Messages in this thread Patch in this message | | | From | Yi Wang <> | Subject | [PATCH] bitmap: fix a unproper remap when mpol_rebind_nodemask() | Date | Mon, 13 Jun 2022 19:29:37 +0800 |
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Consider one situation:
The app have two vmas which mbind() to node 1 and node3 respectively, and its cpuset.mems is 0-3, now set its cpuset.mems to 1,3, according to current bitmap_remap(), we got:
1 => 3 3 => 3
This maybe confused because node 1,3 have already in the new settiing region but both nodes are binded to the same node 3 now.
Actually we found the situation on a very old libvirt and qemu, but this can be easily reproduced in the current kernel, so we try to fix it.
A possible fix way is to ignore the bits in @src have already existed in @new.
Signed-off-by: Yi Wang <wang.yi59@zte.com.cn> --- lib/bitmap.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/lib/bitmap.c b/lib/bitmap.c index b18e31ea6e66..b77bf1b3852e 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -1006,8 +1006,8 @@ unsigned int bitmap_ord_to_pos(const unsigned long *buf, unsigned int ord, unsig * @dst point to the same location, then this routine copies @src * to @dst. * - * The positions of unset bits in @old are mapped to themselves - * (the identify map). + * The positions of unset bits in @old or bits in @src have already + * existed in @new are mapped to themselves (the identify map). * * Apply the above specified mapping to @src, placing the result in * @dst, clearing any bits previously set in @dst. @@ -1033,7 +1033,7 @@ void bitmap_remap(unsigned long *dst, const unsigned long *src, for_each_set_bit(oldbit, src, nbits) { int n = bitmap_pos_to_ord(old, oldbit, nbits); - if (n < 0 || w == 0) + if (n < 0 || w == 0 || test_bit(oldbit, new)) set_bit(oldbit, dst); /* identity map */ else set_bit(bitmap_ord_to_pos(new, n % w, nbits), dst); -- 2.33.0.rc0.dirty
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