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Re: [PATCH RFC PKS/PMEM 24/58] fs/freevxfs: Utilize new kmap_thread()
- To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
- From: Ira Weiny <ira.weiny@xxxxxxxxx>
- Date: Tue, 13 Oct 2020 13:52:49 -0700
- Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, x86@xxxxxxxxxx, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, Dan Williams <dan.j.williams@xxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, linux-doc@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-nvdimm@xxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-kselftest@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxxxxxx, bpf@xxxxxxxxxxxxxxx, kexec@xxxxxxxxxxxxxxxxxxx, linux-bcache@xxxxxxxxxxxxxxx, linux-mtd@xxxxxxxxxxxxxxxxxxx, devel@xxxxxxxxxxxxxxxxxxxx, linux-efi@xxxxxxxxxxxxxxx, linux-mmc@xxxxxxxxxxxxxxx, linux-scsi@xxxxxxxxxxxxxxx, target-devel@xxxxxxxxxxxxxxx, linux-nfs@xxxxxxxxxxxxxxx, ceph-devel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-aio@xxxxxxxxx, io-uring@xxxxxxxxxxxxxxx, linux-erofs@xxxxxxxxxxxxxxxx, linux-um@xxxxxxxxxxxxxxxxxxx, linux-ntfs-dev@xxxxxxxxxxxxxxxxxxxxx, reiserfs-devel@xxxxxxxxxxxxxxx, linux-f2fs-devel@xxxxxxxxxxxxxxxxxxxxx, linux-nilfs@xxxxxxxxxxxxxxx, cluster-devel@xxxxxxxxxx, ecryptfs@xxxxxxxxxxxxxxx, linux-cifs@xxxxxxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx, linux-afs@xxxxxxxxxxxxxxxxxxx, linux-rdma@xxxxxxxxxxxxxxx, amd-gfx@xxxxxxxxxxxxxxxxxxxxx, dri-devel@xxxxxxxxxxxxxxxxxxxxx, intel-gfx@xxxxxxxxxxxxxxxxxxxxx, drbd-dev@xxxxxxxxxxxxxxxx, linux-block@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-cachefs@xxxxxxxxxx, samba-technical@xxxxxxxxxxxxxxx, intel-wired-lan@xxxxxxxxxxxxxxxx
- Delivery-date: Tue, 13 Oct 2020 20:53:46 +0000
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.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@xxxxxxxxxxxxxxxxxxxxxxxxx/
Ira
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