From: Anton Altaparmakov <aia21@cam.ac.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: akpm@osdl.org, torvalds@osdl.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/11] FUSE - core
Date: Fri, 14 Jan 2005 14:14:12 +0000 (GMT) [thread overview]
Message-ID: <Pine.LNX.4.60.0501141409500.18572@hermes-1.csi.cam.ac.uk> (raw)
In-Reply-To: <E1CpS73-0001kC-00@dorka.pomaz.szeredi.hu>
On Fri, 14 Jan 2005, Miklos Szeredi wrote:
> > > +static struct inode *fuse_alloc_inode(struct super_block *sb)
> > > +{
> > > + struct inode *inode;
> > > + struct fuse_inode *fi;
> > > +
> > > + inode = kmem_cache_alloc(fuse_inode_cachep, SLAB_KERNEL);
> >
> > This should probably be SLAB_NOFS as FUSE is a file system so you don't
> > want allocations to go off submitting i/o to your file system. Much
> > better to be safe and always use the _NOFS versions in you kernel fs code.
>
> Well, I don't think it matters in this case, since inode allocation is
> not part of processing I/O, so no deadlock is possible. See also
> alloc_inode() in fs/inode.c which also uses SLAB_KERNEL.
That may well be possible. I prefer to take a more cautious approach and
only use _NOFS variants within NTFS, whether it is strictly necessary or
not. That way I never need to worry as to whether a deadlock is or isn't
possible. The problem simply goes away...
[snip]
> In actual fact the whole GFP_NOFS argument doesn't apply to FUSE
> _at_all_, since dirty pages are never allowed. Which is because
> userspace can't easily be taught about GFP_NOFS allocations, and
> otherwise could deadlock on page writeback.
Yes, I remember the thread about the deadlock on page writeback.
I prefer the _NOFS regardless (and others will probably disagree) because
it also means that if a machine is seriously running out of memory the fs
will give up with -ENOMEM much more readily with _NOFS rather than
increasing the memory pressure even further. As I said, others probably
disagree with me...
Best regards,
Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net
WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
next prev parent reply other threads:[~2005-01-14 14:14 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-01-11 16:25 [PATCH 2/11] FUSE - core Miklos Szeredi
2005-01-12 22:36 ` Andrew Morton
2005-01-13 5:31 ` Miklos Szeredi
2005-01-14 13:55 ` Anton Altaparmakov
2005-01-14 14:07 ` Miklos Szeredi
2005-01-14 14:14 ` Anton Altaparmakov [this message]
2005-01-14 14:32 ` Miklos Szeredi
-- strict thread matches above, loose matches on Subject: below --
2005-01-10 18:58 Miklos Szeredi
2005-01-10 21:40 ` Mike Waychison
2005-01-10 22:28 ` Miklos Szeredi
2005-02-14 22:43 ` Faraz Ahmed
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