[PATCH 0/2] lib/raid: replace __get_free_pages() call with kmalloc()

[PATCH 0/2] lib/raid: replace __get_free_pages() call with kmalloc()

[Mike Rapoport (Microsoft)]

This is a (tiny) part of larger work of replacing page allocator calls
with kmalloc:

Also in git:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/lib

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
Mike Rapoport (Microsoft) (2):
      lib/raid: use kmalloc() in calibrate_xor_blocks()
      lib/raid6: use kmalloc() in raid6_select_algo()

 lib/raid/xor/xor-core.c | 5 +++--
 lib/raid6/algos.c       | 6 +++---
 2 files changed, 6 insertions(+), 5 deletions(-)
---
base-commit: 5d6919055dec134de3c40167a490f33c74c12581
change-id: 20260520-lib-8afb92134307

Best regards,
--  
Sincerely yours,
Mike.

[PATCH 1/2] lib/raid: use kmalloc() in calibrate_xor_blocks()

[Mike Rapoport (Microsoft)]

The xor benchmark allocates an order 2 (4 pages) scratch buffer that is
used purely as a CPU-only XOR working area.

For such large allocations kmalloc() would fall back to alloc_pages() but
still kmalloc() is a better API as it does not require unnecessary
castings and may provide more debugging possibilities.

Replace __get_free_pages() call with kmalloc().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 lib/raid/xor/xor-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
index bd4e6e434418..50931fbf0324 100644
--- a/lib/raid/xor/xor-core.c
+++ b/lib/raid/xor/xor-core.c
@@ -8,6 +8,7 @@
 
 #include <linux/module.h>
 #include <linux/gfp.h>
+#include <linux/slab.h>
 #include <linux/raid/xor.h>
 #include <linux/jiffies.h>
 #include <linux/preempt.h>
@@ -114,7 +115,7 @@ static int __init calibrate_xor_blocks(void)
 	if (forced_template)
 		return 0;
 
-	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
+	b1 = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
 	if (!b1) {
 		pr_warn("xor: Yikes!  No memory available.\n");
 		return -ENOMEM;
@@ -132,7 +133,7 @@ static int __init calibrate_xor_blocks(void)
 	pr_info("xor: using function: %s (%d MB/sec)\n",
 	       fastest->name, fastest->speed);
 
-	free_pages((unsigned long)b1, 2);
+	kfree(b1);
 	return 0;
 }
 

-- 
2.53.0

Re: [PATCH 1/2] lib/raid: use kmalloc() in calibrate_xor_blocks()

[David Laight]

On Wed, 20 May 2026 11:17:51 +0300
"Mike Rapoport (Microsoft)" <rppt@kernel.org> wrote:

> The xor benchmark allocates an order 2 (4 pages) scratch buffer that is
> used purely as a CPU-only XOR working area.
> 
> For such large allocations kmalloc() would fall back to alloc_pages() but
> still kmalloc() is a better API as it does not require unnecessary
> castings and may provide more debugging possibilities.
> 
> Replace __get_free_pages() call with kmalloc().

You might want to use kvalloc() here.
It is less likely to fail.

-- David

> 
> Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  lib/raid/xor/xor-core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
> index bd4e6e434418..50931fbf0324 100644
> --- a/lib/raid/xor/xor-core.c
> +++ b/lib/raid/xor/xor-core.c
> @@ -8,6 +8,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/gfp.h>
> +#include <linux/slab.h>
>  #include <linux/raid/xor.h>
>  #include <linux/jiffies.h>
>  #include <linux/preempt.h>
> @@ -114,7 +115,7 @@ static int __init calibrate_xor_blocks(void)
>  	if (forced_template)
>  		return 0;
>  
> -	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
> +	b1 = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
>  	if (!b1) {
>  		pr_warn("xor: Yikes!  No memory available.\n");
>  		return -ENOMEM;
> @@ -132,7 +133,7 @@ static int __init calibrate_xor_blocks(void)
>  	pr_info("xor: using function: %s (%d MB/sec)\n",
>  	       fastest->name, fastest->speed);
>  
> -	free_pages((unsigned long)b1, 2);
> +	kfree(b1);
>  	return 0;
>  }
>  
> 

[PATCH 2/2] lib/raid6: use kmalloc() in raid6_select_algo()

[Mike Rapoport (Microsoft)]

raid6_select_algo() allocates an order 3 (8 pages) buffer that is used
as a scratch area for selection of the best algorithm.

For such large allocations kmalloc() would fall back to alloc_pages() but
still kmalloc() is a better API as it does not require unnecessary
castings and may provide more debugging possibilities.

Replace __get_free_pages() call with kmalloc().

Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 lib/raid6/algos.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index 799e0e5eac26..89e627c62e30 100644
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -12,6 +12,7 @@
  */
 
 #include <linux/raid/pq.h>
+#include <linux/slab.h>
 #ifndef __KERNEL__
 #include <sys/mman.h>
 #include <stdio.h>
@@ -129,7 +130,6 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
 #endif
 
 #define RAID6_TEST_DISKS	8
-#define RAID6_TEST_DISKS_ORDER	3
 
 static inline const struct raid6_recov_calls *raid6_choose_recov(void)
 {
@@ -250,7 +250,7 @@ int __init raid6_select_algo(void)
 	int i, cycle;
 
 	/* prepare the buffer and fill it circularly with gfmul table */
-	disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER);
+	disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL);
 	if (!disk_ptr) {
 		pr_err("raid6: Yikes!  No memory available.\n");
 		return -ENOMEM;
@@ -275,7 +275,7 @@ int __init raid6_select_algo(void)
 	/* select raid recover functions */
 	rec_best = raid6_choose_recov();
 
-	free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
+	kfree(disk_ptr);
 
 	return gen_best && rec_best ? 0 : -EINVAL;
 }

-- 
2.53.0

Re: [PATCH 2/2] lib/raid6: use kmalloc() in raid6_select_algo()

[David Laight]

On Wed, 20 May 2026 11:17:52 +0300
"Mike Rapoport (Microsoft)" <rppt@kernel.org> wrote:

> raid6_select_algo() allocates an order 3 (8 pages) buffer that is used
> as a scratch area for selection of the best algorithm.

Should this code really be using a 4k buffer rather than a PAGE_SIZE one?

-- David

> 
> For such large allocations kmalloc() would fall back to alloc_pages() but
> still kmalloc() is a better API as it does not require unnecessary
> castings and may provide more debugging possibilities.
> 
> Replace __get_free_pages() call with kmalloc().
> 
> Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  lib/raid6/algos.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
> index 799e0e5eac26..89e627c62e30 100644
> --- a/lib/raid6/algos.c
> +++ b/lib/raid6/algos.c
> @@ -12,6 +12,7 @@
>   */
>  
>  #include <linux/raid/pq.h>
> +#include <linux/slab.h>
>  #ifndef __KERNEL__
>  #include <sys/mman.h>
>  #include <stdio.h>
> @@ -129,7 +130,6 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
>  #endif
>  
>  #define RAID6_TEST_DISKS	8
> -#define RAID6_TEST_DISKS_ORDER	3
>  
>  static inline const struct raid6_recov_calls *raid6_choose_recov(void)
>  {
> @@ -250,7 +250,7 @@ int __init raid6_select_algo(void)
>  	int i, cycle;
>  
>  	/* prepare the buffer and fill it circularly with gfmul table */
> -	disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER);
> +	disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL);
>  	if (!disk_ptr) {
>  		pr_err("raid6: Yikes!  No memory available.\n");
>  		return -ENOMEM;
> @@ -275,7 +275,7 @@ int __init raid6_select_algo(void)
>  	/* select raid recover functions */
>  	rec_best = raid6_choose_recov();
>  
> -	free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
> +	kfree(disk_ptr);
>  
>  	return gen_best && rec_best ? 0 : -EINVAL;
>  }
> 

Re: [PATCH 2/2] lib/raid6: use kmalloc() in raid6_select_algo()

[Mike Rapoport]

On Wed, May 20, 2026 at 02:06:57PM +0100, David Laight wrote:
> On Wed, 20 May 2026 11:17:52 +0300
> "Mike Rapoport (Microsoft)" <rppt@kernel.org> wrote:
> 
> > raid6_select_algo() allocates an order 3 (8 pages) buffer that is used
> > as a scratch area for selection of the best algorithm.
> 
> Should this code really be using a 4k buffer rather than a PAGE_SIZE one?

Why?
 
> -- David
> 
> > 
> > For such large allocations kmalloc() would fall back to alloc_pages() but
> > still kmalloc() is a better API as it does not require unnecessary
> > castings and may provide more debugging possibilities.
> > 
> > Replace __get_free_pages() call with kmalloc().
> > 
> > Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> >  lib/raid6/algos.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
> > index 799e0e5eac26..89e627c62e30 100644
> > --- a/lib/raid6/algos.c
> > +++ b/lib/raid6/algos.c
> > @@ -12,6 +12,7 @@
> >   */
> >  
> >  #include <linux/raid/pq.h>
> > +#include <linux/slab.h>
> >  #ifndef __KERNEL__
> >  #include <sys/mman.h>
> >  #include <stdio.h>
> > @@ -129,7 +130,6 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
> >  #endif
> >  
> >  #define RAID6_TEST_DISKS	8
> > -#define RAID6_TEST_DISKS_ORDER	3
> >  
> >  static inline const struct raid6_recov_calls *raid6_choose_recov(void)
> >  {
> > @@ -250,7 +250,7 @@ int __init raid6_select_algo(void)
> >  	int i, cycle;
> >  
> >  	/* prepare the buffer and fill it circularly with gfmul table */
> > -	disk_ptr = (char *)__get_free_pages(GFP_KERNEL, RAID6_TEST_DISKS_ORDER);
> > +	disk_ptr = kmalloc(PAGE_SIZE * RAID6_TEST_DISKS, GFP_KERNEL);
> >  	if (!disk_ptr) {
> >  		pr_err("raid6: Yikes!  No memory available.\n");
> >  		return -ENOMEM;
> > @@ -275,7 +275,7 @@ int __init raid6_select_algo(void)
> >  	/* select raid recover functions */
> >  	rec_best = raid6_choose_recov();
> >  
> > -	free_pages((unsigned long)disk_ptr, RAID6_TEST_DISKS_ORDER);
> > +	kfree(disk_ptr);
> >  
> >  	return gen_best && rec_best ? 0 : -EINVAL;
> >  }
> > 
> 
> 

-- 
Sincerely yours,
Mike.