Messages in this thread |  | | Date | Thu, 30 Nov 2006 10:57:10 +0100 | From | Sébastien Dugué <> | Subject | Re: [PATCH -mm 1/5][AIO] - Rework compat_sys_io_submit |
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On Wed, 29 Nov 2006 16:47:47 -0800, Zach Brown <zach.brown@oracle.com> wrote:
> On Nov 29, 2006, at 2:32 AM, Sébastien Dugué wrote: > > > compat_sys_io_submit() cleanup > > > > > > Cleanup compat_sys_io_submit by duplicating some of the native > > syscall > > logic in the compat layer and directly calling io_submit_one() instead > > of fooling the syscall into thinking it is called from a native 64-bit > > caller. > > > > This is needed for the completion notification patch to avoid having > > to rewrite each iocb on the caller stack for sys_io_submit() to > > find the > > sigevents. > > You could explicitly mention that this eliminates: > > - the overhead of copying nr pointers on the userspace caller's stack > > - the arbitrary PAGE_SIZE/(sizeof(void *)) limit on the number of > iocbs that can be submitted > > Those alone make this worth merging.
Right, will add.
> > > + if (unlikely(!access_ok(VERIFY_READ, iocb, (nr * sizeof(u32))))) > > + return -EFAULT; > > I'm glad you got that right :) I no doubt would have initially > hoisted these little checks into a shared helper function and missed > that detail of getting the size of the access_ok() right in the > compat case.
Thanks.
> > > + put_ioctx(ctx); > > + > > + return i? i: ret; > > sys_io_getevents() reads:
uh! ^^^^^^^^^ you must be meaning sys_io_submit()?
> > put_ioctx(ctx); > return i ? i : ret; > > So while this compat_sys_io_submit() logic seems fine and I would be > comfortable with it landing as-is, I'd also appreciate it if we > didn't introduce differences between the two functions when it seems > just as easy to make them the same. (That chunk is just one > example. There's whitespace, missing unlikely()s, etc). >
OK, will fix.
Thanks,
Sébastien.
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