Re: [PATCH 3/2] fstests: test FALLOC_FL_UNSHARE when pagecache is not loaded

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

"Darrick J. Wong" <djwong@kernel.org> writes:

> Add a regression test for funsharing uncached files to ensure that we
> actually manage the pagecache state correctly.
>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  tests/xfs/1936     |   88 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/xfs/1936.out |    4 ++
>  2 files changed, 92 insertions(+)
>  create mode 100755 tests/xfs/1936
>  create mode 100644 tests/xfs/1936.out

1936? I am not sure how that works though. 
./new I guess automatically gives the testcase no. for a new testcase right.

>
> diff --git a/tests/xfs/1936 b/tests/xfs/1936
> new file mode 100755
> index 0000000000..bcf9b6b478
> --- /dev/null
> +++ b/tests/xfs/1936
> @@ -0,0 +1,88 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2023 Oracle.  All Rights Reserved.
> +#
> +# FS QA Test 1936
> +#
> +# This is a regression test for the kernel commit noted below.  The stale
> +# memory exposure can be exploited by creating a file with shared blocks,
> +# evicting the page cache for that file, and then funshareing at least one
> +# memory page's worth of data.  iomap will mark the page uptodate and dirty
> +# without ever reading the ondisk contents.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick unshare clone
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -r -f $tmp.* $testdir
> +}
> +
> +# real QA test starts here
> +
> +# Import common functions.
> +. ./common/filter
> +. ./common/attr
> +. ./common/reflink
> +
> +_fixed_by_git_commit kernel XXXXXXXXXXXXX \
> +	"iomap: don't skip reading in !uptodate folios when unsharing a range"
> +
> +# real QA test starts here
> +_require_test_reflink
> +_require_cp_reflink
> +_require_xfs_io_command "funshare"
> +
> +testdir=$TEST_DIR/test-$seq
> +rm -rf $testdir
> +mkdir $testdir
> +
> +# Create a file that is at least four pages in size and aligned to the
> +# file allocation unit size so that we don't trigger any unnecessary zeroing.
> +pagesz=$(_get_page_size)
> +alloc_unit=$(_get_file_block_size $TEST_DIR)
> +filesz=$(( ( (4 * pagesz) + alloc_unit - 1) / alloc_unit * alloc_unit))
> +
> +echo "Create the original file and a clone"
> +_pwrite_byte 0x61 0 $filesz $testdir/file2.chk >> $seqres.full
> +_pwrite_byte 0x61 0 $filesz $testdir/file1 >> $seqres.full
> +_cp_reflink $testdir/file1 $testdir/file2
> +_cp_reflink $testdir/file1 $testdir/file3
> +
> +_test_cycle_mount
> +
> +cat $testdir/file3 > /dev/null
> +
> +echo "Funshare at least one pagecache page"
> +$XFS_IO_PROG -c "funshare 0 $filesz" $testdir/file2
> +$XFS_IO_PROG -c "funshare 0 $filesz" $testdir/file3
> +_pwrite_byte 0x61 0 $filesz $testdir/file2.chk >> $seqres.full

We don't need to write the bytes again to file2.chk. We already wrote above.
Otherwise looks right to me. Nice testcase indeed.

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>


> +
> +echo "Check contents"
> +
> +# file2 wasn't cached when it was unshared, but it should match
> +if ! cmp -s $testdir/file2.chk $testdir/file2; then
> +	echo "file2.chk does not match file2"
> +
> +	echo "file2.chk contents" >> $seqres.full
> +	od -tx1 -Ad -c $testdir/file2.chk >> $seqres.full
> +	echo "file2 contents" >> $seqres.full
> +	od -tx1 -Ad -c $testdir/file2 >> $seqres.full
> +	echo "end bad contents" >> $seqres.full
> +fi
> +
> +# file3 was cached when it was unshared, and it should match
> +if ! cmp -s $testdir/file2.chk $testdir/file3; then
> +	echo "file2.chk does not match file3"
> +
> +	echo "file2.chk contents" >> $seqres.full
> +	od -tx1 -Ad -c $testdir/file2.chk >> $seqres.full
> +	echo "file3 contents" >> $seqres.full
> +	od -tx1 -Ad -c $testdir/file3 >> $seqres.full
> +	echo "end bad contents" >> $seqres.full
> +fi
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/xfs/1936.out b/tests/xfs/1936.out
> new file mode 100644
> index 0000000000..c7c820ced5
> --- /dev/null
> +++ b/tests/xfs/1936.out
> @@ -0,0 +1,4 @@
> +QA output created by 1936
> +Create the original file and a clone
> +Funshare at least one pagecache page
> +Check contents