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SubjectRe: [PATCH 1/1] um: ubd: Fix data corruption
On 2010-10-05 22:31, Chris Frey wrote:
> On Tue, Oct 05, 2010 at 10:23:19AM +0200, Tejun Heo wrote:
>> Hmmmm, can you please give a shot at the following one? Thank you.
>
> I applied this patch on top of stock 2.6.35.5 as usual (no other patches)
> and tested on my maverick image as before. I ran a fsck.ext3 on the
> filesystem image from the host before my test, just to make sure, and
> there were no errors.
>
> Unfortunately, this patch does not fix the issue either. I get errors
> in the guest like the following:

So how about this? Note that I haven't even compiled this. The request
handling logic really should be fixed in there, it's horribly
inefficient.

diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 1bcd208..c272cf6 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -163,6 +163,7 @@ struct ubd {
struct scatterlist sg[MAX_SG];
struct request *request;
int start_sg, end_sg;
+ unsigned int rq_offset;
};

#define DEFAULT_COW { \
@@ -187,6 +188,7 @@ struct ubd {
.request = NULL, \
.start_sg = 0, \
.end_sg = 0, \
+ .rq_offset 0, \
}

/* Protected by ubd_lock */
@@ -466,6 +468,8 @@ static void ubd_handler(void)
int n;

while(1){
+ struct ubd *dev;
+
n = os_read_file(thread_fd, &req,
sizeof(struct io_thread_req *));
if(n != sizeof(req)){
@@ -476,6 +480,11 @@ static void ubd_handler(void)
return;
}

+ /*
+ * Clear internal offset, block core will update request state
+ */
+ dev = req->req->q->queuedata;
+ dev->rq_offset = 0;
blk_end_request(req->req, 0, req->length);
kfree(req);
}
@@ -1241,10 +1250,11 @@ static void do_ubd_request(struct request_queue *q)
dev->request = req;
dev->start_sg = 0;
dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
+ dev->rq_offset = 0;
}

req = dev->request;
- sector = blk_rq_pos(req);
+ sector = blk_rq_pos(req) + dev->rq_offset;
while(dev->start_sg < dev->end_sg){
struct scatterlist *sg = &dev->sg[dev->start_sg];

@@ -1272,6 +1282,7 @@ static void do_ubd_request(struct request_queue *q)
return;
}

+ dev->rq_offset += sg->length >> 9;
dev->start_sg++;
}
dev->end_sg = 0;
--
Jens Axboe



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