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SubjectRe: [PATCH v20 3/7 RESEND] xbitmap: add more operations

First of all, the test-suite doesn't build, so I don't know whether you
ran it or not. Then I added the xb_find_set() call below, and it fails
the assert, so you should probably fix that.

diff --git a/lib/xbitmap.c b/lib/xbitmap.c
index f03a0f9f9e29..b29af08a7597 100644
--- a/lib/xbitmap.c
+++ b/lib/xbitmap.c
@@ -249,11 +249,12 @@ void xbitmap_check_bit(unsigned long bit)
assert(!xb_test_bit(&xb1, bit));
assert(xb_set_bit(&xb1, bit) == 0);
assert(xb_test_bit(&xb1, bit));
- assert(xb_clear_bit(&xb1, bit) == 0);
+ xb_clear_bit(&xb1, bit);
assert(xb_empty(&xb1));
- assert(xb_clear_bit(&xb1, bit) == 0);
+ xb_clear_bit(&xb1, bit);
assert(xb_empty(&xb1));
xb_preload_end();
+ assert(xb_find_set(&xb1, ULONG_MAX, 0) == bit);
}

static void xbitmap_check_bit_range(void)
diff --git a/tools/testing/radix-tree/Makefile b/tools/testing/radix-tree/Makefile
index 34ece7883629..adf36e34dd77 100644
--- a/tools/testing/radix-tree/Makefile
+++ b/tools/testing/radix-tree/Makefile
@@ -1,9 +1,9 @@
# SPDX-License-Identifier: GPL-2.0

CFLAGS += -I. -I../../include -g -O2 -Wall -D_LGPL_SOURCE -fsanitize=address
-LDFLAGS += -fsanitize=address
-LDLIBS+= -lpthread -lurcu
-TARGETS = main idr-test multiorder
+LDFLAGS += -fsanitize=address $(LDLIBS)
+LDLIBS := -lpthread -lurcu
+TARGETS = main idr-test multiorder xbitmap
CORE_OFILES := radix-tree.o idr.o linux.o test.o find_bit.o
OFILES = main.o $(CORE_OFILES) regression1.o regression2.o regression3.o \
tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o \
On Thu, Dec 21, 2017 at 10:30:06AM +0800, Wei Wang wrote:
> v20 RESEND Changes:
> - fixed the !node path
> - added the test cases for the !node path
> - change __builtin_constant_p(start & 7) to __builtin_constant_p(start)

Why would you do such a thing? Just copy the kernel definitions.

> diff --git a/include/linux/xbitmap.h b/include/linux/xbitmap.h
> index 108f929..ede1029 100644
> --- a/include/linux/xbitmap.h
> +++ b/include/linux/xbitmap.h
> @@ -35,6 +35,12 @@ static inline void xb_init(struct xb *xb)
> int xb_set_bit(struct xb *xb, unsigned long bit);
> bool xb_test_bit(const struct xb *xb, unsigned long bit);
> void xb_clear_bit(struct xb *xb, unsigned long bit);
> +void xb_clear_bit_range(struct xb *xb, unsigned long start,
> + unsigned long nbits);

This is xb_zero(). I thought we talked about this before?

> +unsigned long xb_find_set(struct xb *xb, unsigned long size,
> + unsigned long offset);
> +unsigned long xb_find_zero(struct xb *xb, unsigned long size,
> + unsigned long offset);

Since you're using xb_find_zero(), I think we need the tags from the IDR.
At that point, I'm not sure there's a point in keeping the xbitmap and the
IDR as separate data structures.

> +/**
> + * xb_find_set - find the next set bit in a range of bits
> + * @xb: the xbitmap to search from
> + * @offset: the offset in the range to start searching
> + * @size: the size of the range
> + *
> + * Returns: the found bit or, @size if no set bit is found.
> + */
> +unsigned long xb_find_set(struct xb *xb, unsigned long size,
> + unsigned long offset)
> +{
> + struct radix_tree_root *root = &xb->xbrt;
> + struct radix_tree_node *node;
> + void __rcu **slot;
> + struct ida_bitmap *bitmap;
> + unsigned long index = offset / IDA_BITMAP_BITS;
> + unsigned long index_end = size / IDA_BITMAP_BITS;
> + unsigned long bit = offset % IDA_BITMAP_BITS;
> +
> + if (unlikely(offset >= size))
> + return size;
> +
> + while (index <= index_end) {
> + unsigned long ret;
> + unsigned int nbits = size - index * IDA_BITMAP_BITS;
> +
> + bitmap = __radix_tree_lookup(root, index, &node, &slot);
> +
> + if (!node && !bitmap)
> + return size;
> +
> + if (bitmap) {
> + if (nbits > IDA_BITMAP_BITS)
> + nbits = IDA_BITMAP_BITS;
> +
> + ret = find_next_bit(bitmap->bitmap, nbits, bit);
> + if (ret != nbits)
> + return ret + index * IDA_BITMAP_BITS;
> + }
> + bit = 0;
> + index++;
> + }
> +
> + return size;
> +}
> +EXPORT_SYMBOL(xb_find_set);

This is going to be slower than the implementation I sent yesterday. If I
call:
xb_init(xb);
xb_set_bit(xb, ULONG_MAX);
xb_find_set(xb, ULONG_MAX, 0);

it's going to call __radix_tree_lookup() 16 quadrillion times.
My implementation will walk the tree precisely once.

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