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>

2 files changed, 17 insertions, 1 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 8605f8a74df9..bd7ac793be19 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -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 */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3e59182de9df..6022f44043f2 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.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;
 };
 
 /*