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.
+ 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.
+ put_ioctx(ctx);
+
+ return i? i: ret;
sys_io_getevents() reads:
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).
- z-
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