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 22D68224CF for ; Wed, 11 Sep 2024 03:06:27 +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=1726023987; cv=none; b=d5dHkmwAlvbvhiTPflZz5pQ4mOihSJMIKLHS3bwBXt/kg9vvdRTzvWT7LNebhzwVuCFK9jftS6lfoDXauRVEnMi0uisDrXKPZTdiCDnW9CfZ29iY6pOXy25o74LtfaSUmOohpoZuvF7NHGZST2YtBfK59KL5FGszNDfIhTEDegQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726023987; c=relaxed/simple; bh=ta0cFIxUrVPGw1Tmjosf+SAT1/5RHdhMnYyT7R228b4=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=ttvQlwNoxv7ouTzWG/0A5Ph2TZbwZh45RGwdZSQh1i/bV8nBP5SIAzuMsZG3Ma0nfPOy/YzwfTb0GnLZO2fVDyroNKNJ6sRm/KeLhqTOSkES+YNjHS7VXR4uHte/uIfD37YPcExL8MkACaQT26WrbDi+B5XqTEVQpmDn0YYGQpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=r8bR7mv7; 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="r8bR7mv7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ABE57C4CEC3; Wed, 11 Sep 2024 03:06:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726023987; bh=ta0cFIxUrVPGw1Tmjosf+SAT1/5RHdhMnYyT7R228b4=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=r8bR7mv7IBeFSZZw43d/cTlxDeOIVvFOqHu8zm9TvTUtzJRdjSTcLWNRkgKefYMKm DO8GVMgRK1No87sOciBl+/gdgtE8lktLNfyEgIev4xJA41DQ3k2Kfts0Nfb5ZIA7ER 7KbowNJ9wmWjrKg6q+Oo4LcsgFuNdP5rmjAHpycEFvbpWZ1hNSuJdB1mFi8cSpnlhH CJS5Oj49VQHEoITQFokdmDjedUWI80GQDMHCt2sdNucrgKbBvgzfB+Zcnmlj8Uk+O9 DEAIrXwJC4TBjIRVjIAKEa4GYdzmzpwWTGq+pBWCHJionkvLkEe5uqgQH/IpcGkILR aGKxi2YE37g6w== Message-ID: <44f5168e-3931-438e-8a85-3866f797f9b6@kernel.org> Date: Wed, 11 Sep 2024 11:06:22 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, jaegeuk@kernel.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [f2fs-dev] [PATCH] f2fs: fix to tag STATX_DIOALIGN only if inode support dio To: Eric Biggers References: <20240910125753.80502-1-chao@kernel.org> <20240910170600.GB2642@sol.localdomain> Content-Language: en-US From: Chao Yu In-Reply-To: <20240910170600.GB2642@sol.localdomain> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024/9/11 1:06, Eric Biggers wrote: > On Tue, Sep 10, 2024 at 08:57:53PM +0800, Chao Yu via Linux-f2fs-devel wrote: >> After commit 5c8764f8679e ("f2fs: fix to force buffered IO on inline_data >> inode"), f2fs starts to force using buffered IO on inline_data inode. >> >> And also, it will cause f2fs_getattr() returning invalid zeroed value on >> .dio_mem_align and .dio_offset_align fields, however, STATX_DIOALIGN flag >> was been tagged. User may use zeroed .stx_dio_offset_align value >> since STATX_DIOALIGN was been tagged, then it causes a deadloop during >> generic/465 test due to below logic: >> >> align=stx_dio_offset_align(it equals to zero) >> page_size=4096 >> while [ $align -le $page_size ]; do >> echo "$AIO_TEST -a $align -d $testfile.$align" >> $seqres.full >> $AIO_TEST -a $align -d $testfile.$align 2>&1 | tee -a $seqres.full >> align=$((align * 2)) >> done >> >> Quoted from description of statx manual: >> >> " If a filesystem does not support a field or if it has an >> unrepresentable value (for instance, a file with an exotic type), >> then the mask bit corresponding to that field will be cleared in >> stx_mask even if the user asked for it and a dummy value will be >> filled in for compatibility purposes if one is available (e.g., >> a dummy UID and GID may be specified to mount under some >> circumstances)." >> >> We should not set STATX_DIOALIGN flag in kstat.stx_mask if inode >> does not support DIO, so that it can indicate related fields contain >> dummy value, and avoid following incorrect use of them. >> >> Fixes: c8c02272a9f7 ("f2fs: support STATX_DIOALIGN") > > When claiming to be Fixing a commit, please make sure to Cc the author of that > commit. No problem, will make sure they were Cced. > >> Signed-off-by: Chao Yu >> --- >> fs/f2fs/file.c | 11 ++++------- >> 1 file changed, 4 insertions(+), 7 deletions(-) >> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c >> index 99903eafa7fe..f0b8b77e93ba 100644 >> --- a/fs/f2fs/file.c >> +++ b/fs/f2fs/file.c >> @@ -906,14 +906,11 @@ int f2fs_getattr(struct mnt_idmap *idmap, const struct path *path, >> * f2fs sometimes supports DIO reads but not DIO writes. STATX_DIOALIGN >> * cannot represent that, so in that case we report no DIO support. >> */ >> - if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) { >> - unsigned int bsize = i_blocksize(inode); >> - >> + if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode) && >> + !f2fs_force_buffered_io(inode, WRITE)) { >> + stat->dio_mem_align = F2FS_BLKSIZE; >> + stat->dio_offset_align = F2FS_BLKSIZE; >> stat->result_mask |= STATX_DIOALIGN; >> - if (!f2fs_force_buffered_io(inode, WRITE)) { >> - stat->dio_mem_align = bsize; >> - stat->dio_offset_align = bsize; >> - } >> } >> >> flags = fi->i_flags; > > No, this patch is wrong and the existing code is correct. The cases are: Yes, you're right, thanks for pointing out this! > > STATX_DIOALIGN set and stx_dio_*_align nonzero: > File supports DIO. > > STATX_DIOALIGN set and stx_dio_*_align zero: > File doesn't support DIO. > > STATX_DIOALIGN unset: > Filesystem doesn't support STATX_DIOALIGN, so it's unknown whether the > file supports DIO or not. Above description is clear to me. > > Please see the statx(2) manual page which explains this too. However, below manual seems not very clear about explaining what does it mean about STATX_DIOALIGN is set or not? At least not so clear like above description. stx_dio_mem_align The alignment (in bytes) required for user memory buffers for direct I/O (O_DIRECT) on this file, or 0 if direct I/O is not supported on this file. STATX_DIOALIGN (stx_dio_mem_align and stx_dio_offset_align) is supported on block devices since Linux 6.1. The support on regular files varies by filesystem; it is supported by ext4, f2fs, and xfs since Linux 6.1. stx_dio_offset_align The alignment (in bytes) required for file offsets and I/O segment lengths for direct I/O (O_DIRECT) on this file, or 0 if direct I/O is not supported on this file. This will only be nonzero if stx_dio_mem_align is nonzero, and vice versa. Thanks, > > - Eric