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.
> +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.
> + return -EAGAIN;
> + memset(bitmap, 0, sizeof(*bitmap));
> + bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
> + rcu_assign_pointer(*slot, bitmap);
> + }
> +
> + if (!bitmap) {
> + if (ebit < BITS_PER_LONG) {
> + bitmap = (void *)((1UL << ebit) |
> + RADIX_TREE_EXCEPTIONAL_ENTRY);
> + __radix_tree_replace(root, node, slot, bitmap, NULL,
> + NULL);
> + return 0;
> + }
> + bitmap = this_cpu_xchg(ida_bitmap, NULL);
> + if (!bitmap)
Same here.
> + return -EAGAIN;
> + memset(bitmap, 0, sizeof(*bitmap));
> + __radix_tree_replace(root, node, slot, bitmap, NULL, NULL);
> + }
> +
> + __set_bit(bit, bitmap->bitmap);
> + return 0;
> +}
> +void xb_clear_bit(struct xb *xb, unsigned long bit)
> +{
> + 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;
> +
> + bitmap = __radix_tree_lookup(root, index, &node, &slot);
> + if (radix_tree_exception(bitmap)) {
> + unsigned long tmp = (unsigned long)bitmap;
> +
> + if (ebit >= BITS_PER_LONG)
> + return;
> + tmp &= ~(1UL << ebit);
> + if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY)
> + __radix_tree_delete(root, node, slot);
> + else
> + rcu_assign_pointer(*slot, (void *)tmp);
> + return;
> + }
> +
> + if (!bitmap)
> + return;
> +
> + __clear_bit(bit, bitmap->bitmap);
> + if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
Please write locking rules, in order to explain how double kfree() and/or
use-after-free can be avoided.
> + kfree(bitmap);
> + __radix_tree_delete(root, node, slot);
> + }
> +}
> +void xb_clear_bit_range(struct xb *xb, unsigned long start, unsigned long end)
> +{
> + struct radix_tree_root *root = &xb->xbrt;
> + struct radix_tree_node *node;
> + void **slot;
> + struct ida_bitmap *bitmap;
> + unsigned int nbits;
> +
> + for (; start < end; start = (start | (IDA_BITMAP_BITS - 1)) + 1) {
> + unsigned long index = start / IDA_BITMAP_BITS;
> + unsigned long bit = start % IDA_BITMAP_BITS;
> +
> + bitmap = __radix_tree_lookup(root, index, &node, &slot);
> + if (radix_tree_exception(bitmap)) {
> + unsigned long ebit = bit + 2;
> + unsigned long tmp = (unsigned long)bitmap;
> +
> + nbits = min(end - start + 1, BITS_PER_LONG - ebit);
> +
> + if (ebit >= BITS_PER_LONG)
> + continue;
> + bitmap_clear(&tmp, ebit, nbits);
> + if (tmp == RADIX_TREE_EXCEPTIONAL_ENTRY)
> + __radix_tree_delete(root, node, slot);
> + else
> + rcu_assign_pointer(*slot, (void *)tmp);
> + } else if (bitmap) {
> + nbits = min(end - start + 1, IDA_BITMAP_BITS - bit);
> +
> + if (nbits != IDA_BITMAP_BITS)
> + bitmap_clear(bitmap->bitmap, bit, nbits);
> +
> + if (nbits == IDA_BITMAP_BITS ||
> + bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) {
Same here.
> + kfree(bitmap);
> + __radix_tree_delete(root, node, slot);
> + }
> + }
> + }
> +}
> +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?
> + return false;
> + return (unsigned long)bitmap & (1UL << bit);
> + }
> +
> + return test_bit(bit, bitmap->bitmap);
> +}
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