From mboxrd@z Thu Jan 1 00:00:00 1970 From: Coly Li Date: Mon, 12 Oct 2020 07:40:27 +0000 Subject: Re: [PATCH RFC PKS/PMEM 48/58] drivers/md: Utilize new kmap_thread() Message-Id: <026a7658-6c43-6510-a8b5-32f29de7b281@suse.de> List-Id: References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-49-ira.weiny@intel.com> <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> In-Reply-To: <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Ira Weiny 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 On 2020/10/12 13:28, Ira Weiny wrote: > 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. I understand it now, the idea is fine to me. Acked-by: Coly Li Thanks. Coly Li