[PATCH v3 0/14] btrfs: Introduce macro to iterate over slots

[PATCH v3 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 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       |  33 +++++++
 fs/btrfs/ctree.h       |  24 ++++++
 fs/btrfs/dev-replace.c |  41 ++-------
 fs/btrfs/dir-item.c    |  31 ++-----
 fs/btrfs/inode.c       |  35 +++-----
 fs/btrfs/send.c        | 229 ++++++++++++++-----------------------------------
 fs/btrfs/volumes.c     |  26 ++----
 fs/btrfs/xattr.c       |  41 +++------
 9 files changed, 168 insertions(+), 318 deletions(-)

[PATCH v3 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 | 33 +++++++++++++++++++++++++++++++++
 fs/btrfs/ctree.h | 24 ++++++++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index a7db3f6f1b7b..d735bd472616 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -2277,6 +2277,39 @@ 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 947f04789389..98091334b749 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2976,6 +2976,30 @@ 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 v3 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 v3 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 | 41 ++++++++---------------------------------
 1 file changed, 8 insertions(+), 33 deletions(-)

diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 62b9651ea662..3357739f427f 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 +533,25 @@ 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 v3 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..d7a24f17292d 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 v3 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 76e530f76e3c..144ca1a9d57f 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) {
@@ -5838,8 +5821,10 @@ 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);
 
-- 
2.35.1

[PATCH v3 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 | 38 +++++++++++---------------------------
 1 file changed, 11 insertions(+), 27 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 201eb2628aea..09715d98145a 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2680,61 +2680,45 @@ 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;
+		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 v3 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 09715d98145a..7b6d1a65793e 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -2922,6 +2922,7 @@ 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;
@@ -2948,23 +2949,9 @@ 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;
@@ -2999,8 +2986,10 @@ 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 v3 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 7b6d1a65793e..bb797f411daf 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3557,7 +3557,7 @@ 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.
  */
@@ -3569,6 +3569,7 @@ 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;
 
@@ -3589,26 +3590,12 @@ 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 &&
@@ -3646,10 +3633,12 @@ 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 v3 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 bb797f411daf..e54f168b6fc6 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4518,13 +4518,12 @@ 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;
 
@@ -4540,7 +4539,7 @@ 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;
 	}
@@ -4548,24 +4547,7 @@ 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))
@@ -4574,8 +4556,11 @@ 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 v3 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 | 36 +++++++++---------------------------
 1 file changed, 9 insertions(+), 27 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index e54f168b6fc6..2057aca8c3eb 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4822,13 +4822,12 @@ 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)
@@ -4839,39 +4838,22 @@ 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 v3 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 | 38 +++++++++-----------------------------
 1 file changed, 9 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 2057aca8c3eb..7e40c73bb912 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -5899,13 +5899,12 @@ 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();
@@ -5915,41 +5914,22 @@ 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 v3 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 7e40c73bb912..af3668279875 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -6119,8 +6119,11 @@ 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();
@@ -6130,39 +6133,26 @@ 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, &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 v3 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 | 26 +++++++++-----------------
 1 file changed, 9 insertions(+), 17 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b07d382d53a8..302efb5881e9 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 +7619,17 @@ 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 +7654,11 @@ 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 v3 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 | 41 ++++++++++++-----------------------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 99abf41b89b9..4b894625b67b 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 +344,14 @@ 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 v3 0/14] btrfs: Introduce macro to iterate over slots

[David Sterba]

On Wed, Mar 02, 2022 at 05:48:15PM +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 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)

I still see some of the style issues not addressed in your version, I'll
point them out in the first example I find but it needs to be fixed in
all of them. Otherwise it looks good. As we're near the code freeze for
5.17 I'm not sure I could put it there so it's 5.18 at the latest.

Re: [PATCH v3 01/14] btrfs: Introduce btrfs_for_each_slot iterator macro

[David Sterba]

On Wed, Mar 02, 2022 at 05:48:16PM +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.
> 
> Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
> Signed-off-by: Gabriel Niebler <gniebler@suse.com>
> ---
>  fs/btrfs/ctree.c | 33 +++++++++++++++++++++++++++++++++
>  fs/btrfs/ctree.h | 24 ++++++++++++++++++++++++
>  2 files changed, 57 insertions(+)
> 
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index a7db3f6f1b7b..d735bd472616 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -2277,6 +2277,39 @@ int btrfs_search_backwards(struct btrfs_root *root, struct btrfs_key *key,
>  	return ret;
>  }
>  
> +/* Search for a valid slot for the given path.

Multi-line comments should start with
/*
 * Text ...
 * ...
 */

> + *
> + * @root: The root node of the tree.
> + * @key: Will contain a valid item if found.
> + * @path: The starting point to validate the slot.

Please align the descriptions, an example is here
https://btrfs.wiki.kernel.org/index.php/Development_notes#Comments

> + *
> + * 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];

Newline between declarations and statements.

> +		/* this is where we start walking through the path */

The comments should read like a sentence, so the first letter should be
uppercase unless it's an identifier.

> +		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 947f04789389..98091334b749 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -2976,6 +2976,30 @@ 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]++						  \

As the arguments can be more than just an identifier it's safer to put
them in ( ) in the definition, ie root/key/found_key/path/iter_ret
shouls be all (root) etc

Re: [PATCH v3 03/14] btrfs: Use btrfs_for_each_slot in mark_block_group_to_copy

[David Sterba]

On Wed, Mar 02, 2022 at 05:48:18PM +0100, Gabriel Niebler wrote:
> 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 | 41 ++++++++---------------------------------
>  1 file changed, 8 insertions(+), 33 deletions(-)
> 
> diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
> index 62b9651ea662..3357739f427f 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 +533,25 @@ 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;
>  	}

No { } around single statement conditions 'if'

Re: [PATCH v3 12/14] btrfs: Use btrfs_for_each_slot in btrfs_unlink_all_paths

[Josef Bacik]

On Wed, Mar 02, 2022 at 05:48:27PM +0100, Gabriel Niebler wrote:
> 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 7e40c73bb912..af3668279875 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -6119,8 +6119,11 @@ 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();
> @@ -6130,39 +6133,26 @@ 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, &key, 1,
>  					record_parent_ref, &ctx);

This patch is causing btrfs/168 to fail, this should be &found_key, not &key.
Thanks,

Josef