[PATCH v4 0/14] btrfs: Introduce macro to iterate over slots

[PATCH v4 0/14] btrfs: Introduce macro to iterate over slots

[Gabriel Niebler]

There is a common pattern when searching for a key in btrfs:

* Call btrfs_search_slot to find the slot for the key
* Enter an endless loop:
	* If the found slot is larger than the no. of items in the current leaf,
	  check the next leaf
	* If it's still not found in the next leaf, terminate the loop
	* Otherwise do something with the found key
	* Increment the current slot and continue

To reduce code duplication, we can replace this code pattern with an iterator
macro, similar to the existing for_each_X macros found elsewhere in the kernel.
This also makes the code easier to understand for newcomers by putting a name
to the encapsulated functionality.

This patchset survived a complete fstest run.

Changes from v3:
 * Surround arguments with (…) in iterator macro definition (David)
 * Fix btrfs_unlink_all_paths after key/found_key confusion broke btrfs/168
   (Josef)
 * Various stylistic improvements (David)
 
Changes from v2:
 * Rename btrfs_valid_slot to btrfs_get_next_valid_item (Nikolay)
 * Fix comment formatting (David)
 * Remove redundant parentheses and indentation in loop condition (David)
 * Remove redundant iter_ret var and reuse ret instead (Nikolay)
 * Make termination condition more consistent in btrfs_unlink_all_paths
   (Nikolay)
 * Improved patch organisation by splitting into one patch per function (David)
 * Improve doc comment for btrfs_get_next_valid_item (Gabriel)
 * Remove `out` label and assoc. gotos from id_create_dir (Gabriel)
 * Initialise `ret` in process_all_refs and process_all_new_xattrs (Gabriel)
 * Remove unneeded btrfs_item_key_to_cpu call from loop body in
   btrfs_read_chunk_tree (Gabriel)

Changes from v1:
 * Separate xattr changes from the macro introducing code (Johannes)

Changes from RFC:
 * Add documentation to btrfs_for_each_slot macro and btrfs_valid_slot function
   (David)
 * Add documentation about the ret variable used as a macro argument (David)
 * Match function argument from prototype and implementation (David)
 * Changed ({ }) block to only () in btrfs_for_each_slot macro (David)
 * Add more patches to show the code being reduced by using this approach
   (Nikolay)

Marcos Paulo de Souza (14):
  btrfs: Introduce btrfs_for_each_slot iterator macro
  btrfs: Use btrfs_for_each_slot in find_first_block_group
  btrfs: Use btrfs_for_each_slot in mark_block_group_to_copy
  btrfs: Use btrfs_for_each_slot in btrfs_search_dir_index_item
  btrfs: Use btrfs_for_each_slot in btrfs_real_readdir
  btrfs: Use btrfs_for_each_slot in did_create_dir
  btrfs: Use btrfs_for_each_slot in can_rmdir
  btrfs: Use btrfs_for_each_slot in is_ancestor
  btrfs: Use btrfs_for_each_slot in process_all_refs
  btrfs: Use btrfs_for_each_slot in process_all_new_xattrs
  btrfs: Use btrfs_for_each_slot in process_all_extents
  btrfs: Use btrfs_for_each_slot in btrfs_unlink_all_paths
  btrfs: Use btrfs_for_each_slot in btrfs_read_chunk_tree
  btrfs: Use btrfs_for_each_slot in btrfs_listxattr

 fs/btrfs/block-group.c |  26 +-----
 fs/btrfs/ctree.c       |  35 ++++++++
 fs/btrfs/ctree.h       |  25 ++++++
 fs/btrfs/dev-replace.c |  40 ++-------
 fs/btrfs/dir-item.c    |  31 ++-----
 fs/btrfs/inode.c       |  35 +++-----
 fs/btrfs/send.c        | 229 +++++++++++++------------------------------------
 fs/btrfs/volumes.c     |  25 ++----
 fs/btrfs/xattr.c       |  40 +++------
 9 files changed, 167 insertions(+), 319 deletions(-)

[PATCH v4 01/14] btrfs: Introduce btrfs_for_each_slot iterator macro

[Gabriel Niebler]

There is a common pattern when searching for a key in btrfs:

* Call btrfs_search_slot to find the slot for the key
* Enter an endless loop:
	* If the found slot is larger than the no. of items in the current leaf,
	  check the next leaf
	* If it's still not found in the next leaf, terminate the loop
	* Otherwise do something with the found key
	* Increment the current slot and continue

To reduce code duplication, we can replace this code pattern with an iterator
macro, similar to the existing for_each_X macros found elsewhere in the kernel.
This also makes the code easier to understand for newcomers by putting a name
to the encapsulated functionality.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/ctree.c | 35 +++++++++++++++++++++++++++++++++++
 fs/btrfs/ctree.h | 25 +++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a7db3f6f1b7b..13f1011bf2b4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2277,6 +2277,41 @@ int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key,
 	return ret;
 }
 
+/*
+ * Search for a valid slot for the given path.
+ *
+ * @root:	The root node of the tree.
+ * @key:	Will contain a valid item if found.
+ * @path:	The starting point to validate the slot.
+ *
+ * Return 0 if the item is valid, 1 if not found and < 0 if error.
+ */
+int btrfs_get_next_valid_item(struct btrfs_root *root, struct btrfs_key *key,
+			      struct btrfs_path *path)
+{
+	while (1) {
+		int ret;
+		const int slot = path->slots[0];
+		const struct extent_buffer *leaf = path->nodes[0];
+
+		/* This is where we start walking through the path. */
+		if (slot >= btrfs_header_nritems(leaf)) {
+			/*
+			 * If we've reached the last slot in this leaf we need
+			 * to go to the next leaf and reset the path.
+			 */
+			ret = btrfs_next_leaf(root, path);
+			if (ret)
+				return ret;
+			continue;
+		}
+		/* Store the found, valid item in @key. */
+		btrfs_item_key_to_cpu(leaf, key, slot);
+		break;
+	}
+	return 0;
+}
+
 /*
  * adjust the pointers going up the tree, starting at level
  * making sure the right key of each node is points to 'key'.
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ebb2d109e8bb..5bacfa69457c 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2986,6 +2986,31 @@ int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
 int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key,
 			   struct btrfs_path *path);
 
+int btrfs_get_next_valid_item(struct btrfs_root *root, struct btrfs_key *key,
+			      struct btrfs_path *path);
+
+/*
+ * Search in @root for a given @key, and store the slot found in @found_key.
+ *
+ * @root:	The root node of the tree.
+ * @key:	The key we are looking for.
+ * @found_key:	Will hold the found item.
+ * @path:	Holds the current slot/leaf.
+ * @iter_ret:	Contains the value returned from btrfs_search_slot or
+ * 		btrfs_get_next_valid_item, whichever was executed last.
+ *
+ * The iter_ret is an output variable that will contain the return value of
+ * btrfs_search_slot, if it encountered an error, or the value returned from
+ * btrfs_get_next_valid_item, otherwise. That return value can be 0, if a valid
+ * slot was found, 1 if there were no more leaves, and <0 if there was an error.
+ */
+#define btrfs_for_each_slot(root, key, found_key, path, iter_ret)		\
+	for (iter_ret = btrfs_search_slot(NULL, (root), (key), (path), 0, 0);	\
+		(iter_ret) >= 0 &&						\
+		(iter_ret = btrfs_get_next_valid_item((root), (found_key), (path))) == 0; \
+		(path)->slots[0]++						\
+	)
+
 static inline int btrfs_next_old_item(struct btrfs_root *root,
 				      struct btrfs_path *p, u64 time_seq)
 {
-- 
2.35.1

[PATCH V4 02/14] btrfs: Use btrfs_for_each_slot in find_first_block_group

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/block-group.c | 26 ++------------------------
 1 file changed, 2 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 8202ad6aa131..aafd7909d0f8 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1686,35 +1686,13 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info,
 	struct btrfs_root *root = btrfs_block_group_root(fs_info);
 	int ret;
 	struct btrfs_key found_key;
-	struct extent_buffer *leaf;
-	int slot;
-
-	ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
-	if (ret < 0)
-		return ret;
-
-	while (1) {
-		slot = path->slots[0];
-		leaf = path->nodes[0];
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret == 0)
-				continue;
-			if (ret < 0)
-				goto out;
-			break;
-		}
-		btrfs_item_key_to_cpu(leaf, &found_key, slot);
 
+	btrfs_for_each_slot(root, key, &found_key, path, ret) {
 		if (found_key.objectid >= key->objectid &&
 		    found_key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
-			ret = read_bg_from_eb(fs_info, &found_key, path);
-			break;
+			return read_bg_from_eb(fs_info, &found_key, path);
 		}
-
-		path->slots[0]++;
 	}
-out:
 	return ret;
 }
 
-- 
2.35.1

[PATCH v4 03/14] btrfs: Use btrfs_for_each_slot in mark_block_group_to_copy

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/dev-replace.c | 40 +++++++---------------------------------
 1 file changed, 7 insertions(+), 33 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 62b9651ea662..3fb807dc5243 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -470,6 +470,7 @@ static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 	struct btrfs_dev_extent *dev_extent = NULL;
 	struct btrfs_block_group *cache;
 	struct btrfs_trans_handle *trans;
+	int iter_ret = 0;
 	int ret = 0;
 	u64 chunk_offset;
 
@@ -520,29 +521,8 @@ static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 	key.type = BTRFS_DEV_EXTENT_KEY;
 	key.offset = 0;
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto free_path;
-	if (ret > 0) {
-		if (path->slots[0] >=
-		    btrfs_header_nritems(path->nodes[0])) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto free_path;
-			if (ret > 0) {
-				ret = 0;
-				goto free_path;
-			}
-		} else {
-			ret = 0;
-		}
-	}
-
-	while (1) {
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		struct extent_buffer *leaf = path->nodes[0];
-		int slot = path->slots[0];
-
-		btrfs_item_key_to_cpu(leaf, &found_key, slot);
 
 		if (found_key.objectid != src_dev->devid)
 			break;
@@ -553,30 +533,24 @@ static int mark_block_group_to_copy(struct btrfs_fs_info *fs_info,
 		if (found_key.offset < key.offset)
 			break;
 
-		dev_extent = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
+		dev_extent = btrfs_item_ptr(leaf, path->slots[0],
+					    struct btrfs_dev_extent);
 
 		chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dev_extent);
 
 		cache = btrfs_lookup_block_group(fs_info, chunk_offset);
 		if (!cache)
-			goto skip;
+			continue;
 
 		spin_lock(&cache->lock);
 		cache->to_copy = 1;
 		spin_unlock(&cache->lock);
 
 		btrfs_put_block_group(cache);
-
-skip:
-		ret = btrfs_next_item(root, path);
-		if (ret != 0) {
-			if (ret > 0)
-				ret = 0;
-			break;
-		}
 	}
+	if (iter_ret < 0)
+		ret = iter_ret;
 
-free_path:
 	btrfs_free_path(path);
 unlock:
 	mutex_unlock(&fs_info->chunk_mutex);
-- 
2.35.1

[PATCH v4 04/14] btrfs: Use btrfs_for_each_slot in btrfs_search_dir_index_item

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/dir-item.c | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
index 3b532bab0755..7f1e6c48910f 100644
--- a/fs/btrfs/dir-item.c
+++ b/fs/btrfs/dir-item.c
@@ -325,36 +325,15 @@ btrfs_search_dir_index_item(struct btrfs_root *root,
 			    struct btrfs_path *path, u64 dirid,
 			    const char *name, int name_len)
 {
-	struct extent_buffer *leaf;
 	struct btrfs_dir_item *di;
 	struct btrfs_key key;
-	u32 nritems;
 	int ret;
 
 	key.objectid = dirid;
 	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = 0;
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		return ERR_PTR(ret);
-
-	leaf = path->nodes[0];
-	nritems = btrfs_header_nritems(leaf);
-
-	while (1) {
-		if (path->slots[0] >= nritems) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				return ERR_PTR(ret);
-			if (ret > 0)
-				break;
-			leaf = path->nodes[0];
-			nritems = btrfs_header_nritems(leaf);
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+	btrfs_for_each_slot(root, &key, &key, path, ret) {
 		if (key.objectid != dirid || key.type != BTRFS_DIR_INDEX_KEY)
 			break;
 
@@ -362,10 +341,12 @@ btrfs_search_dir_index_item(struct btrfs_root *root,
 					       name, name_len);
 		if (di)
 			return di;
-
-		path->slots[0]++;
 	}
-	return NULL;
+	/* Fix return code if key was not found in next leaf. */
+	if (ret > 0)
+		ret = 0;
+
+	return ERR_PTR(ret);
 }
 
 struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
-- 
2.35.1

[PATCH v4 05/14] btrfs: Use btrfs_for_each_slot in btrfs_real_readdir

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/inode.c | 35 ++++++++++-------------------------
 1 file changed, 10 insertions(+), 25 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5bbea5ec31fc..ca0de91eeece 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5755,8 +5755,6 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 	struct list_head ins_list;
 	struct list_head del_list;
 	int ret;
-	struct extent_buffer *leaf;
-	int slot;
 	char *name_ptr;
 	int name_len;
 	int entries = 0;
@@ -5783,35 +5781,20 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 	key.offset = ctx->pos;
 	key.objectid = btrfs_ino(BTRFS_I(inode));
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto err;
-
-	while (1) {
+	btrfs_for_each_slot(root, &key, &found_key, path, ret) {
 		struct dir_entry *entry;
-
-		leaf = path->nodes[0];
-		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto err;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(leaf, &found_key, slot);
+		struct extent_buffer *leaf = path->nodes[0];
 
 		if (found_key.objectid != key.objectid)
 			break;
 		if (found_key.type != BTRFS_DIR_INDEX_KEY)
 			break;
 		if (found_key.offset < ctx->pos)
-			goto next;
+			continue;
 		if (btrfs_should_delete_dir_index(&del_list, found_key.offset))
-			goto next;
-		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
+			continue;
+		di = btrfs_item_ptr(leaf, path->slots[0],
+				    struct btrfs_dir_item);
 		name_len = btrfs_dir_name_len(leaf, di);
 		if ((total_len + sizeof(struct dir_entry) + name_len) >=
 		    PAGE_SIZE) {
@@ -5838,9 +5821,11 @@ static int btrfs_real_readdir(struct file *file, struct dir_context *ctx)
 		entries++;
 		addr += sizeof(struct dir_entry) + name_len;
 		total_len += sizeof(struct dir_entry) + name_len;
-next:
-		path->slots[0]++;
 	}
+	/* Catch error encountered while searching */
+	if (ret < 0)
+		goto err;
+
 	btrfs_release_path(path);
 
 	ret = btrfs_filldir(private->filldir_buf, entries, ctx);
-- 
2.35.1

[PATCH v4 06/14] btrfs: Use btrfs_for_each_slot in did_create_dir

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 40 +++++++++++-----------------------------
 1 file changed, 11 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 201eb2628aea..417aed3ab592 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2680,61 +2680,43 @@ static int send_create_inode(struct send_ctx *sctx, u64 ino)
 static int did_create_dir(struct send_ctx *sctx, u64 dir)
 {
 	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_path *path = NULL;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
 	struct btrfs_key di_key;
-	struct extent_buffer *eb;
 	struct btrfs_dir_item *di;
-	int slot;
 
 	path = alloc_path_for_send();
-	if (!path) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (!path)
+		return -ENOMEM;
 
 	key.objectid = dir;
 	key.type = BTRFS_DIR_INDEX_KEY;
 	key.offset = 0;
-	ret = btrfs_search_slot(NULL, sctx->send_root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
 
-	while (1) {
-		eb = path->nodes[0];
-		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(eb)) {
-			ret = btrfs_next_leaf(sctx->send_root, path);
-			if (ret < 0) {
-				goto out;
-			} else if (ret > 0) {
-				ret = 0;
-				break;
-			}
-			continue;
-		}
+	btrfs_for_each_slot(sctx->send_root, &key, &found_key, path, iter_ret) {
+		struct extent_buffer *eb = path->nodes[0];
 
-		btrfs_item_key_to_cpu(eb, &found_key, slot);
 		if (found_key.objectid != key.objectid ||
 		    found_key.type != key.type) {
 			ret = 0;
-			goto out;
+			break;
 		}
 
-		di = btrfs_item_ptr(eb, slot, struct btrfs_dir_item);
+		di = btrfs_item_ptr(eb, path->slots[0], struct btrfs_dir_item);
 		btrfs_dir_item_key_to_cpu(eb, di, &di_key);
 
 		if (di_key.type != BTRFS_ROOT_ITEM_KEY &&
 		    di_key.objectid < sctx->send_progress) {
 			ret = 1;
-			goto out;
+			break;
 		}
-
-		path->slots[0]++;
 	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0)
+		ret = iter_ret;
 
-out:
 	btrfs_free_path(path);
 	return ret;
 }
-- 
2.35.1

[PATCH v4 07/14] btrfs: Use btrfs_for_each_slot in can_rmdir

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 23 ++++++-----------------
 1 file changed, 6 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 417aed3ab592..5ecb8e39f449 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2920,6 +2920,7 @@ static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 dir_gen,
 		     u64 send_progress)
 {
 	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_root *root = sctx->parent_root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
@@ -2946,23 +2947,9 @@ static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 dir_gen,
 	if (odi)
 		key.offset = odi->last_dir_index_offset;
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (1) {
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		struct waiting_dir_move *dm;
 
-		if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto out;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
-				      path->slots[0]);
 		if (found_key.objectid != key.objectid ||
 		    found_key.type != key.type)
 			break;
@@ -2997,8 +2984,10 @@ static int can_rmdir(struct send_ctx *sctx, u64 dir, u64 dir_gen,
 			ret = 0;
 			goto out;
 		}
-
-		path->slots[0]++;
+	}
+	if (iter_ret < 0) {
+		ret = iter_ret;
+		goto out;
 	}
 	free_orphan_dir_info(sctx, odi);
 
-- 
2.35.1

[PATCH v4 08/14] btrfs: Use btrfs_for_each_slot in is_ancestor

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 25 +++++++------------------
 1 file changed, 7 insertions(+), 18 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 5ecb8e39f449..cad9b36ebdf8 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3555,7 +3555,7 @@ static int check_ino_in_path(struct btrfs_root *root,
 }
 
 /*
- * Check if ino ino1 is an ancestor of inode ino2 in the given root for any
+ * Check if inode ino1 is an ancestor of inode ino2 in the given root for any
  * possible path (in case ino2 is not a directory and has multiple hard links).
  * Return 1 if true, 0 if false and < 0 on error.
  */
@@ -3567,6 +3567,7 @@ static int is_ancestor(struct btrfs_root *root,
 {
 	bool free_fs_path = false;
 	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_path *path = NULL;
 	struct btrfs_key key;
 
@@ -3587,26 +3588,12 @@ static int is_ancestor(struct btrfs_root *root,
 	key.type = BTRFS_INODE_REF_KEY;
 	key.offset = 0;
 
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (true) {
+	btrfs_for_each_slot(root, &key, &key, path, iter_ret) {
 		struct extent_buffer *leaf = path->nodes[0];
 		int slot = path->slots[0];
 		u32 cur_offset = 0;
 		u32 item_size;
 
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto out;
-			if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(leaf, &key, slot);
 		if (key.objectid != ino2)
 			break;
 		if (key.type != BTRFS_INODE_REF_KEY &&
@@ -3644,10 +3631,12 @@ static int is_ancestor(struct btrfs_root *root,
 			if (ret)
 				goto out;
 		}
-		path->slots[0]++;
 	}
 	ret = 0;
- out:
+	if (iter_ret < 0)
+		ret = iter_ret;
+
+out:
 	btrfs_free_path(path);
 	if (free_fs_path)
 		fs_path_free(fs_path);
-- 
2.35.1

[PATCH v4 09/14] btrfs: Use btrfs_for_each_slot in process_all_refs

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 33 +++++++++------------------------
 1 file changed, 9 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index cad9b36ebdf8..2e35edd8d08e 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4516,13 +4516,12 @@ static int record_changed_ref(struct send_ctx *sctx)
 static int process_all_refs(struct send_ctx *sctx,
 			    enum btrfs_compare_tree_result cmd)
 {
-	int ret;
+	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_root *root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
-	struct extent_buffer *eb;
-	int slot;
 	iterate_inode_ref_t cb;
 	int pending_move = 0;
 
@@ -4538,7 +4537,7 @@ static int process_all_refs(struct send_ctx *sctx,
 		cb = __record_deleted_ref;
 	} else {
 		btrfs_err(sctx->send_root->fs_info,
-				"Wrong command %d in process_all_refs", cmd);
+			  "Wrong command %d in process_all_refs", cmd);
 		ret = -EINVAL;
 		goto out;
 	}
@@ -4546,24 +4545,7 @@ static int process_all_refs(struct send_ctx *sctx,
 	key.objectid = sctx->cmp_key->objectid;
 	key.type = BTRFS_INODE_REF_KEY;
 	key.offset = 0;
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (1) {
-		eb = path->nodes[0];
-		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(eb)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto out;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(eb, &found_key, slot);
-
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		if (found_key.objectid != key.objectid ||
 		    (found_key.type != BTRFS_INODE_REF_KEY &&
 		     found_key.type != BTRFS_INODE_EXTREF_KEY))
@@ -4572,8 +4554,11 @@ static int process_all_refs(struct send_ctx *sctx,
 		ret = iterate_inode_ref(root, path, &found_key, 0, cb, sctx);
 		if (ret < 0)
 			goto out;
-
-		path->slots[0]++;
+	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0) {
+		ret = iter_ret;
+		goto out;
 	}
 	btrfs_release_path(path);
 
-- 
2.35.1

[PATCH v4 10/14] btrfs: Use btrfs_for_each_slot in process_all_new_xattrs

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 35 ++++++++---------------------------
 1 file changed, 8 insertions(+), 27 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 2e35edd8d08e..14c343cdf76c 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4820,13 +4820,12 @@ static int process_changed_xattr(struct send_ctx *sctx)
 
 static int process_all_new_xattrs(struct send_ctx *sctx)
 {
-	int ret;
+	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_root *root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
-	struct extent_buffer *eb;
-	int slot;
 
 	path = alloc_path_for_send();
 	if (!path)
@@ -4837,39 +4836,21 @@ static int process_all_new_xattrs(struct send_ctx *sctx)
 	key.objectid = sctx->cmp_key->objectid;
 	key.type = BTRFS_XATTR_ITEM_KEY;
 	key.offset = 0;
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (1) {
-		eb = path->nodes[0];
-		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(eb)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0) {
-				goto out;
-			} else if (ret > 0) {
-				ret = 0;
-				break;
-			}
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(eb, &found_key, slot);
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		if (found_key.objectid != key.objectid ||
 		    found_key.type != key.type) {
 			ret = 0;
-			goto out;
+			break;
 		}
 
 		ret = iterate_dir_item(root, path, __process_new_xattr, sctx);
 		if (ret < 0)
-			goto out;
-
-		path->slots[0]++;
+			break;
 	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0)
+		ret = iter_ret;
 
-out:
 	btrfs_free_path(path);
 	return ret;
 }
-- 
2.35.1

[PATCH v4 11/14] btrfs: Use btrfs_for_each_slot in process_all_extents

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 37 ++++++++-----------------------------
 1 file changed, 8 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 14c343cdf76c..573ea102f8ab 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5896,13 +5896,12 @@ static int process_extent(struct send_ctx *sctx,
 
 static int process_all_extents(struct send_ctx *sctx)
 {
-	int ret;
+	int ret = 0;
+	int iter_ret = 0;
 	struct btrfs_root *root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	struct btrfs_key found_key;
-	struct extent_buffer *eb;
-	int slot;
 
 	root = sctx->send_root;
 	path = alloc_path_for_send();
@@ -5912,41 +5911,21 @@ static int process_all_extents(struct send_ctx *sctx)
 	key.objectid = sctx->cmp_key->objectid;
 	key.type = BTRFS_EXTENT_DATA_KEY;
 	key.offset = 0;
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (1) {
-		eb = path->nodes[0];
-		slot = path->slots[0];
-
-		if (slot >= btrfs_header_nritems(eb)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0) {
-				goto out;
-			} else if (ret > 0) {
-				ret = 0;
-				break;
-			}
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(eb, &found_key, slot);
-
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		if (found_key.objectid != key.objectid ||
 		    found_key.type != key.type) {
 			ret = 0;
-			goto out;
+			break;
 		}
 
 		ret = process_extent(sctx, path, &found_key);
 		if (ret < 0)
-			goto out;
-
-		path->slots[0]++;
+			break;
 	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0)
+		ret = iter_ret;
 
-out:
 	btrfs_free_path(path);
 	return ret;
 }
-- 
2.35.1

[PATCH v4 12/14] btrfs: Use btrfs_for_each_slot in btrfs_unlink_all_paths

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/send.c | 36 +++++++++++++-----------------------
 1 file changed, 13 insertions(+), 23 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 573ea102f8ab..b339f919bb75 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -6115,8 +6115,11 @@ static int btrfs_unlink_all_paths(struct send_ctx *sctx)
 {
 	LIST_HEAD(deleted_refs);
 	struct btrfs_path *path;
+	struct btrfs_root *root = sctx->parent_root;
 	struct btrfs_key key;
+	struct btrfs_key found_key;
 	struct parent_paths_ctx ctx;
+	int iter_ret = 0;
 	int ret;
 
 	path = alloc_path_for_send();
@@ -6126,39 +6129,26 @@ static int btrfs_unlink_all_paths(struct send_ctx *sctx)
 	key.objectid = sctx->cur_ino;
 	key.type = BTRFS_INODE_REF_KEY;
 	key.offset = 0;
-	ret = btrfs_search_slot(NULL, sctx->parent_root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
 
 	ctx.refs = &deleted_refs;
 	ctx.sctx = sctx;
 
-	while (true) {
-		struct extent_buffer *eb = path->nodes[0];
-		int slot = path->slots[0];
-
-		if (slot >= btrfs_header_nritems(eb)) {
-			ret = btrfs_next_leaf(sctx->parent_root, path);
-			if (ret < 0)
-				goto out;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(eb, &key, slot);
-		if (key.objectid != sctx->cur_ino)
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
+		if (found_key.objectid != key.objectid)
 			break;
-		if (key.type != BTRFS_INODE_REF_KEY &&
-		    key.type != BTRFS_INODE_EXTREF_KEY)
+		if (found_key.type != key.type &&
+		    found_key.type != BTRFS_INODE_EXTREF_KEY)
 			break;
 
-		ret = iterate_inode_ref(sctx->parent_root, path, &key, 1,
+		ret = iterate_inode_ref(root, path, &found_key, 1,
 					record_parent_ref, &ctx);
 		if (ret < 0)
 			goto out;
-
-		path->slots[0]++;
+	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0) {
+		ret = iter_ret;
+		goto out;
 	}
 
 	while (!list_empty(&deleted_refs)) {
-- 
2.35.1

[PATCH v4 13/14] btrfs: Use btrfs_for_each_slot in btrfs_read_chunk_tree

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/volumes.c | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b07d382d53a8..3185ececc672 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7575,6 +7575,7 @@ int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
 	struct btrfs_key found_key;
 	int ret;
 	int slot;
+	int iter_ret = 0;
 	u64 total_dev = 0;
 	u64 last_ra_node = 0;
 
@@ -7618,30 +7619,18 @@ int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
 	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
 	key.offset = 0;
 	key.type = 0;
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto error;
-	while (1) {
-		struct extent_buffer *node;
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
+		struct extent_buffer *node = path->nodes[1];
 
 		leaf = path->nodes[0];
 		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret == 0)
-				continue;
-			if (ret < 0)
-				goto error;
-			break;
-		}
-		node = path->nodes[1];
+
 		if (node) {
 			if (last_ra_node != node->start) {
 				readahead_tree_node_children(node);
 				last_ra_node = node->start;
 			}
 		}
-		btrfs_item_key_to_cpu(leaf, &found_key, slot);
 		if (found_key.type == BTRFS_DEV_ITEM_KEY) {
 			struct btrfs_dev_item *dev_item;
 			dev_item = btrfs_item_ptr(leaf, slot,
@@ -7666,7 +7655,11 @@ int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
 			if (ret)
 				goto error;
 		}
-		path->slots[0]++;
+	}
+	/* Catch error found on iteration */
+	if (iter_ret < 0) {
+		ret = iter_ret;
+		goto error;
 	}
 
 	/*
-- 
2.35.1

[PATCH v4 14/14] btrfs: Use btrfs_for_each_slot in btrfs_listxattr

[Gabriel Niebler]

This function can be simplified by refactoring to use the new iterator macro.

No functional changes.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: Gabriel Niebler <gniebler@suse.com>
---
 fs/btrfs/xattr.c | 40 +++++++++++-----------------------------
 1 file changed, 11 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 99abf41b89b9..b96ffd775b41 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -271,10 +271,12 @@ int btrfs_setxattr_trans(struct inode *inode, const char *name,
 
 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 {
+	struct btrfs_key found_key;
 	struct btrfs_key key;
 	struct inode *inode = d_inode(dentry);
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 	struct btrfs_path *path;
+	int iter_ret = 0;
 	int ret = 0;
 	size_t total_size = 0, size_left = size;
 
@@ -293,44 +295,23 @@ ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 	path->reada = READA_FORWARD;
 
 	/* search for our xattrs */
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto err;
-
-	while (1) {
+	btrfs_for_each_slot(root, &key, &found_key, path, iter_ret) {
 		struct extent_buffer *leaf;
 		int slot;
 		struct btrfs_dir_item *di;
-		struct btrfs_key found_key;
 		u32 item_size;
 		u32 cur;
 
 		leaf = path->nodes[0];
 		slot = path->slots[0];
 
-		/* this is where we start walking through the path */
-		if (slot >= btrfs_header_nritems(leaf)) {
-			/*
-			 * if we've reached the last slot in this leaf we need
-			 * to go to the next leaf and reset everything
-			 */
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto err;
-			else if (ret > 0)
-				break;
-			continue;
-		}
-
-		btrfs_item_key_to_cpu(leaf, &found_key, slot);
-
 		/* check to make sure this item is what we want */
 		if (found_key.objectid != key.objectid)
 			break;
 		if (found_key.type > BTRFS_XATTR_ITEM_KEY)
 			break;
 		if (found_key.type < BTRFS_XATTR_ITEM_KEY)
-			goto next_item;
+			continue;
 
 		di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
 		item_size = btrfs_item_size(leaf, slot);
@@ -350,8 +331,8 @@ ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 				goto next;
 
 			if (!buffer || (name_len + 1) > size_left) {
-				ret = -ERANGE;
-				goto err;
+			        iter_ret = -ERANGE;
+				break;
 			}
 
 			read_extent_buffer(leaf, buffer, name_ptr, name_len);
@@ -363,12 +344,13 @@ ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 			cur += this_len;
 			di = (struct btrfs_dir_item *)((char *)di + this_len);
 		}
-next_item:
-		path->slots[0]++;
 	}
-	ret = total_size;
 
-err:
+	if (iter_ret < 0)
+		ret = iter_ret;
+	else
+		ret = total_size;
+
 	btrfs_free_path(path);
 
 	return ret;
-- 
2.35.1

Re: [PATCH v4 0/14] btrfs: Introduce macro to iterate over slots

[David Sterba]

On Wed, Mar 09, 2022 at 02:50:37PM +0100, Gabriel Niebler wrote:
> There is a common pattern when searching for a key in btrfs:
> 
> * Call btrfs_search_slot to find the slot for the key
> * Enter an endless loop:
> 	* If the found slot is larger than the no. of items in the current leaf,
> 	  check the next leaf
> 	* If it's still not found in the next leaf, terminate the loop
> 	* Otherwise do something with the found key
> 	* Increment the current slot and continue
> 
> To reduce code duplication, we can replace this code pattern with an iterator
> macro, similar to the existing for_each_X macros found elsewhere in the kernel.
> This also makes the code easier to understand for newcomers by putting a name
> to the encapsulated functionality.
> 
> This patchset survived a complete fstest run.
> 
> Changes from v3:
>  * Surround arguments with (…) in iterator macro definition (David)
>  * Fix btrfs_unlink_all_paths after key/found_key confusion broke btrfs/168
>    (Josef)
>  * Various stylistic improvements (David)

Added to misc-next with some fixups, thanks.