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 05933225A52; Thu, 6 Feb 2025 21:54:04 +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=1738878846; cv=none; b=rwxAwUnua8D3t9tX+FrmXkBBTUU6Q6ltIO6QG264S8hxccqfwopG21nrHz9sm9f41XNBHWA0BtsDdsw1FtrEt7c8qQc2WmhkInHye/V5n9q6VNV/j5w4+ANhXwrZsmCGcbLq+xwQUICu+bhTLMQhFy/Ziuvu1TIAlYS34ZKDCFs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738878846; c=relaxed/simple; bh=qsgx0yG3fcFdIMBY6CpY/hBjuwM/XNFWm9F5VbOcvG0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Z2rpI32JZBVw56LfI8/zUDy1H53ACjVBfalZAGBpv30LD43WqrUQxfid39WyJor2TSWHT6VhIXrvwxwVM1qch07VPSCY0J1YD1ChfhTBQ9LCXQ0igQaK4wzqG7B6Ks7GpkL7eztTSB89bKmhdVelHbAljl2NiJswGkGwSmD66us= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Nbpxy3cj; 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="Nbpxy3cj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DC77C4CEDD; Thu, 6 Feb 2025 21:54:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1738878844; bh=qsgx0yG3fcFdIMBY6CpY/hBjuwM/XNFWm9F5VbOcvG0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Nbpxy3cjXe+w4jv96P9uoxABJhsdJXsbL+i+KHnvpgfSzrl77cTAQcYDhpwuO6I3n ZarvMmT5fwIyzcyQXdBlrVdOgdAwztVFn8gWbPj/O4UNRXVDYo/g1fihd8otcsqo1G B9jvcmJp7b8vuOcGMslNsxXofiktfSB2yyqCsZNMtBwjyRkJ7CbpG7NetE1xnmhbql ujj4rZhkaSn8hVips2jsnp0GdRKifF6BVO+shhj/AJ0L7sSsgvLKY+LWQGjG4RdoVe IazMxkX9KLrkrOz5ajF6BN+xuFr+DUmRJ4/fxkZ3iIU84++YgvNWRpu9KQMcFyqYVC HJTQtxBeodVqg== Date: Thu, 6 Feb 2025 13:54:03 -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 09/10] xfs: Update atomic write max size Message-ID: <20250206215403.GY21808@frogsfrogsfrogs> References: <20250204120127.2396727-1-john.g.garry@oracle.com> <20250204120127.2396727-10-john.g.garry@oracle.com> <20250205194115.GV21808@frogsfrogsfrogs> 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: On Thu, Feb 06, 2025 at 09:15:16AM +0000, John Garry wrote: > On 05/02/2025 19:41, Darrick J. Wong wrote: > > On Tue, Feb 04, 2025 at 12:01:26PM +0000, John Garry wrote: > > > Now that CoW-based atomic writes are supported, update the max size of an > > > atomic write. > > > > > > For simplicity, limit at the max of what the mounted bdev can support in > > > terms of atomic write limits. Maybe in future we will have a better way > > > to advertise this optimised limit. > > > > > > In addition, the max atomic write size needs to be aligned to the agsize. > > > Currently when attempting to use HW offload, we just check that the > > > mapping startblock is aligned. However, that is just the startblock within > > > the AG, and the AG may not be properly aligned to the underlying block > > > device atomic write limits. > > > > > > As such, limit atomic writes to the greatest power-of-2 which fits in an > > > AG, so that aligning to the startblock will be mean that we are also > > > aligned to the disk block. > > Right, "startblock" is a bit vague > > > > > I don't understand this sentence -- what are we "aligning to the > > startblock"? I think you're saying that you want to limit the size of > > untorn writes to the greatest power-of-two factor of the agsize so that > > allocations for an untorn write will always be aligned compatibly with > > the alignment requirements of the storage for an untorn write? > > Yes, that's it. I'll borrow your wording :) > > > > > > Signed-off-by: John Garry > > > --- > > > fs/xfs/xfs_iops.c | 7 ++++++- > > > fs/xfs/xfs_mount.c | 28 ++++++++++++++++++++++++++++ > > > fs/xfs/xfs_mount.h | 1 + > > > 3 files changed, 35 insertions(+), 1 deletion(-) > > > > > > diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c > > > index ea79fb246e33..95681d6c2bcd 100644 > > > --- a/fs/xfs/xfs_iops.c > > > +++ b/fs/xfs/xfs_iops.c > > > @@ -606,12 +606,17 @@ xfs_get_atomic_write_attr( > > > unsigned int *unit_min, > > > unsigned int *unit_max) > > > { > > > + struct xfs_buftarg *target = xfs_inode_buftarg(ip); > > > + struct xfs_mount *mp = ip->i_mount; > > > + > > > if (!xfs_inode_can_atomicwrite(ip)) { > > > *unit_min = *unit_max = 0; > > > return; > > > } > > > - *unit_min = *unit_max = ip->i_mount->m_sb.sb_blocksize; > > > + *unit_min = ip->i_mount->m_sb.sb_blocksize; > > > + *unit_max = min_t(unsigned int, XFS_FSB_TO_B(mp, mp->awu_max), > > > + target->bt_bdev_awu_max); > > > } > > > static void > > > diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c > > > index 477c5262cf91..4e60347f6b7e 100644 > > > --- a/fs/xfs/xfs_mount.c > > > +++ b/fs/xfs/xfs_mount.c > > > @@ -651,6 +651,32 @@ xfs_agbtree_compute_maxlevels( > > > levels = max(levels, mp->m_rmap_maxlevels); > > > mp->m_agbtree_maxlevels = max(levels, mp->m_refc_maxlevels); > > > } > > > +static inline void > > > +xfs_mp_compute_awu_max( > > > > xfs_compute_awu_max() ? > > ok > > > > > > + struct xfs_mount *mp) > > > +{ > > > + xfs_agblock_t agsize = mp->m_sb.sb_agblocks; > > > + xfs_agblock_t awu_max; > > > + > > > + if (!xfs_has_reflink(mp)) { > > > + mp->awu_max = 1; > > > + return; > > > + } > > > + > > > + /* > > > + * Find highest power-of-2 evenly divisible into agsize and which > > > + * also fits into an unsigned int field. > > > + */ > > > + awu_max = 1; > > > + while (1) { > > > + if (agsize % (awu_max * 2)) > > > + break; > > > + if (XFS_FSB_TO_B(mp, awu_max * 2) > UINT_MAX) > > > + break; > > > + awu_max *= 2; > > > + } > > > + mp->awu_max = awu_max; > > > > I think you need two awu_maxes here -- one for the data device, and > > another for the realtime device. > How about we just don't support rtdev initially for this CoW-based method, > i.e. stick at 1x FSB awu max? I guess, but that's more unfinished business. --D > > The rt computation is probably more > > complex since I think it's the greatest power of two that fits in the rt > > extent size if it isn't a power of two;> or the greatest power of two> > that fits in the rtgroup if rtgroups are enabled; or probably just no > > limit otherwise. > > > > Thanks, > John >