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SubjectRe: [PATCH 2/2] udf: reduce stack usage of udf_get_filename
On Wed, 19 Nov 2008 16:26:22 +0100 Jan Kara <jack@suse.cz> wrote:

> On Tue 18-11-08 16:19:38, Andrew Morton wrote:
> > On Sun, 16 Nov 2008 19:02:45 +0100
> > Marcin Slusarz <marcin.slusarz@gmail.com> wrote:
> >
> > > + filename = kmalloc(sizeof(struct ustr), GFP_NOFS);
> >
> > I suspect that we could have used the superior GFP_KERNEL everywhere in
> > both these patches. But I'll let Jan worry about that ;)
> Definitely not in the second case - that one is called from inside
> readdir, lookup and symlink resolution code so that could lead to deadlocks
> IMHO.
> Regarding the first case in process_sequence, that is called only from
> udf_fill_super(). So there it might be safe to use GFP_KERNEL but I'm not
> quite sure either... So I'd leave GFP_NOFS there.
>

The reason for using GFP_NOFS is to prevent deadlocks when direct
memory reclaim reenters the filesystem code. But I don't think there's
ever a case when direct reclaim would enter the namespace part of a
filesystem - it is only expected to touch the pagecache (ie: data)
operations: writepage(), block allocator, etc.




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