[PATCH v2 33/35] fs: introduce a get_qsize() to file_operations

[Dongsheng Yang]

get_qsize() is used to allow inode to decide how much of the quota size
in itself. If file system implements the own get_qsize(), ioctl of
FIOQSIZe will call it to get quota size. If not implemented, get the
quota size in a generic way.

Signed-off-by: Dongsheng Yang <yangds.fnst at cn.fujitsu.com>
---
 fs/ioctl.c         | 31 ++++++++++++++++++++++++-------
 include/linux/fs.h |  1 +
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index 5d01d26..2c567db 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -545,6 +545,29 @@ static int ioctl_fsthaw(struct file *filp)
 	return thaw_super(sb);
 }
 
+static int ioctl_fioqsize(struct file *filp, int __user *argp)
+{
+	struct inode *inode = file_inode(filp);
+	loff_t res = 0;
+	int error = 0;
+
+	if (filp->f_op->get_qsize) {
+		res = filp->f_op->get_qsize(inode);
+		error = copy_to_user(argp, &res, sizeof(res)) ?
+				-EFAULT : 0;
+	} else {
+                if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
+                    S_ISLNK(inode->i_mode)) {
+                        res = inode_get_bytes(inode);
+                        error = copy_to_user(argp, &res, sizeof(res)) ?
+                                        -EFAULT : 0;
+                } else {
+                        error = -ENOTTY;
+		}
+	}
+	return error;
+}
+
 /*
  * When you add any new common ioctls to the switches above and below
  * please update compat_sys_ioctl() too.
@@ -577,13 +600,7 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
 		break;
 
 	case FIOQSIZE:
-		if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode) ||
-		    S_ISLNK(inode->i_mode)) {
-			loff_t res = inode_get_bytes(inode);
-			error = copy_to_user(argp, &res, sizeof(res)) ?
-					-EFAULT : 0;
-		} else
-			error = -ENOTTY;
+		error = ioctl_fioqsize(filp, argp);
 		break;
 
 	case FIFREEZE:
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 860b235..70695d3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1601,6 +1601,7 @@ struct file_operations {
 	long (*fallocate)(struct file *file, int mode, loff_t offset,
 			  loff_t len);
 	void (*show_fdinfo)(struct seq_file *m, struct file *f);
+	ssize_t (*get_qsize) (struct inode *);
 #ifndef CONFIG_MMU
 	unsigned (*mmap_capabilities)(struct file *);
 #endif
-- 
1.8.4.2