On Wed, Aug 08, 2012 at 11:52:51PM -0700, Tejun Heo wrote: > On Wed, Aug 08, 2012 at 07:56:10PM -0700, Kent Overstreet wrote: > > > So, bio_clone() loses its function comment. Also, does it even make > > > sense to call bio_clone() from fs_bio_set? > > > > I'll re add the function comment if you want, just for a single line > > wrapper I don't know if it's worth the cost - comments get out of date, > > and they're more stuff to wade through. > > People actually look at docbook generated docs. I don't know why but > they do. It's a utility function at block layer. Please just add the > comment. Will do then. > > > Let's say it's so, then > > > what's the difference from using _kmalloc variant? > > > > bio_kmalloc() fails if nr_iovecs > 1024, bio_alloc_bioset() fails if > > nr_iovecs > 256 > > > > and bio_alloc_bioset() is mempool backed, bio_kmalloc() is not. > > > > AFAICT that's it. > > So, the thing is being mempool backed doesn't mean anything if > multiple layers use the pool. It's worse than just using kmalloc, because then you've introduced the possibility of deadlock. > I *suspect* fs_bio_set is supposed to > be used by fs layer - ie. where bios originate. The reason why I > wondered about bio_clone() is that bio_clone() is almost always used > from stacking drivers and stacking driver tapping into fs reserve is > buggy. So, I'm wondering whether cloning from fs_bio_set should be > supported at all. That's actually a really good point. I just grepped and there's actually only 3 callers - I thought there'd be more. That should be easy to fix, at least. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
