Re: [PATCH 1/1] generic: test FALLOC_FL_UNSHARE when pagecache is not loaded

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

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

> From: Darrick J. Wong <djwong@kernel.org>
>
> 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
>
>
> diff --git a/tests/xfs/1936 b/tests/xfs/1936
> new file mode 100755
> index 0000000000..e07b8f4796
> --- /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

We might as well remove above imports if we are not using those in this test.

> +. ./common/reflink
> +
> +_fixed_by_git_commit kernel XXXXXXXXXXXXX \
> +	"iomap: don't skip reading in !uptodate folios when unsharing a range"

Once I guess it is merged, we will have the commit-id. Ohh wait, we have
it already right? 

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=35d30c9cf12730a1e37053dfde4007c7cc452d1a

With that the testcode looks good to me. Thanks for finding an easy
reproducer. Please feel free to add - 

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

-ritesh