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11 Oct 2020 22:28:22 -0700 Date: Sun, 11 Oct 2020 22:28:18 -0700 From: Ira Weiny To: Coly Li Subject: Re: [PATCH RFC PKS/PMEM 48/58] drivers/md: Utilize new kmap_thread() Message-ID: <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-49-ira.weiny@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) X-BeenThere: driverdev-devel@linuxdriverproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Driver Project Developer List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , linux-mmc@vger.kernel.org, Dave Hansen , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, samba-technical@lists.samba.org, Thomas Gleixner , drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, ceph-devel@vger.kernel.org, amd-gfx@lists.freedesktop.org, io-uring@vger.kernel.org, cluster-devel@redhat.com, Ingo Molnar , intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Kent Overstreet , Fenghua Yu , linux-afs@lists.infradead.org, linux-um@lists.infradead.org, intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov , Andy Lutomirski , Dan Williams , Andrew Morton , linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: driverdev-devel-bounces@linuxdriverproject.org Sender: "devel" On Sat, Oct 10, 2020 at 10:20:34AM +0800, Coly Li wrote: > On 2020/10/10 03:50, ira.weiny@intel.com wrote: > > From: Ira Weiny > > > > These kmap() calls are localized to a single thread. To avoid the over > > head of global PKRS updates use the new kmap_thread() call. > > > > Hi Ira, > > There were a number of options considered. > > 1) Attempt to change all the thread local kmap() calls to kmap_atomic() > 2) Introduce a flags parameter to kmap() to indicate if the mapping > should be global or not > 3) Change ~20-30 call sites to 'kmap_global()' to indicate that they > require a global mapping of the pages > 4) Change ~209 call sites to 'kmap_thread()' to indicate that the > mapping is to be used within that thread of execution only > > > I copied the above information from patch 00/58 to this message. The > idea behind kmap_thread() is fine to me, but as you said the new api is > very easy to be missed in new code (even for me). I would like to be > supportive to option 2) introduce a flag to kmap(), then we won't forget > the new thread-localized kmap method, and people won't ask why a > _thread() function is called but no kthread created. Thanks for the feedback. I'm going to hold off making any changes until others weigh in. FWIW, I kind of like option 2 as well. But there is already kmap_atomic() so it seemed like kmap_XXXX() was more in line with the current API. Thanks, Ira > > Thanks. > > > Coly Li > _______________________________________________ devel mailing list devel@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel