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Groups > linux.kernel > #1408619

Re: Linux 4.7-rc1

From Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups linux.kernel
Subject Re: Linux 4.7-rc1
Date 2016-05-29 19:30 +0200
Message-ID <rEcHg-LW-15@gated-at.bofh.it> (permalink)
References <rEcnU-Fq-11@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Sun, May 29, 2016 at 10:00:25AM -0700, Linus Torvalds wrote:

> Anyway, enough blathering. Go out and test. And in particular, if
> you're a low-level filesystem person, or involved in other ways in
> path component lookup (security layer etc), go check that everything
> looks ok, and if your filesystem isn't one that does parallel lookups
> or readdirs yet (because locking issues), take a look at that too.

Um...  Unlike readdir, which is an opt-in precisely because more state
is involved, lookups are *not* - they are not even opt-out.  They are
done in parallel with each other, period.  Out-of-tree filesystems will
need to audit their ->lookup() instances, of course, but everything
in-tree should be finished in that respect.

lookup/lookup has only one kind of exclusion - no lookups on the same name
in the same directory happening in parallel.  lookup/(directory modifiers) is
still there, of course.  So is readdir/modifiers and modifiers/modifiers.
What is fs-dependent (for now) is lookup/readdir and readdir/readdir.
The latter has per-struct-file exclusion in all cases; if we are using
->iterate_shared(), that's all there is.  If ->iterate() is still being
used, we get lookup/readdir and readdir/readdir exclusion, as we used to.

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Thread

Linux 4.7-rc1 Linus Torvalds <torvalds@linux-foundation.org> - 2016-05-29 19:10 +0200
  Re: Linux 4.7-rc1 Al Viro <viro@ZenIV.linux.org.uk> - 2016-05-29 19:30 +0200
  linux-next: stats (Was: Linux 4.7-rc1) Stephen Rothwell <sfr@canb.auug.org.au> - 2016-05-30 02:50 +0200

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