lib: percpu_counter_sub
Hugh spotted that some code does:
percpu_counter_add(&counter, -unsignedlong)
which, when the amount argument is of type s32, sort-of works thanks to
two's-complement. However when we'd change the type to s64 this breaks on 32bit
machines, because the promotion rules zero extend the unsigned number.
Provide percpu_counter_sub() to hide the s64 cast. That is:
percpu_counter_sub(&counter, foo)
is equal to:
percpu_counter_add(&counter, -(s64)foo);
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
index 53be251..9157fcf 100644
--- a/fs/ext2/balloc.c
+++ b/fs/ext2/balloc.c
@@ -124,7 +124,7 @@
return 0;
}
- percpu_counter_add(&sbi->s_freeblocks_counter, -count);
+ percpu_counter_sub(&sbi->s_freeblocks_counter, count);
sb->s_dirt = 1;
return count;
}