[patch 10/10] uml: use always a separate io thread for UBD

[patch 10/10] uml: use always a separate io thread for UBD

[blaisorblade_spam]

Currently, ubd=sync is different from replacing ubd#= with ubd#s=. This is
against Principle of Least Surprise, so remove this difference.

Also the current ubd=sync behaviour is completely useless: it is to make sure
that when the kernel has synched its I/O to the virtual disk, the host does
not invalidate this with his caching; this causes ReiserFS corruption.

But since actually we call end_request() only after the io_thread has done its
work, we never lie to the block layer. Using O_SYNC as we do when replacing
ubd#= with ubd#s= is enough.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>
---

 linux-2.6.9-current-paolo/arch/um/drivers/ubd_kern.c |    6 ++++--
 1 files changed, 4 insertions(+), 2 deletions(-)

diff -puN arch/um/drivers/ubd_kern.c~uml-use-always-io-thread arch/um/drivers/ubd_kern.c
--- linux-2.6.9-current/arch/um/drivers/ubd_kern.c~uml-use-always-io-thread	2004-10-12 01:22:17.061952232 +0200
+++ linux-2.6.9-current-paolo/arch/um/drivers/ubd_kern.c	2004-10-12 01:22:17.064951776 +0200
@@ -773,9 +773,11 @@ int ubd_driver_init(void){
 	unsigned long stack;
 	int err;
 
+	/* Set by CONFIG_BLK_DEV_UBD_SYNC or ubd=sync.*/
 	if(global_openflags.s){
-		printk(KERN_INFO "ubd : Synchronous mode\n");
-		return(0);
+		printk(KERN_INFO "ubd: Synchronous mode\n");
+		/* Letting ubd=sync be like using ubd#s= instead of ubd#= is
+		 * enough. So use anyway the io thread. */
 	}
 	stack = alloc_stack(0, 0);
 	io_pid = start_io_thread(stack + PAGE_SIZE - sizeof(void *), 
_