diff mbox series

[PULL,13/22] bitmap: fix bitmap_count_one

Message ID 20190306114227.9125-14-dgilbert@redhat.com
State New
Headers show
Series None | expand

Commit Message

Dr. David Alan Gilbert March 6, 2019, 11:42 a.m. UTC 
From: Wei Wang <wei.w.wang@intel.com>

BITMAP_LAST_WORD_MASK(nbits) returns 0xffffffff when "nbits=0", which
makes bitmap_count_one fail to handle the "nbits=0" case. It appears to be
preferred to remain BITMAP_LAST_WORD_MASK identical to the kernel
implementation that it is ported from.

So this patch fixes bitmap_count_one to handle the nbits=0 case.

Inital Discussion Link:
https://www.mail-archive.com/qemu-devel@nongnu.org/msg554316.html
Signed-off-by: Wei Wang <wei.w.wang@intel.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Dr. David Alan Gilbert <dgilbert@redhat.com>
CC: Peter Xu <peterx@redhat.com>
Message-Id: <1544516693-5395-2-git-send-email-wei.w.wang@intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 include/qemu/bitmap.h | 4 ++++
 1 file changed, 4 insertions(+)
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Patch

diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 509eeddece..679f1bdce4 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -221,6 +221,10 @@  static inline int bitmap_intersects(const unsigned long *src1,
 
 static inline long bitmap_count_one(const unsigned long *bitmap, long nbits)
 {
+    if (unlikely(!nbits)) {
+        return 0;
+    }
+
     if (small_nbits(nbits)) {
         return ctpopl(*bitmap & BITMAP_LAST_WORD_MASK(nbits));
     } else {