Re: [PATCH] radix_tree_tag_get() is not as safe as the docs makeout

From: Linus Torvalds
Date: Tue Apr 06 2010 - 15:43:34 EST

On Tue, 6 Apr 2010, David Howells wrote:
> radix_tree_tag_get() is not safe to use concurrently with radix_tree_tag_set()
> or radix_tree_tag_clear(). The problem is that the double tag_get() in
> radix_tree_tag_get():
[ snip snip ]

Looks like a reasonable patch, but the one thing you didn't say is whether
there is any code that relies on the incorrectly documented behavior?

How did you find this? Do we need to fix actual code too? The only user
seems to be your fscache/page.c thing, and I'm not seeing any locking
except for the rcu locking that is apparently not sufficient.

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