Btrfs: allocate extent state and check the result properly

It doesn't allocate extent_state and check the result properly:
- in set_extent_bit, it doesn't allocate extent_state if the path is not
  allowed wait

- in clear_extent_bit, it doesn't check the result after atomic-ly allocate,
  we trigger BUG_ON() if it's fail

- if allocate fail, we trigger BUG_ON instead of returning -ENOMEM since
  the return value of clear_extent_bit() is ignored by many callers

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index ba41da5..9ccea86 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -439,6 +439,15 @@ static int clear_state_bit(struct extent_io_tree *tree,
        return ret;
 }
 
+static struct extent_state *
+alloc_extent_state_atomic(struct extent_state *prealloc)
+{
+       if (!prealloc)
+               prealloc = alloc_extent_state(GFP_ATOMIC);
+
+       return prealloc;
+}
+
 /*
  * clear some bits on a range in the tree.  This may require splitting
  * or inserting elements in the tree, so the gfp mask is used to
@@ -476,8 +485,7 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 again:
        if (!prealloc && (mask & __GFP_WAIT)) {
                prealloc = alloc_extent_state(mask);
-               if (!prealloc)
-                       return -ENOMEM;
+               BUG_ON(!prealloc);
        }
 
        spin_lock(&tree->lock);
@@ -529,8 +537,8 @@ hit_next:
         */
 
        if (state->start < start) {
-               if (!prealloc)
-                       prealloc = alloc_extent_state(GFP_ATOMIC);
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, start);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
@@ -551,8 +559,8 @@ hit_next:
         * on the first half
         */
        if (state->start <= end && state->end > end) {
-               if (!prealloc)
-                       prealloc = alloc_extent_state(GFP_ATOMIC);
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, end + 1);
                BUG_ON(err == -EEXIST);
                if (wake)
@@ -725,8 +733,7 @@ int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 again:
        if (!prealloc && (mask & __GFP_WAIT)) {
                prealloc = alloc_extent_state(mask);
-               if (!prealloc)
-                       return -ENOMEM;
+               BUG_ON(!prealloc);
        }
 
        spin_lock(&tree->lock);
@@ -743,6 +750,8 @@ again:
         */
        node = tree_search(tree, start);
        if (!node) {
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = insert_state(tree, prealloc, start, end, &bits);
                prealloc = NULL;
                BUG_ON(err == -EEXIST);
@@ -811,6 +820,9 @@ hit_next:
                        err = -EEXIST;
                        goto out;
                }
+
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, start);
                BUG_ON(err == -EEXIST);
                prealloc = NULL;
@@ -841,6 +853,9 @@ hit_next:
                        this_end = end;
                else
                        this_end = last_start - 1;
+
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = insert_state(tree, prealloc, start, this_end,
                                   &bits);
                BUG_ON(err == -EEXIST);
@@ -865,6 +880,9 @@ hit_next:
                        err = -EEXIST;
                        goto out;
                }
+
+               prealloc = alloc_extent_state_atomic(prealloc);
+               BUG_ON(!prealloc);
                err = split_state(tree, state, prealloc, end + 1);
                BUG_ON(err == -EEXIST);