[PATCH 6/8] fsfreeze: add vfs ioctl to check freeze state

[Fernando Luis Vázquez Cao <fernando_b1@xxxxxxxxxxxxx>]

The FIISFROZEN ioctl can be use by HA and monitoring software to check
the freeze state of a mounted filesystem.

Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx>
---

diff -urNp vfs-orig/fs/compat_ioctl.c vfs/fs/compat_ioctl.c
--- vfs-orig/fs/compat_ioctl.c	2012-07-04 18:57:54.000000000 +0900
+++ vfs/fs/compat_ioctl.c	2012-07-12 17:25:37.592626439 +0900
@@ -885,6 +885,7 @@ COMPATIBLE_IOCTL(FIGETBSZ)
 /* 'X' - originally XFS but some now in the VFS */
 COMPATIBLE_IOCTL(FIFREEZE)
 COMPATIBLE_IOCTL(FITHAW)
+COMPATIBLE_IOCTL(FIISFROZEN)
 COMPATIBLE_IOCTL(KDGETKEYCODE)
 COMPATIBLE_IOCTL(KDSETKEYCODE)
 COMPATIBLE_IOCTL(KDGKBTYPE)
diff -urNp vfs-orig/fs/ioctl.c vfs/fs/ioctl.c
--- vfs-orig/fs/ioctl.c	2012-07-04 18:57:54.000000000 +0900
+++ vfs/fs/ioctl.c	2012-07-12 17:25:37.592626439 +0900
@@ -536,6 +536,16 @@ static int ioctl_fsthaw(struct file *fil
 	return thaw_super(sb);
 }
 
+static int ioctl_fs_isfrozen(struct file *filp)
+{
+	struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	return isfrozen_super(sb);
+}
+
 /*
  * When you add any new common ioctls to the switches above and below
  * please update compat_sys_ioctl() too.
@@ -585,6 +595,12 @@ int do_vfs_ioctl(struct file *filp, unsi
 		error = ioctl_fsthaw(filp);
 		break;
 
+	case FIISFROZEN:
+		error = ioctl_fs_isfrozen(filp);
+		if (error >= 0)
+			return put_user(error, (int __user *)arg);
+		break;
+
 	case FS_IOC_FIEMAP:
 		return ioctl_fiemap(filp, arg);
 
diff -urNp vfs-orig/fs/super.c vfs/fs/super.c
--- vfs-orig/fs/super.c	2012-07-12 17:24:40.096620156 +0900
+++ vfs/fs/super.c	2012-07-12 17:25:37.600627115 +0900
@@ -1336,3 +1336,8 @@ void emergency_thaw_all(void)
 		schedule_work(work);
 	}
 }
+
+int isfrozen_super(struct super_block *sb)
+{
+	return sb->s_frozen > SB_UNFROZEN ? 1 : 0;
+}
diff -urNp vfs-orig/include/linux/fs.h vfs/include/linux/fs.h
--- vfs-orig/include/linux/fs.h	2012-07-12 17:24:40.116622271 +0900
+++ vfs/include/linux/fs.h	2012-07-12 17:25:37.600627115 +0900
@@ -340,6 +340,7 @@ struct inodes_stat_t {
 #define FIFREEZE	_IOWR('X', 119, int)	/* Freeze */
 #define FITHAW		_IOWR('X', 120, int)	/* Thaw */
 #define FITRIM		_IOWR('X', 121, struct fstrim_range)	/* Trim */
+#define FIISFROZEN	_IOR('X', 122, int)	/* get sb freeze state */
 
 #define	FS_IOC_GETFLAGS			_IOR('f', 1, long)
 #define	FS_IOC_SETFLAGS			_IOW('f', 2, long)
@@ -1947,6 +1948,7 @@ extern int fd_statfs(int, struct kstatfs
 extern int vfs_ustat(dev_t, struct kstatfs *);
 extern int freeze_super(struct super_block *super);
 extern int thaw_super(struct super_block *super);
+extern int isfrozen_super(struct super_block *sb);
 extern bool our_mnt(struct vfsmount *mnt);
 
 extern int current_umask(void);


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