btrfs: use cached_state for btrfs_check_nocow_lock

Now that try_lock_extent() takes a cached_state, plumb the cached_state
through btrfs_try_lock_ordered_range() and then use a cached_state in
btrfs_check_nocow_lock everywhere to avoid extra tree searches on the
extent_io_tree.
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/file.c

@@ -1373,6 +1373,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	struct btrfs_root *root = inode->root;
+	struct extent_state *cached_state = NULL;
 	u64 lockstart, lockend;
 	u64 num_bytes;
 	int ret;
@@ -1389,12 +1390,14 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
 	num_bytes = lockend - lockstart + 1;
 
 	if (nowait) {
-		if (!btrfs_try_lock_ordered_range(inode, lockstart, lockend)) {
+		if (!btrfs_try_lock_ordered_range(inode, lockstart, lockend,
+						  &cached_state)) {
 			btrfs_drew_write_unlock(&root->snapshot_lock);
 			return -EAGAIN;
 		}
 	} else {
-		btrfs_lock_and_flush_ordered_range(inode, lockstart, lockend, NULL);
+		btrfs_lock_and_flush_ordered_range(inode, lockstart, lockend,
+						   &cached_state);
 	}
 	ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes,
 			NULL, NULL, NULL, nowait, false);
@@ -1403,7 +1406,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos,
 	else
 		*write_bytes = min_t(size_t, *write_bytes ,
 				     num_bytes - pos + lockstart);
-	unlock_extent(&inode->io_tree, lockstart, lockend, NULL);
+	unlock_extent(&inode->io_tree, lockstart, lockend, &cached_state);
 
 	return ret;
 }

fs/btrfs/ordered-data.c

@@ -1069,11 +1069,12 @@ void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
  * Return true if btrfs_lock_ordered_range does not return any extents,
  * otherwise false.
  */
-bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end)
+bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end,
+				  struct extent_state **cached_state)
 {
 	struct btrfs_ordered_extent *ordered;
 
-	if (!try_lock_extent(&inode->io_tree, start, end, NULL))
+	if (!try_lock_extent(&inode->io_tree, start, end, cached_state))
 		return false;
 
 	ordered = btrfs_lookup_ordered_range(inode, start, end - start + 1);
@@ -1081,7 +1082,7 @@ bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end)
 		return true;
 
 	btrfs_put_ordered_extent(ordered);
-	unlock_extent(&inode->io_tree, start, end, NULL);
+	unlock_extent(&inode->io_tree, start, end, cached_state);
 
 	return false;
 }

fs/btrfs/ordered-data.h

@@ -206,7 +206,8 @@ void btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr,
 void btrfs_lock_and_flush_ordered_range(struct btrfs_inode *inode, u64 start,
 					u64 end,
 					struct extent_state **cached_state);
-bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end);
+bool btrfs_try_lock_ordered_range(struct btrfs_inode *inode, u64 start, u64 end,
+				  struct extent_state **cached_state);
 int btrfs_split_ordered_extent(struct btrfs_ordered_extent *ordered, u64 pre,
 			       u64 post);
 int __init ordered_data_init(void);