On Sat, Jul 15, 2017 at 4:54 AM, Liu Bo <bo.li.liu@xxxxxxxxxx> wrote: > On Fri, Jul 14, 2017 at 08:22:31AM -0600, Jens Axboe wrote: >> On 07/14/2017 07:47 AM, Ming Lei wrote: >> >> @@ -156,6 +156,9 @@ static inline void *bio_data(struct bio *bio) >> >> /* >> >> * drivers should _never_ use the all version - the bio may have been split >> >> * before it got to the driver and the driver won't own all of it >> >> + * >> >> + * Note that cloned bios must not use this as their bi_vcnt may be invalid and >> >> + * this could lead to silent corruptions. >> >> */ >> >> #define bio_for_each_segment_all(bvl, bio, i) \ >> >> for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++) >> >> -- >> >> 2.13.0 >> >> >> > >> > Maybe we can add a warning here if it is a cloned bio. >> >> I think that's a good idea, it's easy for people to get this wrong, and >> the consequences can be dire. How about something like this? >> >> diff --git a/include/linux/bio.h b/include/linux/bio.h >> index 7b1cf4ba0902..13b6ac6eae29 100644 >> --- a/include/linux/bio.h >> +++ b/include/linux/bio.h >> @@ -155,9 +155,12 @@ static inline void *bio_data(struct bio *bio) >> >> /* >> * drivers should _never_ use the all version - the bio may have been split >> - * before it got to the driver and the driver won't own all of it >> + * before it got to the driver and the driver won't own all of it. >> + * >> + * Don't use this on cloned bio's. >> */ >> #define bio_for_each_segment_all(bvl, bio, i) \ >> + WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)); \ >> for (i = 0, bvl = (bio)->bi_io_vec; i < (bio)->bi_vcnt; i++, bvl++) >> >> static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter, >> > > This patch gave me a crash, I'm double checking it.. Hi Liu Bo, Looks one extra warning shouldn't have trigger a crash, please double check and update with us. I just start a VM and run a quick test on ext4, btrfs, looks everything is fine, and not see any warning. -- Ming Lei
