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Sat, 10 Jun 2023 10:57:17 -0700 (PDT) Received: from sumitra.com ([59.95.149.54]) by smtp.gmail.com with ESMTPSA id i21-20020aa78d95000000b0064d34ace753sm4438844pfr.114.2023.06.10.10.57.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 10 Jun 2023 10:57:17 -0700 (PDT) Date: Sat, 10 Jun 2023 10:57:12 -0700 From: Sumitra Sharma To: =?iso-8859-1?B?Suly9G1l?= Glisse , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Ira Weiny , Fabio , Deepak R Varma Subject: [PATCH v2] lib: Replace kmap() with kmap_local_page() Message-ID: <20230610175712.GA348514@sumitra.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 3BFC72000F X-Stat-Signature: yhgnqdq9j9x9c1hb5oqqkbjkgtgoe8he X-Rspam-User: X-HE-Tag: 1686419839-575060 X-HE-Meta: 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 CvVmpCXf 12iYhmxMvw+gHOSivsXh3G8aYOXVmg4QgtYRmGjSLd2zzN2rDF61xp2CZ8Z8rYmRtCwK5jCxu/mc3CVo0veSm4WKZ+SF/goq705jyo52WVVErDGM8D/JtxlRwtiIdAdTB8GDr4f0J3Nsy3jO2yd4U7IIdUAYlEzQUk/gjUXsu6Vx2/Z+LvfaerfkCmUneCTYu1qB6EQtKe+xwMWOTlzSUUZKjPXRUGIl2xnNUvrMWeTc08CXUb3CJTN0TPwQPL8YRugYQdGSqrc2RDkAgrR6BVu8HXyqXHoR34X3EBgfjWu/Z95xZBVkvzQWHRCur1py2jXNBO0IA2b3ykX4Zzg1AJgRAlqu8sY1LUN1hCRoTWaW8OjtB2awM6KUANeZca8kCUs8+H9Pt1pfhK6j4s975V54szVbPysjfSk45B/EpgeE7TRKaHmk75E52uEitswOqUOzx7mi384M0R3kkRC+QZvmREQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: kmap() has been deprecated in favor of the kmap_local_page() due to high cost, restricted mapping space, the overhead of a global lock for synchronization, and making the process sleep in the absence of free slots. kmap_local_page() is faster than kmap() and offers thread-local and CPU-local mappings, take pagefaults in a local kmap region and preserves preemption by saving the mappings of outgoing tasks and restoring those of the incoming one during a context switch. The mappings are kept thread local in the functions “dmirror_do_read” and “dmirror_do_write” in test_hmm.c Therefore, replace kmap() with kmap_local_page() and use mempcy_from/to_page() to avoid open coding kmap_local_page() + memcpy() + kunmap_local(). Remove the unused variable “tmp”. Suggested-by: Fabio M. De Francesco Signed-off-by: Sumitra Sharma --- Changes in v2: - Change commit subject and description. - Remove unnecessary type casting (char *). lib/test_hmm.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 67e6f83fe0f8..717dcb830127 100644 --- a/lib/test_hmm.c +++ b/lib/test_hmm.c @@ -368,16 +368,13 @@ static int dmirror_do_read(struct dmirror *dmirror, unsigned long start, for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) { void *entry; struct page *page; - void *tmp; entry = xa_load(&dmirror->pt, pfn); page = xa_untag_pointer(entry); if (!page) return -ENOENT; - tmp = kmap(page); - memcpy(ptr, tmp, PAGE_SIZE); - kunmap(page); + memcpy_from_page(ptr, page, 0, PAGE_SIZE); ptr += PAGE_SIZE; bounce->cpages++; @@ -437,16 +434,13 @@ static int dmirror_do_write(struct dmirror *dmirror, unsigned long start, for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) { void *entry; struct page *page; - void *tmp; entry = xa_load(&dmirror->pt, pfn); page = xa_untag_pointer(entry); if (!page || xa_pointer_tag(entry) != DPT_XA_TAG_WRITE) return -ENOENT; - tmp = kmap(page); - memcpy(tmp, ptr, PAGE_SIZE); - kunmap(page); + memcpy_to_page(page, 0, ptr, PAGE_SIZE); ptr += PAGE_SIZE; bounce->cpages++; -- 2.25.1