ollision.  However, now
that random numbers are used instead, collisions are much more likely.

This is fixed by finding a hole in the rbtree where the next unused serial
number ought to be and using that by going almost back to the top of the
insertion routine and redoing the insertion with the new serial number rather
than trying to be clever and attempting to work out the insertion point
pointer directly.

This fixes kernel BZ #7727.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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