From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE3301A9FA8; Tue, 12 Aug 2025 17:19:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755019177; cv=none; b=qU0PMNNiSdtxX0yPhLNUIbq+slikfDfLBZ3nScT5pS/RFWqYla0ZQVLjaUu1OghrCOcnkLQWC2R9mkXqEu/XRBwkHVs/QIABooy5OC0pPPYtxTh2LPfZ1n4h0ZRD68NIO+cFI39qMFyI9NizKZUJ9O97dr0ES7RRDnhmXjsYTD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755019177; c=relaxed/simple; bh=WIIuEzR92MmSZ+HKRr6ZkaI56dvR/J7/Nn+zRfscpZY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=j8lPrcsyfconnt/0Sqy2mCaLoB5NNS1jUpSw3SBgGqH8MYFivYILE3ip3+qnpv7TDQk1Geyk5qpweENRILW415fVIEnP8L7lte+pheWaa1JC127u+Vy7n35685sTOuyO3dBtwSJov8vtp6h6dby/n3y7w325sHiXLMWD9isNidk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hU/fy6i3; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hU/fy6i3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 615C5C4CEF0; Tue, 12 Aug 2025 17:19:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755019176; bh=WIIuEzR92MmSZ+HKRr6ZkaI56dvR/J7/Nn+zRfscpZY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hU/fy6i3xv31ZOz5kYVcgc0yIxYlUBxhIcqDwbyg1vnwKLgoRSC7Qijv+recoHZ6c cJfKuHtd6UqceRn7ufr8mn65RSyXdtFM+eoPSUsm3pmetZitjnjIFXNU+pmsJVCX4m iCayd4VU+nGc/lMT/I0580G54adjeHf/23GFLWtZ6LXKQXwYDDTVsi88qnAISWf5hw N+sfdlyWVH8tFytt5EGW1lVArV7cmW6lg5ZlagxV+NZrikRqpJydAc0K0zjuORRCcO rRTY0VO97HEzuRpzmbPL/fn67R7KdkzALcpQAgjv0mKvoyumh/tsYPCjpawIMeIO3L jTpbyfGRaeRtA== Date: Tue, 12 Aug 2025 10:19:35 -0700 From: "Darrick J. Wong" To: Ojaswin Mujoo Cc: Zorro Lang , fstests@vger.kernel.org, Ritesh Harjani , john.g.garry@oracle.com, tytso@mit.edu, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [PATCH v4 11/11] ext4: Atomic write test for extent split across leaf nodes Message-ID: <20250812171935.GD7938@frogsfrogsfrogs> References: <2c241ea2ede39914d29aa59cd06acfc951aed160.1754833177.git.ojaswin@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c241ea2ede39914d29aa59cd06acfc951aed160.1754833177.git.ojaswin@linux.ibm.com> On Sun, Aug 10, 2025 at 07:12:02PM +0530, Ojaswin Mujoo wrote: > In ext4, even if an allocated range is physically and logically > contiguous, it can still be split into 2 extents. This is because ext4 > does not merge extents across leaf nodes. This is an issue for atomic > writes since even for a continuous extent the map block could (in rare > cases) return a shorter map, hence tearning the write. This test creates > such a file and ensures that the atomic write handles this case > correctly > > Signed-off-by: Ojaswin Mujoo > --- > tests/ext4/063 | 129 +++++++++++++++++++++++++++++++++++++++++++++ > tests/ext4/063.out | 2 + > 2 files changed, 131 insertions(+) > create mode 100755 tests/ext4/063 > create mode 100644 tests/ext4/063.out > > diff --git a/tests/ext4/063 b/tests/ext4/063 > new file mode 100755 > index 00000000..40867acb > --- /dev/null > +++ b/tests/ext4/063 > @@ -0,0 +1,129 @@ > +#! /bin/bash > +# SPDX-License-Identifier: GPL-2.0 > +# Copyright (c) 2025 IBM Corporation. All Rights Reserved. > +# > +# In ext4, even if an allocated range is physically and logically contiguous, > +# it can still be split into 2 extents. This is because ext4 does not merge > +# extents across leaf nodes. This is an issue for atomic writes since even for > +# a continuous extent the map block could (in rare cases) return a shorter map, > +# hence tearning the write. This test creates such a file and ensures that the > +# atomic write handles this case correctly > +# > +. ./common/preamble > +. ./common/atomicwrites > +_begin_fstest auto atomicwrites > + > +_require_scratch_write_atomic_multi_fsblock > +_require_atomic_write_test_commands > +_require_command "$DEBUGFS_PROG" debugfs > + > +prep() { > + local bs=`_get_block_size $SCRATCH_MNT` > + local ex_hdr_bytes=12 > + local ex_entry_bytes=12 > + local entries_per_blk=$(( (bs - ex_hdr_bytes) / ex_entry_bytes )) > + > + # fill the extent tree leaf with bs len extents at alternate offsets. > + # The tree should look as follows > + # > + # +---------+---------+ > + # | index 1 | index 2 | > + # +-----+---+-----+---+ > + # +------+ +-----------+ > + # | | > + # +-------+-------+---+---------+ +-----+----+ > + # | ex 1 | ex 2 | | ex n | | ex n+1 | > + # | off:0 | off:2 |...| off:678 | | off:680 | > + # | len:1 | len:1 | | len:1 | | len:1 | > + # +-------+-------+---+---------+ +----------+ > + # > + for i in $(seq 0 $entries_per_blk) > + do > + $XFS_IO_PROG -fc "pwrite -b $bs $((i * 2 * bs)) $bs" $testfile > /dev/null > + done > + sync $testfile > + > + echo >> $seqres.full > + echo "Create file with extents spanning 2 leaves. Extents:">> $seqres.full > + echo "...">> $seqres.full > + $DEBUGFS_PROG -R "ex `basename $testfile`" $SCRATCH_DEV |& tail >> $seqres.full > + > + # Now try to insert a new extent ex(new) between ex(n) and ex(n+1). > + # Since this is a new FS the allocator would find continuous blocks > + # such that ex(n) ex(new) ex(n+1) are physically(and logically) > + # contiguous. However, since we dont merge extents across leaf we will > + # end up with a tree as: > + # > + # +---------+---------+ > + # | index 1 | index 2 | > + # +-----+---+-----+---+ > + # +------+ +------------+ > + # | | > + # +-------+-------+---+---------+ +------+-----------+ > + # | ex 1 | ex 2 | | ex n | | ex n+1 (merged) | > + # | off:0 | off:2 |...| off:678 | | off:679 | > + # | len:1 | len:1 | | len:1 | | len:2 | > + # +-------+-------+---+---------+ +------------------+ > + # Thanks for the nice picture demonstrating what you're trying to test! Reviewed-by: "Darrick J. Wong" --D > + echo >> $seqres.full > + torn_ex_offset=$((((entries_per_blk * 2) - 1) * bs)) > + $XFS_IO_PROG -c "pwrite $torn_ex_offset $bs" $testfile >> /dev/null > + sync $testfile > + > + echo >> $seqres.full > + echo "Perform 1 block write at $torn_ex_offset to create torn extent. Extents:">> $seqres.full > + echo "...">> $seqres.full > + $DEBUGFS_PROG -R "ex `basename $testfile`" $SCRATCH_DEV |& tail >> $seqres.full > + > + _scratch_cycle_mount > +} > + > +_scratch_mkfs >> $seqres.full > +_scratch_mount >> $seqres.full > + > +testfile=$SCRATCH_MNT/testfile > +touch $testfile > +awu_max=$(_get_atomic_write_unit_max $testfile) > + > +echo >> $seqres.full > +echo "# Prepping the file" >> $seqres.full > +prep > + > +torn_aw_offset=$((torn_ex_offset - (torn_ex_offset % awu_max))) > + > +echo >> $seqres.full > +echo "# Performing atomic IO on the torn extent range. Command: " >> $seqres.full > +echo $XFS_IO_PROG -c "open -fsd $testfile" -c "pwrite -S 0x61 -DA -V1 -b $awu_max $torn_aw_offset $awu_max" >> $seqres.full > +$XFS_IO_PROG -c "open -fsd $testfile" -c "pwrite -S 0x61 -DA -V1 -b $awu_max $torn_aw_offset $awu_max" >> $seqres.full > + > +echo >> $seqres.full > +echo "Extent state after atomic write:">> $seqres.full > +echo "...">> $seqres.full > +$DEBUGFS_PROG -R "ex `basename $testfile`" $SCRATCH_DEV |& tail >> $seqres.full > + > +echo >> $seqres.full > +echo "# Checking data integrity" >> $seqres.full > + > +# create a dummy file with expected data > +$XFS_IO_PROG -fc "pwrite -S 0x61 -b $awu_max 0 $awu_max" $testfile.exp >> /dev/null > +expected_data=$(od -An -t x1 -j 0 -N $awu_max $testfile.exp) > + > +# We ensure that the data after atomic writes should match the expected data > +actual_data=$(od -An -t x1 -j $torn_aw_offset -N $awu_max $testfile) > +if [[ "$actual_data" != "$expected_data" ]] > +then > + echo "Checksum match failed at off: $torn_aw_offset size: $awu_max" > + echo > + echo "Expected: " > + echo "$expected_data" > + echo > + echo "Actual contents: " > + echo "$actual_data" > + > + _fail > +fi > + > +echo -n "Data verification at offset $torn_aw_offset suceeded!" >> $seqres.full > +echo "Silence is golden" > +status=0 > +exit > diff --git a/tests/ext4/063.out b/tests/ext4/063.out > new file mode 100644 > index 00000000..de35fc52 > --- /dev/null > +++ b/tests/ext4/063.out > @@ -0,0 +1,2 @@ > +QA output created by 063 > +Silence is golden > -- > 2.49.0 > >