Re: [PATCH] generic: test zero-byte writes to new file

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Feb 14, 2025 at 08:36:25AM -0600, Eric Sandeen wrote:
> On 2/13/25 10:02 PM, Darrick J. Wong wrote:
> > On Thu, Feb 13, 2025 at 09:17:28PM -0600, Eric Sandeen wrote:
> >> On 2/13/25 2:50 PM, Eric Sandeen wrote:
> >>> On 2/13/25 1:51 PM, Darrick J. Wong wrote:
> >>
> >> ...
> >>
> >>>>> +rm -f $TEST_DIR/testfile.$seq
> >>>>> +$XFS_IO_PROG -f -c "pwrite 0 0" $TEST_DIR/testfile.$seq
> >>>>> +test -f $TEST_DIR/testfile.$seq || _fail "file not created"
> >>>>
> >>>> When does the file not get created?
> >>>
> >>> In some unknown error case? ;)
> >>> There's probably no reason for that test, though of course
> >>> it's still expected to pass.
> >>>
> >>> In the various discussions of the exfat bug scattered around
> >>> the internet people kept pointing out that "well, the file does
> >>> get created" so I probably had that on my mind.
> >>
> >> To put a finer point on it, because I can't tell for sure - are
> >> you asking me to take that test out?
> > 
> > Nah, I was just wondering if there was something about the buggy exfat
> > code that either prevented the file from being created, or if the bug
> > was that the empty file got deleted after the zero-byte pwrite and I
> > misunderstood what's going on.
> 
> Ah, I see. No, the observable problem was an -EFAULT on the write,
> and the file /does/ get created as expected. The test probably is
> extraneous to the original bug, because of course open(O_CREAT) and
> write(0) are two separate operations. I was just a bit over-eager
> when writing the test.

<nod> Would you mind resending, but with the rm removed?

--D

> Thanks,
> -Eric
> 
> > (IOWs I think this test is fine, but could the exfat maintainer
> > clarify?)
> > 
> > --D
> > 
> >> Thanks,
> >> -Eric
> >>
> >>
> > 
> 
>