[2/2] btrfs: use num_extent_folios() in for loop bounds

Commit Message

David Sterba Feb. 25, 2025, 5:24 p.m. UTC

As the helper num_extent_folios() is now __pure, we can use it in for
loop without storing its value in a variable explicitly, the compiler
will do this for us.

The effects on btrfs.ko is -200 bytes and there are stack space savings
too:

btrfs_clone_extent_buffer                               -8 (32 -> 24)
btrfs_clear_buffer_dirty                                -8 (48 -> 40)
clear_extent_buffer_uptodate                            -8 (40 -> 32)
set_extent_buffer_dirty                                 -8 (32 -> 24)
write_one_eb                                            -8 (88 -> 80)
set_extent_buffer_uptodate                              -8 (40 -> 32)
read_extent_buffer_pages_nowait                        -16 (64 -> 48)
find_extent_buffer                                      -8 (32 -> 24)

Signed-off-by: David Sterba <[e-mail]>
---
 fs/btrfs/disk-io.c   |  3 +--
 fs/btrfs/extent_io.c | 48 +++++++++++++++++---------------------------
 2 files changed, 19 insertions(+), 32 deletions(-)

Patch

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index a799216aa264..91c7da1ced7d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -182,13 +182,12 @@  static int btrfs_repair_eb_io_failure(const struct extent_buffer *eb,
 				      int mirror_num)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
-	int num_folios = num_extent_folios(eb);
 	int ret = 0;
 
 	if (sb_rdonly(fs_info->sb))
 		return -EROFS;
 
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 		u64 start = max_t(u64, eb->start, folio_pos(folio));
 		u64 end = min_t(u64, eb->start + eb->len,
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 7b0aa332aedc..7fa4ce5d9ead 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1788,7 +1788,6 @@  static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
 	struct btrfs_bio *bbio;
-	const int num_folios = num_extent_folios(eb);
 
 	prepare_eb_write(eb);
 
@@ -1800,7 +1799,7 @@  static noinline_for_stack void write_one_eb(struct extent_buffer *eb,
 	wbc_init_bio(wbc, &bbio->bio);
 	bbio->inode = BTRFS_I(eb->fs_info->btree_inode);
 	bbio->file_offset = eb->start;
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 		u64 range_start = max_t(u64, eb->start, folio_pos(folio));
 		u32 range_len = min_t(u64, folio_pos(folio) + folio_size(folio),
@@ -2677,7 +2676,6 @@  __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
 struct extent_buffer *btrfs_clone_extent_buffer(const struct extent_buffer *src)
 {
 	struct extent_buffer *new;
-	int num_folios = num_extent_folios(src);
 	int ret;
 
 	new = __alloc_extent_buffer(src->fs_info, src->start, src->len);
@@ -2697,7 +2695,7 @@  struct extent_buffer *btrfs_clone_extent_buffer(const struct extent_buffer *src)
 		return NULL;
 	}
 
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(src); i++) {
 		struct folio *folio = new->folios[i];
 
 		ret = attach_extent_buffer_folio(new, folio, NULL);
@@ -2717,7 +2715,6 @@  struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 						  u64 start, unsigned long len)
 {
 	struct extent_buffer *eb;
-	int num_folios = 0;
 	int ret;
 
 	eb = __alloc_extent_buffer(fs_info, start, len);
@@ -2726,13 +2723,12 @@  struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 
 	ret = alloc_eb_folio_array(eb, false);
 	if (ret)
-		goto err;
+		goto out;
 
-	num_folios = num_extent_folios(eb);
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		ret = attach_extent_buffer_folio(eb, eb->folios[i], NULL);
 		if (ret < 0)
-			goto err;
+			goto out_detach;
 	}
 
 	set_extent_buffer_uptodate(eb);
@@ -2740,13 +2736,15 @@  struct extent_buffer *__alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 	set_bit(EXTENT_BUFFER_UNMAPPED, &eb->bflags);
 
 	return eb;
-err:
-	for (int i = 0; i < num_folios; i++) {
+
+out_detach:
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		if (eb->folios[i]) {
 			detach_extent_buffer_folio(eb, eb->folios[i]);
 			folio_put(eb->folios[i]);
 		}
 	}
+out:
 	kmem_cache_free(extent_buffer_cache, eb);
 	return NULL;
 }
@@ -2795,11 +2793,9 @@  static void check_buffer_tree_ref(struct extent_buffer *eb)
 
 static void mark_extent_buffer_accessed(struct extent_buffer *eb)
 {
-	int num_folios= num_extent_folios(eb);
-
 	check_buffer_tree_ref(eb);
 
-	for (int i = 0; i < num_folios; i++)
+	for (int i = 0; i < num_extent_folios(eb); i++)
 		folio_mark_accessed(eb->folios[i]);
 }
 
@@ -3032,7 +3028,6 @@  struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 					  u64 start, u64 owner_root, int level)
 {
 	unsigned long len = fs_info->nodesize;
-	int num_folios;
 	int attached = 0;
 	struct extent_buffer *eb;
 	struct extent_buffer *existing_eb = NULL;
@@ -3096,9 +3091,8 @@  struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 		goto out;
 	}
 
-	num_folios = num_extent_folios(eb);
 	/* Attach all pages to the filemap. */
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio;
 
 		ret = attach_eb_folio_to_filemap(eb, i, prealloc, &existing_eb);
@@ -3192,7 +3186,7 @@  struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
 	 * btree_release_folio will correctly detect that a page belongs to a
 	 * live buffer and won't free them prematurely.
 	 */
-	for (int i = 0; i < num_folios; i++)
+	for (int i = 0; i < num_extent_folios(eb); i++)
 		folio_unlock(eb->folios[i]);
 	return eb;
 
@@ -3338,7 +3332,6 @@  void btrfs_clear_buffer_dirty(struct btrfs_trans_handle *trans,
 			      struct extent_buffer *eb)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
-	const int num_folios = num_extent_folios(eb);
 
 	btrfs_assert_tree_write_locked(eb);
 
@@ -3365,7 +3358,7 @@  void btrfs_clear_buffer_dirty(struct btrfs_trans_handle *trans,
 	percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, -eb->len,
 				 fs_info->dirty_metadata_batch);
 
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 		bool last;
 
@@ -3383,14 +3376,12 @@  void btrfs_clear_buffer_dirty(struct btrfs_trans_handle *trans,
 
 void set_extent_buffer_dirty(struct extent_buffer *eb)
 {
-	int num_folios;
 	bool was_dirty;
 
 	check_buffer_tree_ref(eb);
 
 	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
 
-	num_folios = num_extent_folios(eb);
 	WARN_ON(atomic_read(&eb->refs) == 0);
 	WARN_ON(!test_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags));
 	WARN_ON(test_bit(EXTENT_BUFFER_ZONED_ZEROOUT, &eb->bflags));
@@ -3411,7 +3402,7 @@  void set_extent_buffer_dirty(struct extent_buffer *eb)
 		 */
 		if (subpage)
 			folio_lock(eb->folios[0]);
-		for (int i = 0; i < num_folios; i++)
+		for (int i = 0; i < num_extent_folios(eb); i++)
 			btrfs_meta_folio_set_dirty(eb->fs_info, eb->folios[i],
 						   eb->start, eb->len);
 		if (subpage)
@@ -3421,7 +3412,7 @@  void set_extent_buffer_dirty(struct extent_buffer *eb)
 					 eb->fs_info->dirty_metadata_batch);
 	}
 #ifdef CONFIG_BTRFS_DEBUG
-	for (int i = 0; i < num_folios; i++)
+	for (int i = 0; i < num_extent_folios(eb); i++)
 		ASSERT(folio_test_dirty(eb->folios[i]));
 #endif
 }
@@ -3429,10 +3420,9 @@  void set_extent_buffer_dirty(struct extent_buffer *eb)
 void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
-	int num_folios = num_extent_folios(eb);
 
 	clear_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 
 		if (!folio)
@@ -3445,10 +3435,9 @@  void clear_extent_buffer_uptodate(struct extent_buffer *eb)
 void set_extent_buffer_uptodate(struct extent_buffer *eb)
 {
 	struct btrfs_fs_info *fs_info = eb->fs_info;
-	int num_folios = num_extent_folios(eb);
 
 	set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 
 		btrfs_meta_folio_set_uptodate(fs_info, folio, eb->start, eb->len);
@@ -3496,7 +3485,6 @@  static void end_bbio_meta_read(struct btrfs_bio *bbio)
 int read_extent_buffer_pages_nowait(struct extent_buffer *eb, int mirror_num,
 				    const struct btrfs_tree_parent_check *check)
 {
-	const int num_folios = num_extent_folios(eb);
 	struct btrfs_bio *bbio;
 
 	if (test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
@@ -3537,7 +3525,7 @@  int read_extent_buffer_pages_nowait(struct extent_buffer *eb, int mirror_num,
 	bbio->inode = BTRFS_I(eb->fs_info->btree_inode);
 	bbio->file_offset = eb->start;
 	memcpy(&bbio->parent_check, check, sizeof(*check));
-	for (int i = 0; i < num_folios; i++) {
+	for (int i = 0; i < num_extent_folios(eb); i++) {
 		struct folio *folio = eb->folios[i];
 		u64 range_start = max_t(u64, eb->start, folio_pos(folio));
 		u32 range_len = min_t(u64, folio_pos(folio) + folio_size(folio),