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[PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback

Started byMichal Hocko <mhocko@kernel.org>
First post2016-04-28 15:30 +0200
Last post2016-04-28 18:10 +0200
Articles 8 — 3 participants

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  [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback Michal Hocko <mhocko@kernel.org> - 2016-04-28 15:30 +0200
    [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback Michal Hocko <mhocko@kernel.org> - 2016-04-28 17:00 +0200
      Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc  fallback Mikulas Patocka <mpatocka@redhat.com> - 2016-04-28 17:10 +0200
        Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback Michal Hocko <mhocko@kernel.org> - 2016-04-28 17:30 +0200
          Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc  fallback Mikulas Patocka <mpatocka@redhat.com> - 2016-04-28 17:50 +0200
            Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback Michal Hocko <mhocko@kernel.org> - 2016-04-28 19:00 +0200
    Re: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc  fallback Mike Snitzer <snitzer@redhat.com> - 2016-04-28 17:40 +0200
      Re: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc  fallback Michal Hocko <mhocko@kernel.org> - 2016-04-28 18:10 +0200

#1390166 — [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback

FromMichal Hocko <mhocko@kernel.org>
Date2016-04-28 15:30 +0200
Subject[PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsUb0-3LP-21@gated-at.bofh.it>
From: Michal Hocko <mhocko@suse.com>

Use kvfree rather than DM_PARAMS_[KV]MALLOC specific param flags.

Cc: Shaohua Li <shli@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 drivers/md/dm-ioctl.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index fe0b57d7573c..2b48c49774bc 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1670,19 +1670,14 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
 	return r;
 }
 
-#define DM_PARAMS_KMALLOC	0x0001	/* Params alloced with kmalloc */
-#define DM_PARAMS_VMALLOC	0x0002	/* Params alloced with vmalloc */
-#define DM_WIPE_BUFFER		0x0010	/* Wipe input buffer before returning from ioctl */
+#define DM_WIPE_BUFFER		0x0001	/* Wipe input buffer before returning from ioctl */
 
 static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
 {
 	if (param_flags & DM_WIPE_BUFFER)
 		memset(param, 0, param_size);
 
-	if (param_flags & DM_PARAMS_KMALLOC)
-		kfree(param);
-	if (param_flags & DM_PARAMS_VMALLOC)
-		vfree(param);
+	kvfree(param);
 }
 
 static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
@@ -1714,17 +1709,11 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 	 * Use kmalloc() rather than vmalloc() when we can.
 	 */
 	dmi = NULL;
-	if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
+	if (param_kernel->data_size <= KMALLOC_MAX_SIZE)
 		dmi = kmalloc(param_kernel->data_size, GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
-		if (dmi)
-			*param_flags |= DM_PARAMS_KMALLOC;
-	}
 
-	if (!dmi) {
+	if (!dmi)
 		dmi = __vmalloc(param_kernel->data_size, GFP_KERNEL | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
-		if (dmi)
-			*param_flags |= DM_PARAMS_VMALLOC;
-	}
 
 	if (!dmi) {
 		if (secure_data && clear_user(user, param_kernel->data_size))
-- 
2.8.0.rc3

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#1390284 — [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback

FromMichal Hocko <mhocko@kernel.org>
Date2016-04-28 17:00 +0200
Subject[PATCH] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsVA6-50h-13@gated-at.bofh.it>
In reply to#1390166
From: Michal Hocko <mhocko@suse.com>

Use kvfree rather than DM_PARAMS_[KV]MALLOC specific param flags.

Cc: Shaohua Li <shli@kernel.org>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
Hi,
this is a rebase on top of dropped "dm: clean up GFP_NIO usage" which
should be dropped as per the feedback from Mikulas.

 drivers/md/dm-ioctl.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 2c7ca258c4e4..e66e5b43bc18 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1670,19 +1670,14 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
 	return r;
 }
 
-#define DM_PARAMS_KMALLOC	0x0001	/* Params alloced with kmalloc */
-#define DM_PARAMS_VMALLOC	0x0002	/* Params alloced with vmalloc */
-#define DM_WIPE_BUFFER		0x0010	/* Wipe input buffer before returning from ioctl */
+#define DM_WIPE_BUFFER		0x0001	/* Wipe input buffer before returning from ioctl */
 
 static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
 {
 	if (param_flags & DM_WIPE_BUFFER)
 		memset(param, 0, param_size);
 
-	if (param_flags & DM_PARAMS_KMALLOC)
-		kfree(param);
-	if (param_flags & DM_PARAMS_VMALLOC)
-		vfree(param);
+	kvfree(param);
 }
 
 static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
@@ -1714,19 +1709,14 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 	 * Use kmalloc() rather than vmalloc() when we can.
 	 */
 	dmi = NULL;
-	if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
+	if (param_kernel->data_size <= KMALLOC_MAX_SIZE)
 		dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
-		if (dmi)
-			*param_flags |= DM_PARAMS_KMALLOC;
-	}
 
 	if (!dmi) {
 		unsigned noio_flag;
 		noio_flag = memalloc_noio_save();
 		dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
 		memalloc_noio_restore(noio_flag);
-		if (dmi)
-			*param_flags |= DM_PARAMS_VMALLOC;
 	}
 
 	if (!dmi) {
-- 
2.8.0.rc3

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#1390291 — Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback

FromMikulas Patocka <mpatocka@redhat.com>
Date2016-04-28 17:10 +0200
SubjectRe: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsVJM-5u4-33@gated-at.bofh.it>
In reply to#1390284
Acked-by: Mikulas Patocka <mpatocka@redhat.com>

BTW. we could also use kvmalloc to complement kvfree, proposed here: 
https://www.redhat.com/archives/dm-devel/2015-July/msg00046.html

Mikulas

On Thu, 28 Apr 2016, Michal Hocko wrote:

> From: Michal Hocko <mhocko@suse.com>
> 
> Use kvfree rather than DM_PARAMS_[KV]MALLOC specific param flags.
> 
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: dm-devel@redhat.com
> Signed-off-by: Michal Hocko <mhocko@suse.com>
> ---
> Hi,
> this is a rebase on top of dropped "dm: clean up GFP_NIO usage" which
> should be dropped as per the feedback from Mikulas.
> 
>  drivers/md/dm-ioctl.c | 16 +++-------------
>  1 file changed, 3 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index 2c7ca258c4e4..e66e5b43bc18 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1670,19 +1670,14 @@ static int check_version(unsigned int cmd, struct dm_ioctl __user *user)
>  	return r;
>  }
>  
> -#define DM_PARAMS_KMALLOC	0x0001	/* Params alloced with kmalloc */
> -#define DM_PARAMS_VMALLOC	0x0002	/* Params alloced with vmalloc */
> -#define DM_WIPE_BUFFER		0x0010	/* Wipe input buffer before returning from ioctl */
> +#define DM_WIPE_BUFFER		0x0001	/* Wipe input buffer before returning from ioctl */
>  
>  static void free_params(struct dm_ioctl *param, size_t param_size, int param_flags)
>  {
>  	if (param_flags & DM_WIPE_BUFFER)
>  		memset(param, 0, param_size);
>  
> -	if (param_flags & DM_PARAMS_KMALLOC)
> -		kfree(param);
> -	if (param_flags & DM_PARAMS_VMALLOC)
> -		vfree(param);
> +	kvfree(param);
>  }
>  
>  static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kernel,
> @@ -1714,19 +1709,14 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
>  	 * Use kmalloc() rather than vmalloc() when we can.
>  	 */
>  	dmi = NULL;
> -	if (param_kernel->data_size <= KMALLOC_MAX_SIZE) {
> +	if (param_kernel->data_size <= KMALLOC_MAX_SIZE)
>  		dmi = kmalloc(param_kernel->data_size, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
> -		if (dmi)
> -			*param_flags |= DM_PARAMS_KMALLOC;
> -	}
>  
>  	if (!dmi) {
>  		unsigned noio_flag;
>  		noio_flag = memalloc_noio_save();
>  		dmi = __vmalloc(param_kernel->data_size, GFP_NOIO | __GFP_HIGH | __GFP_HIGHMEM, PAGE_KERNEL);
>  		memalloc_noio_restore(noio_flag);
> -		if (dmi)
> -			*param_flags |= DM_PARAMS_VMALLOC;
>  	}
>  
>  	if (!dmi) {
> -- 
> 2.8.0.rc3
>

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#1390304 — Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback

FromMichal Hocko <mhocko@kernel.org>
Date2016-04-28 17:30 +0200
SubjectRe: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsW37-5Ij-1@gated-at.bofh.it>
In reply to#1390291
On Thu 28-04-16 11:04:05, Mikulas Patocka wrote:
> Acked-by: Mikulas Patocka <mpatocka@redhat.com>

Thanks!

> BTW. we could also use kvmalloc to complement kvfree, proposed here: 
> https://www.redhat.com/archives/dm-devel/2015-July/msg00046.html

If there are sufficient users (I haven't checked other than quick git
grep on KMALLOC_MAX_SIZE and there do not seem that many) who are
sharing the same fallback strategy then why not. But I suspect that some
would rather fallback earlier and even do not attempt larger than e.g.
order-1 requests.
-- 
Michal Hocko
SUSE Labs

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#1390342 — Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback

FromMikulas Patocka <mpatocka@redhat.com>
Date2016-04-28 17:50 +0200
SubjectRe: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsWmv-5UH-31@gated-at.bofh.it>
In reply to#1390304

On Thu, 28 Apr 2016, Michal Hocko wrote:

> On Thu 28-04-16 11:04:05, Mikulas Patocka wrote:
> > Acked-by: Mikulas Patocka <mpatocka@redhat.com>
> 
> Thanks!
> 
> > BTW. we could also use kvmalloc to complement kvfree, proposed here: 
> > https://www.redhat.com/archives/dm-devel/2015-July/msg00046.html
> 
> If there are sufficient users (I haven't checked other than quick git
> grep on KMALLOC_MAX_SIZE

the problem is that kmallocs with large sizes near KMALLOC_MAX_SIZE are 
unreliable, they'll randomly fail if memory is too fragmented.

> and there do not seem that many) who are
> sharing the same fallback strategy then why not. But I suspect that some
> would rather fallback earlier and even do not attempt larger than e.g.
> order-1 requests.
> -- 
> Michal Hocko
> SUSE Labs

There are many users that use one of these patterns:

	if (size <= some_threshold)
		p = kmalloc(size);
	else
		p = vmalloc(size);

or

	p = kmalloc(size);
	if (!p)
		p = vmalloc(size);


For example: alloc_fdmem, seq_buf_alloc, setxattr, getxattr, ipc_alloc, 
pidlist_allocate, get_pages_array, alloc_bucket_locks, 
frame_vector_create. If you grep the kernel for vmalloc, you'll find this 
pattern over and over again.

In alloc_large_system_hash, there is
	table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
- that is clearly wrong because __vmalloc doesn't respect GFP_ATOMIC

Mikulas

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#1390400 — Re: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback

FromMichal Hocko <mhocko@kernel.org>
Date2016-04-28 19:00 +0200
SubjectRe: [PATCH] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsXsf-74R-13@gated-at.bofh.it>
In reply to#1390342
On Thu 28-04-16 11:40:59, Mikulas Patocka wrote:
[...]
> There are many users that use one of these patterns:
> 
> 	if (size <= some_threshold)
> 		p = kmalloc(size);
> 	else
> 		p = vmalloc(size);
> 
> or
> 
> 	p = kmalloc(size);
> 	if (!p)
> 		p = vmalloc(size);
> 
> 
> For example: alloc_fdmem, seq_buf_alloc, setxattr, getxattr, ipc_alloc, 
> pidlist_allocate, get_pages_array, alloc_bucket_locks, 
> frame_vector_create. If you grep the kernel for vmalloc, you'll find this 
> pattern over and over again.

It is certainly good to address a common pattern by a helper if it makes
to code easier to follo IMHO.

> 
> In alloc_large_system_hash, there is
> 	table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);
> - that is clearly wrong because __vmalloc doesn't respect GFP_ATOMIC

I have seen this code some time already. I guess it was Al complaining
about it but then I just forgot about it. I have no idea why GFP_ATOMIC
was used there. This predates git times but it should be
https://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.10/2.6.10-mm1/broken-out/alloc_large_system_hash-numa-interleaving.patch
The changelog is quite verbose but no mention about this ugliness.

So I do agree that the above should be fixed and a common helper might
be interesting but I am afraid we are getting off topic here.

Thanks!
-- 
Michal Hocko
SUSE Labs

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#1390327 — Re: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback

FromMike Snitzer <snitzer@redhat.com>
Date2016-04-28 17:40 +0200
SubjectRe: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsWcO-5NB-31@gated-at.bofh.it>
In reply to#1390166
On Thu, Apr 28 2016 at  9:24am -0400,
Michal Hocko <mhocko@kernel.org> wrote:

> From: Michal Hocko <mhocko@suse.com>
> 
> Use kvfree rather than DM_PARAMS_[KV]MALLOC specific param flags.
> 
> Cc: Shaohua Li <shli@kernel.org>
> Cc: Mikulas Patocka <mpatocka@redhat.com>
> Cc: dm-devel@redhat.com
> Signed-off-by: Michal Hocko <mhocko@suse.com>

Nack, seriously, this is the 3rd time this patch has been attempted.
Did you actually test the change?  It'll crash very quickly, see:

https://www.redhat.com/archives/dm-devel/2016-April/msg00103.html

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#1390354 — Re: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback

FromMichal Hocko <mhocko@kernel.org>
Date2016-04-28 18:10 +0200
SubjectRe: [PATCH 19/20] md: simplify free_params for kmalloc vs vmalloc fallback
Message-ID<rsWFQ-6n2-9@gated-at.bofh.it>
In reply to#1390327
On Thu 28-04-16 11:37:31, Mike Snitzer wrote:
> On Thu, Apr 28 2016 at  9:24am -0400,
> Michal Hocko <mhocko@kernel.org> wrote:
> 
> > From: Michal Hocko <mhocko@suse.com>
> > 
> > Use kvfree rather than DM_PARAMS_[KV]MALLOC specific param flags.
> > 
> > Cc: Shaohua Li <shli@kernel.org>
> > Cc: Mikulas Patocka <mpatocka@redhat.com>
> > Cc: dm-devel@redhat.com
> > Signed-off-by: Michal Hocko <mhocko@suse.com>
> 
> Nack, seriously, this is the 3rd time this patch has been attempted.
> Did you actually test the change?  It'll crash very quickly, see:
> 
> https://www.redhat.com/archives/dm-devel/2016-April/msg00103.html

You are right! My bad I should have checked the other callers!

-- 
Michal Hocko
SUSE Labs

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