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Commit d9b16529 authored by Dexuan Cui's avatar Dexuan Cui Committed by Greg Kroah-Hartman
Browse files

hv: hv_fcopy: drop the obsolete message on transfer failure 



In the case the user-space daemon crashes, hangs or is killed, we
need to down the semaphore, otherwise, after the daemon starts next
time, the obsolete data in fcopy_transaction.message or
fcopy_transaction.fcopy_msg will be used immediately.

Cc: Jason Wang <jasowang@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarDexuan Cui <decui@microsoft.com>
Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d61031ee

drivers/hv/hv_fcopy.c

+27 −0
Original line number Diff line number Diff line
@@ -86,6 +86,18 @@ static void fcopy_work_func(struct work_struct *dummy) 
	 * process the pending transaction.

	 */

	fcopy_respond_to_host(HV_E_FAIL);



	/* In the case the user-space daemon crashes, hangs or is killed, we

	 * need to down the semaphore, otherwise, after the daemon starts next

	 * time, the obsolete data in fcopy_transaction.message or

	 * fcopy_transaction.fcopy_msg will be used immediately.

	 *

	 * NOTE: fcopy_read() happens to get the semaphore (very rare)? We're

	 * still OK, because we've reported the failure to the host.

	 */

	if (down_trylock(&fcopy_transaction.read_sema))

		;



}



static int fcopy_handle_handshake(u32 version)
@@ -344,6 +356,14 @@ static int fcopy_open(struct inode *inode, struct file *f) 
	return 0;

}



/* XXX: there are still some tricky corner cases, e.g.,

 * 1) In a SMP guest, when fcopy_release() runs between

 * schedule_delayed_work() and fcopy_send_data(), there is

 * still a chance an obsolete message will be queued.

 *

 * 2) When the fcopy daemon is running, if we unload the driver,

 * we'll notice a kernel oops when we kill the daemon later.

 */

static int fcopy_release(struct inode *inode, struct file *f)

{

	/*
@@ -351,6 +371,13 @@ static int fcopy_release(struct inode *inode, struct file *f) 
	 */

	in_hand_shake = true;

	opened = false;



	if (cancel_delayed_work_sync(&fcopy_work)) {

		/* We haven't up()-ed the semaphore(very rare)? */

		if (down_trylock(&fcopy_transaction.read_sema))

			;

		fcopy_respond_to_host(HV_E_FAIL);

	}

	return 0;

}