Re: [PATCH 1/3] block: loop: use kmap(page) instead of page_address(page)

[Christoph Hellwig]

On Sun, Mar 22, 2015 at 04:14:52PM +0800, Ming Lei wrote:
> The raw page allocated in lo_send() can be a highmem page,
> so kmap(page) should be used for read/write on the page.
> 
> Also the patch removes kmap()/kunmap() in lo_send() because
> it isn't needed at all.

The description seems odd, what it seems to do is to shift the
kmap from lo_send into do_lo_send_write.  This does not seem
very useful as it now means a kmap per segment instead of just
a single one per I/O.  What would make more sense is to just
not allocate a highmem page.
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