From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Tue, 13 Oct 2020 19:36:43 +0000 Subject: Re: [PATCH RFC PKS/PMEM 33/58] fs/cramfs: Utilize new kmap_thread() Message-Id: <20201013193643.GK20115@casper.infradead.org> List-Id: References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-34-ira.weiny@intel.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Williams Cc: linux-aio@kvack.org, linux-efi , KVM list , Linux Doc Mailing List , Peter Zijlstra , linux-mmc@vger.kernel.org, Dave Hansen , Maling list - DRI developers , Linux MM , target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, samba-technical@lists.samba.org, "Weiny, Ira" , 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 , linux-nvdimm , linux-rdma , X86 ML , amd-gfx list , io-uring@vger.kernel.org, cluster-devel@redhat.com, Ingo Molnar , intel-wired-lan@lists.osuosl.org, xen-devel , linux-ext4 , 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 , Thomas Gleixner , Andrew Morton , linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, Nicolas Pitre , linux-ntfs-dev@lists.sourceforge.net, Netdev , Kexec Mailing List , Linux Kernel Mailing List , linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel , bpf@vger.kernel.org, linuxppc-dev , linux-btrfs Archived-At: List-Archive: List-Post: On Tue, Oct 13, 2020 at 11:44:29AM -0700, Dan Williams wrote: > On Fri, Oct 9, 2020 at 12:52 PM wrote: > > > > From: Ira Weiny > > > > 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. > > > > Cc: Nicolas Pitre > > Signed-off-by: Ira Weiny > > --- > > fs/cramfs/inode.c | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c > > index 912308600d39..003c014a42ed 100644 > > --- a/fs/cramfs/inode.c > > +++ b/fs/cramfs/inode.c > > @@ -247,8 +247,8 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset, > > struct page *page = pages[i]; > > > > if (page) { > > - memcpy(data, kmap(page), PAGE_SIZE); > > - kunmap(page); > > + memcpy(data, kmap_thread(page), PAGE_SIZE); > > + kunmap_thread(page); > > Why does this need a sleepable kmap? This looks like a textbook > kmap_atomic() use case. There's a lot of code of this form. Could we perhaps have: static inline void copy_to_highpage(struct page *to, void *vfrom, unsigned int size) { char *vto = kmap_atomic(to); memcpy(vto, vfrom, size); kunmap_atomic(vto); } in linux/highmem.h ?