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 <dste...@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 <dste...@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 <dste...@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 <dste...@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
>
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