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: Takashi Sato <t-sato@yk.jp.nec.com>
Signed-off-by: Masayuki 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 46 insertions, 0 deletions

diff --git a/fs/ioctl.c b/fs/ioctl.c
index cc3f1aa1cf7b..20b0a8a24c6b 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -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);