btrfs: move ulists to data extent sharedness check context

When calling btrfs_is_data_extent_shared() we pass two ulists that were
allocated by the caller. This is because the single caller, fiemap, calls
btrfs_is_data_extent_shared() multiple times and the ulists can be reused,
instead of allocating new ones before each call and freeing them after
each call.

Now that we have a context structure/object that we pass to
btrfs_is_data_extent_shared(), we can move those ulists to it, and hide
their allocation and the context's allocation in a helper function, as
well as the freeing of the ulists and the context object. This allows to
reduce the number of parameters passed to btrfs_is_data_extent_shared(),
the need to pass the ulists from extent_fiemap() to fiemap_process_hole()
and having the caller deal with allocating and releasing the ulists.

Also rename one of the ulists from 'tmp' / 'tmp_ulist' to 'refs', since
that's a much better name as it reflects what the list is used for (and
matching the argument name for find_parent_nodes()).

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 32 insertions, 11 deletions

diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index 693c99ad4afb..4caff3052da7 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -1655,6 +1655,30 @@ static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx
 	}
 }
 
+struct btrfs_backref_share_check_ctx *btrfs_alloc_backref_share_check_ctx(void)
+{
+	struct btrfs_backref_share_check_ctx *ctx;
+
+	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	ulist_init(&ctx->refs);
+	ulist_init(&ctx->roots);
+
+	return ctx;
+}
+
+void btrfs_free_backref_share_ctx(struct btrfs_backref_share_check_ctx *ctx)
+{
+	if (!ctx)
+		return;
+
+	ulist_release(&ctx->refs);
+	ulist_release(&ctx->roots);
+	kfree(ctx);
+}
+
 /*
  * Check if a data extent is shared or not.
  *
@@ -1662,8 +1686,6 @@ static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx
  * @bytenr:      Logical bytenr of the extent we are checking.
  * @extent_gen:  Generation of the extent (file extent item) or 0 if it is
  *               not known.
- * @roots:       List of roots this extent is shared among.
- * @tmp:         Temporary list used for iteration.
  * @ctx:         A backref sharedness check context.
  *
  * btrfs_is_data_extent_shared uses the backref walking code but will short
@@ -1679,7 +1701,6 @@ static void store_backref_shared_cache(struct btrfs_backref_share_check_ctx *ctx
  */
 int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 				u64 extent_gen,
-				struct ulist *roots, struct ulist *tmp,
 				struct btrfs_backref_share_check_ctx *ctx)
 {
 	struct btrfs_root *root = inode->root;
@@ -1697,8 +1718,8 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 	};
 	int level;
 
-	ulist_init(roots);
-	ulist_init(tmp);
+	ulist_init(&ctx->roots);
+	ulist_init(&ctx->refs);
 
 	trans = btrfs_join_transaction_nostart(root);
 	if (IS_ERR(trans)) {
@@ -1720,8 +1741,8 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 		bool is_shared;
 		bool cached;
 
-		ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, tmp,
-					roots, NULL, &shared, false);
+		ret = find_parent_nodes(trans, fs_info, bytenr, elem.seq, &ctx->refs,
+					&ctx->roots, NULL, &shared, false);
 		if (ret == BACKREF_FOUND_SHARED) {
 			/* this is the only condition under which we return 1 */
 			ret = 1;
@@ -1760,13 +1781,13 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 		 * deal with), we can not use it if we have multiple leaves
 		 * (which implies multiple paths).
 		 */
-		if (level == -1 && tmp->nnodes > 1)
+		if (level == -1 && ctx->refs.nnodes > 1)
 			ctx->use_path_cache = false;
 
 		if (level >= 0)
 			store_backref_shared_cache(ctx, root, bytenr,
 						   level, false);
-		node = ulist_next(tmp, &uiter);
+		node = ulist_next(&ctx->refs, &uiter);
 		if (!node)
 			break;
 		bytenr = node->val;
@@ -1789,8 +1810,8 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr,
 		up_read(&fs_info->commit_root_sem);
 	}
 out:
-	ulist_release(roots);
-	ulist_release(tmp);
+	ulist_release(&ctx->roots);
+	ulist_release(&ctx->refs);
 	return ret;
 }