On Wed, May 16, 2018 at 10:36:14AM +0530, Ritesh Harjani wrote: > 1. if bio_full is true that means no space in bio->bio_io_vec[] no? > Than how come we are still proceeding ahead with only warning? > While originally in bio_add_page we used to return after checking > bio_full. Callers can still call __bio_add_page directly right.
I you don't know if the bio is full or not don't use __bio_add_page, keep using bio_add_page. The WARN_ON is just a debug tool to catch cases where the developer did use it incorrectly. > 2. IF above is correct why don't we set the bio->bi_max_vecs to the size > of the slab instead of keeeping it to nr_iovecs which user requested? > (in bio_alloc_bioset) Because we limit the user to the number that the user requested. Not that this patch changes anything about that. > 3. Could you please help understand why for cloned bio we still allow > __bio_add_page to work? why not WARN and return like in original code? It doesn't work, and I have now added the WARN_ON to deal with any incorrect usage. >> - if (bio->bi_vcnt >= bio->bi_max_vecs) >> - return 0; > Originally here we were supposed to return and not proceed further. > Should __bio_add_page not have similar checks to safeguard crossing > the bio_io_vec[] boundary? No, __bio_add_page is the "I know what I am doing" interface.
