On 11/03/2017 06:55 PM, Tetsuo Handa wrote:
I'm commenting without understanding the logic.
Wei Wang wrote:
+
+bool xb_preload(gfp_t gfp);
+
Want __must_check annotation, for __radix_tree_preload() is marked
with __must_check annotation. By error failing to check result of
xb_preload() will lead to preemption kept disabled unexpectedly.
I don't disagree with this, but I find its wrappers, e.g.
radix_tree_preload() and radix_tree_maybe_preload(), don't seem to have
__must_chek added.
+int xb_set_bit(struct xb *xb, unsigned long bit)
+{
+ int err;
+ unsigned long index = bit / IDA_BITMAP_BITS;
+ struct radix_tree_root *root = &xb->xbrt;
+ struct radix_tree_node *node;
+ void **slot;
+ struct ida_bitmap *bitmap;
+ unsigned long ebit;
+
+ bit %= IDA_BITMAP_BITS;
+ ebit = bit + 2;
+
+ err = __radix_tree_create(root, index, 0, &node, &slot);
+ if (err)
+ return err;
+ bitmap = rcu_dereference_raw(*slot);
+ if (radix_tree_exception(bitmap)) {
+ unsigned long tmp = (unsigned long)bitmap;
+
+ if (ebit < BITS_PER_LONG) {
+ tmp |= 1UL << ebit;
+ rcu_assign_pointer(*slot, (void *)tmp);
+ return 0;
+ }
+ bitmap = this_cpu_xchg(ida_bitmap, NULL);
+ if (!bitmap)
Please write locking rules, in order to explain how memory
allocated by __radix_tree_create() will not leak.
For the memory allocated by __radix_tree_create(), I think we could add:
if (!bitmap) {
__radix_tree_delete(root, node, slot);
break;
}
For the locking rules, how about adding the following "Developer notes:"
at the top of the file:
"
Locks are required to ensure that concurrent calls to xb_set_bit,
xb_preload_and_set_bit, xb_test_bit, xb_clear_bit, xb_clear_bit_range,
xb_find_next_set_bit and xb_find_next_zero_bit, for the same ida bitmap
will not happen.
"
+bool xb_test_bit(struct xb *xb, unsigned long bit)
+{
+ unsigned long index = bit / IDA_BITMAP_BITS;
+ const struct radix_tree_root *root = &xb->xbrt;
+ struct ida_bitmap *bitmap = radix_tree_lookup(root, index);
+
+ bit %= IDA_BITMAP_BITS;
+
+ if (!bitmap)
+ return false;
+ if (radix_tree_exception(bitmap)) {
+ bit += RADIX_TREE_EXCEPTIONAL_SHIFT;
+ if (bit > BITS_PER_LONG)
Why not bit >= BITS_PER_LONG here?
Yes, I think it should be ">=" here. Thanks.
Best,
Wei
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