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SubjectRe: [PATCH v19 1/7] xbitmap: Introduce xbitmap
Hi Matthew,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.15-rc3]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Wei-Wang/Virtio-balloon-Enhancement/20171215-100525
reproduce:
# apt-get install sparse
make ARCH=x86_64 allmodconfig
make C=1 CF=-D__CHECK_ENDIAN__


sparse warnings: (new ones prefixed by >>)


vim +29 lib/xbitmap.c

5
6 /**
7 * xb_set_bit - set a bit in the xbitmap
8 * @xb: the xbitmap tree used to record the bit
9 * @bit: index of the bit to set
10 *
11 * This function is used to set a bit in the xbitmap. If the bitmap that @bit
12 * resides in is not there, the per-cpu ida_bitmap will be taken.
13 *
14 * Returns: 0 on success. %-EAGAIN indicates that @bit was not set.
15 */
16 int xb_set_bit(struct xb *xb, unsigned long bit)
17 {
18 int err;
19 unsigned long index = bit / IDA_BITMAP_BITS;
20 struct radix_tree_root *root = &xb->xbrt;
21 struct radix_tree_node *node;
22 void **slot;
23 struct ida_bitmap *bitmap;
24 unsigned long ebit;
25
26 bit %= IDA_BITMAP_BITS;
27 ebit = bit + 2;
28
> 29 err = __radix_tree_create(root, index, 0, &node, &slot);
30 if (err)
31 return err;
32 bitmap = rcu_dereference_raw(*slot);
33 if (radix_tree_exception(bitmap)) {
34 unsigned long tmp = (unsigned long)bitmap;
35
36 if (ebit < BITS_PER_LONG) {
37 tmp |= 1UL << ebit;
38 rcu_assign_pointer(*slot, (void *)tmp);
39 return 0;
40 }
41 bitmap = this_cpu_xchg(ida_bitmap, NULL);
42 if (!bitmap)
43 return -EAGAIN;
44 memset(bitmap, 0, sizeof(*bitmap));
45 bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
46 rcu_assign_pointer(*slot, bitmap);
47 }
48
49 if (!bitmap) {
50 if (ebit < BITS_PER_LONG) {
51 bitmap = (void *)((1UL << ebit) |
52 RADIX_TREE_EXCEPTIONAL_ENTRY);
> 53 __radix_tree_replace(root, node, slot, bitmap, NULL);
54 return 0;
55 }
56 bitmap = this_cpu_xchg(ida_bitmap, NULL);
57 if (!bitmap)
58 return -EAGAIN;
59 memset(bitmap, 0, sizeof(*bitmap));
60 __radix_tree_replace(root, node, slot, bitmap, NULL);
61 }
62
63 __set_bit(bit, bitmap->bitmap);
64 return 0;
65 }
66 EXPORT_SYMBOL(xb_set_bit);
67

---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation

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