Messages in this thread | | | Date | Tue, 9 Apr 2013 14:04:32 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v3] [RESEND] mm: Make snapshotting pages for stable writes a per-bio operation |
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On Tue, 9 Apr 2013 11:06:17 -0700 "Darrick J. Wong" <darrick.wong@oracle.com> wrote:
> + * Here we write back pagecache data that may be mmaped. Since > + * we cannot afford to clean the page and set PageWriteback > + * here due to lock ordering (page lock ranks above transaction > + * start), the data can change while IO is in flight. Tell the > + * block layer it should bounce the bio pages if stable data > + * during write is required.
I think there are already ab/ba deadlocks between lock_page() and journal_start(). iirc one path was write(), I forget which was the other path. This was 10+ years ago and nobody else noticed and I didn't know how to fix it so I didn't tell anyone ;)
It would be neat to be able to hook things like journal_start() into lockdep but I don't think that lockdep has easy provision for wiring oddball things into its mechanisms.
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