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 A4C2E17333D; Fri, 25 Oct 2024 16:09:43 +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=1729872583; cv=none; b=MnEO2XHggvol/XytjMOzBlA77Mmg5lhamnb5qDGCVCnIj7kpDWGHg2so9zcXahaGjPIFynpE/kVkVKNG+lbGPW1XE6YqMozfd/HPlHuYF5o33FN300SUiQjIP4KdcCFcr5Ld6vgTrxbslx4UXZvJbkKMEzwp/he8joP7u05iSO4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729872583; c=relaxed/simple; bh=MSN2XEY66f4jBsAT7ndKMBQc3NEOSQBib4x+RE82ioQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=t8s960DfQchuO3LBa0PPJMrjbWsvbyyounyGadjZsLEI+AWPrJD2ZohC20O86KVzYLpHhCpwUrAqUoKPM+BSzWjlX6Rn2ts9Pj1NEzYewFOPwdfI6r/RMe+Set/jUEfE2ksb0P7YfnN0+yzGhpmdvMuJUl4yPGEilaQyxIWH/Bg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lVLfDdbv; 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="lVLfDdbv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24E91C4CEC3; Fri, 25 Oct 2024 16:09:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1729872583; bh=MSN2XEY66f4jBsAT7ndKMBQc3NEOSQBib4x+RE82ioQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lVLfDdbvz//coRMXuJCKQp8z8K1FnHrgqCKHX6mR+O+7rGBOivv91o3dBNILvhnaz /SZIHv7q6UaY5p3cmLusqEDCQhloTXJZpjs2e1DsoTEnp/AiRlpve64b2HWIf86wZv pnQAmMyzUfoxRP91Djv7YCgPIIu3zAwS2X5lgjKbRyj1hI6JDk/4mWg5bMzwLTqMj2 E3osqnTBnehMbuXpIKGgCSjM2MXsFQKRIbNQscBlcHnPHv+u701L4juuSPFjpcPhhE iX8NCktPET+9QxqPHmEKB13blpUszm3qC3qUuNpvN7T/Jz2tFNVXTeEJ2o8id3l358 WlE9ZcgUUa8mw== Date: Fri, 25 Oct 2024 09:09:42 -0700 From: "Darrick J. Wong" To: Ritesh Harjani Cc: John Garry , linux-ext4@vger.kernel.org, Theodore Ts'o , Jan Kara , Christoph Hellwig , Ojaswin Mujoo , Dave Chinner , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 1/6] ext4: Add statx support for atomic writes Message-ID: <20241025160942.GJ2386201@frogsfrogsfrogs> References: <314835ec-98bf-472c-8be7-0b26e50cfc9b@oracle.com> <87y12cmr5o.fsf@gmail.com> Precedence: bulk X-Mailing-List: linux-ext4@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: <87y12cmr5o.fsf@gmail.com> On Fri, Oct 25, 2024 at 03:38:03PM +0530, Ritesh Harjani wrote: > John Garry writes: > > > On 25/10/2024 04:45, Ritesh Harjani (IBM) wrote: > >> This patch adds base support for atomic writes via statx getattr. > >> On bs < ps systems, we can create FS with say bs of 16k. That means > >> both atomic write min and max unit can be set to 16k for supporting > >> atomic writes. > >> > >> Later patches adds support for bigalloc as well so that ext4 can also > >> support doing atomic writes for bs = ps systems. > >> > >> Co-developed-by: Ojaswin Mujoo > >> Signed-off-by: Ojaswin Mujoo > >> Signed-off-by: Ritesh Harjani (IBM) > >> --- > >> fs/ext4/ext4.h | 7 ++++++- > >> fs/ext4/inode.c | 14 ++++++++++++++ > >> fs/ext4/super.c | 32 ++++++++++++++++++++++++++++++++ > >> 3 files changed, 52 insertions(+), 1 deletion(-) > >> > >> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h > >> index 44b0d418143c..a41e56c2c628 100644 > >> --- a/fs/ext4/ext4.h > >> +++ b/fs/ext4/ext4.h > >> @@ -1729,6 +1729,10 @@ struct ext4_sb_info { > >> */ > >> struct work_struct s_sb_upd_work; > >> > >> + /* Atomic write unit values */ > >> + unsigned int fs_awu_min; > >> + unsigned int fs_awu_max; > >> + > >> /* Ext4 fast commit sub transaction ID */ > >> atomic_t s_fc_subtid; > >> > >> @@ -1820,7 +1824,8 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) > >> */ > >> enum { > >> EXT4_MF_MNTDIR_SAMPLED, > >> - EXT4_MF_FC_INELIGIBLE /* Fast commit ineligible */ > >> + EXT4_MF_FC_INELIGIBLE, /* Fast commit ineligible */ > >> + EXT4_MF_ATOMIC_WRITE /* Supports atomic write */ > > > > Does this flag really buy us much? > > > > I felt it is cleaner this way than comparing non-zero values of > fs_awu_min and fs_awu_max. What does it mean when MF_ATOMIC_WRITE is set and fs_awu_* are zero? The awu values don't change at runtime, so I think you can save yourself an atomic test by checking (non-atomically) for awu_min>0. (I don't know anything about the flags, those came after my time iirc.) --D > Now that you pointed at it - Maybe a question for others who might have > the history of which one to use when - or do we think there is a scope > of merging the two into just one as a later cleanup? > > I know that s_mount_flags was added for fastcommit and it needed the > state manipulations to be done in atomic way. Similarly s_ext4_flags > also was renamed from s_resize_flags for more general purpose use. Both > of these looks like could be merged isn't it? > > > > >> }; > >> > >> static inline void ext4_set_mount_flag(struct super_block *sb, int bit) > >> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > >> index 54bdd4884fe6..897c028d5bc9 100644 > >> --- a/fs/ext4/inode.c > >> +++ b/fs/ext4/inode.c > >> @@ -5578,6 +5578,20 @@ int ext4_getattr(struct mnt_idmap *idmap, const struct path *path, > >> } > >> } > >> > >> + if (S_ISREG(inode->i_mode) && (request_mask & STATX_WRITE_ATOMIC)) { > >> + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); > >> + unsigned int awu_min, awu_max; > >> + > >> + if (ext4_test_mount_flag(inode->i_sb, EXT4_MF_ATOMIC_WRITE)) { > > > > I'd use ext4_inode_can_atomicwrite() here, similar to what is done for xfs > > > > Sure since it is inode operation, we can check against ext4_inode_can_atomicwrite(). > > > >> + awu_min = sbi->fs_awu_min; > >> + awu_max = sbi->fs_awu_max; > >> + } else { > >> + awu_min = awu_max = 0; > >> + } > >> + > >> + generic_fill_statx_atomic_writes(stat, awu_min, awu_max); > >> + } > >> + > >> flags = ei->i_flags & EXT4_FL_USER_VISIBLE; > >> if (flags & EXT4_APPEND_FL) > >> stat->attributes |= STATX_ATTR_APPEND; > >> diff --git a/fs/ext4/super.c b/fs/ext4/super.c > >> index 16a4ce704460..f5c075aff060 100644 > >> --- a/fs/ext4/super.c > >> +++ b/fs/ext4/super.c > >> @@ -4425,6 +4425,37 @@ static int ext4_handle_clustersize(struct super_block *sb) > >> return 0; > >> } > >> > >> +/* >