[Xen-devel] [Patch] Remove unnecessary tlb flush in blktap_poll

["Stephen C. Tweedie" <sct@xxxxxxxxxx>]

blktap_poll is calling tlb_flush_all() in its main ring buffer polling
loop.  This seems to be superfluous: the hypervisor should be performing
any necessary tlb flushes on grant table operations performed by the
back-end.  Even a simple memory barrier is unnecessary here as the
RING_PUSH_REQUESTS() call performs a wmb() anyway.

And tlb_flush_all() is not exported to modules, so this call prevents
blktap from building as a module.  Just remove it.

Signed-off-by: Stephen Tweedie <sct@xxxxxxxxxx>

diff -r 49d429529228 -r cb125a885a9a 
linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c
--- a/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c  Thu Sep 28 23:24:43 
2006 +0100
+++ b/linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c  Thu Sep 28 23:29:31 
2006 +0100
@@ -680,7 +680,6 @@ static unsigned int blktap_poll(struct f
        
        poll_wait(file, &info->wait, wait);
        if (info->ufe_ring.req_prod_pvt != info->ufe_ring.sring->req_prod) {
-               flush_tlb_all();
                RING_PUSH_REQUESTS(&info->ufe_ring);
                return POLLIN | POLLRDNORM;
        }



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