Linux-XFS Archive on lore.kernel.org
 help / color / Atom feed
From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 3/3] xfs: attach dquots before performing xfs_swap_extents
Date: Wed, 13 Nov 2019 09:14:48 +1100
Message-ID: <20191112221448.GQ4614@dread.disaster.area> (raw)
In-Reply-To: <20191111080503.GC4548@infradead.org>

On Mon, Nov 11, 2019 at 12:05:03AM -0800, Christoph Hellwig wrote:
> On Sun, Nov 10, 2019 at 05:18:34PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Make sure we attach dquots to both inodes before swapping their extents.
> > This was found via manual code inspection by looking for places where we
> > could call xfs_trans_mod_dquot without dquots attached to inodes, and
> > confirmed by instrumenting the kernel and running xfs/328.
> 
> Looks good:
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> 
> Btw, for  while I've been wondering if we could just get rid of the
> concepts of attached dquots.  With the radix-tree/xarray looks up
> are be fairly cheap, and could be done lockless using RCU.  So we could
> try to just kill the concept of attaching the dquot to the inode and
> just look it up once per operation, where operation preferally is
> something high-level like the actual file/inode operation and not a
> low-level thing inside xfs.

If the dquots are not attached to the inode, how would you pass the
3 dquots per inode down the stack to where they are actually used
inside the filesystem? I mean, we have to get the dquots attached to
the transaction so we can update them in xfs_trans_commit ->
xfs_trans_apply_dquot_deltas(), so somehow we'd have to get them
from the high level file/inode operations down to the XFS
transaction context. And things like writeback need dquots attached
for delayed allocation, so various aops would need to do dquot
lookups, too...

I can see the advantage of doing rcu dquot cache lookups in the xfs
context where we are attaching the dquots to the transaction rather
than attaching them to the inode, but I can't see how the "do it at
a high level" aspect of this would work....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-11  1:18 [PATCH 0/3] xfs: various fixes Darrick J. Wong
2019-11-11  1:18 ` [PATCH 1/3] xfs: actually check xfs_btree_check_block return in xfs_btree_islastblock Darrick J. Wong
2019-11-11  7:57   ` Christoph Hellwig
2019-11-11  1:18 ` [PATCH 2/3] xfs: attach dquots and reserve quota blocks during unwritten conversion Darrick J. Wong
2019-11-11  7:59   ` Christoph Hellwig
2019-11-11  1:18 ` [PATCH 3/3] xfs: attach dquots before performing xfs_swap_extents Darrick J. Wong
2019-11-11  8:05   ` Christoph Hellwig
2019-11-12 22:14     ` Dave Chinner [this message]
2019-11-14 14:53       ` Christoph Hellwig

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20191112221448.GQ4614@dread.disaster.area \
    --to=david@fromorbit.com \
    --cc=darrick.wong@oracle.com \
    --cc=hch@infradead.org \
    --cc=linux-xfs@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-XFS Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-xfs/0 linux-xfs/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-xfs linux-xfs/ https://lore.kernel.org/linux-xfs \
		linux-xfs@vger.kernel.org
	public-inbox-index linux-xfs

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-xfs


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git