Re: [PATCH] btrfs: test incremental send on sparse file with trailing hole

[Anand Jain <anand.jain@oracle.com>]

On 2/19/24 17:31, fdmanana@kernel.org wrote:
> From: Filipe Manana <fdmanana@suse.com>
> 
> Test that an incremental send does not issue unnecessary writes for a
> sparse file that got one new extent between its previous extent and the
> file's size.
> 
> This exercises a fix by the following patch:
> 
>    "btrfs: send: don't issue unnecessary zero writes for trailing hole"
> 
> Signed-off-by: Filipe Manana <fdmanana@suse.com>

looks good
Reviewed-by: Anand Jain <anand.jain@oracle.com>

Queued for the upcoming pull request.

Thanks, Anand

> ---
>   tests/btrfs/303     | 92 +++++++++++++++++++++++++++++++++++++++++++++
>   tests/btrfs/303.out | 24 ++++++++++++
>   2 files changed, 116 insertions(+)
>   create mode 100755 tests/btrfs/303
>   create mode 100644 tests/btrfs/303.out
> 
> diff --git a/tests/btrfs/303 b/tests/btrfs/303
> new file mode 100755
> index 00000000..26bcfe41
> --- /dev/null
> +++ b/tests/btrfs/303
> @@ -0,0 +1,92 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (C) 2024 SUSE Linux Products GmbH. All Rights Reserved.
> +#
> +# FS QA Test 303
> +#
> +# Test that an incremental send does not issue unnecessary writes for a sparse
> +# file that got one new extent between its previous extent and the file's size.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick snapshot send fiemap
> +
> +_cleanup()
> +{
> +	cd /
> +	rm -r -f $tmp.*
> +	rm -fr $send_files_dir
> +}
> +
> +. ./common/filter
> +. ./common/punch  # for _filter_fiemap
> +
> +_supported_fs btrfs
> +_require_test
> +_require_scratch
> +_require_xfs_io_command "fiemap"
> +
> +_fixed_by_kernel_commit XXXXXXXXXXXX \
> +	"btrfs: send: don't issue unnecessary zero writes for trailing hole"
> +
> +send_files_dir=$TEST_DIR/btrfs-test-$seq
> +
> +rm -fr $send_files_dir
> +mkdir $send_files_dir
> +
> +_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed"
> +_scratch_mount
> +
> +$XFS_IO_PROG -f -c "truncate 1G" $SCRATCH_MNT/foobar
> +
> +# Now create the base snapshot, which is going to be the parent snapshot for
> +# a later incremental send.
> +$BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT \
> +		 $SCRATCH_MNT/mysnap1 > /dev/null
> +
> +# Create send stream (full send) for the first snapshot.
> +$BTRFS_UTIL_PROG send -f $send_files_dir/1.snap \
> +		 $SCRATCH_MNT/mysnap1 2>&1 1>/dev/null | _filter_scratch
> +
> +# Now write one extent at the beginning of the file and one somewhere in the
> +# middle, leaving a gap between the end of this second extent and the file's
> +# size.
> +$XFS_IO_PROG -c "pwrite -S 0xab -b 64K 0 64K" \
> +	     -c "pwrite -S 0xcd -b 64K 512M 64K" \
> +	     $SCRATCH_MNT/foobar | _filter_xfs_io
> +
> +# Now create a second snapshot which is going to be used for an incremental
> +# send operation.
> +$BTRFS_UTIL_PROG subvolume snapshot -r $SCRATCH_MNT \
> +		 $SCRATCH_MNT/mysnap2 > /dev/null
> +
> +# Create send stream (incremental send) for the second snapshot.
> +$BTRFS_UTIL_PROG send -p $SCRATCH_MNT/mysnap1 -f $send_files_dir/2.snap \
> +		 $SCRATCH_MNT/mysnap2 2>&1 1>/dev/null | _filter_scratch
> +
> +# Now recreate the filesystem by receiving both send streams and verify we get
> +# the same content that the original filesystem had and file foobar has only two
> +# extents with a size of 64K each.
> +_scratch_unmount
> +_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed"
> +_scratch_mount
> +
> +$BTRFS_UTIL_PROG receive -f $send_files_dir/1.snap $SCRATCH_MNT > /dev/null
> +$BTRFS_UTIL_PROG receive -f $send_files_dir/2.snap $SCRATCH_MNT > /dev/null
> +
> +echo "File content in the new filesystem:"
> +_hexdump $SCRATCH_MNT/mysnap2/foobar
> +
> +echo "File fiemap in the new filesystem:"
> +# Should have:
> +#
> +# 64K extent at file range [0, 64K[
> +# hole at file range [64K, 512M[
> +# 64K extent at file range [512M, 512M + 64K[
> +# hole at file range [512M + 64K, 1G[
> +$XFS_IO_PROG -r -c "fiemap -v" $SCRATCH_MNT/mysnap2/foobar | _filter_fiemap
> +
> +# File should be using only 128K of data (two 64K extents).
> +echo "Space used by the file: $(du -h $SCRATCH_MNT/mysnap2/foobar | cut -f 1)"
> +
> +status=0
> +exit
> diff --git a/tests/btrfs/303.out b/tests/btrfs/303.out
> new file mode 100644
> index 00000000..7659a794
> --- /dev/null
> +++ b/tests/btrfs/303.out
> @@ -0,0 +1,24 @@
> +QA output created by 303
> +At subvol SCRATCH_MNT/mysnap1
> +wrote 65536/65536 bytes at offset 0
> +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> +wrote 65536/65536 bytes at offset 536870912
> +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> +At subvol SCRATCH_MNT/mysnap2
> +At subvol mysnap1
> +File content in the new filesystem:
> +000000 ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab  >................<
> +*
> +010000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  >................<
> +*
> +20000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd  >................<
> +*
> +20010000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  >................<
> +*
> +40000000
> +File fiemap in the new filesystem:
> +0: [0..127]: data
> +1: [128..1048575]: hole
> +2: [1048576..1048703]: data
> +3: [1048704..2097151]: hole
> +Space used by the file: 128K