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 60EF3DF5C; Wed, 5 Feb 2025 19:47:40 +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=1738784862; cv=none; b=D1eS4sdl94YYtozYTVoTc8a2iOQUTYX42fHA2QWBzH7ElCbhzczzBz+bPX5pYpTyol8upDytEBeXikhSrJDAgFrqUUlXVJWibtTM4epsbD6+LaNXmABa3LMeuRe1nYn0yuBCbR0FRuVY6lxvab+tI3fMDJyw86X4x83uIBptH5g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738784862; c=relaxed/simple; bh=LCmbiWXNKRWpvF7Li6lKrAoivVevoEkM4AvZkVUEa6Q=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tYRop9eace0h89Ajwe0dCN+rfH04KBMdk6J3xTSFLSxwsVWGxZwYB6SeFQLRdIQubAR5U7qtZA03ScPPa3bC3BRLNejFjyaTRwoDULB9NrI4xMD6WwBAJz4Ov+BfNdcxUEZ2xW0BAnCeONwXiGAArPbD2LRXhR5XGGwGwrriN3Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZDe+/0jC; 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="ZDe+/0jC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6114C4CED1; Wed, 5 Feb 2025 19:47:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738784860; bh=LCmbiWXNKRWpvF7Li6lKrAoivVevoEkM4AvZkVUEa6Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZDe+/0jCxav64xKdhlVdFcbwqvmyxvK7fRST3GwOsVzR3a5Pt//v1i330a9x0+pWv vyzgsQU1aQM1ZtUJ+QxEdx24LMwGvIH7n2dSD/42qlomcvSnIVGleI89pAZ6C3bH+Q IbfZ4mnqnyP+tV9qHYtXDJReCqOJiXuQx0lAKixspFxl9oi2yU2OhnOxHelmoZGLGy vHt5B5wDPBGb998IsnfTmf2Lw5Qs+q/8CwsKRquCpMsASX4DW7qezcLrzFHOdzoHPz 3ehCnTy1jrKVmDcXfaMl2Ckpttz/AlkoVR0R+2Hj1L5InP1eTZBfkxvfADxK+cveS3 XZlmlG5SoGz+g== Date: Wed, 5 Feb 2025 11:47:40 -0800 From: "Darrick J. Wong" To: John Garry Cc: brauner@kernel.org, cem@kernel.org, dchinner@redhat.com, hch@lst.de, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ojaswin@linux.ibm.com, ritesh.list@gmail.com, martin.petersen@oracle.com Subject: Re: [PATCH RFC 08/10] xfs: Commit CoW-based atomic writes atomically Message-ID: <20250205194740.GW21808@frogsfrogsfrogs> References: <20250204120127.2396727-1-john.g.garry@oracle.com> <20250204120127.2396727-9-john.g.garry@oracle.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: <20250204120127.2396727-9-john.g.garry@oracle.com> On Tue, Feb 04, 2025 at 12:01:25PM +0000, John Garry wrote: > When completing a CoW-based write, each extent range mapping update is > covered by a separate transaction. > > For a CoW-based atomic write, all mappings must be changed at once, so > change to use a single transaction. > > Signed-off-by: John Garry > --- > fs/xfs/xfs_file.c | 5 ++++- > fs/xfs/xfs_reflink.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_reflink.h | 3 +++ > 3 files changed, 55 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 12af5cdc3094..170d7891f90d 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -527,7 +527,10 @@ xfs_dio_write_end_io( > nofs_flag = memalloc_nofs_save(); > > if (flags & IOMAP_DIO_COW) { > - error = xfs_reflink_end_cow(ip, offset, size); > + if (iocb->ki_flags & IOCB_ATOMIC) > + error = xfs_reflink_end_atomic_cow(ip, offset, size); > + else > + error = xfs_reflink_end_cow(ip, offset, size); > if (error) > goto out; > } > diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c > index dbce333b60eb..60c986300faa 100644 > --- a/fs/xfs/xfs_reflink.c > +++ b/fs/xfs/xfs_reflink.c > @@ -990,6 +990,54 @@ xfs_reflink_end_cow( > trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_); > return error; > } > +int > +xfs_reflink_end_atomic_cow( > + struct xfs_inode *ip, > + xfs_off_t offset, > + xfs_off_t count) > +{ > + xfs_fileoff_t offset_fsb; > + xfs_fileoff_t end_fsb; > + int error = 0; > + struct xfs_mount *mp = ip->i_mount; > + struct xfs_trans *tp; > + unsigned int resblks; > + bool commit = false; > + > + trace_xfs_reflink_end_cow(ip, offset, count); > + > + offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset); > + end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count); > + > + resblks = XFS_NEXTENTADD_SPACE_RES(ip->i_mount, > + (unsigned int)(end_fsb - offset_fsb), > + XFS_DATA_FORK); > + > + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, xfs gained reflink support for realtime volumes in 6.14-rc1, so you now have to calculate for that in here too. > + XFS_TRANS_RESERVE, &tp); > + if (error) > + return error; > + > + xfs_ilock(ip, XFS_ILOCK_EXCL); > + xfs_trans_ijoin(tp, ip, 0); > + > + while (end_fsb > offset_fsb && !error) > + error = xfs_reflink_end_cow_extent_locked(ip, &offset_fsb, > + end_fsb, tp, &commit); Hmm. Attaching intent items to a transaction consumes space in that transaction, so we probably ought to limit the amount that we try to do here. Do you know what that limit is? I don't, but it's roughly tr_logres divided by the average size of a log intent item. This means we need to restrict the size of an untorn write to a double-digit number of fsblocks for safety. The logic in here looks reasonable though. --D > + > + if (error || !commit) > + goto out_cancel; > + > + if (error) > + trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_); > + error = xfs_trans_commit(tp); > + xfs_iunlock(ip, XFS_ILOCK_EXCL); > + return error; > +out_cancel: > + xfs_trans_cancel(tp); > + xfs_iunlock(ip, XFS_ILOCK_EXCL); > + return error; > +} > > /* > * Free all CoW staging blocks that are still referenced by the ondisk refcount > diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h > index ef5c8b2398d8..2c3b096c1386 100644 > --- a/fs/xfs/xfs_reflink.h > +++ b/fs/xfs/xfs_reflink.h > @@ -45,6 +45,9 @@ extern int xfs_reflink_cancel_cow_range(struct xfs_inode *ip, xfs_off_t offset, > xfs_off_t count, bool cancel_real); > extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset, > xfs_off_t count); > + int > +xfs_reflink_end_atomic_cow(struct xfs_inode *ip, xfs_off_t offset, > + xfs_off_t count); > extern int xfs_reflink_recover_cow(struct xfs_mount *mp); > extern loff_t xfs_reflink_remap_range(struct file *file_in, loff_t pos_in, > struct file *file_out, loff_t pos_out, loff_t len, > -- > 2.31.1 > >