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[PATCH v4 0/4] nbd: nbd fixes

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  [PATCH v4 0/4] nbd: nbd fixes "Pranay Kr. Srivastava" <pranjas@gmail.com> - 2016-06-30 13:10 +0200
    [PATCH v4 1/5]nbd: cleanup nbd_set_socket "Pranay Kr. Srivastava" <pranjas@gmail.com> - 2016-06-30 13:10 +0200
      Re: [PATCH v4 1/5]nbd: cleanup nbd_set_socket Pranay Srivastava <pranjas@gmail.com> - 2016-07-07 17:00 +0200
        Re: [PATCH v4 1/5]nbd: cleanup nbd_set_socket Pranay Srivastava <pranjas@gmail.com> - 2016-07-09 09:40 +0200
    [PATCH v4 3/5]nbd: make nbd device wait for its users "Pranay Kr. Srivastava" <pranjas@gmail.com> - 2016-06-30 13:10 +0200
    [PATCH v4 4/5]nbd: use i_size_write to assign nbd device size "Pranay Kr. Srivastava" <pranjas@gmail.com> - 2016-06-30 13:10 +0200
    [PATCH v4 2/5]nbd: fix might_sleep warning on socket shutdown "Pranay Kr. Srivastava" <pranjas@gmail.com> - 2016-06-30 13:10 +0200
      Re: [PATCH v4 2/5]nbd: fix might_sleep warning on socket shutdown Pranay Srivastava <pranjas@gmail.com> - 2016-07-04 09:10 +0200

#1434458 — [PATCH v4 0/4] nbd: nbd fixes

This patch series fixes the following

1) cleanup nbd_set_socket
   Simple fixes to nbd_set_socket.

2) fix might_sleep warning on socket shutdown:
   Fix sock_shutdown to avoid calling kernel_sock_shutdown
   while holding spin_lock.

3) make nbd device wait for its users.
   When a timeout or error occurs then nbd driver simply kills
   the block device. Many filesystem(s) example ext2/ext3 don't
   expect their buffer heads to disappear like that. Fix this
   by making nbd device wait for its users.

   The same work function is used to trigger the kill_bdev as well
   do a sock_shutdown, depending on either a timeout/error occured
   or a disconnect was issued.

   Also avoid scheduling the work_fn in case a timeout for a request
   has already occured.

4) use i_size_write to assign nbd device size
   Instead of directly assigning nbd block device
   size, use i_size_write for modification.

Pranay Kr. Srivastava (4):
  cleanup nbd_set_socket
  fix might_sleep warning on socket shutdown
  make nbd device wait for its users
  use i_size_write to assign nbd device size

 drivers/block/nbd.c | 168 ++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 123 insertions(+), 45 deletions(-)

Changelog:

*) Rebased all patches above on git://git.pengutronix.de/git/mpa/linux-nbd.git,
   commit:7ed71a8704eda7b75fbd0ed73fd0a5b6e469d250

*) Formatting issues, and removed unnecessary code.

*) Splitted the patch to wait for users to create a new patch
   4) use i_size_write to assign nbd device size

-- 
1.9.1

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#1434460 — [PATCH v4 1/5]nbd: cleanup nbd_set_socket

From: "Pranay Kr. Srivastava" <pranaykumar.srivastava@cognizant.com>

This patch
1) uses spin_lock instead of irq version.

2) removes the goto statement in case a socket
   is already assigned with simple if-else statement.

Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
---
 drivers/block/nbd.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 56f7f5d..766c401 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -643,17 +643,12 @@ static int nbd_set_socket(struct nbd_device *nbd, struct socket *sock)
 {
 	int ret = 0;
 
-	spin_lock_irq(&nbd->sock_lock);
-
-	if (nbd->sock) {
+	spin_lock(&nbd->sock_lock);
+	if (nbd->sock)
 		ret = -EBUSY;
-		goto out;
-	}
-
-	nbd->sock = sock;
-
-out:
-	spin_unlock_irq(&nbd->sock_lock);
+	else
+		nbd->sock = sock;
+	spin_unlock(&nbd->sock_lock);
 
 	return ret;
 }
-- 
1.9.1

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#1438663 — Re: [PATCH v4 1/5]nbd: cleanup nbd_set_socket

On Thu, Jun 30, 2016 at 4:32 PM, Pranay Kr. Srivastava
<pranjas@gmail.com> wrote:
> From: "Pranay Kr. Srivastava" <pranaykumar.srivastava@cognizant.com>
>
> This patch
> 1) uses spin_lock instead of irq version.
>
> 2) removes the goto statement in case a socket
>    is already assigned with simple if-else statement.
>
> Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
> ---
>  drivers/block/nbd.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 56f7f5d..766c401 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -643,17 +643,12 @@ static int nbd_set_socket(struct nbd_device *nbd, struct socket *sock)
>  {
>         int ret = 0;
>
> -       spin_lock_irq(&nbd->sock_lock);
> -
> -       if (nbd->sock) {
> +       spin_lock(&nbd->sock_lock);
> +       if (nbd->sock)
>                 ret = -EBUSY;
> -               goto out;
> -       }
> -
> -       nbd->sock = sock;
> -
> -out:
> -       spin_unlock_irq(&nbd->sock_lock);
> +       else
> +               nbd->sock = sock;
> +       spin_unlock(&nbd->sock_lock);
>
>         return ret;
>  }
> --
> 1.9.1
>

Hi Markus,

Did you get a chance to review V4 of this series.

-- 
        ---P.K.S

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#1439904 — Re: [PATCH v4 1/5]nbd: cleanup nbd_set_socket

On Thu, Jul 7, 2016 at 8:26 PM, Pranay Srivastava <pranjas@gmail.com> wrote:
> On Thu, Jun 30, 2016 at 4:32 PM, Pranay Kr. Srivastava
> <pranjas@gmail.com> wrote:
>> From: "Pranay Kr. Srivastava" <pranaykumar.srivastava@cognizant.com>
>>
>> This patch
>> 1) uses spin_lock instead of irq version.
>>
>> 2) removes the goto statement in case a socket
>>    is already assigned with simple if-else statement.
>>
>> Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
>> ---
>>  drivers/block/nbd.c | 15 +++++----------
>>  1 file changed, 5 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
>> index 56f7f5d..766c401 100644
>> --- a/drivers/block/nbd.c
>> +++ b/drivers/block/nbd.c
>> @@ -643,17 +643,12 @@ static int nbd_set_socket(struct nbd_device *nbd, struct socket *sock)
>>  {
>>         int ret = 0;
>>
>> -       spin_lock_irq(&nbd->sock_lock);
>> -
>> -       if (nbd->sock) {
>> +       spin_lock(&nbd->sock_lock);
>> +       if (nbd->sock)
>>                 ret = -EBUSY;
>> -               goto out;
>> -       }
>> -
>> -       nbd->sock = sock;
>> -
>> -out:
>> -       spin_unlock_irq(&nbd->sock_lock);
>> +       else
>> +               nbd->sock = sock;
>> +       spin_unlock(&nbd->sock_lock);
>>
>>         return ret;
>>  }
>> --
>> 1.9.1
>>
>
> Hi Markus,
>
> Did you get a chance to review V4 of this series.
>
> --
>         ---P.K.S

Ping ?

-- 
        ---P.K.S

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#1434461 — [PATCH v4 3/5]nbd: make nbd device wait for its users

When a timeout occurs or a recv fails, then
instead of abruplty killing nbd block device
wait for its users to finish.

This is more required when filesystem(s) like
ext2 or ext3 don't expect their buffer heads to
disappear while the filesystem is mounted.

Each open of a nbd device is refcounted, while
the userland program [nbd-client] doing the
NBD_DO_IT ioctl would now wait for any other users
of this device before invalidating the nbd device.

A timedout or a disconnected device, if in use, can't
be used until it has been resetted. The reset happens
when all tasks having this bdev open closes this bdev.

Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
---
 drivers/block/nbd.c | 106 ++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 87 insertions(+), 19 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index e362d44..fb56dd2 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -72,6 +72,8 @@ struct nbd_device {
 #endif
 	/* This is specifically for calling sock_shutdown, for now. */
 	struct work_struct ws_shutdown;
+	struct kref users;
+	struct completion user_completion;
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -99,6 +101,8 @@ static int max_part;
 static DEFINE_SPINLOCK(nbd_lock);
 
 static void nbd_ws_func_shutdown(struct work_struct *);
+static void nbd_kref_release(struct kref *);
+static int nbd_size_clear(struct nbd_device *, struct block_device *);
 
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
@@ -145,11 +149,9 @@ static int nbd_size_set(struct nbd_device *nbd, struct block_device *bdev,
 			int blocksize, int nr_blocks)
 {
 	int ret;
-
 	ret = set_blocksize(bdev, blocksize);
 	if (ret)
 		return ret;
-
 	nbd->blksize = blocksize;
 	nbd->bytesize = (loff_t)blocksize * (loff_t)nr_blocks;
 
@@ -197,6 +199,9 @@ static void nbd_xmit_timeout(unsigned long arg)
 {
 	struct nbd_device *nbd = (struct nbd_device *)arg;
 
+	if (nbd->timedout)
+		return;
+
 	if (list_empty(&nbd->queue_head))
 		return;
 
@@ -472,8 +477,6 @@ static int nbd_thread_recv(struct nbd_device *nbd, struct block_device *bdev)
 		nbd_end_request(nbd, req);
 	}
 
-	nbd_size_clear(nbd, bdev);
-
 	device_remove_file(disk_to_dev(nbd->disk), &dev_attr_pid);
 
 	nbd->task_recv = NULL;
@@ -650,12 +653,13 @@ static int nbd_set_socket(struct nbd_device *nbd, struct socket *sock)
 	int ret = 0;
 
 	spin_lock(&nbd->sock_lock);
-	if (nbd->sock)
+
+	if (nbd->sock || nbd->timedout)
 		ret = -EBUSY;
 	else
 		nbd->sock = sock;
-	spin_unlock(&nbd->sock_lock);
 
+	spin_unlock(&nbd->sock_lock);
 	return ret;
 }
 
@@ -670,6 +674,7 @@ static void nbd_reset(struct nbd_device *nbd)
 	nbd->flags = 0;
 	nbd->xmit_timeout = 0;
 	INIT_WORK(&nbd->ws_shutdown, nbd_ws_func_shutdown);
+	init_completion(&nbd->user_completion);
 	queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 	del_timer_sync(&nbd->timeout_timer);
 }
@@ -704,6 +709,9 @@ static void nbd_dev_dbg_close(struct nbd_device *nbd);
 static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		       unsigned int cmd, unsigned long arg)
 {
+	if (nbd->timedout || nbd->disconnect)
+		return -EBUSY;
+
 	switch (cmd) {
 	case NBD_DISCONNECT: {
 		struct request sreq;
@@ -733,7 +741,6 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		nbd_clear_que(nbd);
 		BUG_ON(!list_empty(&nbd->queue_head));
 		BUG_ON(!list_empty(&nbd->waiting_queue));
-		kill_bdev(bdev);
 		return 0;
 
 	case NBD_SET_SOCK: {
@@ -752,7 +759,6 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 
 	case NBD_SET_BLKSIZE: {
 		loff_t bsize = div_s64(nbd->bytesize, arg);
-
 		return nbd_size_set(nbd, bdev, arg, bsize);
 	}
 
@@ -804,22 +810,29 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		error = nbd_thread_recv(nbd, bdev);
 		nbd_dev_dbg_close(nbd);
 		kthread_stop(thread);
-		sock_shutdown(nbd);
-
-		mutex_lock(&nbd->tx_lock);
-		nbd->task_recv = NULL;
 
-		nbd_clear_que(nbd);
-		kill_bdev(bdev);
-		nbd_bdev_reset(bdev);
+		sock_shutdown(nbd);
 
 		if (nbd->disconnect) /* user requested, ignore socket errors */
 			error = 0;
 		if (nbd->timedout)
 			error = -ETIMEDOUT;
 
-		nbd_reset(nbd);
+		mutex_lock(&nbd->tx_lock);
+		nbd_clear_que(nbd);
+		nbd->disconnect = true; /* To kill bdev*/
+		mutex_unlock(&nbd->tx_lock);
+		cancel_work_sync(&nbd->ws_shutdown);
+		kref_put(&nbd->users, nbd_kref_release);
+		wait_for_completion(&nbd->user_completion);
 
+		mutex_lock(&bdev->bd_mutex);
+		if (!kref_get_unless_zero(&nbd->users))
+			kref_init(&nbd->users);
+		mutex_unlock(&bdev->bd_mutex);
+
+		mutex_lock(&nbd->tx_lock);
+		nbd_reset(nbd);
 		return error;
 	}
 
@@ -857,19 +870,74 @@ static int nbd_ioctl(struct block_device *bdev, fmode_t mode,
 
 	return error;
 }
+static void nbd_kref_release(struct kref *kref_users)
+{
+	struct nbd_device *nbd = container_of(kref_users, struct nbd_device,
+						users
+						);
+	schedule_work(&nbd->ws_shutdown);
+}
+
+static int nbd_open(struct block_device *bdev, fmode_t mode)
+{
+	struct nbd_device *nbd_dev = bdev->bd_disk->private_data;
+
+	if (!kref_get_unless_zero(&nbd_dev->users))
+		kref_init(&nbd_dev->users);
+
+	pr_debug("Opening nbd_dev %s. Active users = %u\n",
+			bdev->bd_disk->disk_name,
+			atomic_read(&nbd_dev->users.refcount)
+		);
+	return 0;
+}
+
+static void nbd_release(struct gendisk *disk, fmode_t mode)
+{
+	struct nbd_device *nbd_dev = disk->private_data;
+
+	kref_put(&nbd_dev->users,  nbd_kref_release);
+
+	pr_debug("Closing nbd_dev %s. Active users = %u\n",
+			disk->disk_name,
+			atomic_read(&nbd_dev->users.refcount)
+		);
+}
 
 static const struct block_device_operations nbd_fops = {
 	.owner =	THIS_MODULE,
 	.ioctl =	nbd_ioctl,
 	.compat_ioctl =	nbd_ioctl,
+	.open =		nbd_open,
+	.release =	nbd_release
 };
 
+
 static void nbd_ws_func_shutdown(struct work_struct *ws_nbd)
 {
 	struct nbd_device *nbd_dev = container_of(ws_nbd, struct nbd_device,
-			ws_shutdown);
-
-	sock_shutdown(nbd_dev);
+							ws_shutdown
+						);
+
+	struct block_device *bdev = bdget(part_devt(
+						dev_to_part(nbd_to_dev(nbd_dev))
+						)
+					);
+	BUG_ON(!bdev);
+	if (nbd_dev->timedout)
+		sock_shutdown(nbd_dev);
+
+	if (nbd_dev->disconnect) {
+		mutex_lock(&nbd_dev->tx_lock);
+		nbd_dev->task_recv = NULL;
+		nbd_clear_que(nbd_dev);
+		kill_bdev(bdev);
+		nbd_bdev_reset(bdev);
+		mutex_unlock(&nbd_dev->tx_lock);
+		nbd_size_clear(nbd_dev, bdev);
+		complete(&nbd_dev->user_completion);
+	}
+	bdput(bdev);
 }
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
-- 
1.9.1

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#1434462 — [PATCH v4 4/5]nbd: use i_size_write to assign nbd device size

Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
---
 drivers/block/nbd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index fb56dd2..7126878 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -128,7 +128,7 @@ static const char *nbdcmd_to_ascii(int cmd)
 
 static int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev)
 {
-	bdev->bd_inode->i_size = 0;
+	i_size_write(bdev->bd_inode, 0);
 	set_capacity(nbd->disk, 0);
 	kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
 
@@ -140,7 +140,7 @@ static void nbd_size_update(struct nbd_device *nbd, struct block_device *bdev)
 	if (!nbd_is_connected(nbd))
 		return;
 
-	bdev->bd_inode->i_size = nbd->bytesize;
+	i_size_write(bdev->bd_inode, nbd->bytesize);
 	set_capacity(nbd->disk, nbd->bytesize >> 9);
 	kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE);
 }
@@ -682,7 +682,7 @@ static void nbd_reset(struct nbd_device *nbd)
 static void nbd_bdev_reset(struct block_device *bdev)
 {
 	set_device_ro(bdev, false);
-	bdev->bd_inode->i_size = 0;
+	i_size_write(bdev->bd_inode, 0);
 	if (max_part > 0) {
 		blkdev_reread_part(bdev);
 		bdev->bd_invalidated = 1;
-- 
1.9.1

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#1434464 — [PATCH v4 2/5]nbd: fix might_sleep warning on socket shutdown

spinlocked ranges should be small and not contain calls into huge
subfunctions. Fix my mistake and just get the pointer to the socket
instead of doing everything with spinlock held.

Reported-by: Mikulas Patocka <mikulas@twibright.com>
Signed-off-by: Markus Pargmann <mpa@pengutronix.de>

Changelog:
Pranay Kr. Srivastava<pranjas@gmail.com>:

1) Use spin_lock instead of irq version for sock_shutdown.

2) Use system work queue to actually trigger the shutdown of
socket. This solves the issue when kernel_sendmsg is currently
blocked while a timeout occurs.

Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
---
 drivers/block/nbd.c | 57 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 21 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 766c401..e362d44 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -39,6 +39,7 @@
 #include <asm/types.h>
 
 #include <linux/nbd.h>
+#include <linux/workqueue.h>
 
 struct nbd_device {
 	u32 flags;
@@ -69,6 +70,8 @@ struct nbd_device {
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 	struct dentry *dbg_dir;
 #endif
+	/* This is specifically for calling sock_shutdown, for now. */
+	struct work_struct ws_shutdown;
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -95,6 +98,8 @@ static int max_part;
  */
 static DEFINE_SPINLOCK(nbd_lock);
 
+static void nbd_ws_func_shutdown(struct work_struct *);
+
 static inline struct device *nbd_to_dev(struct nbd_device *nbd)
 {
 	return disk_to_dev(nbd->disk);
@@ -172,39 +177,36 @@ static void nbd_end_request(struct nbd_device *nbd, struct request *req)
  */
 static void sock_shutdown(struct nbd_device *nbd)
 {
-	spin_lock_irq(&nbd->sock_lock);
-
-	if (!nbd->sock) {
-		spin_unlock_irq(&nbd->sock_lock);
-		return;
-	}
+	struct socket *sock;
 
-	dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
-	kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
-	sockfd_put(nbd->sock);
+	spin_lock(&nbd->sock_lock);
+	sock = nbd->sock;
 	nbd->sock = NULL;
-	spin_unlock_irq(&nbd->sock_lock);
+	spin_unlock(&nbd->sock_lock);
+
+	if (!sock)
+		return;
 
 	del_timer(&nbd->timeout_timer);
+	dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
+	kernel_sock_shutdown(sock, SHUT_RDWR);
+	sockfd_put(sock);
 }
 
 static void nbd_xmit_timeout(unsigned long arg)
 {
 	struct nbd_device *nbd = (struct nbd_device *)arg;
-	unsigned long flags;
 
 	if (list_empty(&nbd->queue_head))
 		return;
 
-	spin_lock_irqsave(&nbd->sock_lock, flags);
-
 	nbd->timedout = true;
-
-	if (nbd->sock)
-		kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
-
-	spin_unlock_irqrestore(&nbd->sock_lock, flags);
-
+	/*
+	 * Make sure sender thread sees nbd->timedout.
+	 */
+	smp_wmb();
+	schedule_work(&nbd->ws_shutdown);
+	wake_up(&nbd->waiting_wq);
 	dev_err(nbd_to_dev(nbd), "Connection timed out, shutting down connection\n");
 }
 
@@ -588,7 +590,11 @@ static int nbd_thread_send(void *data)
 		spin_unlock_irq(&nbd->queue_lock);
 
 		/* handle request */
-		nbd_handle_req(nbd, req);
+		if (nbd->timedout) {
+			req->errors++;
+			nbd_end_request(nbd, req);
+		} else
+			nbd_handle_req(nbd, req);
 	}
 
 	nbd->task_send = NULL;
@@ -663,6 +669,7 @@ static void nbd_reset(struct nbd_device *nbd)
 	set_capacity(nbd->disk, 0);
 	nbd->flags = 0;
 	nbd->xmit_timeout = 0;
+	INIT_WORK(&nbd->ws_shutdown, nbd_ws_func_shutdown);
 	queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
 	del_timer_sync(&nbd->timeout_timer);
 }
@@ -797,11 +804,11 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		error = nbd_thread_recv(nbd, bdev);
 		nbd_dev_dbg_close(nbd);
 		kthread_stop(thread);
+		sock_shutdown(nbd);
 
 		mutex_lock(&nbd->tx_lock);
 		nbd->task_recv = NULL;
 
-		sock_shutdown(nbd);
 		nbd_clear_que(nbd);
 		kill_bdev(bdev);
 		nbd_bdev_reset(bdev);
@@ -857,6 +864,14 @@ static const struct block_device_operations nbd_fops = {
 	.compat_ioctl =	nbd_ioctl,
 };
 
+static void nbd_ws_func_shutdown(struct work_struct *ws_nbd)
+{
+	struct nbd_device *nbd_dev = container_of(ws_nbd, struct nbd_device,
+			ws_shutdown);
+
+	sock_shutdown(nbd_dev);
+}
+
 #if IS_ENABLED(CONFIG_DEBUG_FS)
 
 static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
-- 
1.9.1

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#1436133 — Re: [PATCH v4 2/5]nbd: fix might_sleep warning on socket shutdown

On Thu, Jun 30, 2016 at 4:32 PM, Pranay Kr. Srivastava
<pranjas@gmail.com> wrote:
> spinlocked ranges should be small and not contain calls into huge
> subfunctions. Fix my mistake and just get the pointer to the socket
> instead of doing everything with spinlock held.
>
> Reported-by: Mikulas Patocka <mikulas@twibright.com>
> Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
>
> Changelog:
> Pranay Kr. Srivastava<pranjas@gmail.com>:
>
> 1) Use spin_lock instead of irq version for sock_shutdown.
>
> 2) Use system work queue to actually trigger the shutdown of
> socket. This solves the issue when kernel_sendmsg is currently
> blocked while a timeout occurs.
>
> Signed-off-by: Pranay Kr. Srivastava <pranjas@gmail.com>
> ---
>  drivers/block/nbd.c | 57 +++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 36 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 766c401..e362d44 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -39,6 +39,7 @@
>  #include <asm/types.h>
>
>  #include <linux/nbd.h>
> +#include <linux/workqueue.h>
>
>  struct nbd_device {
>         u32 flags;
> @@ -69,6 +70,8 @@ struct nbd_device {
>  #if IS_ENABLED(CONFIG_DEBUG_FS)
>         struct dentry *dbg_dir;
>  #endif
> +       /* This is specifically for calling sock_shutdown, for now. */
> +       struct work_struct ws_shutdown;
>  };
>
>  #if IS_ENABLED(CONFIG_DEBUG_FS)
> @@ -95,6 +98,8 @@ static int max_part;
>   */
>  static DEFINE_SPINLOCK(nbd_lock);
>
> +static void nbd_ws_func_shutdown(struct work_struct *);
> +
>  static inline struct device *nbd_to_dev(struct nbd_device *nbd)
>  {
>         return disk_to_dev(nbd->disk);
> @@ -172,39 +177,36 @@ static void nbd_end_request(struct nbd_device *nbd, struct request *req)
>   */
>  static void sock_shutdown(struct nbd_device *nbd)
>  {
> -       spin_lock_irq(&nbd->sock_lock);
> -
> -       if (!nbd->sock) {
> -               spin_unlock_irq(&nbd->sock_lock);
> -               return;
> -       }
> +       struct socket *sock;
>
> -       dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
> -       kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
> -       sockfd_put(nbd->sock);
> +       spin_lock(&nbd->sock_lock);
> +       sock = nbd->sock;
>         nbd->sock = NULL;
> -       spin_unlock_irq(&nbd->sock_lock);
> +       spin_unlock(&nbd->sock_lock);
> +
> +       if (!sock)
> +               return;
>
>         del_timer(&nbd->timeout_timer);
> +       dev_warn(disk_to_dev(nbd->disk), "shutting down socket\n");
> +       kernel_sock_shutdown(sock, SHUT_RDWR);
> +       sockfd_put(sock);
>  }
>
>  static void nbd_xmit_timeout(unsigned long arg)
>  {
>         struct nbd_device *nbd = (struct nbd_device *)arg;
> -       unsigned long flags;
>
>         if (list_empty(&nbd->queue_head))
>                 return;
>
> -       spin_lock_irqsave(&nbd->sock_lock, flags);
> -
>         nbd->timedout = true;
> -
> -       if (nbd->sock)
> -               kernel_sock_shutdown(nbd->sock, SHUT_RDWR);
> -
> -       spin_unlock_irqrestore(&nbd->sock_lock, flags);
> -
> +       /*
> +        * Make sure sender thread sees nbd->timedout.
> +        */
> +       smp_wmb();
> +       schedule_work(&nbd->ws_shutdown);
> +       wake_up(&nbd->waiting_wq);
>         dev_err(nbd_to_dev(nbd), "Connection timed out, shutting down connection\n");
>  }
>
> @@ -588,7 +590,11 @@ static int nbd_thread_send(void *data)
>                 spin_unlock_irq(&nbd->queue_lock);
>
>                 /* handle request */
> -               nbd_handle_req(nbd, req);
> +               if (nbd->timedout) {
> +                       req->errors++;
> +                       nbd_end_request(nbd, req);
> +               } else
> +                       nbd_handle_req(nbd, req);
>         }
>
>         nbd->task_send = NULL;
> @@ -663,6 +669,7 @@ static void nbd_reset(struct nbd_device *nbd)
>         set_capacity(nbd->disk, 0);
>         nbd->flags = 0;
>         nbd->xmit_timeout = 0;
> +       INIT_WORK(&nbd->ws_shutdown, nbd_ws_func_shutdown);
>         queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, nbd->disk->queue);
>         del_timer_sync(&nbd->timeout_timer);
>  }
> @@ -797,11 +804,11 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
>                 error = nbd_thread_recv(nbd, bdev);
>                 nbd_dev_dbg_close(nbd);
>                 kthread_stop(thread);
> +               sock_shutdown(nbd);
>
>                 mutex_lock(&nbd->tx_lock);
>                 nbd->task_recv = NULL;
>
> -               sock_shutdown(nbd);
>                 nbd_clear_que(nbd);
>                 kill_bdev(bdev);
>                 nbd_bdev_reset(bdev);
> @@ -857,6 +864,14 @@ static const struct block_device_operations nbd_fops = {
>         .compat_ioctl = nbd_ioctl,
>  };
>
> +static void nbd_ws_func_shutdown(struct work_struct *ws_nbd)
> +{
> +       struct nbd_device *nbd_dev = container_of(ws_nbd, struct nbd_device,
> +                       ws_shutdown);
> +
> +       sock_shutdown(nbd_dev);
> +}
> +
>  #if IS_ENABLED(CONFIG_DEBUG_FS)
>
>  static int nbd_dbg_tasks_show(struct seq_file *s, void *unused)
> --
> 1.9.1
>


Anyone reviewed this?

-- 
        ---P.K.S

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