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Message-Id: <20090128171855.6d5c59c8.akpm@linux-foundation.org>
Date: Wed, 28 Jan 2009 17:18:55 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Pavel Machek <pavel@...e.cz>
Cc: linux-kernel@...r.kernel.org, Paul.Clements@...eleye.com
Subject: Re: nbd: add locking to nbd_ioctl
On Mon, 26 Jan 2009 18:31:33 +0100
Pavel Machek <pavel@...e.cz> wrote:
> The code was written to rely on big kernel lock to protect it from
> races. It mostly works when interface is not abused.
>
> So this uses tx_lock to protect data structures from concurrent use
> between ioctl and worker threads.
>
> Next step will be moving from ioctl to unlocked_ioctl.
I dinked with this rather a lot. Moved all those case statements in a
tabstop (makes it all fit into 80 cols without adding weird
linebreaks), moved a few `return' statements to more logical places,
etc.
Please apply and double-check?
--- a/drivers/block/nbd.c~nbd-add-locking-to-nbd_ioctl-checkpatch-fixes
+++ a/drivers/block/nbd.c
@@ -565,61 +565,59 @@ static int __nbd_ioctl(struct block_devi
unsigned int cmd, unsigned long arg)
{
switch (cmd) {
- case NBD_DISCONNECT:
+ case NBD_DISCONNECT: {
+ struct request sreq;
+
printk(KERN_INFO "%s: NBD_DISCONNECT\n", lo->disk->disk_name);
- {
- struct request sreq;
- blk_rq_init(NULL, &sreq);
- sreq.cmd_type = REQ_TYPE_SPECIAL;
- nbd_cmd(&sreq) = NBD_CMD_DISC;
- /*
- * Set these to sane values in case server implementation
- * fails to check the request type first and also to keep
- * debugging output cleaner.
- */
- sreq.sector = 0;
- sreq.nr_sectors = 0;
- if (!lo->sock)
- return -EINVAL;
- nbd_send_req(lo, &sreq);
- }
+ blk_rq_init(NULL, &sreq);
+ sreq.cmd_type = REQ_TYPE_SPECIAL;
+ nbd_cmd(&sreq) = NBD_CMD_DISC;
+ /*
+ * Set these to sane values in case server implementation
+ * fails to check the request type first and also to keep
+ * debugging output cleaner.
+ */
+ sreq.sector = 0;
+ sreq.nr_sectors = 0;
+ if (!lo->sock)
+ return -EINVAL;
+ nbd_send_req(lo, &sreq);
return 0;
+ }
- case NBD_CLEAR_SOCK:
- {
- struct file *file;
-
- lo->sock = NULL;
- file = lo->file;
- lo->file = NULL;
- nbd_clear_que(lo);
- BUG_ON(!list_empty(&lo->queue_head));
- if (file)
- fput(file);
- }
- return 0;
+ case NBD_CLEAR_SOCK: {
+ struct file *file;
- case NBD_SET_SOCK:
- {
- struct file *file;
- if (lo->file)
- return -EBUSY;
- file = fget(arg);
- if (file) {
- struct inode *inode = file->f_path.dentry->d_inode;
- if (S_ISSOCK(inode->i_mode)) {
- lo->file = file;
- lo->sock = SOCKET_I(inode);
- if (max_part > 0)
- bdev->bd_invalidated = 1;
- return 0;
- } else {
- fput(file);
- }
+ lo->sock = NULL;
+ file = lo->file;
+ lo->file = NULL;
+ nbd_clear_que(lo);
+ BUG_ON(!list_empty(&lo->queue_head));
+ if (file)
+ fput(file);
+ return 0;
+ }
+
+ case NBD_SET_SOCK: {
+ struct file *file;
+ if (lo->file)
+ return -EBUSY;
+ file = fget(arg);
+ if (file) {
+ struct inode *inode = file->f_path.dentry->d_inode;
+ if (S_ISSOCK(inode->i_mode)) {
+ lo->file = file;
+ lo->sock = SOCKET_I(inode);
+ if (max_part > 0)
+ bdev->bd_invalidated = 1;
+ return 0;
+ } else {
+ fput(file);
}
}
return -EINVAL;
+ }
case NBD_SET_BLKSIZE:
lo->blksize = arg;
@@ -647,45 +645,44 @@ static int __nbd_ioctl(struct block_devi
set_capacity(lo->disk, lo->bytesize >> 9);
return 0;
- case NBD_DO_IT:
- {
- struct task_struct *thread;
- struct file *file;
- int error;
-
- if (lo->pid)
- return -EBUSY;
- if (!lo->file)
- return -EINVAL;
-
- mutex_unlock(&lo->tx_lock);
-
- thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);
- if (IS_ERR(thread)) {
- mutex_lock(&lo->tx_lock);
- return PTR_ERR(thread);
- }
- wake_up_process(thread);
- error = nbd_do_it(lo);
- kthread_stop(thread);
+ case NBD_DO_IT: {
+ struct task_struct *thread;
+ struct file *file;
+ int error;
+
+ if (lo->pid)
+ return -EBUSY;
+ if (!lo->file)
+ return -EINVAL;
+
+ mutex_unlock(&lo->tx_lock);
+ thread = kthread_create(nbd_thread, lo, lo->disk->disk_name);
+ if (IS_ERR(thread)) {
mutex_lock(&lo->tx_lock);
- if (error)
- return error;
- sock_shutdown(lo, 0);
- file = lo->file;
- lo->file = NULL;
- nbd_clear_que(lo);
- printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
- if (file)
- fput(file);
- lo->bytesize = 0;
- bdev->bd_inode->i_size = 0;
- set_capacity(lo->disk, 0);
- if (max_part > 0)
- ioctl_by_bdev(bdev, BLKRRPART, 0);
- return lo->harderror;
+ return PTR_ERR(thread);
}
+ wake_up_process(thread);
+ error = nbd_do_it(lo);
+ kthread_stop(thread);
+
+ mutex_lock(&lo->tx_lock);
+ if (error)
+ return error;
+ sock_shutdown(lo, 0);
+ file = lo->file;
+ lo->file = NULL;
+ nbd_clear_que(lo);
+ printk(KERN_WARNING "%s: queue cleared\n", lo->disk->disk_name);
+ if (file)
+ fput(file);
+ lo->bytesize = 0;
+ bdev->bd_inode->i_size = 0;
+ set_capacity(lo->disk, 0);
+ if (max_part > 0)
+ ioctl_by_bdev(bdev, BLKRRPART, 0);
+ return lo->harderror;
+ }
case NBD_CLEAR_QUE:
/*
_
--
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