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Commit 09c0dc68 authored by Linus Torvalds's avatar Linus Torvalds
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Revert "[PATCH] kthread: update loop.c to use kthread" 



This reverts commit c7b2eff0.

Hugh Dickins explains:

 "It seems too little tested: "losetup -d /dev/loop0" fails with
  EINVAL because nothing sets lo_thread; but even when you patch
  loop_thread() to set lo->lo_thread = current, it can't survive
  more than a few dozen iterations of the loop below (with a tmpfs
  mounted on /tst):

	j=0
	cp /dev/zero /tst
	while :
	do
	    let j=j+1
	    echo "Doing pass $j"
	    losetup /dev/loop0 /tst/zero
	    mkfs -t ext2 -b 1024 /dev/loop0 >/dev/null 2>&1
	    mount -t ext2 /dev/loop0 /mnt
	    umount /mnt
	    losetup -d /dev/loop0
	done

  it collapses with failed ioctl then BUG_ON(!bio).

  I think the original lo_done completion was more subtle and safe
  than the kthread conversion has allowed for."

Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 2a2ed2db

drivers/block/loop.c

+13 −11
Original line number Diff line number Diff line
@@ -74,7 +74,6 @@ 
#include <linux/completion.h>

#include <linux/highmem.h>

#include <linux/gfp.h>

#include <linux/kthread.h>



#include <asm/uaccess.h>
@@ -579,6 +578,8 @@ static int loop_thread(void *data) 
	struct loop_device *lo = data;

	struct bio *bio;



	daemonize("loop%d", lo->lo_number);



	/*

	 * loop can be used in an encrypted device,

	 * hence, it mustn't be stopped at all
@@ -591,6 +592,11 @@ static int loop_thread(void *data) 
	lo->lo_state = Lo_bound;

	lo->lo_pending = 1;



	/*

	 * complete it, we are running

	 */

	complete(&lo->lo_done);



	for (;;) {

		int pending;
@@ -623,6 +629,7 @@ static int loop_thread(void *data) 
			break;

	}



	complete(&lo->lo_done);

	return 0;

}
@@ -739,7 +746,6 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file, 
	unsigned lo_blocksize;

	int		lo_flags = 0;

	int		error;

	struct task_struct *tsk;

	loff_t		size;



	/* This is safe, since we have a reference from open(). */
@@ -833,11 +839,10 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file, 


	set_blocksize(bdev, lo_blocksize);



	tsk = kthread_run(loop_thread, lo, "loop%d", lo->lo_number);

	if (IS_ERR(tsk)) {

		error = PTR_ERR(tsk);

	error = kernel_thread(loop_thread, lo, CLONE_KERNEL);

	if (error < 0)

		goto out_putf;

	}

	wait_for_completion(&lo->lo_done);

	return 0;



 out_putf:
@@ -893,9 +898,6 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev) 
	if (lo->lo_state != Lo_bound)

		return -ENXIO;



	if (!lo->lo_thread)

		return -EINVAL;



	if (lo->lo_refcnt > 1)	/* we needed one fd for the ioctl */

		return -EBUSY;
@@ -909,7 +911,7 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev) 
		complete(&lo->lo_bh_done);

	spin_unlock_irq(&lo->lo_lock);



	kthread_stop(lo->lo_thread);

	wait_for_completion(&lo->lo_done);



	lo->lo_backing_file = NULL;
@@ -922,7 +924,6 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev) 
	lo->lo_sizelimit = 0;

	lo->lo_encrypt_key_size = 0;

	lo->lo_flags = 0;

	lo->lo_thread = NULL;

	memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);

	memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);

	memset(lo->lo_file_name, 0, LO_NAME_SIZE);
@@ -1287,6 +1288,7 @@ static int __init loop_init(void) 
		if (!lo->lo_queue)

			goto out_mem4;

		mutex_init(&lo->lo_ctl_mutex);

		init_completion(&lo->lo_done);

		init_completion(&lo->lo_bh_done);

		lo->lo_number = i;

		spin_lock_init(&lo->lo_lock);

include/linux/loop.h

+1 −1
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ struct loop_device { 
	struct bio 		*lo_bio;

	struct bio		*lo_biotail;

	int			lo_state;

	struct task_struct	*lo_thread;

	struct completion	lo_done;

	struct completion	lo_bh_done;

	struct mutex		lo_ctl_mutex;

	int			lo_pending;