[PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[David Sterba]

The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
arrays can be 32KiB large. To avoid allocation failures due to
fragmented memory, use the allocation with fallback to vmalloc.

Signed-off-by: David Sterba <dsterba@suse.com>
---

This depends on the patches that remove the 16MiB restriction in the
dedupe ioctl, but contextually can be applied to the current code too.

https://patchwork.kernel.org/patch/10374941/

 fs/btrfs/ioctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b572e38b4b64..a7f517009cd7 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
 	 * locking. We use an array for the page pointers. Size of the array is
 	 * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
 	 */
-	cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
-	cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
+	cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
+	cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
 	if (!cmp.src_pages || !cmp.dst_pages) {
 		kfree(cmp.src_pages);
 		kfree(cmp.dst_pages);
-- 
2.16.2

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[Filipe Manana]

On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com> wrote:
> The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> arrays can be 32KiB large. To avoid allocation failures due to
> fragmented memory, use the allocation with fallback to vmalloc.
>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>
> This depends on the patches that remove the 16MiB restriction in the
> dedupe ioctl, but contextually can be applied to the current code too.
>
> https://patchwork.kernel.org/patch/10374941/
>
>  fs/btrfs/ioctl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b572e38b4b64..a7f517009cd7 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>          * locking. We use an array for the page pointers. Size of the array is
>          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
>          */
> -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);

Kvzalloc should take 2 parameters and not 3.
Also, aren't the corresponding kvfree() calls missing?

>         if (!cmp.src_pages || !cmp.dst_pages) {
>                 kfree(cmp.src_pages);
>                 kfree(cmp.dst_pages);
> --
> 2.16.2
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[David Sterba]

On Fri, May 11, 2018 at 05:25:50PM +0100, Filipe Manana wrote:
> On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com> wrote:
> > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> > arrays can be 32KiB large. To avoid allocation failures due to
> > fragmented memory, use the allocation with fallback to vmalloc.
> >
> > Signed-off-by: David Sterba <dsterba@suse.com>
> > ---
> >
> > This depends on the patches that remove the 16MiB restriction in the
> > dedupe ioctl, but contextually can be applied to the current code too.
> >
> > https://patchwork.kernel.org/patch/10374941/
> >
> >  fs/btrfs/ioctl.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index b572e38b4b64..a7f517009cd7 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> >          * locking. We use an array for the page pointers. Size of the array is
> >          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
> >          */
> > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> 
> Kvzalloc should take 2 parameters and not 3.

And the right function is kvmalloc_array.

> Also, aren't the corresponding kvfree() calls missing?

Yes, thanks for catching it. The updated version:

From: David Sterba <dsterba@suse.com>
Subject: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
arrays can be 32KiB large. To avoid allocation failures due to
fragmented memory, use the allocation with fallback to vmalloc.

Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/ioctl.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b572e38b4b64..4fcfa05ed960 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3178,12 +3178,13 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
 	 * locking. We use an array for the page pointers. Size of the array is
 	 * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
 	 */
-	cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
-	cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
+	cmp.src_pages = kvmalloc_array(num_pages, sizeof(struct page *),
+				       GFP_KERNEL);
+	cmp.dst_pages = kvmalloc_array(num_pages, sizeof(struct page *),
+				       GFP_KERNEL);
 	if (!cmp.src_pages || !cmp.dst_pages) {
-		kfree(cmp.src_pages);
-		kfree(cmp.dst_pages);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out_free;
 	}
 
 	if (same_inode)
@@ -3211,8 +3212,9 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
 	else
 		btrfs_double_inode_unlock(src, dst);
 
-	kfree(cmp.src_pages);
-	kfree(cmp.dst_pages);
+out_free:
+	kvfree(cmp.src_pages);
+	kvfree(cmp.dst_pages);
 
 	return ret;
 }
-- 
2.16.2

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[Filipe Manana]

On Fri, May 11, 2018 at 5:49 PM, David Sterba <dsterba@suse.cz> wrote:
> On Fri, May 11, 2018 at 05:25:50PM +0100, Filipe Manana wrote:
>> On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com> wrote:
>> > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
>> > arrays can be 32KiB large. To avoid allocation failures due to
>> > fragmented memory, use the allocation with fallback to vmalloc.
>> >
>> > Signed-off-by: David Sterba <dsterba@suse.com>
>> > ---
>> >
>> > This depends on the patches that remove the 16MiB restriction in the
>> > dedupe ioctl, but contextually can be applied to the current code too.
>> >
>> > https://patchwork.kernel.org/patch/10374941/
>> >
>> >  fs/btrfs/ioctl.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> > index b572e38b4b64..a7f517009cd7 100644
>> > --- a/fs/btrfs/ioctl.c
>> > +++ b/fs/btrfs/ioctl.c
>> > @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>> >          * locking. We use an array for the page pointers. Size of the array is
>> >          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
>> >          */
>> > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>> > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>> > +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>> > +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>>
>> Kvzalloc should take 2 parameters and not 3.
>
> And the right function is kvmalloc_array.
>
>> Also, aren't the corresponding kvfree() calls missing?
>
> Yes, thanks for catching it. The updated version:
>
> From: David Sterba <dsterba@suse.com>
> Subject: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data
>
> The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> arrays can be 32KiB large. To avoid allocation failures due to
> fragmented memory, use the allocation with fallback to vmalloc.
>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/ioctl.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b572e38b4b64..4fcfa05ed960 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3178,12 +3178,13 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>          * locking. We use an array for the page pointers. Size of the array is
>          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
>          */
> -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> +       cmp.src_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> +                                      GFP_KERNEL);
> +       cmp.dst_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> +                                      GFP_KERNEL);
>         if (!cmp.src_pages || !cmp.dst_pages) {
> -               kfree(cmp.src_pages);
> -               kfree(cmp.dst_pages);
> -               return -ENOMEM;
> +               ret = -ENOMEM;
> +               goto out_free;
>         }
>
>         if (same_inode)
> @@ -3211,8 +3212,9 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>         else
>                 btrfs_double_inode_unlock(src, dst);
>
> -       kfree(cmp.src_pages);
> -       kfree(cmp.dst_pages);
> +out_free:
> +       kvfree(cmp.src_pages);
> +       kvfree(cmp.dst_pages);

kvfree() missing at btrfs_cmp_data_free() too.

>
>         return ret;
>  }
> --
> 2.16.2
>



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[Omar Sandoval]

On Fri, May 11, 2018 at 06:49:16PM +0200, David Sterba wrote:
> On Fri, May 11, 2018 at 05:25:50PM +0100, Filipe Manana wrote:
> > On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com> wrote:
> > > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> > > arrays can be 32KiB large. To avoid allocation failures due to
> > > fragmented memory, use the allocation with fallback to vmalloc.
> > >
> > > Signed-off-by: David Sterba <dsterba@suse.com>
> > > ---
> > >
> > > This depends on the patches that remove the 16MiB restriction in the
> > > dedupe ioctl, but contextually can be applied to the current code too.
> > >
> > > https://patchwork.kernel.org/patch/10374941/
> > >
> > >  fs/btrfs/ioctl.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > > index b572e38b4b64..a7f517009cd7 100644
> > > --- a/fs/btrfs/ioctl.c
> > > +++ b/fs/btrfs/ioctl.c
> > > @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> > >          * locking. We use an array for the page pointers. Size of the array is
> > >          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
> > >          */
> > > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > > +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > > +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > 
> > Kvzalloc should take 2 parameters and not 3.
> 
> And the right function is kvmalloc_array.
> 
> > Also, aren't the corresponding kvfree() calls missing?
> 
> Yes, thanks for catching it. The updated version:
> 
> From: David Sterba <dsterba@suse.com>
> Subject: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data
> 
> The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> arrays can be 32KiB large. To avoid allocation failures due to
> fragmented memory, use the allocation with fallback to vmalloc.
> 
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/ioctl.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b572e38b4b64..4fcfa05ed960 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3178,12 +3178,13 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>  	 * locking. We use an array for the page pointers. Size of the array is
>  	 * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
>  	 */
> -	cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> -	cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> +	cmp.src_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> +				       GFP_KERNEL);
> +	cmp.dst_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> +				       GFP_KERNEL);

kcalloc() implies __GFP_ZERO, do we need that here?

>  	if (!cmp.src_pages || !cmp.dst_pages) {
> -		kfree(cmp.src_pages);
> -		kfree(cmp.dst_pages);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto out_free;
>  	}
>  
>  	if (same_inode)
> @@ -3211,8 +3212,9 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
>  	else
>  		btrfs_double_inode_unlock(src, dst);
>  
> -	kfree(cmp.src_pages);
> -	kfree(cmp.dst_pages);
> +out_free:
> +	kvfree(cmp.src_pages);
> +	kvfree(cmp.dst_pages);
>  
>  	return ret;
>  }
> -- 
> 2.16.2
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[Timofey Titovets]

пт, 11 мая 2018 г. в 20:32, Omar Sandoval <osandov@osandov.com>:

> On Fri, May 11, 2018 at 06:49:16PM +0200, David Sterba wrote:
> > On Fri, May 11, 2018 at 05:25:50PM +0100, Filipe Manana wrote:
> > > On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com>
wrote:
> > > > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> > > > arrays can be 32KiB large. To avoid allocation failures due to
> > > > fragmented memory, use the allocation with fallback to vmalloc.
> > > >
> > > > Signed-off-by: David Sterba <dsterba@suse.com>
> > > > ---
> > > >
> > > > This depends on the patches that remove the 16MiB restriction in the
> > > > dedupe ioctl, but contextually can be applied to the current code
too.
> > > >
> > > > https://patchwork.kernel.org/patch/10374941/
> > > >
> > > >  fs/btrfs/ioctl.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > > > index b572e38b4b64..a7f517009cd7 100644
> > > > --- a/fs/btrfs/ioctl.c
> > > > +++ b/fs/btrfs/ioctl.c
> > > > @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode
*src, u64 loff, u64 olen,
> > > >          * locking. We use an array for the page pointers. Size of
the array is
> > > >          * bounded by len, which is in turn bounded by
BTRFS_MAX_DEDUPE_LEN.
> > > >          */
> > > > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > > > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > > > +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > > > +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > >
> > > Kvzalloc should take 2 parameters and not 3.
> >
> > And the right function is kvmalloc_array.
> >
> > > Also, aren't the corresponding kvfree() calls missing?
> >
> > Yes, thanks for catching it. The updated version:
> >
> > From: David Sterba <dsterba@suse.com>
> > Subject: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data
> >
> > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> > arrays can be 32KiB large. To avoid allocation failures due to
> > fragmented memory, use the allocation with fallback to vmalloc.
> >
> > Signed-off-by: David Sterba <dsterba@suse.com>
> > ---
> >  fs/btrfs/ioctl.c | 16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index b572e38b4b64..4fcfa05ed960 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -3178,12 +3178,13 @@ static int btrfs_extent_same(struct inode *src,
u64 loff, u64 olen,
> >        * locking. We use an array for the page pointers. Size of the
array is
> >        * bounded by len, which is in turn bounded by
BTRFS_MAX_DEDUPE_LEN.
> >        */
> > -     cmp.src_pages = kcalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > -     cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *),
GFP_KERNEL);
> > +     cmp.src_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> > +                                    GFP_KERNEL);
> > +     cmp.dst_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> > +                                    GFP_KERNEL);

> kcalloc() implies __GFP_ZERO, do we need that here?

AFAIK, yes, because:
btrfs_cmp_data_free():
...
pg = cmp->src_pages[i];
if (pg) {...}
..

And we will catch that, if errors happens in gather_extent_pages().

Thanks.
> >       if (!cmp.src_pages || !cmp.dst_pages) {
> > -             kfree(cmp.src_pages);
> > -             kfree(cmp.dst_pages);
> > -             return -ENOMEM;
> > +             ret = -ENOMEM;
> > +             goto out_free;
> >       }
> >
> >       if (same_inode)
> > @@ -3211,8 +3212,9 @@ static int btrfs_extent_same(struct inode *src,
u64 loff, u64 olen,
> >       else
> >               btrfs_double_inode_unlock(src, dst);
> >
> > -     kfree(cmp.src_pages);
> > -     kfree(cmp.dst_pages);
> > +out_free:
> > +     kvfree(cmp.src_pages);
> > +     kvfree(cmp.dst_pages);
> >
> >       return ret;
> >  }
> > --
> > 2.16.2
> >


-- 
Have a nice day,
Timofey.

Re: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data

[David Sterba]

On Fri, May 11, 2018 at 06:16:15PM +0100, Filipe Manana wrote:
> On Fri, May 11, 2018 at 5:49 PM, David Sterba <dsterba@suse.cz> wrote:
> > On Fri, May 11, 2018 at 05:25:50PM +0100, Filipe Manana wrote:
> >> On Fri, May 11, 2018 at 4:57 PM, David Sterba <dsterba@suse.com> wrote:
> >> > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> >> > arrays can be 32KiB large. To avoid allocation failures due to
> >> > fragmented memory, use the allocation with fallback to vmalloc.
> >> >
> >> > Signed-off-by: David Sterba <dsterba@suse.com>
> >> > ---
> >> >
> >> > This depends on the patches that remove the 16MiB restriction in the
> >> > dedupe ioctl, but contextually can be applied to the current code too.
> >> >
> >> > https://patchwork.kernel.org/patch/10374941/
> >> >
> >> >  fs/btrfs/ioctl.c | 4 ++--
> >> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >> >
> >> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> >> > index b572e38b4b64..a7f517009cd7 100644
> >> > --- a/fs/btrfs/ioctl.c
> >> > +++ b/fs/btrfs/ioctl.c
> >> > @@ -3178,8 +3178,8 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> >> >          * locking. We use an array for the page pointers. Size of the array is
> >> >          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
> >> >          */
> >> > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> >> > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> >> > +       cmp.src_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> >> > +       cmp.dst_pages = kvzalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> >>
> >> Kvzalloc should take 2 parameters and not 3.
> >
> > And the right function is kvmalloc_array.
> >
> >> Also, aren't the corresponding kvfree() calls missing?
> >
> > Yes, thanks for catching it. The updated version:
> >
> > From: David Sterba <dsterba@suse.com>
> > Subject: [PATCH] btrfs: use kvzalloc for EXTENT_SAME temporary data
> >
> > The dedupe range is 16 MiB, with 4KiB pages and 8 byte pointers, the
> > arrays can be 32KiB large. To avoid allocation failures due to
> > fragmented memory, use the allocation with fallback to vmalloc.
> >
> > Signed-off-by: David Sterba <dsterba@suse.com>
> > ---
> >  fs/btrfs/ioctl.c | 16 +++++++++-------
> >  1 file changed, 9 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> > index b572e38b4b64..4fcfa05ed960 100644
> > --- a/fs/btrfs/ioctl.c
> > +++ b/fs/btrfs/ioctl.c
> > @@ -3178,12 +3178,13 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> >          * locking. We use an array for the page pointers. Size of the array is
> >          * bounded by len, which is in turn bounded by BTRFS_MAX_DEDUPE_LEN.
> >          */
> > -       cmp.src_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > -       cmp.dst_pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
> > +       cmp.src_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> > +                                      GFP_KERNEL);
> > +       cmp.dst_pages = kvmalloc_array(num_pages, sizeof(struct page *),
> > +                                      GFP_KERNEL);
> >         if (!cmp.src_pages || !cmp.dst_pages) {
> > -               kfree(cmp.src_pages);
> > -               kfree(cmp.dst_pages);
> > -               return -ENOMEM;
> > +               ret = -ENOMEM;
> > +               goto out_free;
> >         }
> >
> >         if (same_inode)
> > @@ -3211,8 +3212,9 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 olen,
> >         else
> >                 btrfs_double_inode_unlock(src, dst);
> >
> > -       kfree(cmp.src_pages);
> > -       kfree(cmp.dst_pages);
> > +out_free:
> > +       kvfree(cmp.src_pages);
> > +       kvfree(cmp.dst_pages);
> 
> kvfree() missing at btrfs_cmp_data_free() too.

Bah, no more quick fixes from me today. I'll drop the patch from the
branch and will have a fresh look another day.