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dma: map_benchmark: turn dma_sg_map_param buf into a flexible array

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The buf pointer was kmalloc_array()'d immediately after the parent
struct allocation, with the count (granule, validated to 1..1024 by
the ioctl) trivially available beforehand.  Move buf to the struct
tail as a flexible array member and fold the two allocations into a
single kzalloc_flex(), dropping the kfree(params->buf) in both the
prepare error path and unprepare.

Add __counted_by for extra runtime analysis.

Assisted-by: Claude:Opus-4.7
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Qinxin Xia <xiaqinxin@huawei.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20260603031758.290538-1-rosenp@gmail.com
This commit is contained in:
Rosen Penev 2026-06-02 20:17:58 -07:00 committed by Marek Szyprowski
parent d5cae2261b
commit 7318301e06
1 changed files with 12 additions and 15 deletions
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27
kernel/dma/map_benchmark.c
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@ -121,35 +121,35 @@ static struct map_benchmark_ops dma_single_map_benchmark_ops = {
struct dma_sg_map_param {
struct sg_table sgt;
struct device *dev;
void **buf;
u32 npages;
u32 dma_dir;
void *buf[] __counted_by(npages);
};
static void *dma_sg_map_benchmark_prepare(struct map_benchmark_data *map)
{
struct dma_sg_map_param *params;
struct scatterlist *sg;
u32 npages;
int i;
struct dma_sg_map_param *params = kzalloc(sizeof(*params), GFP_KERNEL);
if (!params)
return NULL;
/*
* Set the number of scatterlist entries based on the granule.
* In SG mode, 'granule' represents the number of scatterlist entries.
* Each scatterlist entry corresponds to a single page.
*/
params->npages = map->bparam.granule;
npages = map->bparam.granule;
params = kzalloc_flex(*params, buf, npages);
if (!params)
return NULL;
params->npages = npages;
params->dma_dir = map->bparam.dma_dir;
params->dev = map->dev;
params->buf = kmalloc_array(params->npages, sizeof(*params->buf),
GFP_KERNEL);
if (!params->buf)
goto out;
if (sg_alloc_table(&params->sgt, params->npages, GFP_KERNEL))
goto free_buf;
goto free_params;
for_each_sgtable_sg(&params->sgt, sg, i) {
params->buf[i] = (void *)__get_free_page(GFP_KERNEL);
@ -166,9 +166,7 @@ static void *dma_sg_map_benchmark_prepare(struct map_benchmark_data *map)
free_page((unsigned long)params->buf[i]);
sg_free_table(&params->sgt);
free_buf:
kfree(params->buf);
out:
free_params:
kfree(params);
return NULL;
}
@ -183,7 +181,6 @@ static void dma_sg_map_benchmark_unprepare(void *mparam)
sg_free_table(&params->sgt);
kfree(params->buf);
kfree(params);
}