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[188.192.138.212]) by smtp.gmail.com with ESMTPSA id l11sm4095302ejk.53.2020.11.03.05.28.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Nov 2020 05:28:49 -0800 (PST) Subject: Re: [PATCH v3 4/4] scatterlist: add sgl_memset() To: Douglas Gilbert , linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: martin.petersen@oracle.com, axboe@kernel.dk, bvanassche@acm.org References: <20201019191928.77845-1-dgilbert@interlog.com> <20201019191928.77845-5-dgilbert@interlog.com> From: Bodo Stroesser Message-ID: <9a8ab6d9-72cf-1dd2-a9e8-114e7f9f198c@gmail.com> Date: Tue, 3 Nov 2020 14:28:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201019191928.77845-5-dgilbert@interlog.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 19.10.20 um 21:19 schrieb Douglas Gilbert: > The existing sg_zero_buffer() function is a bit restrictive. > For example protection information (PI) blocks are usually > initialized to 0xff bytes. As its name suggests sgl_memset() > is modelled on memset(). One difference is the type of the > val argument which is u8 rather than int. Plus it returns > the number of bytes (over)written. > > Change implementation of sg_zero_buffer() to call this new > function. > > Signed-off-by: Douglas Gilbert > --- > include/linux/scatterlist.h | 3 ++ > lib/scatterlist.c | 65 +++++++++++++++++++++++++------------ > 2 files changed, 48 insertions(+), 20 deletions(-) > > diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h > index ae260dc5fedb..a40012c8a4e6 100644 > --- a/include/linux/scatterlist.h > +++ b/include/linux/scatterlist.h > @@ -329,6 +329,9 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk > struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, > size_t n_bytes); > > +size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip, > + u8 val, size_t n_bytes); > + > /* > * Maximum number of entries that will be allocated in one piece, if > * a list larger than this is required then chaining will be utilized. > diff --git a/lib/scatterlist.c b/lib/scatterlist.c > index 49185536acba..6b430f7293e0 100644 > --- a/lib/scatterlist.c > +++ b/lib/scatterlist.c > @@ -952,26 +952,7 @@ EXPORT_SYMBOL(sg_pcopy_to_buffer); > size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, > size_t buflen, off_t skip) > { > - unsigned int offset = 0; > - struct sg_mapping_iter miter; > - unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; > - > - sg_miter_start(&miter, sgl, nents, sg_flags); > - > - if (!sg_miter_skip(&miter, skip)) > - return false; > - > - while (offset < buflen && sg_miter_next(&miter)) { > - unsigned int len; > - > - len = min(miter.length, buflen - offset); > - memset(miter.addr, 0, len); > - > - offset += len; > - } > - > - sg_miter_stop(&miter); > - return offset; > + return sgl_memset(sgl, nents, skip, 0, buflen); > } > EXPORT_SYMBOL(sg_zero_buffer); > > @@ -1110,3 +1091,47 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk > return equ; > } > EXPORT_SYMBOL(sgl_compare_sgl); > + > +/** > + * sgl_memset - set byte 'val' up to n_bytes times on SG list > + * @sgl: The SG list > + * @nents: Number of SG entries in sgl > + * @skip: Number of bytes to skip before starting > + * @val: byte value to write to sgl > + * @n_bytes: The (maximum) number of bytes to modify > + * > + * Returns: > + * The number of bytes written. > + * > + * Notes: > + * Stops writing if either sgl or n_bytes is exhausted. If n_bytes is > + * set SIZE_MAX then val will be written to each byte until the end > + * of sgl. > + * > + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. > + * > + **/ > +size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip, > + u8 val, size_t n_bytes) > +{ > + size_t offset = 0; > + size_t len; > + struct sg_mapping_iter miter; > + > + if (n_bytes == 0) > + return 0; > + sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); > + if (!sg_miter_skip(&miter, skip)) > + goto fini; > + > + while ((offset < n_bytes) && sg_miter_next(&miter)) { > + len = min(miter.length, n_bytes - offset); > + memset(miter.addr, val, len); > + offset += len; > + } > +fini: > + sg_miter_stop(&miter); > + return offset; > +} > +EXPORT_SYMBOL(sgl_memset); > + > Reviewed-by: Bodo Stroesser