[PATCHv2] btrfs: compression: allocate buckets with workspace

[PATCHv2] btrfs: compression: allocate buckets with workspace

[Rosen Penev]

Convert 3 allocations into one. Simplifies code slightly by removing
extra kfree calls.

SLUB merges same/similar sized structures for the named caches, so not
a huge size concern:

grep 2112 /proc/slabinfo
sighand_cache        593   1335   2112   15   8

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: use normal arrays
 fs/btrfs/compression.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index ffb6b52863a7..c62b5148d5ac 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -651,9 +651,9 @@ struct heuristic_ws {
 	u8 *sample;
 	u32 sample_size;
 	/* Buckets store counters for each byte value */
-	struct bucket_item *bucket;
+	struct bucket_item bucket[BUCKET_SIZE];
 	/* Sorting buffer */
-	struct bucket_item *bucket_b;
+	struct bucket_item bucket_b[BUCKET_SIZE];
 	struct list_head list;
 };
 
@@ -664,8 +664,6 @@ static void free_heuristic_ws(struct list_head *ws)
 	workspace = list_entry(ws, struct heuristic_ws, list);
 
 	kvfree(workspace->sample);
-	kfree(workspace->bucket);
-	kfree(workspace->bucket_b);
 	kfree(workspace);
 }
 
@@ -681,14 +679,6 @@ static struct list_head *alloc_heuristic_ws(struct btrfs_fs_info *fs_info)
 	if (!ws->sample)
 		goto fail;
 
-	ws->bucket = kzalloc_objs(*ws->bucket, BUCKET_SIZE);
-	if (!ws->bucket)
-		goto fail;
-
-	ws->bucket_b = kzalloc_objs(*ws->bucket_b, BUCKET_SIZE);
-	if (!ws->bucket_b)
-		goto fail;
-
 	INIT_LIST_HEAD(&ws->list);
 	return &ws->list;
 fail:
-- 
2.55.0

Re: [PATCHv2] btrfs: compression: allocate buckets with workspace

[David Sterba]

On Fri, Jul 03, 2026 at 03:45:57PM -0700, Rosen Penev wrote:
> Convert 3 allocations into one. Simplifies code slightly by removing
> extra kfree calls.
> 
> SLUB merges same/similar sized structures for the named caches, so not
> a huge size concern:
> 
> grep 2112 /proc/slabinfo
> sighand_cache        593   1335   2112   15   8
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

With slightly updated changelog merged to for-next, thanks.