[PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

[PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

[Alexander Potapenko]

From: Syed Nayyar Waris <syednwaris@gmail.com>

The two new functions allow reading/writing values of length up to
BITS_PER_LONG bits at arbitrary position in the bitmap.

The code was taken from "bitops: Introduce the for_each_set_clump macro"
by Syed Nayyar Waris with a number of changes and simplifications:
 - instead of using roundup(), which adds an unnecessary dependency
   on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
 - indentation is reduced by not using else-clauses (suggested by
   checkpatch for bitmap_get_value());
 - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
   and bitmap_write();
 - some redundant computations are omitted.

Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
Suggested-by: Yury Norov <yury.norov@gmail.com>
Co-developed-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

---
This patch was previously part of the "Implement MTE tag compression for
swapped pages" series
(https://lore.kernel.org/linux-arm-kernel/20231011172836.2579017-4-glider@google.com/T/)

This patch was previously called "lib/bitmap: add
bitmap_{set,get}_value()"
(https://lore.kernel.org/lkml/20230720173956.3674987-2-glider@google.com/)

v11:
 - rearrange whitespace as requested by Andy Shevchenko,
   add Reviewed-by:, update a comment

v10:
 - update comments as requested by Andy Shevchenko

v8:
 - as suggested by Andy Shevchenko, handle reads/writes of more than
   BITS_PER_LONG bits, add a note for 32-bit systems

v7:
 - Address comments by Yury Norov, Andy Shevchenko, Rasmus Villemoes:
   - update code comments;
   - get rid of GENMASK();
   - s/assign_bit/__assign_bit;
   - more vertical whitespace for better readability;
 - more compact code for bitmap_write() (now for real)

v6:
 - As suggested by Yury Norov, do not require bitmap_read(..., 0) to
   return 0.

v5:
 - Address comments by Yury Norov:
   - updated code comments and patch title/description
   - replace GENMASK(nbits - 1, 0) with BITMAP_LAST_WORD_MASK(nbits)
   - more compact bitmap_write() implementation

v4:
 - Address comments by Andy Shevchenko and Yury Norov:
   - prevent passing values >= 64 to GENMASK()
   - fix commit authorship
   - change comments
   - check for unlikely(nbits==0)
   - drop unnecessary const declarations
   - fix kernel-doc comments
   - rename bitmap_{get,set}_value() to bitmap_{read,write}()
---
 include/linux/bitmap.h | 77 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 03644237e1efb..7dd00e2e6d539 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -77,6 +77,10 @@ struct device;
  *  bitmap_to_arr64(buf, src, nbits)            Copy nbits from buf to u64[] dst
  *  bitmap_get_value8(map, start)               Get 8bit value from map at start
  *  bitmap_set_value8(map, value, start)        Set 8bit value to map at start
+ *  bitmap_read(map, start, nbits)              Read an nbits-sized value from
+ *                                              map at start
+ *  bitmap_write(map, value, start, nbits)      Write an nbits-sized value to
+ *                                              map at start
  *
  * Note, bitmap_zero() and bitmap_fill() operate over the region of
  * unsigned longs, that is, bits behind bitmap till the unsigned long
@@ -599,6 +603,79 @@ static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
 	map[index] |= value << offset;
 }
 
+/**
+ * bitmap_read - read a value of n-bits from the memory region
+ * @map: address to the bitmap memory region
+ * @start: bit offset of the n-bit value
+ * @nbits: size of value in bits, nonzero, up to BITS_PER_LONG
+ *
+ * Returns: value of @nbits bits located at the @start bit offset within the
+ * @map memory region. For @nbits = 0 and @nbits > BITS_PER_LONG the return
+ * value is undefined.
+ */
+static inline unsigned long bitmap_read(const unsigned long *map,
+					unsigned long start,
+					unsigned long nbits)
+{
+	size_t index = BIT_WORD(start);
+	unsigned long offset = start % BITS_PER_LONG;
+	unsigned long space = BITS_PER_LONG - offset;
+	unsigned long value_low, value_high;
+
+	if (unlikely(!nbits || nbits > BITS_PER_LONG))
+		return 0;
+
+	if (space >= nbits)
+		return (map[index] >> offset) & BITMAP_LAST_WORD_MASK(nbits);
+
+	value_low = map[index] & BITMAP_FIRST_WORD_MASK(start);
+	value_high = map[index + 1] & BITMAP_LAST_WORD_MASK(start + nbits);
+	return (value_low >> offset) | (value_high << space);
+}
+
+/**
+ * bitmap_write - write n-bit value within a memory region
+ * @map: address to the bitmap memory region
+ * @value: value to write, clamped to nbits
+ * @start: bit offset of the n-bit value
+ * @nbits: size of value in bits, nonzero, up to BITS_PER_LONG.
+ *
+ * bitmap_write() behaves as-if implemented as @nbits calls of __assign_bit(),
+ * i.e. bits beyond @nbits are ignored:
+ *
+ *   for (bit = 0; bit < nbits; bit++)
+ *           __assign_bit(start + bit, bitmap, val & BIT(bit));
+ *
+ * For @nbits == 0 and @nbits > BITS_PER_LONG no writes are performed.
+ */
+static inline void bitmap_write(unsigned long *map, unsigned long value,
+				unsigned long start, unsigned long nbits)
+{
+	size_t index;
+	unsigned long offset;
+	unsigned long space;
+	unsigned long mask;
+	bool fit;
+
+	if (unlikely(!nbits || nbits > BITS_PER_LONG))
+		return;
+
+	mask = BITMAP_LAST_WORD_MASK(nbits);
+	value &= mask;
+	offset = start % BITS_PER_LONG;
+	space = BITS_PER_LONG - offset;
+	fit = space >= nbits;
+	index = BIT_WORD(start);
+
+	map[index] &= (fit ? (~(mask << offset)) : ~BITMAP_FIRST_WORD_MASK(start));
+	map[index] |= value << offset;
+	if (fit)
+		return;
+
+	map[index + 1] &= BITMAP_FIRST_WORD_MASK(start + nbits);
+	map[index + 1] |= (value >> space);
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __LINUX_BITMAP_H */
-- 
2.42.0.869.gea05f2083d-goog


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[PATCH v12 2/3] lib/test_bitmap: add tests for bitmap_{read,write}()

[Alexander Potapenko]

Add basic tests ensuring that values can be added at arbitrary positions
of the bitmap, including those spanning into the adjacent unsigned
longs.

Two new performance tests, test_bitmap_read_perf() and
test_bitmap_write_perf(), can be used to assess future performance
improvements of bitmap_read() and bitmap_write():

[    0.431119][    T1] test_bitmap: Time spent in test_bitmap_read_perf:	615253
[    0.433197][    T1] test_bitmap: Time spent in test_bitmap_write_perf:	916313

(numbers from a Intel(R) Xeon(R) Gold 6154 CPU @ 3.00GHz machine running
QEMU).

Signed-off-by: Alexander Potapenko <glider@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

---
This patch was previously part of the "Implement MTE tag compression for
swapped pages" series
(https://lore.kernel.org/linux-arm-kernel/20231011172836.2579017-4-glider@google.com/T/)

This patch was previously called
"lib/test_bitmap: add tests for bitmap_{set,get}_value()"
(https://lore.kernel.org/lkml/20230720173956.3674987-3-glider@google.com/)
and
"lib/test_bitmap: add tests for bitmap_{set,get}_value_unaligned"
(https://lore.kernel.org/lkml/20230713125706.2884502-3-glider@google.com/)

v12:
 - as suggested by Alexander Lobakin, replace expect_eq_uint() with
   expect_eq_ulong() and a cast

v9:
 - use WRITE_ONCE() to prevent optimizations in test_bitmap_read_perf()
 - update patch description

v8:
 - as requested by Andy Shevchenko, add tests for reading/writing
   sizes > BITS_PER_LONG

v7:
 - as requested by Yury Norov, add performance tests for bitmap_read()
   and bitmap_write()

v6:
 - use bitmap API to initialize test bitmaps
 - as requested by Yury Norov, do not check the return value of
   bitmap_read(..., 0)
 - fix a compiler warning on 32-bit systems

v5:
 - update patch title
 - address Yury Norov's comments:
   - rename the test cases
   - factor out test_bitmap_write_helper() to test writing over
     different background patterns;
   - add a test case copying a nontrivial value bit-by-bit;
   - drop volatile

v4:
 - Address comments by Andy Shevchenko: added Reviewed-by: and a link to
   the previous discussion
 - Address comments by Yury Norov:
   - expand the bitmap to catch more corner cases
   - add code testing that bitmap_set_value() does not touch adjacent
     bits
   - add code testing the nbits==0 case
   - rename bitmap_{get,set}_value() to bitmap_{read,write}()

v3:
 - switch to using bitmap_{set,get}_value()
 - change the expected bit pattern in test_set_get_value(),
   as the test was incorrectly assuming 0 is the LSB.
---
 lib/test_bitmap.c | 179 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 172 insertions(+), 7 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index f2ea9f30c7c5d..2761edbc83d73 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -60,18 +60,17 @@ static const unsigned long exp3_1_0[] __initconst = {
 };
 
 static bool __init
-__check_eq_uint(const char *srcfile, unsigned int line,
-		const unsigned int exp_uint, unsigned int x)
+__check_eq_ulong(const char *srcfile, unsigned int line,
+		 const unsigned long exp_ulong, unsigned long x)
 {
-	if (exp_uint != x) {
-		pr_err("[%s:%u] expected %u, got %u\n",
-			srcfile, line, exp_uint, x);
+	if (exp_ulong != x) {
+		pr_err("[%s:%u] expected %lu, got %lu\n",
+			srcfile, line, exp_ulong, x);
 		return false;
 	}
 	return true;
 }
 
-
 static bool __init
 __check_eq_bitmap(const char *srcfile, unsigned int line,
 		  const unsigned long *exp_bmap, const unsigned long *bmap,
@@ -185,7 +184,8 @@ __check_eq_str(const char *srcfile, unsigned int line,
 		result;							\
 	})
 
-#define expect_eq_uint(...)		__expect_eq(uint, ##__VA_ARGS__)
+#define expect_eq_ulong(...)		__expect_eq(ulong, ##__VA_ARGS__)
+#define expect_eq_uint(x, y)		expect_eq_ulong((unsigned int)(x), (unsigned int)(y))
 #define expect_eq_bitmap(...)		__expect_eq(bitmap, ##__VA_ARGS__)
 #define expect_eq_pbl(...)		__expect_eq(pbl, ##__VA_ARGS__)
 #define expect_eq_u32_array(...)	__expect_eq(u32_array, ##__VA_ARGS__)
@@ -1222,6 +1222,168 @@ static void __init test_bitmap_const_eval(void)
 	BUILD_BUG_ON(~var != ~BIT(25));
 }
 
+/*
+ * Test bitmap should be big enough to include the cases when start is not in
+ * the first word, and start+nbits lands in the following word.
+ */
+#define TEST_BIT_LEN (1000)
+
+/*
+ * Helper function to test bitmap_write() overwriting the chosen byte pattern.
+ */
+static void __init test_bitmap_write_helper(const char *pattern)
+{
+	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+	DECLARE_BITMAP(exp_bitmap, TEST_BIT_LEN);
+	DECLARE_BITMAP(pat_bitmap, TEST_BIT_LEN);
+	unsigned long w, r, bit;
+	int i, n, nbits;
+
+	/*
+	 * Only parse the pattern once and store the result in the intermediate
+	 * bitmap.
+	 */
+	bitmap_parselist(pattern, pat_bitmap, TEST_BIT_LEN);
+
+	/*
+	 * Check that writing a single bit does not accidentally touch the
+	 * adjacent bits.
+	 */
+	for (i = 0; i < TEST_BIT_LEN; i++) {
+		bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+		bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+		for (bit = 0; bit <= 1; bit++) {
+			bitmap_write(bitmap, bit, i, 1);
+			__assign_bit(i, exp_bitmap, bit);
+			expect_eq_bitmap(exp_bitmap, bitmap,
+					 TEST_BIT_LEN);
+		}
+	}
+
+	/* Ensure writing 0 bits does not change anything. */
+	bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+	bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+	for (i = 0; i < TEST_BIT_LEN; i++) {
+		bitmap_write(bitmap, ~0UL, i, 0);
+		expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN);
+	}
+
+	for (nbits = BITS_PER_LONG; nbits >= 1; nbits--) {
+		w = IS_ENABLED(CONFIG_64BIT) ? 0xdeadbeefdeadbeefUL
+					     : 0xdeadbeefUL;
+		w >>= (BITS_PER_LONG - nbits);
+		for (i = 0; i <= TEST_BIT_LEN - nbits; i++) {
+			bitmap_copy(bitmap, pat_bitmap, TEST_BIT_LEN);
+			bitmap_copy(exp_bitmap, pat_bitmap, TEST_BIT_LEN);
+			for (n = 0; n < nbits; n++)
+				__assign_bit(i + n, exp_bitmap, w & BIT(n));
+			bitmap_write(bitmap, w, i, nbits);
+			expect_eq_bitmap(exp_bitmap, bitmap, TEST_BIT_LEN);
+			r = bitmap_read(bitmap, i, nbits);
+			expect_eq_ulong(r, w);
+		}
+	}
+}
+
+static void __init test_bitmap_read_write(void)
+{
+	unsigned char *pattern[3] = {"", "all:1/2", "all"};
+	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+	unsigned long zero_bits = 0, bits_per_long = BITS_PER_LONG;
+	unsigned long val;
+	int i, pi;
+
+	/*
+	 * Reading/writing zero bits should not crash the kernel.
+	 * READ_ONCE() prevents constant folding.
+	 */
+	bitmap_write(NULL, 0, 0, READ_ONCE(zero_bits));
+	/* Return value of bitmap_read() is undefined here. */
+	bitmap_read(NULL, 0, READ_ONCE(zero_bits));
+
+	/*
+	 * Reading/writing more than BITS_PER_LONG bits should not crash the
+	 * kernel. READ_ONCE() prevents constant folding.
+	 */
+	bitmap_write(NULL, 0, 0, READ_ONCE(bits_per_long) + 1);
+	/* Return value of bitmap_read() is undefined here. */
+	bitmap_read(NULL, 0, READ_ONCE(bits_per_long) + 1);
+
+	/*
+	 * Ensure that bitmap_read() reads the same value that was previously
+	 * written, and two consequent values are correctly merged.
+	 * The resulting bit pattern is asymmetric to rule out possible issues
+	 * with bit numeration order.
+	 */
+	for (i = 0; i < TEST_BIT_LEN - 7; i++) {
+		bitmap_zero(bitmap, TEST_BIT_LEN);
+
+		bitmap_write(bitmap, 0b10101UL, i, 5);
+		val = bitmap_read(bitmap, i, 5);
+		expect_eq_ulong(0b10101UL, val);
+
+		bitmap_write(bitmap, 0b101UL, i + 5, 3);
+		val = bitmap_read(bitmap, i + 5, 3);
+		expect_eq_ulong(0b101UL, val);
+
+		val = bitmap_read(bitmap, i, 8);
+		expect_eq_ulong(0b10110101UL, val);
+	}
+
+	for (pi = 0; pi < ARRAY_SIZE(pattern); pi++)
+		test_bitmap_write_helper(pattern[pi]);
+}
+
+static void __init test_bitmap_read_perf(void)
+{
+	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+	unsigned int cnt, nbits, i;
+	unsigned long val;
+	ktime_t time;
+
+	bitmap_fill(bitmap, TEST_BIT_LEN);
+	time = ktime_get();
+	for (cnt = 0; cnt < 5; cnt++) {
+		for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
+			for (i = 0; i < TEST_BIT_LEN; i++) {
+				if (i + nbits > TEST_BIT_LEN)
+					break;
+				/*
+				 * Prevent the compiler from optimizing away the
+				 * bitmap_read() by using its value.
+				 */
+				WRITE_ONCE(val, bitmap_read(bitmap, i, nbits));
+			}
+		}
+	}
+	time = ktime_get() - time;
+	pr_err("Time spent in %s:\t%llu\n", __func__, time);
+}
+
+static void __init test_bitmap_write_perf(void)
+{
+	DECLARE_BITMAP(bitmap, TEST_BIT_LEN);
+	unsigned int cnt, nbits, i;
+	unsigned long val = 0xfeedface;
+	ktime_t time;
+
+	bitmap_zero(bitmap, TEST_BIT_LEN);
+	time = ktime_get();
+	for (cnt = 0; cnt < 5; cnt++) {
+		for (nbits = 1; nbits <= BITS_PER_LONG; nbits++) {
+			for (i = 0; i < TEST_BIT_LEN; i++) {
+				if (i + nbits > TEST_BIT_LEN)
+					break;
+				bitmap_write(bitmap, val, i, nbits);
+			}
+		}
+	}
+	time = ktime_get() - time;
+	pr_err("Time spent in %s:\t%llu\n", __func__, time);
+}
+
+#undef TEST_BIT_LEN
+
 static void __init selftest(void)
 {
 	test_zero_clear();
@@ -1237,6 +1399,9 @@ static void __init selftest(void)
 	test_bitmap_cut();
 	test_bitmap_print_buf();
 	test_bitmap_const_eval();
+	test_bitmap_read_write();
+	test_bitmap_read_perf();
+	test_bitmap_write_perf();
 
 	test_find_nth_bit();
 	test_for_each_set_bit();
-- 
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[PATCH v12 3/3] lib/test_bitmap: use pr_info() for non-error messages

[Alexander Potapenko]

pr_err() messages may be treated as errors by some log readers, so let
us only use them for test failures. For non-error messages, replace them
with pr_info().

Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
---
 lib/test_bitmap.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c
index 2761edbc83d73..8a8af5d28432e 100644
--- a/lib/test_bitmap.c
+++ b/lib/test_bitmap.c
@@ -484,7 +484,7 @@ static void __init test_bitmap_parselist(void)
 		}
 
 		if (ptest.flags & PARSE_TIME)
-			pr_err("parselist: %d: input is '%s' OK, Time: %llu\n",
+			pr_info("parselist: %d: input is '%s' OK, Time: %llu\n",
 					i, ptest.in, time);
 
 #undef ptest
@@ -523,7 +523,7 @@ static void __init test_bitmap_printlist(void)
 		goto out;
 	}
 
-	pr_err("bitmap_print_to_pagebuf: input is '%s', Time: %llu\n", buf, time);
+	pr_info("bitmap_print_to_pagebuf: input is '%s', Time: %llu\n", buf, time);
 out:
 	kfree(buf);
 	kfree(bmap);
@@ -601,7 +601,7 @@ static void __init test_bitmap_parse(void)
 		}
 
 		if (test.flags & PARSE_TIME)
-			pr_err("parse: %d: input is '%s' OK, Time: %llu\n",
+			pr_info("parse: %d: input is '%s' OK, Time: %llu\n",
 					i, test.in, time);
 	}
 }
@@ -1357,7 +1357,7 @@ static void __init test_bitmap_read_perf(void)
 		}
 	}
 	time = ktime_get() - time;
-	pr_err("Time spent in %s:\t%llu\n", __func__, time);
+	pr_info("Time spent in %s:\t%llu\n", __func__, time);
 }
 
 static void __init test_bitmap_write_perf(void)
@@ -1379,7 +1379,7 @@ static void __init test_bitmap_write_perf(void)
 		}
 	}
 	time = ktime_get() - time;
-	pr_err("Time spent in %s:\t%llu\n", __func__, time);
+	pr_info("Time spent in %s:\t%llu\n", __func__, time);
 }
 
 #undef TEST_BIT_LEN
-- 
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Re: [PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

[Alexander Potapenko]

On Thu, Nov 9, 2023 at 4:11 PM Alexander Potapenko <glider@google.com> wrote:
>
> From: Syed Nayyar Waris <syednwaris@gmail.com>
>
> The two new functions allow reading/writing values of length up to
> BITS_PER_LONG bits at arbitrary position in the bitmap.
>
> The code was taken from "bitops: Introduce the for_each_set_clump macro"
> by Syed Nayyar Waris with a number of changes and simplifications:
>  - instead of using roundup(), which adds an unnecessary dependency
>    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
>  - indentation is reduced by not using else-clauses (suggested by
>    checkpatch for bitmap_get_value());
>  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
>    and bitmap_write();
>  - some redundant computations are omitted.
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
> Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
> Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
> Suggested-by: Yury Norov <yury.norov@gmail.com>
> Co-developed-by: Alexander Potapenko <glider@google.com>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

Yury, Andy, do you think anything else is needed for this series?
If not, whom should we ask to take it?

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Re: [PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

[Yury Norov]

On Mon, Dec 04, 2023 at 02:28:09PM +0100, Alexander Potapenko wrote:
> On Thu, Nov 9, 2023 at 4:11 PM Alexander Potapenko <glider@google.com> wrote:
> >
> > From: Syed Nayyar Waris <syednwaris@gmail.com>
> >
> > The two new functions allow reading/writing values of length up to
> > BITS_PER_LONG bits at arbitrary position in the bitmap.
> >
> > The code was taken from "bitops: Introduce the for_each_set_clump macro"
> > by Syed Nayyar Waris with a number of changes and simplifications:
> >  - instead of using roundup(), which adds an unnecessary dependency
> >    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
> >  - indentation is reduced by not using else-clauses (suggested by
> >    checkpatch for bitmap_get_value());
> >  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
> >    and bitmap_write();
> >  - some redundant computations are omitted.
> >
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
> > Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
> > Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
> > Suggested-by: Yury Norov <yury.norov@gmail.com>
> > Co-developed-by: Alexander Potapenko <glider@google.com>
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> 
> Yury, Andy, do you think anything else is needed for this series?
> If not, whom should we ask to take it?

I probably need to revisit it, but generally it looks OK.

But I can't take new API without having real users. Now that your MTE
series is delayed, and Alexander's 'ip_tunnel flags' is not moving as
well, there's non-zero chance to merge dead code.

If you want it to be merged, I'd advise you to walk through the kernel
sources and find good cases where bitmap_read() and bitmap_write() can
be used. Then append this series with such conversions, and I'll be
able to move it.

Thanks,
Yury

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Re: [PATCH v12 1/3] lib/bitmap: add bitmap_{read,write}()

[Alexander Lobakin]

From: Yury Norov <yury.norov@gmail.com>
Date: Mon, 4 Dec 2023 06:22:20 -0800

> On Mon, Dec 04, 2023 at 02:28:09PM +0100, Alexander Potapenko wrote:
>> On Thu, Nov 9, 2023 at 4:11 PM Alexander Potapenko <glider@google.com> wrote:
>>>
>>> From: Syed Nayyar Waris <syednwaris@gmail.com>
>>>
>>> The two new functions allow reading/writing values of length up to
>>> BITS_PER_LONG bits at arbitrary position in the bitmap.
>>>
>>> The code was taken from "bitops: Introduce the for_each_set_clump macro"
>>> by Syed Nayyar Waris with a number of changes and simplifications:
>>>  - instead of using roundup(), which adds an unnecessary dependency
>>>    on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
>>>  - indentation is reduced by not using else-clauses (suggested by
>>>    checkpatch for bitmap_get_value());
>>>  - bitmap_get_value()/bitmap_set_value() are renamed to bitmap_read()
>>>    and bitmap_write();
>>>  - some redundant computations are omitted.
>>>
>>> Cc: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Syed Nayyar Waris <syednwaris@gmail.com>
>>> Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
>>> Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
>>> Suggested-by: Yury Norov <yury.norov@gmail.com>
>>> Co-developed-by: Alexander Potapenko <glider@google.com>
>>> Signed-off-by: Alexander Potapenko <glider@google.com>
>>> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>>
>> Yury, Andy, do you think anything else is needed for this series?
>> If not, whom should we ask to take it?
> 
> I probably need to revisit it, but generally it looks OK.
> 
> But I can't take new API without having real users. Now that your MTE
> series is delayed, and Alexander's 'ip_tunnel flags' is not moving as
> well, there's non-zero chance to merge dead code.

One of the PFCP developers had a quick vacation, we'll send PFCP with
the ip_tunnel bitmap conversion this week.
I'll tell Jakub he'd need to pull boys' tree :D

> 
> If you want it to be merged, I'd advise you to walk through the kernel
> sources and find good cases where bitmap_read() and bitmap_write() can
> be used. Then append this series with such conversions, and I'll be
> able to move it.
> 
> Thanks,
> Yury

Thanks,
Olek

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