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Message-ID: <20240201122216.2634007-2-aleksander.lobakin@intel.com>
Date: Thu, 1 Feb 2024 13:21:56 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Alexander Lobakin <aleksander.lobakin@...el.com>,
Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
Marcin Szycik <marcin.szycik@...ux.intel.com>,
Wojciech Drewek <wojciech.drewek@...el.com>,
Yury Norov <yury.norov@...il.com>,
Andy Shevchenko <andy@...nel.org>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Alexander Potapenko <glider@...gle.com>,
Jiri Pirko <jiri@...nulli.us>,
Ido Schimmel <idosch@...dia.com>,
Przemek Kitszel <przemyslaw.kitszel@...el.com>,
Simon Horman <horms@...nel.org>,
linux-btrfs@...r.kernel.org,
dm-devel@...hat.com,
ntfs3@...ts.linux.dev,
linux-s390@...r.kernel.org,
intel-wired-lan@...ts.osuosl.org,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
Syed Nayyar Waris <syednwaris@...il.com>,
Arnd Bergmann <arnd@...db.de>,
William Breathitt Gray <william.gray@...aro.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH net-next v5 01/21] lib/bitmap: add bitmap_{read,write}()
From: Syed Nayyar Waris <syednwaris@...il.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@...db.de>
Signed-off-by: Syed Nayyar Waris <syednwaris@...il.com>
Signed-off-by: William Breathitt Gray <william.gray@...aro.org>
Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/
Suggested-by: Yury Norov <yury.norov@...il.com>
Co-developed-by: Alexander Potapenko <glider@...gle.com>
Signed-off-by: Alexander Potapenko <glider@...gle.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Acked-by: Yury Norov <yury.norov@...il.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
---
include/linux/bitmap.h | 77 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 99451431e4d6..7ca0379be8c1 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -79,6 +79,10 @@ 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
@@ -636,6 +640,79 @@ 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 */
--
2.43.0
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