[PATCHv2] scsi: st: use kzalloc_array()

[PATCHv2] scsi: st: use kzalloc_array()

[Rosen Penev]

Merge allocations to simpily memory management with kzalloc_array(). No
need to kfree separately.

Add __counted_by for extra runtime analysis. Move counting variable
assignment after allocation as kzalloc_flex() does this with newer
compilers.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: remove the kfree and add a description.
 drivers/scsi/st.c | 13 +++----------
 drivers/scsi/st.h |  3 ++-
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index f1c3c4946637..55238f23f743 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -149,7 +149,7 @@ static struct st_dev_parm {
    mode counts */
 static const char *st_formats[] = {
 	"",  "r", "k", "s", "l", "t", "o", "u",
-	"m", "v", "p", "x", "a", "y", "q", "z"};
+	"m", "v", "p", "x", "a", "y", "q", "z"};

 /* The default definitions have been moved to st_options.h */

@@ -3973,21 +3973,15 @@ static struct st_buffer *new_tape_buffer(int max_sg)
 {
 	struct st_buffer *tb;

-	tb = kzalloc_obj(struct st_buffer);
+	tb = kzalloc_flex(*tb, reserved_pages, max_sg);
 	if (!tb) {
 		printk(KERN_NOTICE "st: Can't allocate new tape buffer.\n");
 		return NULL;
 	}
-	tb->frp_segs = 0;
 	tb->use_sg = max_sg;
+	tb->frp_segs = 0;
 	tb->buffer_size = 0;

-	tb->reserved_pages = kzalloc_objs(struct page *, max_sg);
-	if (!tb->reserved_pages) {
-		kfree(tb);
-		return NULL;
-	}
-
 	return tb;
 }

@@ -4533,7 +4527,6 @@ static void scsi_tape_release(struct kref *kref)

 	if (tpnt->buffer) {
 		normalize_buffer(tpnt->buffer);
-		kfree(tpnt->buffer->reserved_pages);
 		kfree(tpnt->buffer);
 	}

diff --git a/drivers/scsi/st.h b/drivers/scsi/st.h
index 0d7c4b8c2c8a..759f4c43d563 100644
--- a/drivers/scsi/st.h
+++ b/drivers/scsi/st.h
@@ -45,7 +45,6 @@ struct st_buffer {
 	int syscall_result;
 	struct st_request *last_SRpnt;
 	struct st_cmdstatus cmdstat;
-	struct page **reserved_pages;
 	int reserved_page_order;
 	struct page **mapped_pages;
 	struct rq_map_data map_data;
@@ -53,6 +52,8 @@ struct st_buffer {
 	unsigned short use_sg;	/* zero or max number of s/g segments for this adapter */
 	unsigned short sg_segs;		/* number of segments in s/g list */
 	unsigned short frp_segs;	/* number of buffer segments */
+
+	struct page *reserved_pages[] __counted_by(use_sg);
 };

 /* The tape mode definition */
--
2.55.0

Re: [PATCHv2] scsi: st: use kzalloc_array()

["Kai Mäkisara (Kolumbus)"]

On 4. Jul 2026, at 0.53, Rosen Penev <rosenp@gmail.com> wrote:
> 
> Merge allocations to simpily memory management with kzalloc_array(). No
> need to kfree separately.
> 
I fail to see what is the real problem this patch fixes? I am not in favor of rewiritng working code
just because it can be done.

Re: [PATCHv2] scsi: st: use kzalloc_array()

[Damien Le Moal]

On 7/4/26 06:53, Rosen Penev wrote:
> Merge allocations to simpily memory management with kzalloc_array(). No

s/simpily/simplify

> need to kfree separately.
> 
> Add __counted_by for extra runtime analysis. Move counting variable
> assignment after allocation as kzalloc_flex() does this with newer
> compilers.
> 
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

With the typo fixed, this looks OK to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

-- 
Damien Le Moal
Western Digital Research