btrfs: Remove extent_io_ops::set_bit_hook extent_io callback

This callback is used to properly account delalloc extents for data
inodes (ordinary file inodes and freespace v1 inodes). Those can be
easily identified since they have their extent_io trees ->private_data
member point to the inode. Let's exploit this fact to remove the
needless indirection through extent_io_hooks and directly call the
function. Also give the function a name which reflects its purpose -
btrfs_set_delalloc_extent.

This patch also modified test_find_delalloc so that the extent_io_tree
used for testing doesn't have its ->private_data set which would have
caused a crash in btrfs_set_delalloc_extent due to the btrfs_inode->root
member not being initialised. The old version of the code also didn't
call set_bit_hook since the extent_io ops weren't set for the inode.  No
functional changes.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -3150,6 +3150,8 @@ int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *new_root,
 			     struct btrfs_root *parent_root,
 			     u64 new_dirid);
+void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
+			       unsigned *bits);
 int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 			 size_t size, struct bio *bio,
 			 unsigned long bio_flags);

fs/btrfs/extent_io.c

@@ -404,13 +404,6 @@ static void merge_state(struct extent_io_tree *tree,
 	}
 }
 
-static void set_state_cb(struct extent_io_tree *tree,
-			 struct extent_state *state, unsigned *bits)
-{
-	if (tree->ops && tree->ops->set_bit_hook)
-		tree->ops->set_bit_hook(tree->private_data, state, bits);
-}
-
 static void clear_state_cb(struct extent_io_tree *tree,
 			   struct extent_state *state, unsigned *bits)
 {
@@ -809,7 +802,9 @@ static void set_state_bits(struct extent_io_tree *tree,
 	unsigned bits_to_set = *bits & ~EXTENT_CTLBITS;
 	int ret;
 
-	set_state_cb(tree, state, bits);
+	if (tree->private_data && is_data_inode(tree->private_data))
+		btrfs_set_delalloc_extent(tree->private_data, state, bits);
+
 	if ((bits_to_set & EXTENT_DIRTY) && !(state->state & EXTENT_DIRTY)) {
 		u64 range = state->end - state->start + 1;
 		tree->dirty_bytes += range;

fs/btrfs/extent_io.h

@@ -106,8 +106,6 @@ struct extent_io_ops {
 	/*
 	 * Optional hooks, called if the pointer is not NULL
 	 */
-	void (*set_bit_hook)(void *private_data, struct extent_state *state,
-			     unsigned *bits);
 	void (*clear_bit_hook)(void *private_data,
 			struct extent_state *state,
 			unsigned *bits);

fs/btrfs/inode.c

@@ -1755,15 +1755,12 @@ static void btrfs_del_delalloc_inode(struct btrfs_root *root,
 }
 
 /*
- * extent_io.c set_bit_hook, used to track delayed allocation
- * bytes in this file, and to maintain the list of inodes that
- * have pending delalloc work to be done.
+ * Properly track delayed allocation bytes in the inode and to maintain the
+ * list of inodes that have pending delalloc work to be done.
  */
-static void btrfs_set_bit_hook(void *private_data,
-			       struct extent_state *state, unsigned *bits)
+void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
+			       unsigned *bits)
 {
-	struct inode *inode = private_data;
-
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 
 	if ((*bits & EXTENT_DEFRAG) && !(*bits & EXTENT_DELALLOC))
@@ -10512,7 +10509,6 @@ static const struct extent_io_ops btrfs_extent_io_ops = {
 	.readpage_io_failed_hook = btrfs_readpage_io_failed_hook,
 
 	/* optional callbacks */
-	.set_bit_hook = btrfs_set_bit_hook,
 	.clear_bit_hook = btrfs_clear_bit_hook,
 	.merge_extent_hook = btrfs_merge_extent_hook,
 	.split_extent_hook = btrfs_split_extent_hook,

fs/btrfs/tests/extent-io-tests.c

@@ -76,7 +76,7 @@ static int test_find_delalloc(u32 sectorsize)
 		return -ENOMEM;
 	}
 
-	extent_io_tree_init(&tmp, inode);
+	extent_io_tree_init(&tmp, NULL);
 
 	/*
 	 * First go through and create and mark all of our pages dirty, we pin