ int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
                         trans = btrfs_join_transaction_nolock(root, 1);
                 else
                         trans = btrfs_join_transaction(root, 1);
+                if (IS_ERR(trans))
+                        return PTR_ERR(trans);
                 btrfs_set_trans_block_group(trans, inode);
                 if (nolock)
                         ret = btrfs_end_transaction_nolock(trans, root);
@@ -4375,6 +4380,7 @@ void btrfs_dirty_inode(struct inode *inode)
                 return;
 
         trans = btrfs_join_transaction(root, 1);
+        BUG_ON(IS_ERR(trans));
         btrfs_set_trans_block_group(trans, inode);
 
         ret = btrfs_update_inode(trans, root, inode);
@@ -5179,6 +5185,8 @@ again:
                                 em = NULL;
                                 btrfs_release_path(root, path);
                                 trans = btrfs_join_transaction(root, 1);
+                                if (IS_ERR(trans))
+                                        return ERR_CAST(trans);
                                 goto again;
                         }
                         map = kmap(page);
@@ -5283,8 +5291,8 @@ static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
         btrfs_drop_extent_cache(inode, start, start + len - 1, 0);
 
         trans = btrfs_join_transaction(root, 0);
-        if (!trans)
-                return ERR_PTR(-ENOMEM);
+        if (IS_ERR(trans))
+                return ERR_CAST(trans);
 
         trans->block_rsv = &root->fs_info->delalloc_block_rsv;
 
@@ -5508,7 +5516,7 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                  * while we look for nocow cross refs
                  */
                 trans = btrfs_join_transaction(root, 0);
-                if (!trans)
+                if (IS_ERR(trans))
                         goto must_cow;
 
                 if (can_nocow_odirect(trans, inode, start, len) == 1) {
@@ -5643,7 +5651,7 @@ again:
         BUG_ON(!ordered);
 
         trans = btrfs_join_transaction(root, 1);
-        if (!trans) {
+        if (IS_ERR(trans)) {
                 err = -ENOMEM;
                 goto out;
         }
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index edd82becbb9e..04b4fb9144a9 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -203,7 +203,7 @@ static int btrfs_ioctl_setflags(struct file *file, void __user *arg)
 
 
         trans = btrfs_join_transaction(root, 1);
-        BUG_ON(!trans);
+        BUG_ON(IS_ERR(trans));
 
         ret = btrfs_update_inode(trans, root, inode);
         BUG_ON(ret);
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 045c9c2b2d7e..ea9965430241 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2147,6 +2147,12 @@ again:
         }
 
         trans = btrfs_join_transaction(rc->extent_root, 1);
+        if (IS_ERR(trans)) {
+                if (!err)
+                        btrfs_block_rsv_release(rc->extent_root,
+                                                rc->block_rsv, num_bytes);
+                return PTR_ERR(trans);
+        }
 
         if (!err) {
                 if (num_bytes != rc->merging_rsv_size) {
@@ -3222,6 +3228,7 @@ truncate:
         trans = btrfs_join_transaction(root, 0);
         if (IS_ERR(trans)) {
                 btrfs_free_path(path);
+                ret = PTR_ERR(trans);
                 goto out;
         }
 
@@ -3628,6 +3635,7 @@ int prepare_to_relocate(struct reloc_control *rc)
         set_reloc_control(rc);
 
         trans = btrfs_join_transaction(rc->extent_root, 1);
+        BUG_ON(IS_ERR(trans));
         btrfs_commit_transaction(trans, rc->extent_root);
         return 0;
 }
@@ -3804,7 +3812,10 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
 
         /* get rid of pinned extents */
         trans = btrfs_join_transaction(rc->extent_root, 1);
-        btrfs_commit_transaction(trans, rc->extent_root);
+        if (IS_ERR(trans))
+                err = PTR_ERR(trans);
+        else
+                btrfs_commit_transaction(trans, rc->extent_root);
 out_free:
         btrfs_free_block_rsv(rc->extent_root, rc->block_rsv);
         btrfs_free_path(path);
@@ -4125,6 +4136,11 @@ int btrfs_recover_relocation(struct btrfs_root *root)
         set_reloc_control(rc);
 
         trans = btrfs_join_transaction(rc->extent_root, 1);
+        if (IS_ERR(trans)) {
+                unset_reloc_control(rc);
+                err = PTR_ERR(trans);
+                goto out_free;
+        }
 
         rc->merge_reloc_tree = 1;
 
@@ -4154,9 +4170,13 @@ int btrfs_recover_relocation(struct btrfs_root *root)
         unset_reloc_control(rc);
 
         trans = btrfs_join_transaction(rc->extent_root, 1);
-        btrfs_commit_transaction(trans, rc->extent_root);
-out:
+        if (IS_ERR(trans))
+                err = PTR_ERR(trans);
+        else
+                btrfs_commit_transaction(trans, rc->extent_root);
+out_free:
         kfree(rc);
+out:
         while (!list_empty(&reloc_roots)) {
                 reloc_root = list_entry(reloc_roots.next,
                                         struct btrfs_root, root_list);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index bae5c7b8bbe2..3d73c8d93bbb 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1161,6 +1161,11 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
         INIT_DELAYED_WORK(&ac->work, do_async_commit);
         ac->root = root;
         ac->newtrans = btrfs_join_transaction(root, 0);
+        if (IS_ERR(ac->newtrans)) {
+                int err = PTR_ERR(ac->newtrans);
+                kfree(ac);
+                return err;
+        }
 
         /* take transaction reference */
         mutex_lock(&root->fs_info->trans_mutex);