The patch titled
Subject: mm/dmapool.c: avoid duplicate memset within dma_pool_alloc
has been added to the -mm mm-unstable branch. Its filename is
mm-dmapoolc-avoid-duplicate-memset-within-dma_pool_alloc.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-dmapoolc-avoid-duplicate-memset-within-dma_pool_alloc.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Liu Song <liusong@xxxxxxxxxxxxxxxxx>
Subject: mm/dmapool.c: avoid duplicate memset within dma_pool_alloc
Date: Mon, 18 Jul 2022 14:28:10 +0800
In "dma_alloc_from_dev_coherent" and "dma_direct_alloc",
the allocated memory is explicitly set to 0.
A helper function "use_dev_coherent_memory" is introduced here to
determine whether the memory is allocated by "dma_alloc_from_dev_coherent".
And use "get_dma_ops" to determine whether the memory is allocated by
"dma_direct_alloc".
After this modification, memory allocated using "dma_pool_zalloc" can avoid
duplicate memset.
Link: https://lkml.kernel.org/r/1658125690-76930-1-git-send-email-liusong@xxxxxxxxxxxxxxxxx
Signed-off-by: Liu Song <liusong@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/dma-map-ops.h | 5 +++++
mm/dmapool.c | 5 ++++-
2 files changed, 9 insertions(+), 1 deletion(-)
--- a/include/linux/dma-map-ops.h~mm-dmapoolc-avoid-duplicate-memset-within-dma_pool_alloc
+++ a/include/linux/dma-map-ops.h
@@ -183,6 +183,10 @@ int dma_alloc_from_dev_coherent(struct d
int dma_release_from_dev_coherent(struct device *dev, int order, void *vaddr);
int dma_mmap_from_dev_coherent(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, size_t size, int *ret);
+static inline bool use_dev_coherent_memory(struct device *dev)
+{
+ return dev->dma_mem ? true : false;
+}
#else
static inline int dma_declare_coherent_memory(struct device *dev,
phys_addr_t phys_addr, dma_addr_t device_addr, size_t size)
@@ -194,6 +198,7 @@ static inline int dma_declare_coherent_m
#define dma_release_from_dev_coherent(dev, order, vaddr) (0)
#define dma_mmap_from_dev_coherent(dev, vma, vaddr, order, ret) (0)
static inline void dma_release_coherent_memory(struct device *dev) { }
+#define use_dev_coherent_memory(dev) (0)
#endif /* CONFIG_DMA_DECLARE_COHERENT */
#ifdef CONFIG_DMA_GLOBAL_POOL
--- a/mm/dmapool.c~mm-dmapoolc-avoid-duplicate-memset-within-dma_pool_alloc
+++ a/mm/dmapool.c
@@ -21,6 +21,7 @@
#include <linux/device.h>
#include <linux/dma-mapping.h>
+#include <linux/dma-map-ops.h>
#include <linux/dmapool.h>
#include <linux/kernel.h>
#include <linux/list.h>
@@ -372,7 +373,9 @@ void *dma_pool_alloc(struct dma_pool *po
#endif
spin_unlock_irqrestore(&pool->lock, flags);
- if (want_init_on_alloc(mem_flags))
+ if (want_init_on_alloc(mem_flags) &&
+ !use_dev_coherent_memory(pool->dev) &&
+ get_dma_ops(pool->dev))
memset(retval, 0, pool->size);
return retval;
_
Patches currently in -mm which might be from liusong@xxxxxxxxxxxxxxxxx are
mm-dmapoolc-avoid-duplicate-memset-within-dma_pool_alloc.patch
