On Thu, Aug 14, 2014 at 11:50:32PM +0800, Ming Lei wrote: > From: Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> > > This adds an interface that lets kernel callers submit aio iocbs without > going through the user space syscalls. This lets kernel callers avoid > the management limits and overhead of the context. It will also let us > integrate aio operations with other kernel apis that the user space > interface doesn't have access to. > > This patch is based on Dave's posts in below links: > > https://lkml.org/lkml/2013/10/16/365 > https://groups.google.com/forum/#!topic/linux.kernel/l7mogGJZoKQ (And some other werido's posts, almost 5 entire earth years ago: http://permalink.gmane.org/gmane.linux.file-systems/36246) > +struct kiocb *aio_kernel_alloc(gfp_t gfp, unsigned extra) > +{ > + return kzalloc(sizeof(struct kiocb) + extra, gfp); Is kzalloc really necessary? It's insane, but in the past we've had people whine about the cycle costs of zeroing fields that are to be initialized: commit 23aee091d804efa8cc732a31c1ae5d625e1ec886 Author: Jeff Moyer <jmoyer@xxxxxxxxxx> Date: Tue Dec 15 16:47:49 2009 -0800 dio: don't zero out the pages array inside struct dio Maybe add a guard value to the ctx and have submission freak out of it's called without being initialized? If callers really want to zero they can pass in __GFP_ZERO. The extra allocation at the end that's freed is nice, but the callers having a clumsy manual cast to access it isn't nice at all. Can you add a little helper to get a pointer to the extra allocation? That'd let the aio bits allocation the iocbs however the like (slab, per-cpu, whatever) and have extra allocations separate if that ends up making sense. > + iocb->ki_ctx = (void *)-1; The magic -1 is gross. Use a constant? (bonus points for having it use ERR_PTR() :)) > + /* > + * use same policy with userspace aio, req may have been > + * completed already, so release it by aio completion. > + */ > + if (ret != -EIOCBQUEUED) > + iocb->ki_obj.complete(iocb->ki_user_data, ret); I wonder if this needs to handle the restarting error codes like aio_complete() does. commit a0c42bac79731276c9b2f28d54f9e658fcf843a2 Author: Jan Kara <jack@xxxxxxx> Date: Wed Sep 22 13:05:03 2010 -0700 aio: do not return ERESTARTSYS as a result of AIO I like how this has evolved to get rid of the magic key and commands.. just the ki_ctx and calling iter methods, nice stuff. - z -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
