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 463E1282EE for ; Wed, 11 Sep 2024 03:13:05 +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=1726024385; cv=none; b=suzivNGA8zGEhnyt0XQ+FGp+rXZWNtvJGcIpP5vn7hAaV1YDQDZ1Q3bfgB8c2ayTUSmF927+9vy2g9Avm15IOFWiYDjZObO9FhGcTfRf47sNbJgZtaWmkqS42sqrEes1P5HG08Z/EyDCPhqKRk8aDxQ6SExJWsccTbTOt2g7ldg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726024385; c=relaxed/simple; bh=r/VWMEcY649DSLSlsVg09/ckGhtXpJQl4tLw6/IicS4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=aP95xLhKwLI8GxpozJ6xrxspMi8lc8z6VQG73rRvjLcO2hMR3loq04z+Rkz3OD0xQrJ7QeJDj1SrLa72xfzWNTGBSoV8Y41b0JlhGx7ZFGQnWMA+MrPjs//RpeZtokG6rvCEkoWzPYz5qTv4X52ng0frQq1qvn9vEoEM3lVpljY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BClD5gue; 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="BClD5gue" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 07C87C4CECD; Wed, 11 Sep 2024 03:13:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726024385; bh=r/VWMEcY649DSLSlsVg09/ckGhtXpJQl4tLw6/IicS4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BClD5guezY3ZzSEZGN/fqRQZCXm/azwSJV60BYnhoyWy7ouXyaFIM2qrnLIGINXNc d2SQ6lCoT6SkEMrJAxHFNol6cqAVw1IYHOmTsKPiZBn2zWlmVjqiNE/RRsakCnBIYx 6XGtlObO4iTucHtnsrpCy69/6jL4pWPsiBuri5x4Vm/4DK7F5gv0Rlz7pIPr7r/qUb 2vNqdhVcvnrdkvlpIFmcr815gt+aFrNLnxiSstVN7o/UXhnxcVNKmDUXoyROjUJFpg 6104nKvoslXoEw8YQdEGU6NXvbJ3q426JqlCcqGNrCyAMtP+HI/gIfGj+idSADlzAi eB1eBXV4OCR2g== Date: Tue, 10 Sep 2024 20:13:03 -0700 From: Eric Biggers To: Chao Yu Cc: 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 Message-ID: <20240911031303.GA50432@sol.localdomain> References: <20240910125753.80502-1-chao@kernel.org> <20240910170600.GB2642@sol.localdomain> <44f5168e-3931-438e-8a85-3866f797f9b6@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@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: <44f5168e-3931-438e-8a85-3866f797f9b6@kernel.org> On Wed, Sep 11, 2024 at 11:06:22AM +0800, Chao Yu wrote: > 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. > It just works the same way that the other statx mask bits work. See the following paragraph: 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). It might be worth an explicit note in the documentation for stx_dio_mem_align, but I considered it to be covered by the above. - Eric