Merge tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-coregrafted

Pull driver core fixes from Danilo Krummrich:

 - Fix kernfs listxattr() not returning security xattr names (e.g.
   SELinux labels) when the kernfs node has no allocated kernfs_iattrs

 - Fix silent truncation of IRQ vector indices in the Rust PCI
   abstractions

 - Don't select OF from DRIVER_PE_KUNIT_TEST; skip the test when OF is
   disabled instead of silently enabling extra kernel functionality

 - Russ Weight is retiring from kernel development; update the Firmware
   Loader sysfs contact to the driver-core mailing list, add a CREDITS
   entry for Firmware Upload, and update MAINTAINERS accordingly

* tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core:
  MAINTAINERS: Remove Russ Weight from Firmware Loader
  CREDITS: Add CREDITS entry for Firmware Upload
  firmware_loader: Change contact for sysfs nodes
  rust: pci: reject IRQ vector indices that do not fit in u32
  kernfs: preserve security xattrs without allocating iattrs
  drivers: base: test: DRIVER_PE_KUNIT_TEST should not select OF

1 files changed, 901 insertions, 0 deletions

diff --git a/lib/bitmap.c b/lib/bitmap.c
new file mode 100644
index 000000000..ed685127a
--- /dev/null
+++ b/lib/bitmap.c
@@ -0,0 +1,901 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * lib/bitmap.c
+ * Helper functions for bitmap.h.
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/ctype.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+
+/**
+ * DOC: bitmap introduction
+ *
+ * bitmaps provide an array of bits, implemented using an
+ * array of unsigned longs.  The number of valid bits in a
+ * given bitmap does _not_ need to be an exact multiple of
+ * BITS_PER_LONG.
+ *
+ * The possible unused bits in the last, partially used word
+ * of a bitmap are 'don't care'.  The implementation makes
+ * no particular effort to keep them zero.  It ensures that
+ * their value will not affect the results of any operation.
+ * The bitmap operations that return Boolean (bitmap_empty,
+ * for example) or scalar (bitmap_weight, for example) results
+ * carefully filter out these unused bits from impacting their
+ * results.
+ *
+ * The byte ordering of bitmaps is more natural on little
+ * endian architectures.  See the big-endian headers
+ * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
+ * for the best explanations of this ordering.
+ */
+
+bool __bitmap_equal(const unsigned long *bitmap1,
+		    const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k, lim = bits/BITS_PER_LONG;
+	for (k = 0; k < lim; ++k)
+		if (bitmap1[k] != bitmap2[k])
+			return false;
+
+	if (bits % BITS_PER_LONG)
+		if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
+			return false;
+
+	return true;
+}
+EXPORT_SYMBOL(__bitmap_equal);
+
+bool __bitmap_or_equal(const unsigned long *bitmap1,
+		       const unsigned long *bitmap2,
+		       const unsigned long *bitmap3,
+		       unsigned int bits)
+{
+	unsigned int k, lim = bits / BITS_PER_LONG;
+	unsigned long tmp;
+
+	for (k = 0; k < lim; ++k) {
+		if ((bitmap1[k] | bitmap2[k]) != bitmap3[k])
+			return false;
+	}
+
+	if (!(bits % BITS_PER_LONG))
+		return true;
+
+	tmp = (bitmap1[k] | bitmap2[k]) ^ bitmap3[k];
+	return (tmp & BITMAP_LAST_WORD_MASK(bits)) == 0;
+}
+EXPORT_SYMBOL(__bitmap_or_equal);
+
+void __bitmap_complement(unsigned long *dst, const unsigned long *src, unsigned int bits)
+{
+	unsigned int k, lim = BITS_TO_LONGS(bits);
+	for (k = 0; k < lim; ++k)
+		dst[k] = ~src[k];
+}
+EXPORT_SYMBOL(__bitmap_complement);
+
+/**
+ * __bitmap_shift_right - logical right shift of the bits in a bitmap
+ *   @dst : destination bitmap
+ *   @src : source bitmap
+ *   @shift : shift by this many bits
+ *   @nbits : bitmap size, in bits
+ *
+ * Shifting right (dividing) means moving bits in the MS -> LS bit
+ * direction.  Zeros are fed into the vacated MS positions and the
+ * LS bits shifted off the bottom are lost.
+ */
+void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
+			unsigned shift, unsigned nbits)
+{
+	unsigned k, lim = BITS_TO_LONGS(nbits);
+	unsigned off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
+	unsigned long mask = BITMAP_LAST_WORD_MASK(nbits);
+	for (k = 0; off + k < lim; ++k) {
+		unsigned long upper, lower;
+
+		/*
+		 * If shift is not word aligned, take lower rem bits of
+		 * word above and make them the top rem bits of result.
+		 */
+		if (!rem || off + k + 1 >= lim)
+			upper = 0;
+		else {
+			upper = src[off + k + 1];
+			if (off + k + 1 == lim - 1)
+				upper &= mask;
+			upper <<= (BITS_PER_LONG - rem);
+		}
+		lower = src[off + k];
+		if (off + k == lim - 1)
+			lower &= mask;
+		lower >>= rem;
+		dst[k] = lower | upper;
+	}
+	if (off)
+		memset(&dst[lim - off], 0, off*sizeof(unsigned long));
+}
+EXPORT_SYMBOL(__bitmap_shift_right);
+
+
+/**
+ * __bitmap_shift_left - logical left shift of the bits in a bitmap
+ *   @dst : destination bitmap
+ *   @src : source bitmap
+ *   @shift : shift by this many bits
+ *   @nbits : bitmap size, in bits
+ *
+ * Shifting left (multiplying) means moving bits in the LS -> MS
+ * direction.  Zeros are fed into the vacated LS bit positions
+ * and those MS bits shifted off the top are lost.
+ */
+
+void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
+			unsigned int shift, unsigned int nbits)
+{
+	int k;
+	unsigned int lim = BITS_TO_LONGS(nbits);
+	unsigned int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
+	for (k = lim - off - 1; k >= 0; --k) {
+		unsigned long upper, lower;
+
+		/*
+		 * If shift is not word aligned, take upper rem bits of
+		 * word below and make them the bottom rem bits of result.
+		 */
+		if (rem && k > 0)
+			lower = src[k - 1] >> (BITS_PER_LONG - rem);
+		else
+			lower = 0;
+		upper = src[k] << rem;
+		dst[k + off] = lower | upper;
+	}
+	if (off)
+		memset(dst, 0, off*sizeof(unsigned long));
+}
+EXPORT_SYMBOL(__bitmap_shift_left);
+
+/**
+ * bitmap_cut() - remove bit region from bitmap and right shift remaining bits
+ * @dst: destination bitmap, might overlap with src
+ * @src: source bitmap
+ * @first: start bit of region to be removed
+ * @cut: number of bits to remove
+ * @nbits: bitmap size, in bits
+ *
+ * Set the n-th bit of @dst iff the n-th bit of @src is set and
+ * n is less than @first, or the m-th bit of @src is set for any
+ * m such that @first <= n < nbits, and m = n + @cut.
+ *
+ * In pictures, example for a big-endian 32-bit architecture:
+ *
+ * The @src bitmap is::
+ *
+ *   31                                   63
+ *   |                                    |
+ *   10000000 11000001 11110010 00010101  10000000 11000001 01110010 00010101
+ *                   |  |              |                                    |
+ *                  16  14             0                                   32
+ *
+ * if @cut is 3, and @first is 14, bits 14-16 in @src are cut and @dst is::
+ *
+ *   31                                   63
+ *   |                                    |
+ *   10110000 00011000 00110010 00010101  00010000 00011000 00101110 01000010
+ *                      |              |                                    |
+ *                      14 (bit 17     0                                   32
+ *                          from @src)
+ *
+ * Note that @dst and @src might overlap partially or entirely.
+ *
+ * This is implemented in the obvious way, with a shift and carry
+ * step for each moved bit. Optimisation is left as an exercise
+ * for the compiler.
+ */
+void bitmap_cut(unsigned long *dst, const unsigned long *src,
+		unsigned int first, unsigned int cut, unsigned int nbits)
+{
+	unsigned int len = BITS_TO_LONGS(nbits);
+	unsigned long keep = 0, carry;
+	int i;
+
+	if (first % BITS_PER_LONG) {
+		keep = src[first / BITS_PER_LONG] &
+		       (~0UL >> (BITS_PER_LONG - first % BITS_PER_LONG));
+	}
+
+	memmove(dst, src, len * sizeof(*dst));
+
+	while (cut--) {
+		for (i = first / BITS_PER_LONG; i < len; i++) {
+			if (i < len - 1)
+				carry = dst[i + 1] & 1UL;
+			else
+				carry = 0;
+
+			dst[i] = (dst[i] >> 1) | (carry << (BITS_PER_LONG - 1));
+		}
+	}
+
+	dst[first / BITS_PER_LONG] &= ~0UL << (first % BITS_PER_LONG);
+	dst[first / BITS_PER_LONG] |= keep;
+}
+EXPORT_SYMBOL(bitmap_cut);
+
+bool __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k;
+	unsigned int lim = bits/BITS_PER_LONG;
+	unsigned long result = 0;
+
+	for (k = 0; k < lim; k++)
+		result |= (dst[k] = bitmap1[k] & bitmap2[k]);
+	if (bits % BITS_PER_LONG)
+		result |= (dst[k] = bitmap1[k] & bitmap2[k] &
+			   BITMAP_LAST_WORD_MASK(bits));
+	return result != 0;
+}
+EXPORT_SYMBOL(__bitmap_and);
+
+void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k;
+	unsigned int nr = BITS_TO_LONGS(bits);
+
+	for (k = 0; k < nr; k++)
+		dst[k] = bitmap1[k] | bitmap2[k];
+}
+EXPORT_SYMBOL(__bitmap_or);
+
+void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k;
+	unsigned int nr = BITS_TO_LONGS(bits);
+
+	for (k = 0; k < nr; k++)
+		dst[k] = bitmap1[k] ^ bitmap2[k];
+}
+EXPORT_SYMBOL(__bitmap_xor);
+
+bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k;
+	unsigned int lim = bits/BITS_PER_LONG;
+	unsigned long result = 0;
+
+	for (k = 0; k < lim; k++)
+		result |= (dst[k] = bitmap1[k] & ~bitmap2[k]);
+	if (bits % BITS_PER_LONG)
+		result |= (dst[k] = bitmap1[k] & ~bitmap2[k] &
+			   BITMAP_LAST_WORD_MASK(bits));
+	return result != 0;
+}
+EXPORT_SYMBOL(__bitmap_andnot);
+
+void __bitmap_replace(unsigned long *dst,
+		      const unsigned long *old, const unsigned long *new,
+		      const unsigned long *mask, unsigned int nbits)
+{
+	unsigned int k;
+	unsigned int nr = BITS_TO_LONGS(nbits);
+
+	for (k = 0; k < nr; k++)
+		dst[k] = (old[k] & ~mask[k]) | (new[k] & mask[k]);
+}
+EXPORT_SYMBOL(__bitmap_replace);
+
+bool __bitmap_intersects(const unsigned long *bitmap1,
+			 const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k, lim = bits/BITS_PER_LONG;
+	for (k = 0; k < lim; ++k)
+		if (bitmap1[k] & bitmap2[k])
+			return true;
+
+	if (bits % BITS_PER_LONG)
+		if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
+			return true;
+	return false;
+}
+EXPORT_SYMBOL(__bitmap_intersects);
+
+bool __bitmap_subset(const unsigned long *bitmap1,
+		     const unsigned long *bitmap2, unsigned int bits)
+{
+	unsigned int k, lim = bits/BITS_PER_LONG;
+	for (k = 0; k < lim; ++k)
+		if (bitmap1[k] & ~bitmap2[k])
+			return false;
+
+	if (bits % BITS_PER_LONG)
+		if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
+			return false;
+	return true;
+}
+EXPORT_SYMBOL(__bitmap_subset);
+
+#define BITMAP_WEIGHT(FETCH, bits)	\
+({										\
+	unsigned int __bits = (bits), idx, w = 0;				\
+										\
+	for (idx = 0; idx < __bits / BITS_PER_LONG; idx++)			\
+		w += hweight_long(FETCH);					\
+										\
+	if (__bits % BITS_PER_LONG)						\
+		w += hweight_long((FETCH) & BITMAP_LAST_WORD_MASK(__bits));	\
+										\
+	w;									\
+})
+
+unsigned int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
+{
+	return BITMAP_WEIGHT(bitmap[idx], bits);
+}
+EXPORT_SYMBOL(__bitmap_weight);
+
+unsigned int __bitmap_weight_and(const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(bitmap1[idx] & bitmap2[idx], bits);
+}
+EXPORT_SYMBOL(__bitmap_weight_and);
+
+unsigned int __bitmap_weight_andnot(const unsigned long *bitmap1,
+				const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(bitmap1[idx] & ~bitmap2[idx], bits);
+}
+EXPORT_SYMBOL(__bitmap_weight_andnot);
+
+unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] | bitmap2[idx]; dst[idx]; }), bits);
+}
+EXPORT_SYMBOL(__bitmap_weighted_or);
+
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] ^ bitmap2[idx]; dst[idx]; }), bits);
+}
+EXPORT_SYMBOL(__bitmap_weighted_xor);
+
+void __bitmap_set(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_set >= 0) {
+		*p |= mask_to_set;
+		len -= bits_to_set;
+		bits_to_set = BITS_PER_LONG;
+		mask_to_set = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_set &= BITMAP_LAST_WORD_MASK(size);
+		*p |= mask_to_set;
+	}
+}
+EXPORT_SYMBOL(__bitmap_set);
+
+void __bitmap_clear(unsigned long *map, unsigned int start, int len)
+{
+	unsigned long *p = map + BIT_WORD(start);
+	const unsigned int size = start + len;
+	int bits_to_clear = BITS_PER_LONG - (start % BITS_PER_LONG);
+	unsigned long mask_to_clear = BITMAP_FIRST_WORD_MASK(start);
+
+	while (len - bits_to_clear >= 0) {
+		*p &= ~mask_to_clear;
+		len -= bits_to_clear;
+		bits_to_clear = BITS_PER_LONG;
+		mask_to_clear = ~0UL;
+		p++;
+	}
+	if (len) {
+		mask_to_clear &= BITMAP_LAST_WORD_MASK(size);
+		*p &= ~mask_to_clear;
+	}
+}
+EXPORT_SYMBOL(__bitmap_clear);
+
+/**
+ * bitmap_find_next_zero_area_off - find a contiguous aligned zero area
+ * @map: The address to base the search on
+ * @size: The bitmap size in bits
+ * @start: The bitnumber to start searching at
+ * @nr: The number of zeroed bits we're looking for
+ * @align_mask: Alignment mask for zero area
+ * @align_offset: Alignment offset for zero area.
+ *
+ * The @align_mask should be one less than a power of 2; the effect is that
+ * the bit offset of all zero areas this function finds plus @align_offset
+ * is multiple of that power of 2.
+ *
+ * Return: The bit offset of the found area or a value greater than or equal
+ * to @size if no area is found.
+ */
+unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
+					     unsigned long size,
+					     unsigned long start,
+					     unsigned int nr,
+					     unsigned long align_mask,
+					     unsigned long align_offset)
+{
+	unsigned long end, i, off;
+
+	for_each_clear_bit_from(start, map, size) {
+		start = __ALIGN_MASK(start + align_offset, align_mask) - align_offset;
+		end = start + nr;
+		if (end > size)
+			break;
+
+		off = round_down(start, BITS_PER_LONG);
+		i = find_last_bit(map + start / BITS_PER_LONG, end - off) + off;
+		if (i >= end || i < start)
+			return start;
+
+		start = i;
+	}
+
+	return size;
+}
+EXPORT_SYMBOL(bitmap_find_next_zero_area_off);
+
+/**
+ * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
+ *	@buf: pointer to a bitmap
+ *	@pos: a bit position in @buf (0 <= @pos < @nbits)
+ *	@nbits: number of valid bit positions in @buf
+ *
+ * Map the bit at position @pos in @buf (of length @nbits) to the
+ * ordinal of which set bit it is.  If it is not set or if @pos
+ * is not a valid bit position, map to -1.
+ *
+ * If for example, just bits 4 through 7 are set in @buf, then @pos
+ * values 4 through 7 will get mapped to 0 through 3, respectively,
+ * and other @pos values will get mapped to -1.  When @pos value 7
+ * gets mapped to (returns) @ord value 3 in this example, that means
+ * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
+ *
+ * The bit positions 0 through @bits are valid positions in @buf.
+ */
+static int bitmap_pos_to_ord(const unsigned long *buf, unsigned int pos, unsigned int nbits)
+{
+	if (pos >= nbits || !test_bit(pos, buf))
+		return -1;
+
+	return bitmap_weight(buf, pos);
+}
+
+/**
+ * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap
+ *	@dst: remapped result
+ *	@src: subset to be remapped
+ *	@old: defines domain of map
+ *	@new: defines range of map
+ *	@nbits: number of bits in each of these bitmaps
+ *
+ * Let @old and @new define a mapping of bit positions, such that
+ * whatever position is held by the n-th set bit in @old is mapped
+ * to the n-th set bit in @new.  In the more general case, allowing
+ * for the possibility that the weight 'w' of @new is less than the
+ * weight of @old, map the position of the n-th set bit in @old to
+ * the position of the m-th set bit in @new, where m == n % w.
+ *
+ * If either of the @old and @new bitmaps are empty, or if @src and
+ * @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 identity map).
+ *
+ * Apply the above specified mapping to @src, placing the result in
+ * @dst, clearing any bits previously set in @dst.
+ *
+ * For example, lets say that @old has bits 4 through 7 set, and
+ * @new has bits 12 through 15 set.  This defines the mapping of bit
+ * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
+ * bit positions unchanged.  So if say @src comes into this routine
+ * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
+ * 13 and 15 set.
+ */
+void bitmap_remap(unsigned long *dst, const unsigned long *src,
+		const unsigned long *old, const unsigned long *new,
+		unsigned int nbits)
+{
+	unsigned int oldbit, w;
+
+	if (dst == src)		/* following doesn't handle inplace remaps */
+		return;
+	bitmap_zero(dst, nbits);
+
+	w = bitmap_weight(new, nbits);
+	for_each_set_bit(oldbit, src, nbits) {
+		int n = bitmap_pos_to_ord(old, oldbit, nbits);
+
+		if (n < 0 || w == 0)
+			set_bit(oldbit, dst);	/* identity map */
+		else
+			set_bit(find_nth_bit(new, nbits, n % w), dst);
+	}
+}
+EXPORT_SYMBOL(bitmap_remap);
+
+/**
+ * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
+ *	@oldbit: bit position to be mapped
+ *	@old: defines domain of map
+ *	@new: defines range of map
+ *	@bits: number of bits in each of these bitmaps
+ *
+ * Let @old and @new define a mapping of bit positions, such that
+ * whatever position is held by the n-th set bit in @old is mapped
+ * to the n-th set bit in @new.  In the more general case, allowing
+ * for the possibility that the weight 'w' of @new is less than the
+ * weight of @old, map the position of the n-th set bit in @old to
+ * the position of the m-th set bit in @new, where m == n % w.
+ *
+ * The positions of unset bits in @old are mapped to themselves
+ * (the identity map).
+ *
+ * Apply the above specified mapping to bit position @oldbit, returning
+ * the new bit position.
+ *
+ * For example, lets say that @old has bits 4 through 7 set, and
+ * @new has bits 12 through 15 set.  This defines the mapping of bit
+ * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other
+ * bit positions unchanged.  So if say @oldbit is 5, then this routine
+ * returns 13.
+ */
+int bitmap_bitremap(int oldbit, const unsigned long *old,
+				const unsigned long *new, int bits)
+{
+	int w = bitmap_weight(new, bits);
+	int n = bitmap_pos_to_ord(old, oldbit, bits);
+	if (n < 0 || w == 0)
+		return oldbit;
+	else
+		return find_nth_bit(new, bits, n % w);
+}
+EXPORT_SYMBOL(bitmap_bitremap);
+
+#ifdef CONFIG_NUMA
+/**
+ * bitmap_onto - translate one bitmap relative to another
+ *	@dst: resulting translated bitmap
+ * 	@orig: original untranslated bitmap
+ * 	@relmap: bitmap relative to which translated
+ *	@bits: number of bits in each of these bitmaps
+ *
+ * Set the n-th bit of @dst iff there exists some m such that the
+ * n-th bit of @relmap is set, the m-th bit of @orig is set, and
+ * the n-th bit of @relmap is also the m-th _set_ bit of @relmap.
+ * (If you understood the previous sentence the first time your
+ * read it, you're overqualified for your current job.)
+ *
+ * In other words, @orig is mapped onto (surjectively) @dst,
+ * using the map { <n, m> | the n-th bit of @relmap is the
+ * m-th set bit of @relmap }.
+ *
+ * Any set bits in @orig above bit number W, where W is the
+ * weight of (number of set bits in) @relmap are mapped nowhere.
+ * In particular, if for all bits m set in @orig, m >= W, then
+ * @dst will end up empty.  In situations where the possibility
+ * of such an empty result is not desired, one way to avoid it is
+ * to use the bitmap_fold() operator, below, to first fold the
+ * @orig bitmap over itself so that all its set bits x are in the
+ * range 0 <= x < W.  The bitmap_fold() operator does this by
+ * setting the bit (m % W) in @dst, for each bit (m) set in @orig.
+ *
+ * Example [1] for bitmap_onto():
+ *  Let's say @relmap has bits 30-39 set, and @orig has bits
+ *  1, 3, 5, 7, 9 and 11 set.  Then on return from this routine,
+ *  @dst will have bits 31, 33, 35, 37 and 39 set.
+ *
+ *  When bit 0 is set in @orig, it means turn on the bit in
+ *  @dst corresponding to whatever is the first bit (if any)
+ *  that is turned on in @relmap.  Since bit 0 was off in the
+ *  above example, we leave off that bit (bit 30) in @dst.
+ *
+ *  When bit 1 is set in @orig (as in the above example), it
+ *  means turn on the bit in @dst corresponding to whatever
+ *  is the second bit that is turned on in @relmap.  The second
+ *  bit in @relmap that was turned on in the above example was
+ *  bit 31, so we turned on bit 31 in @dst.
+ *
+ *  Similarly, we turned on bits 33, 35, 37 and 39 in @dst,
+ *  because they were the 4th, 6th, 8th and 10th set bits
+ *  set in @relmap, and the 4th, 6th, 8th and 10th bits of
+ *  @orig (i.e. bits 3, 5, 7 and 9) were also set.
+ *
+ *  When bit 11 is set in @orig, it means turn on the bit in
+ *  @dst corresponding to whatever is the twelfth bit that is
+ *  turned on in @relmap.  In the above example, there were
+ *  only ten bits turned on in @relmap (30..39), so that bit
+ *  11 was set in @orig had no affect on @dst.
+ *
+ * Example [2] for bitmap_fold() + bitmap_onto():
+ *  Let's say @relmap has these ten bits set::
+ *
+ *		40 41 42 43 45 48 53 61 74 95
+ *
+ *  (for the curious, that's 40 plus the first ten terms of the
+ *  Fibonacci sequence.)
+ *
+ *  Further lets say we use the following code, invoking
+ *  bitmap_fold() then bitmap_onto, as suggested above to
+ *  avoid the possibility of an empty @dst result::
+ *
+ *	unsigned long *tmp;	// a temporary bitmap's bits
+ *
+ *	bitmap_fold(tmp, orig, bitmap_weight(relmap, bits), bits);
+ *	bitmap_onto(dst, tmp, relmap, bits);
+ *
+ *  Then this table shows what various values of @dst would be, for
+ *  various @orig's.  I list the zero-based positions of each set bit.
+ *  The tmp column shows the intermediate result, as computed by
+ *  using bitmap_fold() to fold the @orig bitmap modulo ten
+ *  (the weight of @relmap):
+ *
+ *      =============== ============== =================
+ *      @orig           tmp            @dst
+ *      0                0             40
+ *      1                1             41
+ *      9                9             95
+ *      10               0             40 [#f1]_
+ *      1 3 5 7          1 3 5 7       41 43 48 61
+ *      0 1 2 3 4        0 1 2 3 4     40 41 42 43 45
+ *      0 9 18 27        0 9 8 7       40 61 74 95
+ *      0 10 20 30       0             40
+ *      0 11 22 33       0 1 2 3       40 41 42 43
+ *      0 12 24 36       0 2 4 6       40 42 45 53
+ *      78 102 211       1 2 8         41 42 74 [#f1]_
+ *      =============== ============== =================
+ *
+ * .. [#f1]
+ *
+ *     For these marked lines, if we hadn't first done bitmap_fold()
+ *     into tmp, then the @dst result would have been empty.
+ *
+ * If either of @orig or @relmap is empty (no set bits), then @dst
+ * will be returned empty.
+ *
+ * If (as explained above) the only set bits in @orig are in positions
+ * m where m >= W, (where W is the weight of @relmap) then @dst will
+ * once again be returned empty.
+ *
+ * All bits in @dst not set by the above rule are cleared.
+ */
+void bitmap_onto(unsigned long *dst, const unsigned long *orig,
+			const unsigned long *relmap, unsigned int bits)
+{
+	unsigned int n, m;	/* same meaning as in above comment */
+
+	if (dst == orig)	/* following doesn't handle inplace mappings */
+		return;
+	bitmap_zero(dst, bits);
+
+	/*
+	 * The following code is a more efficient, but less
+	 * obvious, equivalent to the loop:
+	 *	for (m = 0; m < bitmap_weight(relmap, bits); m++) {
+	 *		n = find_nth_bit(orig, bits, m);
+	 *		if (test_bit(m, orig))
+	 *			set_bit(n, dst);
+	 *	}
+	 */
+
+	m = 0;
+	for_each_set_bit(n, relmap, bits) {
+		/* m == bitmap_pos_to_ord(relmap, n, bits) */
+		if (test_bit(m, orig))
+			set_bit(n, dst);
+		m++;
+	}
+}
+
+/**
+ * bitmap_fold - fold larger bitmap into smaller, modulo specified size
+ *	@dst: resulting smaller bitmap
+ *	@orig: original larger bitmap
+ *	@sz: specified size
+ *	@nbits: number of bits in each of these bitmaps
+ *
+ * For each bit oldbit in @orig, set bit oldbit mod @sz in @dst.
+ * Clear all other bits in @dst.  See further the comment and
+ * Example [2] for bitmap_onto() for why and how to use this.
+ */
+void bitmap_fold(unsigned long *dst, const unsigned long *orig,
+			unsigned int sz, unsigned int nbits)
+{
+	unsigned int oldbit;
+
+	if (dst == orig)	/* following doesn't handle inplace mappings */
+		return;
+	bitmap_zero(dst, nbits);
+
+	for_each_set_bit(oldbit, orig, nbits)
+		set_bit(oldbit % sz, dst);
+}
+#endif /* CONFIG_NUMA */
+
+unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags)
+{
+	return kmalloc_array(BITS_TO_LONGS(nbits), sizeof(unsigned long),
+			     flags);
+}
+EXPORT_SYMBOL(bitmap_alloc);
+
+unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags)
+{
+	return bitmap_alloc(nbits, flags | __GFP_ZERO);
+}
+EXPORT_SYMBOL(bitmap_zalloc);
+
+unsigned long *bitmap_alloc_node(unsigned int nbits, gfp_t flags, int node)
+{
+	return kmalloc_array_node(BITS_TO_LONGS(nbits), sizeof(unsigned long),
+				  flags, node);
+}
+EXPORT_SYMBOL(bitmap_alloc_node);
+
+unsigned long *bitmap_zalloc_node(unsigned int nbits, gfp_t flags, int node)
+{
+	return bitmap_alloc_node(nbits, flags | __GFP_ZERO, node);
+}
+EXPORT_SYMBOL(bitmap_zalloc_node);
+
+void bitmap_free(const unsigned long *bitmap)
+{
+	kfree(bitmap);
+}
+EXPORT_SYMBOL(bitmap_free);
+
+static void devm_bitmap_free(void *data)
+{
+	unsigned long *bitmap = data;
+
+	bitmap_free(bitmap);
+}
+
+unsigned long *devm_bitmap_alloc(struct device *dev,
+				 unsigned int nbits, gfp_t flags)
+{
+	unsigned long *bitmap;
+	int ret;
+
+	bitmap = bitmap_alloc(nbits, flags);
+	if (!bitmap)
+		return NULL;
+
+	ret = devm_add_action_or_reset(dev, devm_bitmap_free, bitmap);
+	if (ret)
+		return NULL;
+
+	return bitmap;
+}
+EXPORT_SYMBOL_GPL(devm_bitmap_alloc);
+
+unsigned long *devm_bitmap_zalloc(struct device *dev,
+				  unsigned int nbits, gfp_t flags)
+{
+	return devm_bitmap_alloc(dev, nbits, flags | __GFP_ZERO);
+}
+EXPORT_SYMBOL_GPL(devm_bitmap_zalloc);
+
+#if BITS_PER_LONG == 64
+/**
+ * bitmap_from_arr32 - copy the contents of u32 array of bits to bitmap
+ *	@bitmap: array of unsigned longs, the destination bitmap
+ *	@buf: array of u32 (in host byte order), the source bitmap
+ *	@nbits: number of bits in @bitmap
+ */
+void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, unsigned int nbits)
+{
+	unsigned int i, halfwords;
+
+	halfwords = DIV_ROUND_UP(nbits, 32);
+	for (i = 0; i < halfwords; i++) {
+		bitmap[i/2] = (unsigned long) buf[i];
+		if (++i < halfwords)
+			bitmap[i/2] |= ((unsigned long) buf[i]) << 32;
+	}
+
+	/* Clear tail bits in last word beyond nbits. */
+	if (nbits % BITS_PER_LONG)
+		bitmap[(halfwords - 1) / 2] &= BITMAP_LAST_WORD_MASK(nbits);
+}
+EXPORT_SYMBOL(bitmap_from_arr32);
+
+/**
+ * bitmap_to_arr32 - copy the contents of bitmap to a u32 array of bits
+ *	@buf: array of u32 (in host byte order), the dest bitmap
+ *	@bitmap: array of unsigned longs, the source bitmap
+ *	@nbits: number of bits in @bitmap
+ */
+void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits)
+{
+	unsigned int i, halfwords;
+
+	halfwords = DIV_ROUND_UP(nbits, 32);
+	for (i = 0; i < halfwords; i++) {
+		buf[i] = (u32) (bitmap[i/2] & UINT_MAX);
+		if (++i < halfwords)
+			buf[i] = (u32) (bitmap[i/2] >> 32);
+	}
+
+	/* Clear tail bits in last element of array beyond nbits. */
+	if (nbits % BITS_PER_LONG)
+		buf[halfwords - 1] &= (u32) (UINT_MAX >> ((-nbits) & 31));
+}
+EXPORT_SYMBOL(bitmap_to_arr32);
+#endif
+
+#if BITS_PER_LONG == 32
+/**
+ * bitmap_from_arr64 - copy the contents of u64 array of bits to bitmap
+ *	@bitmap: array of unsigned longs, the destination bitmap
+ *	@buf: array of u64 (in host byte order), the source bitmap
+ *	@nbits: number of bits in @bitmap
+ */
+void bitmap_from_arr64(unsigned long *bitmap, const u64 *buf, unsigned int nbits)
+{
+	int n;
+
+	for (n = nbits; n > 0; n -= 64) {
+		u64 val = *buf++;
+
+		*bitmap++ = val;
+		if (n > 32)
+			*bitmap++ = val >> 32;
+	}
+
+	/*
+	 * Clear tail bits in the last word beyond nbits.
+	 *
+	 * Negative index is OK because here we point to the word next
+	 * to the last word of the bitmap, except for nbits == 0, which
+	 * is tested implicitly.
+	 */
+	if (nbits % BITS_PER_LONG)
+		bitmap[-1] &= BITMAP_LAST_WORD_MASK(nbits);
+}
+EXPORT_SYMBOL(bitmap_from_arr64);
+
+/**
+ * bitmap_to_arr64 - copy the contents of bitmap to a u64 array of bits
+ *	@buf: array of u64 (in host byte order), the dest bitmap
+ *	@bitmap: array of unsigned longs, the source bitmap
+ *	@nbits: number of bits in @bitmap
+ */
+void bitmap_to_arr64(u64 *buf, const unsigned long *bitmap, unsigned int nbits)
+{
+	const unsigned long *end = bitmap + BITS_TO_LONGS(nbits);
+
+	while (bitmap < end) {
+		*buf = *bitmap++;
+		if (bitmap < end)
+			*buf |= (u64)(*bitmap++) << 32;
+		buf++;
+	}
+
+	/* Clear tail bits in the last element of array beyond nbits. */
+	if (nbits % 64)
+		buf[-1] &= GENMASK_ULL((nbits - 1) % 64, 0);
+}
+EXPORT_SYMBOL(bitmap_to_arr64);
+#endif