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

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
......@@ -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)
......
......@@ -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);
sb->s_frozen = SB_UNFROZEN;
smp_wmb();
wake_up(&sb->s_wait_unfrozen);
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);
......
......@@ -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);
......
......@@ -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 */
......@@ -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;
};
/*
......
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