From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ira Weiny <ira.weiny@intel.com>
Date: Tue, 13 Oct 2020 20:52:49 +0000
Subject: Re: [PATCH RFC PKS/PMEM 24/58] fs/freevxfs: Utilize new kmap_thread()
Message-Id: <20201013205248.GJ2046448@iweiny-DESK2.sc.intel.com>
List-Id: <target-devel.vger.kernel.org>
References: <20201009195033.3208459-1-ira.weiny@intel.com>
 <20201009195033.3208459-25-ira.weiny@intel.com>
 <20201013112544.GA5249@infradead.org>
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To: Christoph Hellwig <hch@infradead.org>
Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, linux-mmc@vger.kernel.org, Dave Hansen <dave.hansen@linux.intel.com>, 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 <tglx@linutronix.de>, 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 <mingo@redhat.com>, intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Fenghua Yu <fenghua.yu@intel.com>, 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 <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, Dan Williams <dan.j.williams@intel.com>, Andrew Morton <akpm@linux-foundation.org>, 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 Tue, Oct 13, 2020 at 12:25:44PM +0100, Christoph Hellwig wrote:
> > -	kaddr = kmap(pp);
> > +	kaddr = kmap_thread(pp);
> >  	memcpy(kaddr, vip->vii_immed.vi_immed + offset, PAGE_SIZE);
> > -	kunmap(pp);
> > +	kunmap_thread(pp);
> 
> You only Cced me on this particular patch, which means I have absolutely
> no idea what kmap_thread and kunmap_thread actually do, and thus can't
> provide an informed review.

Sorry the list was so big I struggled with who to CC and on which patches.

> 
> That being said I think your life would be a lot easier if you add
> helpers for the above code sequence and its counterpart that copies
> to a potential hughmem page first, as that hides the implementation
> details from most users.

Matthew Wilcox and Al Viro have suggested similar ideas.

https://lore.kernel.org/lkml/20201013205012.GI2046448@iweiny-DESK2.sc.intel.com/

Ira