[PATCH 7/8] fsfreeze: add block device ioctl to check freeze state

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The BLKISFROZEN ioctl can be use by HA and monitoring software to check
the freeze state of the filesystem sitting on top of a block device.
This will not work for filesystems that can handle multiple devices,
i.e. btrfs.

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/block/compat_ioctl.c vfs/block/compat_ioctl.c
--- vfs-orig/block/compat_ioctl.c	2012-07-04 18:57:54.000000000 +0900
+++ vfs/block/compat_ioctl.c	2012-07-12 17:29:01.608639153 +0900
@@ -746,6 +746,13 @@ long compat_blkdev_ioctl(struct file *fi
 	case BLKTRACETEARDOWN: /* compatible */
 		ret = blk_trace_ioctl(bdev, cmd, compat_ptr(arg));
 		return ret;
+	case BLKISFROZEN:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		ret = isfrozen_bdev(bdev);
+		if (ret >= 0)
+			return compat_put_int(arg, ret);
+		return ret;
 	default:
 		if (disk->fops->compat_ioctl)
 			ret = disk->fops->compat_ioctl(bdev, mode, cmd, arg);
diff -urNp vfs-orig/block/ioctl.c vfs/block/ioctl.c
--- vfs-orig/block/ioctl.c	2012-07-04 18:57:54.000000000 +0900
+++ vfs/block/ioctl.c	2012-07-12 17:29:01.608639153 +0900
@@ -343,6 +343,13 @@ int blkdev_ioctl(struct block_device *bd
 	case BLKTRACETEARDOWN:
 		ret = blk_trace_ioctl(bdev, cmd, (char __user *) arg);
 		break;
+	case BLKISFROZEN:
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+		ret = isfrozen_bdev(bdev);
+		if (ret >= 0)
+			return put_int(arg, ret);
+		return ret;
 	default:
 		ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
 	}
diff -urNp vfs-orig/fs/block_dev.c vfs/fs/block_dev.c
--- vfs-orig/fs/block_dev.c	2012-07-12 17:11:42.480606884 +0900
+++ vfs/fs/block_dev.c	2012-07-12 17:29:01.616637572 +0900
@@ -329,6 +329,11 @@ out:
 }
 EXPORT_SYMBOL(thaw_bdev);
 
+int isfrozen_bdev(struct block_device *bdev)
+{
+	return bdev->bd_fsfreeze_count > 0;
+}
+
 static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
 {
 	return block_write_full_page(page, blkdev_get_block, wbc);
diff -urNp vfs-orig/include/linux/fs.h vfs/include/linux/fs.h
--- vfs-orig/include/linux/fs.h	2012-07-12 17:28:15.556654469 +0900
+++ vfs/include/linux/fs.h	2012-07-12 17:29:01.616637572 +0900
@@ -333,6 +333,7 @@ struct inodes_stat_t {
 #define BLKDISCARDZEROES _IO(0x12,124)
 #define BLKSECDISCARD _IO(0x12,125)
 #define BLKROTATIONAL _IO(0x12,126)
+#define BLKISFROZEN _IOR(0x12,127, int)	/* get file system freeze state */
 
 #define BMAP_IOCTL 1		/* obsolete - kept for compatibility */
 #define FIBMAP	   _IO(0x00,1)	/* bmap access */
@@ -2112,6 +2113,7 @@ extern void kill_bdev(struct block_devic
 extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
 extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
+extern int isfrozen_bdev(struct block_device *bdev);
 extern int fsync_bdev(struct block_device *);
 #else
 static inline void bd_forget(struct inode *inode) {}
@@ -2128,6 +2130,11 @@ static inline int thaw_bdev(struct block
 {
 	return 0;
 }
+
+static int isfrozen_bdev(struct block_device *bdev)
+{
+	return 0;
+}
 #endif
 extern int sync_filesystem(struct super_block *);
 extern const struct file_operations def_blk_fops;


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