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Commit fcccf502 authored by Takashi Sato's avatar Takashi Sato Committed by Linus Torvalds
Browse files

filesystem freeze: implement generic freeze feature 



The ioctls for the generic freeze feature are below.
o Freeze the filesystem
  int ioctl(int fd, int FIFREEZE, arg)
    fd: The file descriptor of the mountpoint
    FIFREEZE: request code for the freeze
    arg: Ignored
    Return value: 0 if the operation succeeds. Otherwise, -1

o Unfreeze the filesystem
  int ioctl(int fd, int FITHAW, arg)
    fd: The file descriptor of the mountpoint
    FITHAW: request code for unfreeze
    arg: Ignored
    Return value: 0 if the operation succeeds. Otherwise, -1
    Error number: If the filesystem has already been unfrozen,
                  errno is set to EINVAL.

[akpm@linux-foundation.org: fix CONFIG_BLOCK=n]
Signed-off-by: default avatarTakashi Sato <t-sato@yk.jp.nec.com>
Signed-off-by: default avatarMasayuki Hamaguchi <m-hamaguchi@ys.jp.nec.com>
Cc: <xfs-masters@oss.sgi.com>
Cc: <linux-ext4@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Kleikamp <shaggy@austin.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Alasdair G Kergon <agk@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c4be0c1d

fs/block_dev.c

+2 −0
Original line number Diff line number Diff line
@@ -285,6 +285,8 @@ static void init_once(void *foo) 
	INIT_LIST_HEAD(&bdev->bd_holder_list);

#endif

	inode_init_once(&ei->vfs_inode);

	/* Initialize mutex for freeze. */

	mutex_init(&bdev->bd_fsfreeze_mutex);

}



static inline void __bd_forget(struct inode *inode)

fs/buffer.c

+65 −9
Original line number Diff line number Diff line
@@ -203,10 +203,25 @@ int fsync_bdev(struct block_device *bdev) 
 * happen on bdev until thaw_bdev() is called.

 * If a superblock is found on this device, we take the s_umount semaphore

 * on it to make sure nobody unmounts until the snapshot creation is done.

 * The reference counter (bd_fsfreeze_count) guarantees that only the last

 * unfreeze process can unfreeze the frozen filesystem actually when multiple

 * freeze requests arrive simultaneously. It counts up in freeze_bdev() and

 * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze

 * actually.

 */

struct super_block *freeze_bdev(struct block_device *bdev)

{

	struct super_block *sb;

	int error = 0;



	mutex_lock(&bdev->bd_fsfreeze_mutex);

	if (bdev->bd_fsfreeze_count > 0) {

		bdev->bd_fsfreeze_count++;

		sb = get_super(bdev);

		mutex_unlock(&bdev->bd_fsfreeze_mutex);

		return sb;

	}

	bdev->bd_fsfreeze_count++;



	down(&bdev->bd_mount_sem);

	sb = get_super(bdev);
@@ -221,11 +236,24 @@ struct super_block *freeze_bdev(struct block_device *bdev) 


		sync_blockdev(sb->s_bdev);



		if (sb->s_op->freeze_fs)

			sb->s_op->freeze_fs(sb);

		if (sb->s_op->freeze_fs) {

			error = sb->s_op->freeze_fs(sb);

			if (error) {

				printk(KERN_ERR

					"VFS:Filesystem freeze failed\n");

				sb->s_frozen = SB_UNFROZEN;

				drop_super(sb);

				up(&bdev->bd_mount_sem);

				bdev->bd_fsfreeze_count--;

				mutex_unlock(&bdev->bd_fsfreeze_mutex);

				return ERR_PTR(error);

			}

		}

	}



	sync_blockdev(bdev);

	mutex_unlock(&bdev->bd_fsfreeze_mutex);



	return sb;	/* thaw_bdev releases s->s_umount and bd_mount_sem */

}

EXPORT_SYMBOL(freeze_bdev);
@@ -237,20 +265,48 @@ EXPORT_SYMBOL(freeze_bdev); 
 *

 * Unlocks the filesystem and marks it writeable again after freeze_bdev().

 */

void thaw_bdev(struct block_device *bdev, struct super_block *sb)

int thaw_bdev(struct block_device *bdev, struct super_block *sb)

{

	int error = 0;



	mutex_lock(&bdev->bd_fsfreeze_mutex);

	if (!bdev->bd_fsfreeze_count) {

		mutex_unlock(&bdev->bd_fsfreeze_mutex);

		return -EINVAL;

	}



	bdev->bd_fsfreeze_count--;

	if (bdev->bd_fsfreeze_count > 0) {

		if (sb)

			drop_super(sb);

		mutex_unlock(&bdev->bd_fsfreeze_mutex);

		return 0;

	}



	if (sb) {

		BUG_ON(sb->s_bdev != bdev);



		if (sb->s_op->unfreeze_fs)

			sb->s_op->unfreeze_fs(sb);

		if (!(sb->s_flags & MS_RDONLY)) {

			if (sb->s_op->unfreeze_fs) {

				error = sb->s_op->unfreeze_fs(sb);

				if (error) {

					printk(KERN_ERR

						"VFS:Filesystem thaw failed\n");

					sb->s_frozen = SB_FREEZE_TRANS;

					bdev->bd_fsfreeze_count++;

					mutex_unlock(&bdev->bd_fsfreeze_mutex);

					return error;

				}

			}

			sb->s_frozen = SB_UNFROZEN;

			smp_wmb();

			wake_up(&sb->s_wait_unfrozen);

		}

		drop_super(sb);

	}



	up(&bdev->bd_mount_sem);

	mutex_unlock(&bdev->bd_fsfreeze_mutex);

	return 0;

}

EXPORT_SYMBOL(thaw_bdev);

fs/ioctl.c

+46 −0
Original line number Diff line number Diff line
@@ -439,6 +439,43 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp, 
	return error;

}



static int ioctl_fsfreeze(struct file *filp)

{

	struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	/* If filesystem doesn't support freeze feature, return. */

	if (sb->s_op->freeze_fs == NULL)

		return -EOPNOTSUPP;



	/* If a blockdevice-backed filesystem isn't specified, return. */

	if (sb->s_bdev == NULL)

		return -EINVAL;



	/* Freeze */

	sb = freeze_bdev(sb->s_bdev);

	if (IS_ERR(sb))

		return PTR_ERR(sb);

	return 0;

}



static int ioctl_fsthaw(struct file *filp)

{

	struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;



	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	/* If a blockdevice-backed filesystem isn't specified, return EINVAL. */

	if (sb->s_bdev == NULL)

		return -EINVAL;



	/* Thaw */

	return thaw_bdev(sb->s_bdev, sb);

}



/*

 * When you add any new common ioctls to the switches above and below

 * please update compat_sys_ioctl() too.
@@ -486,6 +523,15 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd, 
		} else

			error = -ENOTTY;

		break;



	case FIFREEZE:

		error = ioctl_fsfreeze(filp);

		break;



	case FITHAW:

		error = ioctl_fsthaw(filp);

		break;



	default:

		if (S_ISREG(filp->f_path.dentry->d_inode->i_mode))

			error = file_ioctl(filp, cmd, arg);

include/linux/buffer_head.h

+10 −1
Original line number Diff line number Diff line
@@ -171,7 +171,7 @@ void __wait_on_buffer(struct buffer_head *); 
wait_queue_head_t *bh_waitq_head(struct buffer_head *bh);

int fsync_bdev(struct block_device *);

struct super_block *freeze_bdev(struct block_device *);

void thaw_bdev(struct block_device *, struct super_block *);

int thaw_bdev(struct block_device *, struct super_block *);

int fsync_super(struct super_block *);

int fsync_no_super(struct block_device *);

struct buffer_head *__find_get_block(struct block_device *bdev, sector_t block,
@@ -346,6 +346,15 @@ static inline int remove_inode_buffers(struct inode *inode) { return 1; } 
static inline int sync_mapping_buffers(struct address_space *mapping) { return 0; }

static inline void invalidate_bdev(struct block_device *bdev) {}



static inline struct super_block *freeze_bdev(struct block_device *sb)

{

	return NULL;

}



static inline int thaw_bdev(struct block_device *bdev, struct super_block *sb)

{

	return 0;

}



#endif /* CONFIG_BLOCK */

#endif /* _LINUX_BUFFER_HEAD_H */

include/linux/fs.h

+7 −0
Original line number Diff line number Diff line
@@ -234,6 +234,8 @@ struct inodes_stat_t { 
#define BMAP_IOCTL 1		/* obsolete - kept for compatibility */

#define FIBMAP	   _IO(0x00,1)	/* bmap access */

#define FIGETBSZ   _IO(0x00,2)	/* get the block size used for bmap */

#define FIFREEZE	_IOWR('X', 119, int)	/* Freeze */

#define FITHAW		_IOWR('X', 120, int)	/* Thaw */



#define	FS_IOC_GETFLAGS			_IOR('f', 1, long)

#define	FS_IOC_SETFLAGS			_IOW('f', 2, long)
@@ -591,6 +593,11 @@ struct block_device { 
	 * care to not mess up bd_private for that case.

	 */

	unsigned long		bd_private;



	/* The counter of freeze processes */

	int			bd_fsfreeze_count;

	/* Mutex for freeze */

	struct mutex		bd_fsfreeze_mutex;

};



/*