On Thu, 2009-12-17 at 20:36 +0100, Jens Axboe wrote: > On Thu, Dec 17 2009, Linus Torvalds wrote: > > > > > > On Thu, 17 Dec 2009, tytso@xxxxxxx wrote: > > > > > > Sure, but there's some rumors/oral traditions going around that some > > > block devices want bio address which are page aligned, because they > > > want to play some kind of refcounting game, > > > > Yeah, you might be right at that. > > > > > And it's Weird Shit(tm) (aka iSCSI, AoE) type drivers, that most of us > > > don't have access to, so just because it works Just Fine on SATA doesn't > > > mean anything. > > > > > > And none of this is documented anywhere, which is frustrating as hell. > > > Just rumors that "if you do this, AoE/iSCSI will corrupt your file > > > systems". > > > > ACK. Jens? > > I've heard those rumours too, and I don't even know if they are true. > Who has a pointer to such a bug report and/or issue? The block layer > itself doesn't not have any such requirements, and the only places where > we play page games is for bio's that were explicitly mapped with pages > by itself (like mapping user data).o OK, so what happened is that prior to the map single fix commit df46b9a44ceb5af2ea2351ce8e28ae7bd840b00f Author: Mike Christie <michaelc@xxxxxxxxxxx> Date: Mon Jun 20 14:04:44 2005 +0200 [PATCH] Add blk_rq_map_kern() bio could only accept user space buffers, so we had a special path for kernel allocated buffers. That commit unified the path (with a separate block API) so we could now submit kmalloc'd buffers via block APIs. So the rule now is we can accept any user mapped area via blk_rq_map_user and any kmalloc'd area via blk_rq_map_kern(). We might not be able to do a stack area (depending on how the arch maps the stack) and we definitely cannot do a vmalloc'd area. So it sounds like we only need a blk_rq_map_vmalloc() using the same techniques as the patch set and we're good to go. > We fix driver crap like that, we don't work around it. It's a BUG. James -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html