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NBD: allow nbd to be used locally

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This patch allows Network Block Device to be mounted locally (nbd-client to
nbd-server over 127.0.0.1).

It creates a kthread to avoid the deadlock described in NBD tools
documentation.  So, if nbd-client hangs waiting for pages, the kblockd thread
can continue its work and free pages.

I have tested the patch to verify that it avoids the hang that always occurs
when writing to a localhost nbd connection.  I have also tested to verify that
no performance degradation results from the additional thread and queue.

Patch originally from Laurent Vivier.

Signed-off-by: Paul Clements <paul.clements@steeleye.com>
Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Laurent Vivier 2008-04-29 01:02:46 -07:00 • committed by Linus Torvalds
parent 8c4dd60682
commit 48cf6061b3
2 changed files with 98 additions and 50 deletions
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4
include/linux/nbd.h
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@ -56,9 +56,11 @@ struct nbd_device {
int magic;
spinlock_t queue_lock;
struct list_head queue_head;/* Requests are added here... */
struct list_head queue_head; /* Requests waiting result */
struct request *active_req;
wait_queue_head_t active_wq;
struct list_head waiting_queue; /* Requests to be sent */
wait_queue_head_t waiting_wq;
struct mutex tx_lock;
struct gendisk *disk;