| Message ID | 20220302164829.17524-2-gniebler@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: Introduce macro to iterate over slots | expand |
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
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) {