mm/page_alloc.c: eliminate unsigned confusion in __rmqueue_fallback

Since current_order starts as MAX_ORDER-1 and is then only decremented,
the second half of the loop condition seems superfluous.  However, if
order is 0, we may decrement current_order past 0, making it UINT_MAX.
This is obviously too subtle ([1], [2]).

Since we need to add some comment anyway, change the two variables to
signed, making the counting-down for loop look more familiar, and
apparently also making gcc generate slightly smaller code.

[1] https://lkml.org/lkml/2016/6/20/493
[2] https://lkml.org/lkml/2017/6/19/345

[[email protected]: fix up reject fixupping]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Rasmus Villemoes <[email protected]>
Reported-by: Hao Lee <[email protected]>
Acked-by: Wei Yang <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions