From: Al Viro <viro@ZenIV.linux.org.uk>
To: Hugh Dickins <hughd@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Dominique Martinet <asmadeus@codewreck.org>,
"J. Bruce Fields" <bfields@fieldses.org>,
Dominique Martinet <dominique.martinet@cea.fr>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
David Howells <dhowells@redhat.com>
Subject: Re: [git pull] vfs.git spurious ENOTDIR fix
Date: Sun, 2 Aug 2015 05:39:47 +0100 [thread overview]
Message-ID: <20150802043947.GB17109@ZenIV.linux.org.uk> (raw)
In-Reply-To: <alpine.LSU.2.11.1508012045250.17084@eggly.anvils>
On Sat, Aug 01, 2015 at 09:06:55PM -0700, Hugh Dickins wrote:
> (I don't actually understand why the clearing of DCACHE_ENTRY_TYPE in
> dentry_iput() is not of continuing concern; but don't worry, there's
> plenty I don't understand - so long as you're both satisfied that
> it's not a concern, no need to persuade me.)
Because before we even get to dentry_iput(), we evict the fucker from hash.
And that will do dentry_rcuwalk_invalidate(dentry), which will bump ->d_seq
*AFTER* having it unhashed. Now look at __d_lookup_rcu() - there we fetch
->d_seq, then verify that it's still hashed.
So having hit dentry_iput() means that everyone who'd found it via RCU
lookup will be guaranteed a ->d_seq mismatch. The same goes for things
like d_drop() and d_instantiate(). Look for dentry_rcuwalk_invalidate()
callers in there...
Clearing DCACHE_ENTRY_TYPE there is fine - dentry *is* made negative there,
after all. What we want is to have ->d_inode stable at least as long as
->d_seq remains so.
next prev parent reply other threads:[~2015-08-02 4:39 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-31 17:46 v4.2-rc dcache regression, probably 75a6f82a0d10 Hugh Dickins
2015-07-31 17:59 ` Dominique Martinet
2015-07-31 18:00 ` J. Bruce Fields
2015-07-31 18:42 ` Linus Torvalds
2015-07-31 19:42 ` Hugh Dickins
2015-07-31 20:50 ` Dominique Martinet
2015-07-31 22:52 ` Linus Torvalds
2015-08-01 0:20 ` Hugh Dickins
2015-08-01 5:58 ` Dominique Martinet
2015-08-01 7:26 ` Al Viro
2015-08-01 10:19 ` Dominique Martinet
2015-08-01 10:50 ` Dominique Martinet
2015-08-01 16:09 ` Linus Torvalds
2015-08-01 17:09 ` Al Viro
2015-08-02 0:14 ` [git pull] vfs.git spurious ENOTDIR fix Al Viro
2015-08-02 0:23 ` Al Viro
2015-08-02 0:42 ` Linus Torvalds
2015-08-02 0:57 ` Linus Torvalds
2015-08-02 1:41 ` Al Viro
2015-08-02 2:39 ` Linus Torvalds
2015-08-02 4:06 ` Hugh Dickins
2015-08-02 4:39 ` Al Viro [this message]
2015-08-02 4:42 ` Linus Torvalds
2015-08-02 18:53 ` Hugh Dickins
2015-08-01 0:09 ` v4.2-rc dcache regression, probably 75a6f82a0d10 Hugh Dickins
2015-08-01 4:20 ` Hugh Dickins
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