On Mon, Jun 07, 2021 at 07:55:22PM +0800, Coly Li wrote:
On 6/7/21 7:06 PM, Christoph Hellwig wrote:
On Mon, Jun 07, 2021 at 06:35:39PM +0800, Coly Li wrote:
- /* Limitation for valid replace key size and cache_bio bvecs number */
- size_limit = min_t(unsigned int, bio_max_segs(UINT_MAX) * PAGE_SECTORS,
(1 << KEY_SIZE_BITS) - 1);bio_max_segs kaps the argument to BIO_MAX_VECS, so you might as well
It was suggested to not directly access BIO_MAX_VECS by you, maybe I misunderstood you.
Yes, drivers really should not care about it. But hiding that behind a tiny wrapper doesn't help either.
directly write BIO_MAX_VECS. Can you explain the PAGE_SECTORS here a bit more? Does this code path use discontiguous per-sector allocations? Preferably in a comment.
It is just because bch_bio_map() assume the maximum bio size is 1MB. It was not true since the multiple pages bvecs was merged in mainline kernel. The PAGE_SECTORS part is legacy for 1MB maximum size bio (256*4KB), it should be fixed/improved later to use multiple pages for bio size > 1MB and replace bch_bio_map().
bch_bio_map and bch_bio_alloc_pages that poke directly into the bio are the root cause of a lot of these problems.
I had a series fixing some of that but Kent did not like it. Drivers must not diretly access bi_vcnt or directly build bios.
Not any more. Now the line limit is 100 characters. Though I still prefer 80 characters, place 86 characters in single line makes the change more obvious.
It makes it really hard to read in a normal terminal.