linux-kernel - Re: [PATCH 1/2] fs: avoid fdput() after failed fdget() in ksys_sync_file

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Message-ID: <20200508022139.GD11244@42.do-not-panic.com>
Date:   Fri, 8 May 2020 02:21:39 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Shuah Khan <skhan@...uxfoundation.org>, axboe@...nel.dk,
        zohar@...ux.vnet.ibm.com, keescook@...omium.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] fs: avoid fdput() after failed fdget() in
 ksys_sync_file_range()

On Fri, May 08, 2020 at 01:24:22AM +0100, Al Viro wrote:
> 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...

This makes it easier to read.

  Luis