On 2024/1/24 10:21, Neal Gompa wrote:
On Mon, Jan 22, 2024 at 10:49 PM Qu Wenruo <wqu@xxxxxxxx> wrote:[BUG] There is a report about reading a zstd compressed inline file extent would lead to either a VM_BUG_ON() crash, or lead to incorrect file content. [CAUSE] The root cause is a incorrect memcpy_to_page() call, which uses incorrect page offset, and can lead to either the VM_BUG_ON() as we may write beyond the page boundary, or writes into the incorrect offset of the page. [TEST CASE] The test case would: - Mount with the specified compress algorithm - Create a 4K file - Verify the 4K file is all inlined and compressed - Verify the content of the initial write - Cycle mount to drop all the page cache - Verify the content of the file again - Unmount and fsck the fs This workload would be applied to all supported compression algorithms. And it can catch the problem correctly by triggering VM_BUG_ON(), as our workload would result decompressed extent size to be 4K, and would trigger the VM_BUG_ON() 100%. And with the revert or the new fix, the test case can pass safely. Signed-off-by: Qu Wenruo <wqu@xxxxxxxx> --- tests/btrfs/310 | 81 +++++++++++++++++++++++++++++++++++++++++++++ tests/btrfs/310.out | 2 ++ 2 files changed, 83 insertions(+) create mode 100755 tests/btrfs/310 create mode 100644 tests/btrfs/310.out diff --git a/tests/btrfs/310 b/tests/btrfs/310 new file mode 100755 index 00000000..b514a8bc --- /dev/null +++ b/tests/btrfs/310 @@ -0,0 +1,81 @@ +#! /bin/bash +# SPDX-License-Identifier: GPL-2.0 +# Copyright (C) 2024 SUSE Linux Products GmbH. All Rights Reserved. +# +# FS QA Test 310 +# +# Make sure reading on an compressed inline extent is behaving correctly +# +. ./common/preamble +_begin_fstest auto quick compress + +# Import common functions. +# . ./common/filter + +# real QA test starts here + +# Modify as appropriate. +_supported_fs btrfs +_require_scratch + +# This test require inlined compressed extents creation, and all the writes +# are designed for 4K sector size. +_require_btrfs_inline_extents_creation +_require_btrfs_support_sectorsize 4096 + +_fixed_by_kernel_commit e01a83e12604 \ + "Revert \"btrfs: zstd: fix and simplify the inline extent decompression\"" + +# The correct md5 for the correct 4K file filled with "0xcd" +md5sum_correct="5fed275e7617a806f94c173746a2a723" + +workload() +{ + local algo="$1" + + echo "=== Testing compression algorithm ${algo} ===" >> $seqres.full + _scratch_mkfs >> $seqres.full + _scratch_mount -o compress=${algo} + + _pwrite_byte 0xcd 0 4k "$SCRATCH_MNT/inline_file" > /dev/null + result=$(_md5_checksum "$SCRATCH_MNT/inline_file") + echo "after initial write, md5sum=${result}" >> $seqres.full + if [ "$result" != "$md5sum_correct" ]; then + _fail "initial write results incorrect content for \"$algo\"" + fi + sync + + $XFS_IO_PROG -c "fiemap -v" $SCRATCH_MNT/inline_file | tail -n 1 > $tmp.fiemap + cat $tmp.fiemap >> $seqres.full + # Make sure we got an inlined compressed file extent. + # 0x200 means inlined, 0x100 means not block aligned, 0x8 means encoded + # (compressed in this case), and 0x1 means the last extent. + if ! grep -q "0x309" $tmp.fiemap; then + rm -f -- $tmp.fiemap + _notrun "No compressed inline extent created, maybe subpage?" + fi + rm -f -- $tmp.fiemap + + # Unmount to clear the page cache. + _scratch_cycle_mount + + # For v6.8-rc1 without the revert or the newer fix, this can + # crash or lead to incorrect contents for zstd. + result=$(_md5_checksum "$SCRATCH_MNT/inline_file") + echo "after cycle mount, md5sum=${result}" >> $seqres.full + if [ "$result" != "$md5sum_correct" ]; then + _fail "read for compressed inline extent failed for \"$algo\"" + fi + _scratch_unmount + _check_scratch_fs +} + +algo_list=($(_btrfs_compression_algos)) +for algo in ${algo_list[@]}; do + workload $algo +done + +echo "Silence is golden" + +status=0 +exit diff --git a/tests/btrfs/310.out b/tests/btrfs/310.out new file mode 100644 index 00000000..7b9eaf78 --- /dev/null +++ b/tests/btrfs/310.out @@ -0,0 +1,2 @@ +QA output created by 310 +Silence is golden -- 2.42.0This looks reasonable to me, but how is $_btrfs_compression_algos defined? Does it include all the algorithm options supported in Btrfs?
It fetches all the supported compression algo through the sysfs interfaces: /sys/fs/btrfs/features/compress_* Along with the default supported zlib compression. Thanks, Qu
