From: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
To: Yury Norov <yury.norov@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Cc: "dave.hansen@intel.com" <dave.hansen@intel.com>,
"linux@rasmusvillemoes.dk" <linux@rasmusvillemoes.dk>,
"rafael@kernel.org" <rafael@kernel.org>,
"rdunlap@infradead.org" <rdunlap@infradead.org>,
"agordeev@linux.ibm.com" <agordeev@linux.ibm.com>,
"sbrivio@redhat.com" <sbrivio@redhat.com>,
"jianpeng.ma@intel.com" <jianpeng.ma@intel.com>,
"valentin.schneider@arm.com" <valentin.schneider@arm.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"bristot@redhat.com" <bristot@redhat.com>,
"guodong.xu@linaro.org" <guodong.xu@linaro.org>,
tangchengchang <tangchengchang@huawei.com>,
"Zengtao (B)" <prime.zeng@hisilicon.com>,
yangyicong <yangyicong@huawei.com>,
"tim.c.chen@linux.intel.com" <tim.c.chen@linux.intel.com>,
Linuxarm <linuxarm@huawei.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"andriy.shevchenko@linux.intel.com"
<andriy.shevchenko@linux.intel.com>
Subject: RE: [PATCH] bitmap: extend comment to bitmap_print_to_buf
Date: Thu, 29 Jul 2021 06:04:09 +0000 [thread overview]
Message-ID: <eec4210a5d724cccb2931a3f4403e5be@hisilicon.com> (raw)
In-Reply-To: <20210728185831.215079-1-yury.norov@gmail.com>
> -----Original Message-----
> From: Yury Norov [mailto:yury.norov@gmail.com]
> Sent: Thursday, July 29, 2021 6:59 AM
> To: linux-kernel@vger.kernel.org; gregkh@linuxfoundation.org; Song Bao Hua
> (Barry Song) <song.bao.hua@hisilicon.com>
> Cc: Yury Norov <yury.norov@gmail.com>; dave.hansen@intel.com;
> linux@rasmusvillemoes.dk; rafael@kernel.org; rdunlap@infradead.org;
> agordeev@linux.ibm.com; sbrivio@redhat.com; jianpeng.ma@intel.com;
> valentin.schneider@arm.com; peterz@infradead.org; bristot@redhat.com;
> guodong.xu@linaro.org; tangchengchang <tangchengchang@huawei.com>; Zengtao (B)
> <prime.zeng@hisilicon.com>; yangyicong <yangyicong@huawei.com>;
> tim.c.chen@linux.intel.com; Linuxarm <linuxarm@huawei.com>;
> akpm@linux-foundation.org; andriy.shevchenko@linux.intel.com
> Subject: [PATCH] bitmap: extend comment to bitmap_print_to_buf
>
> Extend comment to new function to warn potential users about caveats.
>
> Signed-off-by: Yury Norov <yury.norov@gmail.com>
> ---
Looks awesome. Thanks, Yury. I have integrated your patch into
the latest series v8.
> lib/bitmap.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 56bcffe2fa8c..b9f557ca668c 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -545,6 +545,24 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
> * mainly serves bin_attribute which doesn't work with exact one page, and it
> * can break the size limit of converted decimal list and hexadecimal bitmask.
> *
> + * WARNING!
> + *
> + * This function is not a replacement for sprintf() or
> bitmap_print_to_pagebuf().
> + * It is intended to workaround sysfs limitations discussed above and should
> be
> + * used carefully in general case for the following reasons:
> + * - Time complexity is O(nbits^2/count), comparing to O(nbits) for snprintf().
> + * - Memory complexity is O(nbits), comparing to O(1) for snprintf().
> + * - @off and @count are NOT offset and number of bits to print.
> + * - If printing part of bitmap as list, the resulting string is not a correct
> + * list representation of bitmap. Particularly, some bits within or out of
> + * related interval may be erroneously set or unset. The format of the string
> + * may be broken, so bitmap_parselist-like parser may fail parsing it.
> + * - If printing the whole bitmap as list by parts, user must ensure the order
> + * of calls of the function such that the offset is incremented linearly.
> + * - If printing the whole bitmap as list by parts, user must keep bitmap
> + * unchanged between the very first and very last call. Otherwise concatenated
> + * result may be incorrect, and format may be broken.
> + *
> * Returns the number of characters actually printed to @buf
> */
> int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> --
> 2.30.2
Thanks
Barry
prev parent reply other threads:[~2021-07-29 6:04 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 11:58 [PATCH v7 0/4] use bin_attribute to break the size limitation of cpumap ABI Barry Song
2021-07-15 11:58 ` [PATCH v7 1/4] cpumask: introduce cpumap_print_to_buf to support large bitmask and list Barry Song
2021-07-15 15:28 ` Yury Norov
2021-07-15 21:08 ` Song Bao Hua (Barry Song)
2021-07-16 0:57 ` Song Bao Hua (Barry Song)
2021-07-15 11:58 ` [PATCH v7 2/4] topology: use bin_attribute to break the size limitation of cpumap ABI Barry Song
2021-07-16 8:49 ` Song Bao Hua (Barry Song)
2021-07-16 20:04 ` Yury Norov
2021-07-17 0:16 ` Song Bao Hua (Barry Song)
2021-07-17 1:12 ` Yury Norov
2021-07-19 9:07 ` andriy.shevchenko
2021-07-19 11:10 ` Song Bao Hua (Barry Song)
2021-07-19 17:10 ` Yury Norov
2021-07-21 9:30 ` Song Bao Hua (Barry Song)
2021-07-15 11:58 ` [PATCH v7 3/4] drivers/base/node.c: " Barry Song
2021-07-15 11:58 ` [PATCH v7 4/4] lib: test_bitmap: add bitmap_print_to_buf test cases Barry Song
2021-07-15 12:09 ` Andy Shevchenko
2021-07-15 20:47 ` Yury Norov
2021-07-15 21:32 ` Andy Shevchenko
2021-07-15 23:23 ` Yury Norov
2021-07-16 0:41 ` Song Bao Hua (Barry Song)
2021-07-21 11:40 ` Greg Kroah-Hartman
2021-07-22 17:09 ` Yury Norov
2021-07-22 17:47 ` Greg Kroah-Hartman
2021-07-22 18:27 ` Yury Norov
2021-07-22 18:36 ` Andy Shevchenko
2021-07-22 18:45 ` Greg Kroah-Hartman
2021-07-28 9:08 ` Song Bao Hua (Barry Song)
2021-07-28 9:24 ` Andy Shevchenko
2021-07-15 15:36 ` Yury Norov
2021-07-28 13:41 ` [PATCH v7 0/4] use bin_attribute to break the size limitation of cpumap ABI Greg KH
2021-07-28 14:53 ` Yury Norov
2021-07-28 15:25 ` Greg KH
2021-07-28 18:58 ` [PATCH] bitmap: extend comment to bitmap_print_to_buf Yury Norov
2021-07-29 6:04 ` Song Bao Hua (Barry Song) [this message]
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