Re: [PATCH] blk-mq: fix updating tags depth

[Marco Patalano <mpatalan@redhat.com>]

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Tested by: Marco Patalano <mpatalan@redhat.com>

On Thu, Aug 2, 2018 at 6:23 AM, Ming Lei <ming.lei@redhat.com> wrote:

> The passed 'nr' from userspace represents the total depth, meantime
> inside 'struct blk_mq_tags', 'nr_tags' stores the total tag depth,
> and 'nr_reserved_tags' stores the reserved part.
>
> There are two issues in blk_mq_tag_update_depth() now:
>
> 1) for growing tags, we should have used the passed 'nr', and keep the
> number of reserved tags not changed.
>
> 2) the passed 'nr' should have been used for checking against
> 'tags->nr_tags', instead of number of the normal part.
>
> This patch fixes the above two cases, and avoids kernel crash caused
> by wrong resizing sbitmap queue.
>
> Cc: Marco Patalano <mpatalan@redhat.com>
> Cc: "Ewan D. Milne" <emilne@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Bart Van Assche <bart.vanassche@sandisk.com>
> Cc: Omar Sandoval <osandov@fb.com>
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  block/blk-mq-tag.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index 09b2ee6694fb..c43b3398d7b4 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -399,8 +399,6 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>         if (tdepth <= tags->nr_reserved_tags)
>                 return -EINVAL;
>
> -       tdepth -= tags->nr_reserved_tags;
> -
>         /*
>          * If we are allowed to grow beyond the original size, allocate
>          * a new set of tags before freeing the old one.
> @@ -420,7 +418,8 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>                 if (tdepth > 16 * BLKDEV_MAX_RQ)
>                         return -EINVAL;
>
> -               new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth, 0);
> +               new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth,
> +                               tags->nr_reserved_tags);
>                 if (!new)
>                         return -ENOMEM;
>                 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth);
> @@ -437,7 +436,8 @@ int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx,
>                  * Don't need (or can't) update reserved tags here, they
>                  * remain static and should never need resizing.
>                  */
> -               sbitmap_queue_resize(&tags->bitmap_tags, tdepth);
> +               sbitmap_queue_resize(&tags->bitmap_tags,
> +                               tdepth - tags->nr_reserved_tags);
>         }
>
>         return 0;
> --
> 2.9.5
>
>

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