[PATCH 4/9] fibmap: Use bmap instead of ->bmap method in ioctl_fibmap

[Carlos Maiolino <cmaiolino@xxxxxxxxxx>]

Now we have the possibility of proper error return in bmap, use bmap()
function in ioctl_fibmap() instead of calling ->bmap method directly.

Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
---
Changelog:

	V6:
		- Add a dummy bmap() definition so build does not break if
		  CONFIG_BLOCK is not set
			Reported-by: kbuild test robot <lkp@xxxxxxxxx>
	V4:
		- Ensure ioctl_fibmap() returns 0 in case of error returned from
		  bmap(). Otherwise we'll be changing the user interface (which
		  returns 0 in case of error)
	V3:
		- Rename usr_blk to ur_block
	V2:
		- Use a local sector_t variable to asign the block number
		  instead of using direct casting.

 fs/ioctl.c         | 29 +++++++++++++++++++----------
 include/linux/fs.h |  7 +++++++
 2 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/fs/ioctl.c b/fs/ioctl.c
index fef3a6bf7c78..6b589c873bc2 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -53,19 +53,28 @@ EXPORT_SYMBOL(vfs_ioctl);
 
 static int ioctl_fibmap(struct file *filp, int __user *p)
 {
-	struct address_space *mapping = filp->f_mapping;
-	int res, block;
+	struct inode *inode = file_inode(filp);
+	int error, ur_block;
+	sector_t block;
 
-	/* do we support this mess? */
-	if (!mapping->a_ops->bmap)
-		return -EINVAL;
 	if (!capable(CAP_SYS_RAWIO))
 		return -EPERM;
-	res = get_user(block, p);
-	if (res)
-		return res;
-	res = mapping->a_ops->bmap(mapping, block);
-	return put_user(res, p);
+
+	error = get_user(ur_block, p);
+	if (error)
+		return error;
+
+	block = ur_block;
+	error = bmap(inode, &block);
+
+	if (error)
+		ur_block = 0;
+	else
+		ur_block = block;
+
+	error = put_user(ur_block, p);
+
+	return error;
 }
 
 /**
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d787ceefc937..f1fbd8298ca4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2859,9 +2859,16 @@ static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count)
 
 extern void emergency_sync(void);
 extern void emergency_remount(void);
+
 #ifdef CONFIG_BLOCK
 extern int bmap(struct inode *, sector_t *);
+#else
+static inline int bmap(struct inode *,  sector_t *)
+{
+	return -EINVAL;
+}
 #endif
+
 extern int notify_change(struct dentry *, struct iattr *, struct inode **);
 extern int inode_permission(struct inode *, int);
 extern int generic_permission(struct inode *, int);
-- 
2.20.1