Re: [PATCH 1/2] fs: avoid fdput() after failed fdget() in ksys_sync_file_range()

Al Viro
2020-05-08T00:24:32Z

On Fri, May 08, 2020 at 01:05:09AM +0100, Al Viro wrote:
> On Thu, May 07, 2020 at 05:57:09PM -0600, Shuah Khan wrote:
> > Fix ksys_sync_file_range() to avoid fdput() after a failed fdget().
> > fdput() doesn't do fput() on this file since FDPUT_FPUT isn't set
> > in fd.flags. Fix it anyway since failed fdget() doesn't require
> > a fdput().
> >
> > This was introdcued in a commit to add sync_file_range() helper.
>
> Er... What's the point microoptimizing the slow path here?

PS: I'm not saying the patch is incorrect, but Fixes: is IMO over the
top. And looking at that thing,
{
struct fd f = fdget(fd);
int ret;

if (unlikely(!f.file))
return -EBADF;

ret = sync_file_range(f.file, offset, nbytes, flags);
fdput(f);
return ret;
}

might be cleaner, but that's a matter of taste...