From: Christoph Hellwig <hch@infradead.org>
To: darrick.wong@oracle.com
Cc: linux-xfs@vger.kernel.org
Subject: Re: only do a single COW fork lookup in writeback
Date: Sat, 24 Sep 2016 20:47:28 -0700 [thread overview]
Message-ID: <20160925034728.GA21561@infradead.org> (raw)
In-Reply-To: <1474730361-5234-1-git-send-email-hch@lst.de>
On Sat, Sep 24, 2016 at 08:19:19AM -0700, Christoph Hellwig wrote:
> 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.
FYI, based on further analsys I suspect that a xfs_reflink_end_cow
called from xfs_end_io cause the extent index to be invalid during
the xfs_reflink_find_cow_mapping mapping, as that can easily shift
the extent indices around and race with writeback elsewhere on the
same file.
prev parent reply other threads:[~2016-09-25 3:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-24 15:19 only do a single COW fork lookup in writeback Christoph Hellwig
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 ` Christoph Hellwig [this message]
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=20160925034728.GA21561@infradead.org \
--to=hch@infradead.org \
--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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.