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Mon, 18 Jul 2022 10:59:19 -0700 (PDT) X-Google-Smtp-Source: AGRyM1vzdChWB9q8LkVDbvCIlsFlTiCCSoRDDzSbjMUHsgmQY2kr5TSRGH90VgB1RC4jYS4+V2mKPQ== X-Received: by 2002:a05:622a:294:b0:31e:e442:ce4 with SMTP id z20-20020a05622a029400b0031ee4420ce4mr8539722qtw.146.1658167159077; Mon, 18 Jul 2022 10:59:19 -0700 (PDT) Received: from zlang-mailbox ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id bm17-20020a05620a199100b006b5cccf62fbsm10001757qkb.46.2022.07.18.10.59.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Jul 2022 10:59:18 -0700 (PDT) Date: Tue, 19 Jul 2022 01:59:12 +0800 From: Zorro Lang To: Qu Wenruo Cc: linux-btrfs@vger.kernel.org, fstests@vger.kernel.org, Johannes Thumshirn Subject: Re: [PATCH RFC] fstests: btrfs: add a tests case to make sure btrfs can handle certain interleaved free space correctly Message-ID: <20220718175912.5mhc7hhkysgadvqd@zlang-mailbox> References: <20220718061823.26147-1-wqu@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220718061823.26147-1-wqu@suse.com> Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Mon, Jul 18, 2022 at 02:18:23PM +0800, Qu Wenruo wrote: > This is a future-proof test mostly for future zoned raid-stripe-tree > (RST) and P/Q COW based RAID56 implementation. > > Unlike regular devices, zoned device can not do overwrite without > resetting (reclaim) a whole zone. > > And for the RST and P/Q COW based RAID56, the idea is to CoW the parity > stripe to other location. > > But all above behaviors introduce some limitation, if we fill the fs, > then free half of the space interleaved. > > - For basic zoned btrfs (aka SINGLE profile for now) > Normally this means we have no free space at all. > > Thankfully zoned btrfs has GC and reserved zones to reclaim those > half filled zones. > In theory we should be able to do new writes. > > - For future RST with P/Q CoW for RAID56, on non-zoned device. > This is more complex, in this case, we should have the following > full stripe layout for every full stripe: > 0 64K > Disk A |XXXXXXXXXXXXXXXXXXXXXXXXXXX| (Data 1) > Disk B | | (Data 2) > Disk C |XXXXXXXXXXXXXXXXXXXXXXXXXXX| (P stripe) > > Although in theory we can write into Disk B, but we have to find > a free space for the new Parity. > > But all other full stripe are like this, which means we're deadlocking > to find a pure free space without sub-stripe writing. > > This means, even for non-zoned btrfs, we still need GC and reserved > space to handle P/Q CoW properly. > > Another thing specific to this test case is, to reduce the runtime, I > use 256M as the mkfs size for each device. > (A full run with KASAN enabled kernel already takes over 700 seconds) > > So far this can only works for non-zoned disks, as 256M is too small for > zoned devices to have enough zones. > > Thus need extra advice from zoned device guys. > > Cc: Johannes Thumshirn > Signed-off-by: Qu Wenruo > --- I think this patch need more review from btrfs list. I just review this patch from fstests side as below ... > tests/btrfs/261 | 129 ++++++++++++++++++++++++++++++++++++++++++++ > tests/btrfs/261.out | 2 + > 2 files changed, 131 insertions(+) > create mode 100755 tests/btrfs/261 > create mode 100644 tests/btrfs/261.out > > diff --git a/tests/btrfs/261 b/tests/btrfs/261 > new file mode 100755 > index 00000000..01da4759 > --- /dev/null > +++ b/tests/btrfs/261 > @@ -0,0 +1,129 @@ > +#! /bin/bash > +# SPDX-License-Identifier: GPL-2.0 > +# Copyright (C) 2022 SUSE Linux Products GmbH. All Rights Reserved. > +# > +# FS QA Test 261 > +# > +# Make sure all supported profiles (including future zoned RAID56) have proper > +# way to handle fs with interleaved filled space, and can still write data > +# into the fs. > +# > +# This is mostly inspired by some discussion on P/Q COW for RAID56, even for > +# regular devices, this can be problematic if we fill the fs then delete > +# half of the extents interleavedly. Without proper GC and extra reserved > +# space, such CoW P/Q way should run out of space (even one data stripe is > +# free, there is no place to CoW its P/Q). > +# > +. ./common/preamble > +_begin_fstest auto enospc raid > + > +# Override the default cleanup function. > +# _cleanup() > +# { > +# cd / > +# rm -r -f $tmp.* > +# } This _cleanup looks like nothing special, you can remove it, to use the default one. > + > +# Import common functions. > +. ./common/filter > + > +# real QA test starts here > + > +# Modify as appropriate. ^^^ Remove this line please. > +_supported_fs btrfs > +# we check scratch dev after each loop > +_require_scratch_nocheck > +_require_scratch_dev_pool 4 > + > +fill_fs() There's a help named _fill_fs() in common/populate file. I'm not sure if there are special things in your fill_fs function, better to check if our common helper can help you? > +{ > + for (( i = 0;; i += 2 )); do > + $XFS_IO_PROG -f -c "pwrite 0 64K" $SCRATCH_MNT/file_$i \ > + &> /dev/null > + if [ $? -ne 0 ]; then > + break > + fi > + $XFS_IO_PROG -f -c "pwrite 0 64K" $SCRATCH_MNT/file_$(($i + 1)) \ > + &> /dev/null > + if [ $? -ne 0 ]; then > + break > + fi > + > + # Only sync after data 1M writes. > + if [ $(( $i % 8)) -eq 0 ]; then > + sync > + fi > + done > + > + # Sync what hasn't yet synced. > + sync > + > + echo "fs filled with $i full stripe write" >> $seqres.full > + > + # Delete half of the files created above, which should leave > + # the fs half empty. For RAID56 this would leave all of its full > + # stripes to be have one full data stripe, one free data stripe, > + # and one P/Q stripe still in use. > + rm -rf -- $SCRATCH_MNT/file_*[02468] > + > + # Sync to make sure above deleted files really got freed. > + sync > +} > + > +run_test() > +{ > + local profile=$1 > + local nr_dev=$2 > + > + echo "=== profile=$profile nr_dev=$nr_dev ===" >> $seqres.full > + _scratch_dev_pool_get $nr_dev > + # -b is for each device. > + # Here we use 256M to reduce the runtime. > + _scratch_pool_mkfs -b 256M -m$profile -d$profile >>$seqres.full 2>&1 Do you need to make sure this mkfs successed at here? > + # make sure we created btrfs with desired options > + if [ $? -ne 0 ]; then > + echo "mkfs $mkfs_opts failed" > + return > + fi > + _scratch_mount >>$seqres.full 2>&1 If _scratch_mount fails, the testing will exit directly. So generally we don't need to fill out stdout/stderr. Or you actually want to use _try_scratch_mount at here? > + > + fill_fs > + > + # Now try to write 4M data, with the fs half empty we should be > + # able to do that. > + # For zoned devices, this will test if the GC and reserved zones > + # can handle such cases properly. > + $XFS_IO_PROG -f -c "pwrite 0 4M" -c sync $SCRATCH_MNT/final_write \ > + >> $seqres.full 2>&1 > + if [ $? -ne 0 ]; then > + echo "The final write failed" > + fi > + > + _scratch_unmount > + # we called _require_scratch_nocheck instead of _require_scratch > + # do check after test for each profile config > + _check_scratch_fs > + echo >> $seqres.full > + _scratch_dev_pool_put > +} > + > +# Here we don't use _btrfs_profile_configs as that doesn't include > +# the number of devices, but for full stripe writes for RAID56, we > +# need to ensure nr_data must be 2, so here we manually specify > +# the profile and number of devices. > +run_test "single" "1" > + > +# Zoned only support > +if _scratch_btrfs_is_zoned; then > + exit I think this "exit" will fail this test directly, due to status=1 currectly. You can use _require_non_zoned_device() to run this case for non-zoned device only. Or if ! _scratch_btrfs_is_zoned;then run_test "raid0" "2" run_test "raid1" "2" run_test "raid10" "4" run_test "raid5" "3" run_test "raid6" "4" fi As this case is "Silence is golden". I'm not sure what do you really need at here, can these help? Thanks, Zorro > +fi > + > +run_test "raid0" "2" > +run_test "raid1" "2" > +run_test "raid10" "4" > +run_test "raid5" "3" > +run_test "raid6" "4" > + > +echo "Silence is golden" > +status=0 > +exit > diff --git a/tests/btrfs/261.out b/tests/btrfs/261.out > new file mode 100644 > index 00000000..679ddc0f > --- /dev/null > +++ b/tests/btrfs/261.out > @@ -0,0 +1,2 @@ > +QA output created by 261 > +Silence is golden > -- > 2.36.1 >