From: Yury Norov <yury.norov@gmail.com>
To: Alexander Lobakin <aleksander.lobakin@intel.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Alexander Potapenko <glider@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Eric Dumazet <edumazet@google.com>,
David Ahern <dsahern@kernel.org>,
Przemek Kitszel <przemyslaw.kitszel@intel.com>,
Simon Horman <simon.horman@corigine.com>,
netdev@vger.kernel.org, linux-btrfs@vger.kernel.org,
dm-devel@redhat.com, ntfs3@lists.linux.dev,
linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/14] bitmap: extend bitmap_{get,set}_value8() to bitmap_{get,set}_bits()
Date: Mon, 9 Oct 2023 09:31:15 -0700 [thread overview]
Message-ID: <ZSQq02A9mTireK71@yury-ThinkPad> (raw)
In-Reply-To: <20231009151026.66145-10-aleksander.lobakin@intel.com>
+ Alexander Potapenko <glider@google.com>
On Mon, Oct 09, 2023 at 05:10:21PM +0200, Alexander Lobakin wrote:
> Sometimes there's need to get a 8/16/...-bit piece of a bitmap at a
> particular offset. Currently, there are only bitmap_{get,set}_value8()
> to do that for 8 bits and that's it.
And also a series from Alexander Potapenko, which I really hope will
get into the -next really soon. It introduces bitmap_read/write which
can set up to BITS_PER_LONG at once, with no limitations on alignment
of position and length:
https://lore.kernel.org/linux-arm-kernel/ZRXbOoKHHafCWQCW@yury-ThinkPad/T/#mc311037494229647088b3a84b9f0d9b50bf227cb
Can you consider building your series on top of it?
> Instead of introducing a separate pair for u16 and so on, which doesn't
> scale well, extend the existing functions to be able to pass the wanted
> value width. Make both offset and width arbitrary, but in order to not
> over complicate the current logic and keep the helpers as optimized as
> the current ones, require the width to be a pow-2 value and the offset
> to be a multiple of the width, while the target piece should not cross
> a %BITS_PER_LONG boundary and stay within one long.
> Avoid adjusting all the already existing callsites by defining oneliner
> wrapper macros named after the former functions. bloat-o-meter shows
> almost no difference (+1-2 bytes in a couple of places), meaning the
> new helpers get optimized just nicely.
>
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
> ---
> include/linux/bitmap.h | 51 ++++++++++++++++++++++++++++++------------
> 1 file changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 63e422f8ba3d..9c010a7fa331 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -6,8 +6,10 @@
>
> #include <linux/align.h>
> #include <linux/bitops.h>
> +#include <linux/bug.h>
> #include <linux/find.h>
> #include <linux/limits.h>
> +#include <linux/log2.h>
> #include <linux/string.h>
> #include <linux/types.h>
>
> @@ -569,38 +571,59 @@ static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
> }
>
> /**
> - * bitmap_get_value8 - get an 8-bit value within a memory region
> + * bitmap_get_bits - get a 8/16/32/64-bit value within a memory region
> * @map: address to the bitmap memory region
> - * @start: bit offset of the 8-bit value; must be a multiple of 8
> + * @start: bit offset of the value; must be a multiple of @len
> + * @len: bit width of the value; must be a power of two
> *
> - * Returns the 8-bit value located at the @start bit offset within the @src
> - * memory region.
> + * Return: the 8/16/32/64-bit value located at the @start bit offset within
> + * the @src memory region. Its position (@start + @len) can't cross
> + * a ``BITS_PER_LONG`` boundary.
> */
> -static inline unsigned long bitmap_get_value8(const unsigned long *map,
> - unsigned long start)
> +static inline unsigned long bitmap_get_bits(const unsigned long *map,
> + unsigned long start, size_t len)
> {
> const size_t index = BIT_WORD(start);
> const unsigned long offset = start % BITS_PER_LONG;
>
> - return (map[index] >> offset) & 0xFF;
> + if (WARN_ON_ONCE(!is_power_of_2(len) || offset % len ||
> + offset + len > BITS_PER_LONG))
> + return 0;
> +
> + return (map[index] >> offset) & GENMASK(len - 1, 0);
> }
>
> /**
> - * bitmap_set_value8 - set an 8-bit value within a memory region
> + * bitmap_set_bits - set a 8/16/32/64-bit value within a memory region
> * @map: address to the bitmap memory region
> - * @value: the 8-bit value; values wider than 8 bits may clobber bitmap
> - * @start: bit offset of the 8-bit value; must be a multiple of 8
> + * @start: bit offset of the value; must be a multiple of @len
> + * @value: new value to set
> + * @len: bit width of the value; must be a power of two
> + *
> + * Replaces the 8/16/32/64-bit value located at the @start bit offset within
> + * the @src memory region with the new @value. Its position (@start + @len)
> + * can't cross a ``BITS_PER_LONG`` boundary.
> */
> -static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
> - unsigned long start)
> +static inline void bitmap_set_bits(unsigned long *map, unsigned long start,
> + unsigned long value, size_t len)
> {
> const size_t index = BIT_WORD(start);
> const unsigned long offset = start % BITS_PER_LONG;
> + unsigned long mask = GENMASK(len - 1, 0);
>
> - map[index] &= ~(0xFFUL << offset);
> - map[index] |= value << offset;
> + if (WARN_ON_ONCE(!is_power_of_2(len) || offset % len ||
> + offset + len > BITS_PER_LONG))
> + return;
> +
> + map[index] &= ~(mask << offset);
> + map[index] |= (value & mask) << offset;
> }
>
> +#define bitmap_get_value8(map, start) \
> + bitmap_get_bits(map, start, BITS_PER_BYTE)
> +#define bitmap_set_value8(map, value, start) \
> + bitmap_set_bits(map, start, value, BITS_PER_BYTE)
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* __LINUX_BITMAP_H */
> --
> 2.41.0
next prev parent reply other threads:[~2023-10-09 16:31 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-09 15:10 [PATCH 00/14] ip_tunnel: convert __be16 tunnel flags to bitmaps Alexander Lobakin
2023-10-09 15:10 ` [PATCH 01/14] bitops: add missing prototype check Alexander Lobakin
2023-10-09 15:10 ` [PATCH 02/14] bitops: make BYTES_TO_BITS() treewide-available Alexander Lobakin
2023-10-09 15:10 ` [PATCH 03/14] bitops: let the compiler optimize __assign_bit() Alexander Lobakin
2023-10-09 16:18 ` Yury Norov
2023-10-11 7:25 ` Alexander Lobakin
2023-10-09 15:10 ` [PATCH 04/14] linkmode: convert linkmode_{test,set,clear,mod}_bit() to macros Alexander Lobakin
2023-10-09 15:10 ` [PATCH 05/14] s390/cio: rename bitmap_size() -> idset_bitmap_size() Alexander Lobakin
2023-10-09 16:35 ` Yury Norov
2023-10-11 7:28 ` Alexander Lobakin
2023-10-09 15:10 ` [PATCH 06/14] fs/ntfs3: rename bitmap_size() -> ntfs3_bitmap_size() Alexander Lobakin
2023-10-09 16:50 ` Yury Norov
2023-10-11 7:36 ` Alexander Lobakin
2023-10-09 15:10 ` [PATCH 07/14] btrfs: rename bitmap_set_bits() -> btrfs_bitmap_set_bits() Alexander Lobakin
2023-10-09 15:23 ` David Sterba
2023-10-09 15:10 ` [PATCH 08/14] bitmap: introduce generic optimized bitmap_size() Alexander Lobakin
2023-10-09 17:04 ` Yury Norov
2023-10-09 15:10 ` [PATCH 09/14] bitmap: extend bitmap_{get,set}_value8() to bitmap_{get,set}_bits() Alexander Lobakin
2023-10-09 16:31 ` Yury Norov [this message]
2023-10-11 9:33 ` Alexander Lobakin
2023-10-11 10:36 ` Andy Shevchenko
2023-10-15 2:20 ` Yury Norov
2023-10-09 15:10 ` [PATCH 10/14] ip_tunnel: use a separate struct to store tunnel params in the kernel Alexander Lobakin
2023-10-09 15:10 ` [PATCH 11/14] ip_tunnel: convert __be16 tunnel flags to bitmaps Alexander Lobakin
2023-10-09 15:10 ` [PATCH 12/14] lib/bitmap: add compile-time test for __assign_bit() optimization Alexander Lobakin
2023-10-09 15:10 ` [PATCH 13/14] lib/bitmap: add tests for bitmap_{get,set}_bits() Alexander Lobakin
2023-10-09 15:10 ` [PATCH 14/14] lib/bitmap: add tests for IP tunnel flags conversion helpers Alexander Lobakin
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