Re: [PATCH v3 10/16] bcache: handle cache prio_buckets and disk_buckets properly for bucket size > 8MB

Hannes Reinecke
2020-07-15T15:38:28Z

On 7/15/20 4:30 PM, colyli@suse.de wrote:
> From: Coly Li <colyli@suse.de>
>
> Similar to c->uuids, struct cache's prio_buckets and disk_buckets also
> have the potential memory allocation failure during cache registration
> if the bucket size > 8MB.
>
> ca->prio_buckets can be stored on cache device in multiple buckets, its
> in-memory space is allocated by kzalloc() interface but normally
> allocated by alloc_pages() because the size > KMALLOC_MAX_CACHE_SIZE.
>
> So allocation of ca->prio_buckets has the MAX_ORDER restriction too. If
> the bucket size > 8MB, by default the page allocator will fail because
> the page order > 11 (default MAX_ORDER value). ca->prio_buckets should
> also use meta_bucket_bytes(), meta_bucket_pages() to decide its memory
> size and use alloc_meta_bucket_pages() to allocate pages, to avoid the
> allocation failure during cache set registration when bucket size > 8MB.
>
> ca->disk_buckets is a single bucket size memory buffer, it is used to
> iterate each bucket of ca->prio_buckets, and compose the bio based on
> memory of ca->disk_buckets, then write ca->disk_buckets memory to cache
> disk one-by-one for each bucket of ca->prio_buckets. ca->disk_buckets
> should have in-memory size exact to the meta_bucket_pages(), this is the
> size that ca->prio_buckets will be stored into each on-disk bucket.
>
> This patch fixes the above issues and handle cache's prio_buckets and
> disk_buckets properly for bucket size larger than 8MB.
>
> Signed-off-by: Coly Li <colyli@suse.de>
> ---
> drivers/md/bcache/bcache.h | 9 +++++----
> drivers/md/bcache/super.c | 10 +++++-----
> 2 files changed, 10 insertions(+), 9 deletions(-)
>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
--
Dr. Hannes Reinecke Teamlead Storage & Networking
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