Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big

[Christoph Hellwig]

On Tue, Mar 29, 2016 at 03:01:10PM -0700, Shaohua Li wrote:
> The problem is bcache allocates a big bio (with bio_alloc). The bio is
> split with blk_queue_split, but it isn't split to small size because
> queue limit. the bio is cloned later in md, which uses bio_alloc_bioset.
> bio_alloc_bioset itself can't allocate big size bio.

bcache should be fixed to not allocate larger than allowed bios then.
And handling too large arguments to bio_alloc_bioset is still useful to
avoid the checks in the callers and make it robust.