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Subject[patch 10/10] uml: use always a separate io thread for UBD
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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 *),
_
-
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