From: Christoph Hellwig <hch@lst.de>
To: darrick.wong@oracle.com
Cc: linux-xfs@vger.kernel.org
Subject: only do a single COW fork lookup in writeback
Date: Sat, 24 Sep 2016 08:19:19 -0700 [thread overview]
Message-ID: <1474730361-5234-1-git-send-email-hch@lst.de> (raw)
I've got a bug report with a slightly older version of the reflink
code, in which I get a bogus NULL xfs_bmbt_rec_host pointer back from
xfs_iext_bno_to_ext in xfs_reflink_find_cow_mapping. I've not
reproduced that bug myself yet, but what's clear from the report is
that it's not just inefficient but also potentially dangerous to
do the blind dereference in xfs_reflink_find_cow_mapping after
we dropped the ilock from the previous xfs_reflink_find_cow_mapping
call.
So just combine that two into one function, and then rewrite the
COW writeback code to only do a single call in the second step.
I think that also cleans up the writeback code quite a bit and
makes it much easier to follow as well.
next reply other threads:[~2016-09-24 15:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-24 15:19 Christoph Hellwig [this message]
2016-09-24 15:19 ` [PATCH 1/2] xfs: kill xfs_reflink_is_cow_pending Christoph Hellwig
2016-09-26 21:08 ` Darrick J. Wong
2016-09-24 15:19 ` [PATCH 2/2] xfs: rewrite the COW writeback mapping code Christoph Hellwig
2016-09-26 21:35 ` Darrick J. Wong
2016-09-27 18:48 ` Christoph Hellwig
2016-09-25 3:47 ` only do a single COW fork lookup in writeback Christoph Hellwig
Reply instructions:
You may reply publicly 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=1474730361-5234-1-git-send-email-hch@lst.de \
--to=hch@lst.de \
--cc=darrick.wong@oracle.com \
--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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).