From: Alexander Potapenko <glider@google.com>
To: glider@google.com, catalin.marinas@arm.com, will@kernel.org,
pcc@google.com, andreyknvl@gmail.com,
andriy.shevchenko@linux.intel.com, aleksander.lobakin@intel.com,
linux@rasmusvillemoes.dk, yury.norov@gmail.com
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, eugenis@google.com,
syednwaris@gmail.com, william.gray@linaro.org,
Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH v6 1/5] lib/bitmap: add bitmap_{read,write}()
Date: Fri, 6 Oct 2023 15:45:25 +0200 [thread overview]
Message-ID: <20231006134529.2816540-2-glider@google.com> (raw)
In-Reply-To: <20231006134529.2816540-1-glider@google.com>
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>
---
This patch was previously called "lib/bitmap: add
bitmap_{set,get}_value()"
(https://lore.kernel.org/lkml/20230720173956.3674987-2-glider@google.com/)
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 | 68 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 68 insertions(+)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 03644237e1efb..e72c054d21d48 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -76,7 +76,11 @@ struct device;
* bitmap_to_arr32(buf, src, nbits) Copy nbits from buf to u32[] dst
* 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_read(map, start, nbits) Read an nbits-sized value from
+ * map at start
* bitmap_set_value8(map, value, start) Set 8bit value to 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
@@ -583,6 +587,33 @@ static inline unsigned long bitmap_get_value8(const unsigned long *map,
return (map[index] >> offset) & 0xFF;
}
+/**
+ * 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 located at the @start bit offset within the @map
+ * memory region.
+ */
+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))
+ return 0;
+ if (space >= nbits)
+ return (map[index] >> offset) & GENMASK(nbits - 1, 0);
+ 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_set_value8 - set an 8-bit value within a memory region
* @map: address to the bitmap memory region
@@ -599,6 +630,43 @@ static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
map[index] |= value << offset;
}
+/**
+ * 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 similarly to @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));
+ */
+static inline void bitmap_write(unsigned long *map,
+ unsigned long value,
+ 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 mask;
+
+ if (unlikely(!nbits))
+ return;
+ mask = BITMAP_LAST_WORD_MASK(nbits);
+ value &= mask;
+ if (space >= nbits) {
+ map[index] &= ~(mask << offset);
+ map[index] |= value << offset;
+ return;
+ }
+ map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
+ map[index] |= value << offset;
+ map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
+ map[index + 1] |= (value >> space);
+}
+
#endif /* __ASSEMBLY__ */
#endif /* __LINUX_BITMAP_H */
--
2.42.0.609.gbb76f46606-goog
next prev parent reply other threads:[~2023-10-06 13:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-06 13:45 [PATCH v6 0/5] Implement MTE tag compression for swapped pages Alexander Potapenko
2023-10-06 13:45 ` Alexander Potapenko [this message]
2023-10-06 14:47 ` [PATCH v6 1/5] lib/bitmap: add bitmap_{read,write}() Andy Shevchenko
2023-10-06 16:53 ` Yury Norov
2023-10-10 8:16 ` Alexander Potapenko
2023-10-10 9:43 ` Alexander Potapenko
2023-10-06 22:35 ` Yury Norov
2023-10-10 9:17 ` Alexander Potapenko
2023-10-10 11:03 ` Rasmus Villemoes
2023-10-10 12:14 ` Alexander Potapenko
2023-10-06 13:45 ` [PATCH v6 2/5] lib/test_bitmap: add tests for bitmap_{read,write}() Alexander Potapenko
2023-10-06 13:45 ` [PATCH v6 3/5] arm64: mte: implement CONFIG_ARM64_MTE_COMP Alexander Potapenko
2023-10-06 13:45 ` [PATCH v6 4/5] arm64: mte: add a test for MTE tags compression Alexander Potapenko
2023-10-06 13:45 ` [PATCH v6 5/5] arm64: mte: add compression support to mteswap.c Alexander Potapenko
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