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Sat, 10 Oct 2020 00:39:54 +0000 Date: Sat, 10 Oct 2020 01:39:54 +0100 From: Matthew Wilcox To: Eric Biggers Cc: ira.weiny@intel.com, Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra , linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, 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, ceph-devel@vger.kernel.org, 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, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, cluster-devel@redhat.com, linux-cachefs@redhat.com, intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Fenghua Yu , ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, intel-gfx@lists.freedesktop.org, linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Jaegeuk Kim , Dan Williams , io-uring@vger.kernel.org, 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 Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread() Message-ID: <20201010003954.GW20115@casper.infradead.org> References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-23-ira.weiny@intel.com> <20201009213434.GA839@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201009213434.GA839@sol.localdomain> 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: On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote: > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote: > > The kmap() calls in this FS are localized to a single thread. To avoid > > the over head of global PKRS updates use the new kmap_thread() call. > > > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page( > > > > static inline void f2fs_copy_page(struct page *src, struct page *dst) > > { > > - char *src_kaddr = kmap(src); > > - char *dst_kaddr = kmap(dst); > > + char *src_kaddr = kmap_thread(src); > > + char *dst_kaddr = kmap_thread(dst); > > > > memcpy(dst_kaddr, src_kaddr, PAGE_SIZE); > > - kunmap(dst); > > - kunmap(src); > > + kunmap_thread(dst); > > + kunmap_thread(src); > > } > > Wouldn't it make more sense to switch cases like this to kmap_atomic()? > The pages are only mapped to do a memcpy(), then they're immediately unmapped. Maybe you missed the earlier thread from Thomas trying to do something similar for rather different reasons ... https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/