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Message-ID: <20200228045255.GJ23230@ZenIV.linux.org.uk>
Date: Fri, 28 Feb 2020 04:52:55 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Ian Kent <raven@...maw.net>
Cc: Matthew Wilcox <willy@...radead.org>,
Andreas Dilger <adilger@...ger.ca>,
Waiman Long <longman@...hat.com>,
Jonathan Corbet <corbet@....net>,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
Iurii Zaikin <yzaikin@...gle.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>,
linux-doc@...r.kernel.org,
Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
Eric Biggers <ebiggers@...gle.com>,
Dave Chinner <david@...morbit.com>,
Eric Sandeen <sandeen@...hat.com>
Subject: Re: [PATCH 00/11] fs/dcache: Limit # of negative dentries
On Fri, Feb 28, 2020 at 12:36:09PM +0800, Ian Kent wrote:
> And let's not forget that file systems are the primary
> source of these and not all create them on lookups.
> I may be mistaken, but I think ext4 does not while xfs
> definitely does.
Both ext4 and xfs bloody well *DO* create hashed negative
dentries on lookups. There is a pathological case when
they are trying to be case-insensitive (and in that situation
we are SOL - if somebody insists upon mounting with
-o make-it-suck, that's what they bloody well get).
Casefondling idiocy aside, negative lookups are hashed.
On all normal filesystems. Look for d_splice_alias()
getting passed NULL inode - that's where ->lookup()
instances normally create those.
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