On Thu, 29 Nov 2012, Linus Torvalds wrote: > 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 Yes. 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. Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
