On Thu, Nov 29, 2012 at 10:23 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
>
>
> If you remove that percpu rw lock, you also need to rewrite direct i/o
> code.
>
> In theory, block device direct i/o doesn't need buffer block size at all.
> But in practice, it shares a lot of code with filesystem direct i/o, it
> reads the block size multiple times and it crashes if it changes.
If it's a filesystem, then the size will never change while it is mounted.
So only the direct-block-device case needs to be worried about, no?
And that uses __generic_file_aio_write() and friends, which in turn
use the readpage/writepage functions.
So for block devices, it should be sufficient to make
readpage/writepage (with the writing obviously having all the
"write_begin/write_end/fullpage" variants) be safe as far as I can
see.
Linus
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