On Tue, Nov 15, 2016 at 8:13 AM, Shaohua Li <shli@xxxxxxxxxx> wrote: > On Sat, Nov 12, 2016 at 09:42:38AM -0800, Christoph Hellwig wrote: >> On Fri, Nov 11, 2016 at 11:02:23AM -0800, Shaohua Li wrote: >> > > It's mostly about the RAID1 and RAID10 code which does a lot of funny >> > > things with the bi_iov_vec and bi_vcnt fields, which we'd prefer that >> > > drivers don't touch. One example is the r1buf_pool_alloc code, >> > > which I think should simply use bio_clone for the MD_RECOVERY_REQUESTED >> > > case, which would also take care of r1buf_pool_free. I'm not sure >> > > about all the others cases, as some bits don't fully make sense to me, >> > >> > The problem is we use the iov_vec to track the pages allocated. We will read >> > data to the pages and write out later for resync. If we add new fields to track >> > the pages in r1bio, we could use standard API bio_kmalloc/bio_add_page and >> > avoid the tricky parts. This should work for both the resync and writebehind >> > cases. >> >> I don't think we need to track the pages specificly - if we clone >> a bio we share the bio_vec, e.g. for the !MD_RECOVERY_REQUESTED >> we do one bio_kmalloc, then bio_alloc_pages then clone it for the >> others bios. for MD_RECOVERY_REQUESTED we do a bio_kmalloc + >> bio_alloc_pages for each. > > Sure, for r1buf_pool_alloc, what you suggested should work well. There are a > lot of other places we are using bi_vcnt/bi_io_vec. I'm not sure if it's easy > to replace them with bio iterator. But having a separate data structue to track > the memory we read/rewite/sync and so on definitively will make things easier. > I'm not saying to add the extra data structure in bio but instead in r1bio. >From view of multipage bvec, r1buf_pool_alloc() is fine because the direct access to bi_vcnt/bi_io_vec just happens on a new allocated bio. For other cases, if pages aren't added to one bio via bio_add_page(), and the bio isn't cloned from somewhere, it should be safe to keep current usage about accessing to bi_vcnt/bi_io_vec. But it is cleaner to use bio iterator helpers than direct access. Thanks, Ming Lei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
