btrfs: replace many BUG_ONs with proper error handling

 btrfs currently handles most errors with BUG_ON. This patch is a work-in-
 progress but aims to handle most errors other than internal logic
 errors and ENOMEM more gracefully.

 This iteration prevents most crashes but can run into lockups with
 the page lock on occasion when the timing "works out."

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

1 files changed, 31 insertions, 14 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 0eb80cc4ec81..d83260d7498f 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -452,7 +452,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
                         split = alloc_extent_map();
                 if (!split2)
                         split2 = alloc_extent_map();
-                BUG_ON(!split || !split2);
+                BUG_ON(!split || !split2); /* -ENOMEM */
 
                 write_lock(&em_tree->lock);
                 em = lookup_extent_mapping(em_tree, start, len);
@@ -494,7 +494,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
                         split->flags = flags;
                         split->compress_type = em->compress_type;
                         ret = add_extent_mapping(em_tree, split);
-                        BUG_ON(ret);
+                        BUG_ON(ret); /* Logic error */
                         free_extent_map(split);
                         split = split2;
                         split2 = NULL;
@@ -520,7 +520,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
                         }
 
                         ret = add_extent_mapping(em_tree, split);
-                        BUG_ON(ret);
+                        BUG_ON(ret); /* Logic error */
                         free_extent_map(split);
                         split = NULL;
                 }
@@ -679,7 +679,7 @@ next_slot:
                                                 root->root_key.objectid,
                                                 new_key.objectid,
                                                 start - extent_offset, 0);
-                                BUG_ON(ret);
+                                BUG_ON(ret); /* -ENOMEM */
                                 *hint_byte = disk_bytenr;
                         }
                         key.offset = start;
@@ -754,7 +754,7 @@ next_slot:
                                                 root->root_key.objectid,
                                                 key.objectid, key.offset -
                                                 extent_offset, 0);
-                                BUG_ON(ret);
+                                BUG_ON(ret); /* -ENOMEM */
                                 inode_sub_bytes(inode,
                                                 extent_end - key.offset);
                                 *hint_byte = disk_bytenr;
@@ -770,7 +770,10 @@ next_slot:
 
                         ret = btrfs_del_items(trans, root, path, del_slot,
                                               del_nr);
-                        BUG_ON(ret);
+                        if (ret) {
+                                btrfs_abort_transaction(trans, root, ret);
+                                goto out;
+                        }
 
                         del_nr = 0;
                         del_slot = 0;
@@ -782,11 +785,13 @@ next_slot:
                 BUG_ON(1);
         }
 
-        if (del_nr > 0) {
+        if (!ret && del_nr > 0) {
                 ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
-                BUG_ON(ret);
+                if (ret)
+                        btrfs_abort_transaction(trans, root, ret);
         }
 
+out:
         btrfs_free_path(path);
         return ret;
 }
@@ -944,7 +949,10 @@ again:
                         btrfs_release_path(path);
                         goto again;
                 }
-                BUG_ON(ret < 0);
+                if (ret < 0) {
+                        btrfs_abort_transaction(trans, root, ret);
+                        goto out;
+                }
 
                 leaf = path->nodes[0];
                 fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
@@ -963,7 +971,7 @@ again:
                 ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0,
                                            root->root_key.objectid,
                                            ino, orig_offset, 0);
-                BUG_ON(ret);
+                BUG_ON(ret); /* -ENOMEM */
 
                 if (split == start) {
                         key.offset = start;
@@ -990,7 +998,7 @@ again:
                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
                                         0, root->root_key.objectid,
                                         ino, orig_offset, 0);
-                BUG_ON(ret);
+                BUG_ON(ret); /* -ENOMEM */
         }
         other_start = 0;
         other_end = start;
@@ -1007,7 +1015,7 @@ again:
                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
                                         0, root->root_key.objectid,
                                         ino, orig_offset, 0);
-                BUG_ON(ret);
+                BUG_ON(ret); /* -ENOMEM */
         }
         if (del_nr == 0) {
                 fi = btrfs_item_ptr(leaf, path->slots[0],
@@ -1025,7 +1033,10 @@ again:
                 btrfs_mark_buffer_dirty(leaf);
 
                 ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
-                BUG_ON(ret);
+                if (ret < 0) {
+                        btrfs_abort_transaction(trans, root, ret);
+                        goto out;
+                }
         }
 out:
         btrfs_free_path(path);
@@ -1666,7 +1677,13 @@ static long btrfs_fallocate(struct file *file, int mode,
 
                 em = btrfs_get_extent(inode, NULL, 0, cur_offset,
                                       alloc_end - cur_offset, 0);
-                BUG_ON(IS_ERR_OR_NULL(em));
+                if (IS_ERR_OR_NULL(em)) {
+                        if (!em)
+                                ret = -ENOMEM;
+                        else
+                                ret = PTR_ERR(em);
+                        break;
+                }
                 last_byte = min(extent_map_end(em), alloc_end);
                 actual_end = min_t(u64, extent_map_end(em), offset + len);
                 last_byte = (last_byte + mask) & ~mask;