[PATCH v2 0/4] mm: add dma_pool_zalloc() & pci_pool_zalloc()

[PATCH v2 0/4] mm: add dma_pool_zalloc() & pci_pool_zalloc()

[Sean O. Stalley]

Currently a call to dma_pool_alloc() with a ___GFP_ZERO flag returns
a non-zeroed memory region.

This patchset adds support for the __GFP_ZERO flag to dma_pool_alloc(),
adds 2 wrapper functions for allocing zeroed memory from a pool, 
and provides a coccinelle script for finding & replacing instances of
dma_pool_alloc() followed by memset(0) with a single dma_pool_zalloc() call.

Changes from v1 to v2:
	- don't memset() POOL_POISON_ALLOCATED in dma_pool_alloc() if
	  __GFP_ZERO is set
	- Ran test to see how often pool_alloc_page() is called


There was some concern that this always calls memset() to zero,
instead of passing __GFP_ZERO into the page allocator.
[https://lkml.org/lkml/2015/7/15/881]

I ran a test on my system to get an idea of how often dma_pool_alloc()
calls into pool_alloc_page().

After Boot:	[   30.119863] alloc_calls:541, page_allocs:7
After an hour:	[ 3600.951031] alloc_calls:9566, page_allocs:12
After copying 1GB file onto a USB drive:
		[ 4260.657148] alloc_calls:17225, page_allocs:12

It doesn't look like dma_pool_alloc() calls down to the page allocator
very often (at least on my system).


Sean O. Stalley (4):
  mm: Add support for __GFP_ZERO flag to dma_pool_alloc()
  mm: Add dma_pool_zalloc() call to DMA API
  pci: mm: Add pci_pool_zalloc() call
  coccinelle: mm: scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci

 Documentation/DMA-API.txt                          |  7 ++
 include/linux/dmapool.h                            |  6 ++
 include/linux/pci.h                                |  2 +
 mm/dmapool.c                                       |  9 ++-
 .../coccinelle/api/alloc/pool_zalloc-simple.cocci  | 84 ++++++++++++++++++++++
 5 files changed, 106 insertions(+), 2 deletions(-)
 create mode 100644 scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci

-- 
1.9.1

[PATCH v2 1/4] mm: Add support for __GFP_ZERO flag to dma_pool_alloc()

[Sean O. Stalley]

Currently the __GFP_ZERO flag is ignored by dma_pool_alloc().
Make dma_pool_alloc() zero the memory if this flag is set.

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
---
 mm/dmapool.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/dmapool.c b/mm/dmapool.c
index fd5fe43..bd49386 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -334,7 +334,7 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
 	/* pool_alloc_page() might sleep, so temporarily drop &pool->lock */
 	spin_unlock_irqrestore(&pool->lock, flags);
 
-	page = pool_alloc_page(pool, mem_flags);
+	page = pool_alloc_page(pool, mem_flags & (~__GFP_ZERO));
 	if (!page)
 		return NULL;
 
@@ -372,9 +372,14 @@ void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
 			break;
 		}
 	}
-	memset(retval, POOL_POISON_ALLOCATED, pool->size);
+	if (!(mem_flags & __GFP_ZERO))
+		memset(retval, POOL_POISON_ALLOCATED, pool->size);
 #endif
 	spin_unlock_irqrestore(&pool->lock, flags);
+
+	if (mem_flags & __GFP_ZERO)
+		memset(retval, 0, pool->size);
+
 	return retval;
 }
 EXPORT_SYMBOL(dma_pool_alloc);
-- 
1.9.1

[PATCH v2 2/4] mm: Add dma_pool_zalloc() call to DMA API

[Sean O. Stalley]

Add a wrapper function for dma_pool_alloc() to get zeroed memory.

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
---
 Documentation/DMA-API.txt | 7 +++++++
 include/linux/dmapool.h   | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 5208840..988f757 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -104,6 +104,13 @@ crossing restrictions, pass 0 for alloc; passing 4096 says memory allocated
 from this pool must not cross 4KByte boundaries.
 
 
+	void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
+			      dma_addr_t *handle)
+
+Wraps dma_pool_alloc() and also zeroes the returned memory if the
+allocation attempt succeeded.
+
+
 	void *dma_pool_alloc(struct dma_pool *pool, gfp_t gfp_flags,
 			dma_addr_t *dma_handle);
 
diff --git a/include/linux/dmapool.h b/include/linux/dmapool.h
index 022e34f..6d8079b 100644
--- a/include/linux/dmapool.h
+++ b/include/linux/dmapool.h
@@ -22,6 +22,12 @@ void dma_pool_destroy(struct dma_pool *pool);
 void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
 		     dma_addr_t *handle);
 
+static inline void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
+				    dma_addr_t *handle)
+{
+	return dma_pool_alloc(pool, mem_flags | __GFP_ZERO, handle);
+}
+
 void dma_pool_free(struct dma_pool *pool, void *vaddr, dma_addr_t addr);
 
 /*
-- 
1.9.1

[PATCH v2 3/4] pci: mm: Add pci_pool_zalloc() call

[Sean O. Stalley]

Add a wrapper function for pci_pool_alloc() to get zeroed memory.

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
---
 include/linux/pci.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 755a2cd..e6ec7d9 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1176,6 +1176,8 @@ int pci_set_vga_state(struct pci_dev *pdev, bool decode,
 		dma_pool_create(name, &pdev->dev, size, align, allocation)
 #define	pci_pool_destroy(pool) dma_pool_destroy(pool)
 #define	pci_pool_alloc(pool, flags, handle) dma_pool_alloc(pool, flags, handle)
+#define	pci_pool_zalloc(pool, flags, handle) \
+		dma_pool_zalloc(pool, flags, handle)
 #define	pci_pool_free(pool, vaddr, addr) dma_pool_free(pool, vaddr, addr)
 
 enum pci_dma_burst_strategy {
-- 
1.9.1

[PATCH v2 4/4] coccinelle: mm: scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci

[Sean O. Stalley]

add [pci|dma]_pool_zalloc coccinelle check.
replaces instances of [pci|dma]_pool_alloc() followed by memset(0)
with [pci|dma]_pool_zalloc().

Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
---
 .../coccinelle/api/alloc/pool_zalloc-simple.cocci  | 84 ++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci

diff --git a/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci b/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci
new file mode 100644
index 0000000..9b7eb32
--- /dev/null
+++ b/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci
@@ -0,0 +1,84 @@
+///
+/// Use *_pool_zalloc rather than *_pool_alloc followed by memset with 0
+///
+// Copyright: (C) 2015 Intel Corp.  GPLv2.
+// Options: --no-includes --include-headers
+//
+// Keywords: dma_pool_zalloc, pci_pool_zalloc
+//
+
+virtual context
+virtual patch
+virtual org
+virtual report
+
+//----------------------------------------------------------
+//  For context mode
+//----------------------------------------------------------
+
+@depends on context@
+expression x;
+statement S;
+@@
+
+* x = \(dma_pool_alloc\|pci_pool_alloc\)(...);
+  if ((x==NULL) || ...) S
+* memset(x,0, ...);
+
+//----------------------------------------------------------
+//  For patch mode
+//----------------------------------------------------------
+
+@depends on patch@
+expression x;
+expression a,b,c;
+statement S;
+@@
+
+- x = dma_pool_alloc(a,b,c);
++ x = dma_pool_zalloc(a,b,c);
+  if ((x==NULL) || ...) S
+- memset(x,0,...);
+
+@depends on patch@
+expression x;
+expression a,b,c;
+statement S;
+@@
+
+- x = pci_pool_alloc(a,b,c);
++ x = pci_pool_zalloc(a,b,c);
+  if ((x==NULL) || ...) S
+- memset(x,0,...);
+
+//----------------------------------------------------------
+//  For org and report mode
+//----------------------------------------------------------
+
+@r depends on org || report@
+expression x;
+expression a,b,c;
+statement S;
+position p;
+@@
+
+ x = @p\(dma_pool_alloc\|pci_pool_alloc\)(a,b,c);
+ if ((x==NULL) || ...) S
+ memset(x,0, ...);
+
+@script:python depends on org@
+p << r.p;
+x << r.x;
+@@
+
+msg="%s" % (x)
+msg_safe=msg.replace("[","@(").replace("]",")")
+coccilib.org.print_todo(p[0], msg_safe)
+
+@script:python depends on report@
+p << r.p;
+x << r.x;
+@@
+
+msg="WARNING: *_pool_zalloc should be used for %s, instead of *_pool_alloc/memset" % (x)
+coccilib.report.print_report(p[0], msg)
-- 
1.9.1

Re: [PATCH v2 4/4] coccinelle: mm: scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci

[Julia Lawall]

Acked-by: Julia Lawall <julia.lawall@lip6.fr>

On Fri, 31 Jul 2015, Sean O. Stalley wrote:

> add [pci|dma]_pool_zalloc coccinelle check.
> replaces instances of [pci|dma]_pool_alloc() followed by memset(0)
> with [pci|dma]_pool_zalloc().
> 
> Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>
> ---
>  .../coccinelle/api/alloc/pool_zalloc-simple.cocci  | 84 ++++++++++++++++++++++
>  1 file changed, 84 insertions(+)
>  create mode 100644 scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci
> 
> diff --git a/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci b/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci
> new file mode 100644
> index 0000000..9b7eb32
> --- /dev/null
> +++ b/scripts/coccinelle/api/alloc/pool_zalloc-simple.cocci
> @@ -0,0 +1,84 @@
> +///
> +/// Use *_pool_zalloc rather than *_pool_alloc followed by memset with 0
> +///
> +// Copyright: (C) 2015 Intel Corp.  GPLv2.
> +// Options: --no-includes --include-headers
> +//
> +// Keywords: dma_pool_zalloc, pci_pool_zalloc
> +//
> +
> +virtual context
> +virtual patch
> +virtual org
> +virtual report
> +
> +//----------------------------------------------------------
> +//  For context mode
> +//----------------------------------------------------------
> +
> +@depends on context@
> +expression x;
> +statement S;
> +@@
> +
> +* x = \(dma_pool_alloc\|pci_pool_alloc\)(...);
> +  if ((x==NULL) || ...) S
> +* memset(x,0, ...);
> +
> +//----------------------------------------------------------
> +//  For patch mode
> +//----------------------------------------------------------
> +
> +@depends on patch@
> +expression x;
> +expression a,b,c;
> +statement S;
> +@@
> +
> +- x = dma_pool_alloc(a,b,c);
> ++ x = dma_pool_zalloc(a,b,c);
> +  if ((x==NULL) || ...) S
> +- memset(x,0,...);
> +
> +@depends on patch@
> +expression x;
> +expression a,b,c;
> +statement S;
> +@@
> +
> +- x = pci_pool_alloc(a,b,c);
> ++ x = pci_pool_zalloc(a,b,c);
> +  if ((x==NULL) || ...) S
> +- memset(x,0,...);
> +
> +//----------------------------------------------------------
> +//  For org and report mode
> +//----------------------------------------------------------
> +
> +@r depends on org || report@
> +expression x;
> +expression a,b,c;
> +statement S;
> +position p;
> +@@
> +
> + x = @p\(dma_pool_alloc\|pci_pool_alloc\)(a,b,c);
> + if ((x==NULL) || ...) S
> + memset(x,0, ...);
> +
> +@script:python depends on org@
> +p << r.p;
> +x << r.x;
> +@@
> +
> +msg="%s" % (x)
> +msg_safe=msg.replace("[","@(").replace("]",")")
> +coccilib.org.print_todo(p[0], msg_safe)
> +
> +@script:python depends on report@
> +p << r.p;
> +x << r.x;
> +@@
> +
> +msg="WARNING: *_pool_zalloc should be used for %s, instead of *_pool_alloc/memset" % (x)
> +coccilib.report.print_report(p[0], msg)
> -- 
> 1.9.1
> 
> 

Re: [PATCH v2 1/4] mm: Add support for __GFP_ZERO flag to dma_pool_alloc()

[David Rientjes]

On Fri, 31 Jul 2015, Sean O. Stalley wrote:

> Currently the __GFP_ZERO flag is ignored by dma_pool_alloc().
> Make dma_pool_alloc() zero the memory if this flag is set.
> 
> Signed-off-by: Sean O. Stalley <sean.stalley@intel.com>

Acked-by: David Rientjes <rientjes@google.com>

This has impacted us as well, and I'm glad to see it fixed.