Re: [PATCH v2] Do a proper locking for mmap and block size change

[Linus Torvalds]

On Wed, Nov 28, 2012 at 2:01 PM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
>
> This sounds sensible. I'm sending this patch.

This looks much better.

I think I'll apply this for 3.7 (since it's too late to do anything
fancier), and then for 3.8 I will rip out all the locking entirely,
because looking at the fs/buffer.c patch I wrote up, it's all totally
unnecessary.

Adding a ACCESS_ONCE() to the read of the i_blkbits value (when
creating new buffers) simply makes the whole locking thing pointless.
Just make the page lock protect the block size, and make it per-page,
and we're done.

No RCU grace period crap, no expedited mess, no nothing.

                      Linus
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