2 files changed, 68 insertions, 62 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 9e268ddedfbd..d5c8ee7d9815 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -54,11 +54,15 @@
 #include <linux/errno.h>
 #include <linux/file.h>
 #include <linux/ioctl.h>
+#include <linux/compiler.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
 #include <net/sock.h>
 
 #include <linux/devfs_fs_kernel.h>
 
 #include <asm/uaccess.h>
+#include <asm/system.h>
 #include <asm/types.h>
 
 #include <linux/nbd.h>
@@ -230,14 +234,6 @@ static int nbd_send_req(struct nbd_device *lo, struct request *req)
         request.len = htonl(size);
         memcpy(request.handle, &req, sizeof(req));
 
-        down(&lo->tx_lock);
-
-        if (!sock || !lo->sock) {
-                printk(KERN_ERR "%s: Attempted send on closed socket\n",
-                                lo->disk->disk_name);
-                goto error_out;
-        }
-
         dprintk(DBG_TX, "%s: request %p: sending control (%s@%llu,%luB)\n",
                         lo->disk->disk_name, req,
                         nbdcmd_to_ascii(nbd_cmd(req)),
@@ -276,11 +272,9 @@ static int nbd_send_req(struct nbd_device *lo, struct request *req)
                         }
                 }
         }
-        up(&lo->tx_lock);
         return 0;
 
 error_out:
-        up(&lo->tx_lock);
         return 1;
 }
 
@@ -289,9 +283,14 @@ static struct request *nbd_find_request(struct nbd_device *lo, char *handle)
         struct request *req;
         struct list_head *tmp;
         struct request *xreq;
+        int err;
 
         memcpy(&xreq, handle, sizeof(xreq));
 
+        err = wait_event_interruptible(lo->active_wq, lo->active_req != xreq);
+        if (unlikely(err))
+                goto out;
+
         spin_lock(&lo->queue_lock);
         list_for_each(tmp, &lo->queue_head) {
                 req = list_entry(tmp, struct request, queuelist);
@@ -302,7 +301,11 @@ static struct request *nbd_find_request(struct nbd_device *lo, char *handle)
                 return req;
         }
         spin_unlock(&lo->queue_lock);
-        return NULL;
+
+        err = -ENOENT;
+
+out:
+        return ERR_PTR(err);
 }
 
 static inline int sock_recv_bvec(struct socket *sock, struct bio_vec *bvec)
@@ -331,7 +334,11 @@ static struct request *nbd_read_stat(struct nbd_device *lo)
                 goto harderror;
         }
         req = nbd_find_request(lo, reply.handle);
-        if (req == NULL) {
+        if (unlikely(IS_ERR(req))) {
+                result = PTR_ERR(req);
+                if (result != -ENOENT)
+                        goto harderror;
+
                 printk(KERN_ERR "%s: Unexpected reply (%p)\n",
                                 lo->disk->disk_name, reply.handle);
                 result = -EBADR;
@@ -395,19 +402,24 @@ static void nbd_clear_que(struct nbd_device *lo)
 
         BUG_ON(lo->magic != LO_MAGIC);
 
-        do {
-                req = NULL;
-                spin_lock(&lo->queue_lock);
-                if (!list_empty(&lo->queue_head)) {
-                        req = list_entry(lo->queue_head.next, struct request, queuelist);
-                        list_del_init(&req->queuelist);
-                }
-                spin_unlock(&lo->queue_lock);
-                if (req) {
-                        req->errors++;
-                        nbd_end_request(req);
-                }
-        } while (req);
+        /*
+         * Because we have set lo->sock to NULL under the tx_lock, all
+         * modifications to the list must have completed by now.  For
+         * the same reason, the active_req must be NULL.
+         *
+         * As a consequence, we don't need to take the spin lock while
+         * purging the list here.
+         */
+        BUG_ON(lo->sock);
+        BUG_ON(lo->active_req);
+
+        while (!list_empty(&lo->queue_head)) {
+                req = list_entry(lo->queue_head.next, struct request,
+                                 queuelist);
+                list_del_init(&req->queuelist);
+                req->errors++;
+                nbd_end_request(req);
+        }
 }
 
 /*
@@ -435,11 +447,6 @@ static void do_nbd_request(request_queue_t * q)
 
                 BUG_ON(lo->magic != LO_MAGIC);
 
-                if (!lo->file) {
-                        printk(KERN_ERR "%s: Request when not-ready\n",
-                                        lo->disk->disk_name);
-                        goto error_out;
-                }
                 nbd_cmd(req) = NBD_CMD_READ;
                 if (rq_data_dir(req) == WRITE) {
                         nbd_cmd(req) = NBD_CMD_WRITE;
@@ -453,32 +460,34 @@ static void do_nbd_request(request_queue_t * q)
                 req->errors = 0;
                 spin_unlock_irq(q->queue_lock);
 
-                spin_lock(&lo->queue_lock);
-
-                if (!lo->file) {
-                        spin_unlock(&lo->queue_lock);
-                        printk(KERN_ERR "%s: failed between accept and semaphore, file lost\n",
-                                        lo->disk->disk_name);
+                down(&lo->tx_lock);
+                if (unlikely(!lo->sock)) {
+                        up(&lo->tx_lock);
+                        printk(KERN_ERR "%s: Attempted send on closed socket\n",
+                               lo->disk->disk_name);
                         req->errors++;
                         nbd_end_request(req);
                         spin_lock_irq(q->queue_lock);
                         continue;
                 }
 
-                list_add(&req->queuelist, &lo->queue_head);
-                spin_unlock(&lo->queue_lock);
+                lo->active_req = req;
 
                 if (nbd_send_req(lo, req) != 0) {
                         printk(KERN_ERR "%s: Request send failed\n",
                                         lo->disk->disk_name);
-                        if (nbd_find_request(lo, (char *)&req) != NULL) {
-                                /* we still own req */
-                                req->errors++;
-                                nbd_end_request(req);
-                        } else /* we're racing with nbd_clear_que */
-                                printk(KERN_DEBUG "nbd: can't find req\n");
+                        req->errors++;
+                        nbd_end_request(req);
+                } else {
+                        spin_lock(&lo->queue_lock);
+                        list_add(&req->queuelist, &lo->queue_head);
+                        spin_unlock(&lo->queue_lock);
                 }
 
+                lo->active_req = NULL;
+                up(&lo->tx_lock);
+                wake_up_all(&lo->active_wq);
+
                 spin_lock_irq(q->queue_lock);
                 continue;
 
@@ -529,17 +538,10 @@ static int nbd_ioctl(struct inode *inode, struct file *file,
                 down(&lo->tx_lock);
                 lo->sock = NULL;
                 up(&lo->tx_lock);
-                spin_lock(&lo->queue_lock);
                 file = lo->file;
                 lo->file = NULL;
-                spin_unlock(&lo->queue_lock);
                 nbd_clear_que(lo);
-                spin_lock(&lo->queue_lock);
-                if (!list_empty(&lo->queue_head)) {
-                        printk(KERN_ERR "nbd: disconnect: some requests are in progress -> please try again.\n");
-                        error = -EBUSY;
-                }
-                spin_unlock(&lo->queue_lock);
+                BUG_ON(!list_empty(&lo->queue_head));
                 if (file)
                         fput(file);
                 return error;
@@ -598,24 +600,19 @@ static int nbd_ioctl(struct inode *inode, struct file *file,
                         lo->sock = NULL;
                 }
                 up(&lo->tx_lock);
-                spin_lock(&lo->queue_lock);
                 file = lo->file;
                 lo->file = NULL;
-                spin_unlock(&lo->queue_lock);
                 nbd_clear_que(lo);
                 printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
                 if (file)
                         fput(file);
                 return lo->harderror;
         case NBD_CLEAR_QUE:
-                down(&lo->tx_lock);
-                if (lo->sock) {
-                        up(&lo->tx_lock);
-                        return 0; /* probably should be error, but that would
-                                   * break "nbd-client -d", so just return 0 */
-                }
-                up(&lo->tx_lock);
-                nbd_clear_que(lo);
+                /*
+                 * This is for compatibility only.  The queue is always cleared
+                 * by NBD_DO_IT or NBD_CLEAR_SOCK.
+                 */
+                BUG_ON(!lo->sock && !list_empty(&lo->queue_head));
                 return 0;
         case NBD_PRINT_DEBUG:
                 printk(KERN_INFO "%s: next = %p, prev = %p, head = %p\n",
@@ -688,6 +685,7 @@ static int __init nbd_init(void)
                 spin_lock_init(&nbd_dev[i].queue_lock);
                 INIT_LIST_HEAD(&nbd_dev[i].queue_head);
                 init_MUTEX(&nbd_dev[i].tx_lock);
+                init_waitqueue_head(&nbd_dev[i].active_wq);
                 nbd_dev[i].blksize = 1024;
                 nbd_dev[i].bytesize = 0x7ffffc00ULL << 10; /* 2TB */
                 disk->major = NBD_MAJOR;
diff --git a/include/linux/nbd.h b/include/linux/nbd.h
index 090e210e98f0..f95d51fae733 100644
--- a/include/linux/nbd.h
+++ b/include/linux/nbd.h
@@ -37,18 +37,26 @@ enum {
 /* userspace doesn't need the nbd_device structure */
 #ifdef __KERNEL__
 
+#include <linux/wait.h>
+
 /* values for flags field */
 #define NBD_READ_ONLY 0x0001
 #define NBD_WRITE_NOCHK 0x0002
 
+struct request;
+
 struct nbd_device {
         int flags;
         int harderror;          /* Code of hard error                   */
         struct socket * sock;
         struct file * file;     /* If == NULL, device is not ready, yet */
         int magic;
+
         spinlock_t queue_lock;
         struct list_head queue_head;/* Requests are added here...       */
+        struct request *active_req;
+        wait_queue_head_t active_wq;
+
         struct semaphore tx_lock;
         struct gendisk *disk;
         int blksize;