ceph: fix incorrect kmalloc size of pagevec mempool

The kmalloc size of pagevec mempool is incorrectly calculated.
It misses the size of page pointer and only accounts the number for the array.

Fixes: a0102bda5bc0 ("ceph: move sb->wb_pagevec_pool to be a global mempool")
Signed-off-by: ethanwu <ethanwu@synology.com>
---
 fs/ceph/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

On 7/11/24 14:47, ethanwu wrote:
> The kmalloc size of pagevec mempool is incorrectly calculated.
> It misses the size of page pointer and only accounts the number for the array.
>
> Fixes: a0102bda5bc0 ("ceph: move sb->wb_pagevec_pool to be a global mempool")
> Signed-off-by: ethanwu <ethanwu@synology.com>
> ---
>   fs/ceph/super.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 885cb5d4e771..46f640514561 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -961,7 +961,8 @@ static int __init init_caches(void)
>   	if (!ceph_mds_request_cachep)
>   		goto bad_mds_req;
>   
> -	ceph_wb_pagevec_pool = mempool_create_kmalloc_pool(10, CEPH_MAX_WRITE_SIZE >> PAGE_SHIFT);
> +	ceph_wb_pagevec_pool = mempool_create_kmalloc_pool(10,
> +				(CEPH_MAX_WRITE_SIZE >> PAGE_SHIFT) * sizeof(struct page *));
>   	if (!ceph_wb_pagevec_pool)
>   		goto bad_pagevec_pool;
>   

Good cache, LGTM.

Reviewed-by: Xiubo Li <xiubli@redhat.com>

On Mon, Jul 15, 2024 at 4:10 AM Xiubo Li <xiubli@redhat.com> wrote:
>
>
> On 7/11/24 14:47, ethanwu wrote:
> > The kmalloc size of pagevec mempool is incorrectly calculated.
> > It misses the size of page pointer and only accounts the number for the array.
> >
> > Fixes: a0102bda5bc0 ("ceph: move sb->wb_pagevec_pool to be a global mempool")
> > Signed-off-by: ethanwu <ethanwu@synology.com>
> > ---
> >   fs/ceph/super.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> > index 885cb5d4e771..46f640514561 100644
> > --- a/fs/ceph/super.c
> > +++ b/fs/ceph/super.c
> > @@ -961,7 +961,8 @@ static int __init init_caches(void)
> >       if (!ceph_mds_request_cachep)
> >               goto bad_mds_req;
> >
> > -     ceph_wb_pagevec_pool = mempool_create_kmalloc_pool(10, CEPH_MAX_WRITE_SIZE >> PAGE_SHIFT);
> > +     ceph_wb_pagevec_pool = mempool_create_kmalloc_pool(10,
> > +                             (CEPH_MAX_WRITE_SIZE >> PAGE_SHIFT) * sizeof(struct page *));
> >       if (!ceph_wb_pagevec_pool)
> >               goto bad_pagevec_pool;
> >
>
> Good cache, LGTM.

I don't think this matters in practice since 64M / 4K = 16K * 10 = 160K
of memory reserved just for page pointers is already quite a lot...

However, since commit a0102bda5bc0 is talking about moving a pool to be
global without adjusting its parameters, I agree that this fix is valid.

Thanks,

                Ilya