Re: [RFC PATCH 2/2] mm, fs: daxfile, an interface for byte-addressable updates to pmem

On Tue, Jun 20, 2017 at 09:42:55AM -0600, Ross Zwisler wrote:

On Mon, Jun 19, 2017 at 10:22:14PM -0700, Darrick J. Wong wrote:
<>

quoted

Fourth, the VFS entry points for things like read, write, truncate,
utimes, fallocate, etc. all just bail out if S_IOMAP_FROZEN is set on a
file, so that the block map cannot be modified.  mmap is still allowed,
as we've discussed.  /Maybe/ we can allow fallocate to extend a file
with zeroed extents (it will be slow) as I've heard murmurs about
wanting to be able to extend a file, maybe not.

Read and write should still be allowed, right?

<shrug> I had thought the usage model was pretty slanted towards mmap,
but it's not a big deal to turn read/writes into glorified memcpy,
provided we reject the io request if it goes past EOF.

--D

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