From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756321AbaIQSe0 (ORCPT ); Wed, 17 Sep 2014 14:34:26 -0400 Received: from e9.ny.us.ibm.com ([32.97.182.139]:60294 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755670AbaIQSeY (ORCPT ); Wed, 17 Sep 2014 14:34:24 -0400 From: Sukadev Bhattiprolu To: Arnaldo Carvalho de Melo , ak@linux.intel.com, Jiri Olsa , peterz@infradead.org, eranian@google.com, Paul Mackerras Cc: dev@codyps.com, Michael Ellerman , Anshuman Khandual , , linuxppc-dev@lists.ozlabs.org Subject: [PATCH 2/4] Simplify catalog_read() Date: Wed, 17 Sep 2014 11:33:05 -0700 Message-Id: <1410978787-7375-3-git-send-email-sukadev@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1410978787-7375-1-git-send-email-sukadev@linux.vnet.ibm.com> References: <1410978787-7375-1-git-send-email-sukadev@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14091718-7182-0000-0000-0000007A25DA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org catalog_read() implements the read interface for the sysfs file /sys/bus/event_source/devices/hv_24x7/interface/catalog It essentially takes a buffer, an offset and count as parameters to the read() call. It makes a hypervisor call to read a specific page from the catalog and copy the required bytes into the given buffer. Each call to catalog_read() returns at most one 4K page. Given these requirements, we should be able to simplify the catalog_read(). Signed-off-by: Sukadev Bhattiprolu --- arch/powerpc/perf/hv-24x7.c | 92 +++++-------------------------------------- 1 file changed, 10 insertions(+), 82 deletions(-) diff --git a/arch/powerpc/perf/hv-24x7.c b/arch/powerpc/perf/hv-24x7.c index 2f2215c..9427ef7 100644 --- a/arch/powerpc/perf/hv-24x7.c +++ b/arch/powerpc/perf/hv-24x7.c @@ -75,86 +75,6 @@ static struct attribute_group format_group = { static struct kmem_cache *hv_page_cache; -/* - * read_offset_data - copy data from one buffer to another while treating the - * source buffer as a small view on the total avaliable - * source data. - * - * @dest: buffer to copy into - * @dest_len: length of @dest in bytes - * @requested_offset: the offset within the source data we want. Must be > 0 - * @src: buffer to copy data from - * @src_len: length of @src in bytes - * @source_offset: the offset in the sorce data that (src,src_len) refers to. - * Must be > 0 - * - * returns the number of bytes copied. - * - * The following ascii art shows the various buffer possitioning we need to - * handle, assigns some arbitrary varibles to points on the buffer, and then - * shows how we fiddle with those values to get things we care about (copy - * start in src and copy len) - * - * s = @src buffer - * d = @dest buffer - * '.' areas in d are written to. - * - * u - * x w v z - * d |.........| - * s |----------------------| - * - * u - * x w z v - * d |........------| - * s |------------------| - * - * x w u,z,v - * d |........| - * s |------------------| - * - * x,w u,v,z - * d |..................| - * s |------------------| - * - * x u - * w v z - * d |........| - * s |------------------| - * - * x z w v - * d |------| - * s |------| - * - * x = source_offset - * w = requested_offset - * z = source_offset + src_len - * v = requested_offset + dest_len - * - * w_offset_in_s = w - x = requested_offset - source_offset - * z_offset_in_s = z - x = src_len - * v_offset_in_s = v - x = request_offset + dest_len - src_len - */ -static ssize_t read_offset_data(void *dest, size_t dest_len, - loff_t requested_offset, void *src, - size_t src_len, loff_t source_offset) -{ - size_t w_offset_in_s = requested_offset - source_offset; - size_t z_offset_in_s = src_len; - size_t v_offset_in_s = requested_offset + dest_len - src_len; - size_t u_offset_in_s = min(z_offset_in_s, v_offset_in_s); - size_t copy_len = u_offset_in_s - w_offset_in_s; - - if (requested_offset < 0 || source_offset < 0) - return -EINVAL; - - if (z_offset_in_s <= w_offset_in_s) - return 0; - - memcpy(dest, src + w_offset_in_s, copy_len); - return copy_len; -} - static unsigned long h_get_24x7_catalog_page_(unsigned long phys_4096, unsigned long version, unsigned long index) @@ -185,6 +105,8 @@ static ssize_t catalog_read(struct file *filp, struct kobject *kobj, ssize_t ret = 0; size_t catalog_len = 0, catalog_page_len = 0, page_count = 0; loff_t page_offset = 0; + loff_t offset_in_page; + size_t copy_len; uint64_t catalog_version_num = 0; void *page = kmem_cache_alloc(hv_page_cache, GFP_USER); struct hv_24x7_catalog_page_0 *page_0 = page; @@ -203,6 +125,7 @@ static ssize_t catalog_read(struct file *filp, struct kobject *kobj, page_offset = offset / 4096; page_count = count / 4096; + offset_in_page = count % 4096; if (page_offset >= catalog_page_len) goto e_free; @@ -216,8 +139,13 @@ static ssize_t catalog_read(struct file *filp, struct kobject *kobj, } } - ret = read_offset_data(buf, count, offset, - page, 4096, page_offset * 4096); + copy_len = 4096 - offset_in_page; + if (copy_len > count) + copy_len = count; + + memcpy(buf, page+offset_in_page, copy_len); + ret = copy_len; + e_free: if (hret) pr_err("h_get_24x7_catalog_page(ver=%lld, page=%lld) failed:" -- 1.7.9.5