From: Filipe Manana <fdmanana@suse.com>
Date: Wed, 15 Apr 2026 12:31:05 +0000 (+0100)
Subject: btrfs: remove start field from struct btrfs_free_space_ctl
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=5e4b57f77ca3e39bde9681e4d79ea564bbd4fece;p=thirdparty%2Flinux.git

btrfs: remove start field from struct btrfs_free_space_ctl

There's no need for the start field, we can take it from the block group.
This reduces the structure size from 152 bytes down to 144 bytes, so on
a 4K page system we can now fit 28 structures instead of 26.

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

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 07567fd456347..af557a581e2cf 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -1568,10 +1568,10 @@ static inline u64 offset_to_bitmap(struct btrfs_free_space_ctl *ctl,
 	u64 bytes_per_bitmap;
 
 	bytes_per_bitmap = BITS_PER_BITMAP * ctl->unit;
-	bitmap_start = offset - ctl->start;
+	bitmap_start = offset - ctl->block_group->start;
 	bitmap_start = div64_u64(bitmap_start, bytes_per_bitmap);
 	bitmap_start *= bytes_per_bitmap;
-	bitmap_start += ctl->start;
+	bitmap_start += ctl->block_group->start;
 
 	return bitmap_start;
 }
@@ -2050,9 +2050,9 @@ again:
 		 * to match our requested alignment
 		 */
 		if (*bytes >= align) {
-			tmp = entry->offset - ctl->start + align - 1;
+			tmp = entry->offset - ctl->block_group->start + align - 1;
 			tmp = div64_u64(tmp, align);
-			tmp = tmp * align + ctl->start;
+			tmp = tmp * align + ctl->block_group->start;
 			align_off = tmp - entry->offset;
 		} else {
 			align_off = 0;
@@ -2947,7 +2947,6 @@ void btrfs_init_free_space_ctl(struct btrfs_block_group *block_group,
 
 	spin_lock_init(&ctl->tree_lock);
 	ctl->unit = fs_info->sectorsize;
-	ctl->start = block_group->start;
 	ctl->block_group = block_group;
 	ctl->op = &free_space_op;
 	ctl->free_space_bytes = RB_ROOT_CACHED;
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 33fc3b2456485..e75482fb2d69f 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -82,7 +82,6 @@ struct btrfs_free_space_ctl {
 	int free_extents;
 	int total_bitmaps;
 	int unit;
-	u64 start;
 	s32 discardable_extents[BTRFS_STAT_NR_ENTRIES];
 	s64 discardable_bytes[BTRFS_STAT_NR_ENTRIES];
 	const struct btrfs_free_space_op *op;