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Date: Fri, 18 Nov 2016 11:19:45 +0800
From: Eryu Guan <eguan@redhat.com>
Subject: Re: [PATCH] generic: test concurrent non-overlapping direct I/O on
 the same extents
Message-ID: <20161118031945.GD27776@eguan.usersys.redhat.com>
References: <1edb45d8895de8fe347e800a5fd22b0f6eafb181.1479342541.git.osandov@fb.com>
 <20161117052611.GX27776@eguan.usersys.redhat.com>
 <20161117181412.GA21816@vader.DHCP.thefacebook.com>
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Sender: fstests-owner@vger.kernel.org
To: Omar Sandoval <osandov@osandov.com>
Cc: fstests@vger.kernel.org, linux-btrfs@vger.kernel.org, kernel-team@fb.com
List-ID: <fstests@vger.kernel.org>

On Thu, Nov 17, 2016 at 10:14:12AM -0800, Omar Sandoval wrote:
> On Thu, Nov 17, 2016 at 01:26:11PM +0800, Eryu Guan wrote:
> > On Wed, Nov 16, 2016 at 04:29:34PM -0800, Omar Sandoval wrote:
> > > From: Omar Sandoval <osandov@fb.com>
> > > 
> > > There have been a couple of logic bugs in `btrfs_get_extent()` which
> > > could lead to spurious -EEXIST errors from read or write. This test
> > > exercises those conditions by having two threads race to add an extent
> > > to the extent map.
> > > 
> > > This is fixed by Linux commit 8dff9c853410 ("Btrfs: deal with duplciates
> > > during extent_map insertion in btrfs_get_extent") and the patch "Btrfs:
> > > deal with existing encompassing extent map in btrfs_get_extent()"
> > > (http://marc.info/?l=linux-btrfs&m=147873402311143&w=2).
> > > 
> > > Although the bug is Btrfs-specific, nothing about the test is.
> > > 
> > > Signed-off-by: Omar Sandoval <osandov@fb.com>
> > > ---
> > [snip]
> > > +# real QA test starts here
> > > +
> > > +_supported_fs generic
> > > +_supported_os Linux
> > > +_require_test
> > > +_require_xfs_io_command "falloc"
> > > +_require_test_program "dio-interleaved"
> > > +
> > > +extent_size="$(($(stat -f -c '%S' "$TEST_DIR") * 2))"
> > 
> > There's a helper to get fs block size: "get_block_size".
> > 
> > > +num_extents=1024
> > > +testfile="$TEST_DIR/$$-testfile"
> > > +
> > > +truncate -s 0 "$testfile"
> > 
> > I prefer using xfs_io to do the truncate, 
> > 
> > $XFS_IO_PROG -fc "truncate 0" "$testfile"
> > 
> > Because in rare cases truncate(1) may be unavailable, e.g. RHEL5,
> > usually it's not a big issue, but xfs_io works all the time, we have a
> > better way, so why not :)
> > 
> > > +for ((off = 0; off < num_extents * extent_size; off += extent_size)); do
> > > +	xfs_io -c "falloc $off $extent_size" "$testfile"
> > 
> > Use $XFS_IO_PROG not bare xfs_io.
> > 
> > I can fix all the tiny issues at commit time.
> > 
> > Thanks,
> > Eryu
> 
> Thank you, Eryu, that's all okay with me. I also had a typo here:
> 
> diff --git a/src/dio-interleaved.c b/src/dio-interleaved.c
> index 831a191..6b04c99 100644
> --- a/src/dio-interleaved.c
> +++ b/src/dio-interleaved.c
> @@ -58,7 +58,7 @@ int main(int argc, char **argv)
>  	int fd;
>  
>  	if (argc != 4) {
> -		fprintf(stderr, "usage: %s SECTORSIZE NUM_EXTENTS PATH\n",
> +		fprintf(stderr, "usage: %s EXTENT_SIZE NUM_EXTENTS PATH\n",
>  			argv[0]);
>  		return EXIT_FAILURE;
>  	}
> 
> 
> Feel free to fix this at commit time, too, or I can send a v2 if you
> prefer.

Thanks! I'll fix them all.

Eryu