Re: [PATCH] generic: add a test to ensure that page is properly filled before write

[Eryu Guan <guan@eryu.me>]

On Sat, Jun 12, 2021 at 08:31:54AM -0400, Jeff Layton wrote:
> We had a broken optimization in cephfs and netfs lib that could cause
> part of a page to be improperly zeroed-out when writing to an offset
> that was beyond the EOF but in an existing page.
> 
> Add a simple test that would have caught this.
> 
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
>  tests/generic/XXX     | 53 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/XXX.out |  5 ++++

Ah, all the 'XXX' in this test should be replaced with proper seq
number.

>  tests/generic/group   |  1 +
>  3 files changed, 59 insertions(+)
>  create mode 100755 tests/generic/XXX
>  create mode 100644 tests/generic/XXX.out
> 
> diff --git a/tests/generic/XXX b/tests/generic/XXX
> new file mode 100755
> index 000000000000..0ddaaa544609
> --- /dev/null
> +++ b/tests/generic/XXX
> @@ -0,0 +1,53 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2021, Jeff Layton <jlayton@redhat.com>
> +#
> +# FS QA Test No. XXX
> +#
> +# Open a file and write a little data to it. Unmount (to clean out the cache)
> +# and then mount again. Then write some data to it beyond the EOF and ensure
> +# the result is correct. Prompted by a bug in ceph_write_begin. See:
> +#
> +# https://lore.kernel.org/ceph-devel/97002.1623448034@warthog.procyon.org.uk/T/#m9f34b328623b493c529505e12f64f4dfdbddfb27

This looks like a thread 9 months ago. Was the fix merged? If so, it'd
be better to reference the kernel commit here.

Otherwise test looks fine to me.

Thanks,
Eryu

> +#
> +seq=`basename $0`
> +seqres=$RESULT_DIR/$seq
> +echo "QA output created by $seq"
> +
> +here=`pwd`
> +status=1    # failure is the default!
> +trap "_cleanup; exit \$status" 0 1 2 3 15
> +
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -f $testfile
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +
> +_supported_fs generic
> +_require_test
> +
> +rm -f $seqres.full
> +
> +testfile="$TEST_DIR/test_write_begin.$$"
> +
> +# write some data to file and fsync it out
> +$XFS_IO_PROG -f -c "pwrite -q 0 32" $testfile
> +
> +# cycle the mount to clean out the pagecache
> +_test_cycle_mount
> +
> +# now, write to the file (near the end)
> +$XFS_IO_PROG -c "pwrite -q 32 32" $testfile
> +
> +# dump what we think is in there
> +echo "The result should be 64 bytes filled with 0xcd:"
> +hexdump -C $testfile
> +
> +status=0
> +exit
> diff --git a/tests/generic/XXX.out b/tests/generic/XXX.out
> new file mode 100644
> index 000000000000..4e7653858e51
> --- /dev/null
> +++ b/tests/generic/XXX.out
> @@ -0,0 +1,5 @@
> +QA output created by XXX
> +The result should be 64 bytes filled with 0xcd:
> +00000000  cd cd cd cd cd cd cd cd  cd cd cd cd cd cd cd cd  |................|
> +*
> +00000040
> diff --git a/tests/generic/group b/tests/generic/group
> index 9a636b23f243..204a9b548f78 100644
> --- a/tests/generic/group
> +++ b/tests/generic/group
> @@ -641,3 +641,4 @@
>  636 auto quick swap
>  637 auto quick dir
>  638 auto quick rw
> +XXX auto quick rw
> -- 
> 2.31.1
>