dlmfs: clean up dlmfs_file_{read,write}() a bit

The damn file is constant-sized - 64 bytes.  IOW,
	* i_size_read() is pointless
	* so's dynamic allocation
	* so's the 'size' argument of user_dlm_read_lvb()
	* ... and so's open-coding simple_read_from_buffer(), while we are at it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ocfs2/dlmfs/dlmfs.c

@@ -221,47 +221,17 @@ static __poll_t dlmfs_file_poll(struct file *file, poll_table *wait)
 	return event;
 }
 
-static ssize_t dlmfs_file_read(struct file *filp,
+static ssize_t dlmfs_file_read(struct file *file,
 			       char __user *buf,
 			       size_t count,
 			       loff_t *ppos)
 {
-	int bytes_left;
-	ssize_t got;
-	char *lvb_buf;
-	struct inode *inode = file_inode(filp);
-
-	mlog(0, "inode %lu, count = %zu, *ppos = %llu\n",
-		inode->i_ino, count, *ppos);
+	char lvb[DLM_LVB_LEN];
 
-	if (*ppos >= i_size_read(inode))
+	if (!user_dlm_read_lvb(file_inode(file), lvb))
 		return 0;
 
-	/* don't read past the lvb */
-	if (count > i_size_read(inode) - *ppos)
-		count = i_size_read(inode) - *ppos;
-
-	if (!count)
-		return 0;
-
-	lvb_buf = kmalloc(count, GFP_NOFS);
-	if (!lvb_buf)
-		return -ENOMEM;
-
-	got = user_dlm_read_lvb(inode, lvb_buf, count);
-	if (got) {
-		BUG_ON(got != count);
-		bytes_left = copy_to_user(buf, lvb_buf, count);
-		count -= bytes_left;
-	} else
-		count = 0;
-
-	kfree(lvb_buf);
-
-	*ppos = *ppos + count;
-
-	mlog(0, "read %zu bytes\n", count);
-	return count;
+	return simple_read_from_buffer(buf, count, ppos, lvb, sizeof(lvb));
 }
 
 static ssize_t dlmfs_file_write(struct file *filp,
@@ -269,34 +239,28 @@ static ssize_t dlmfs_file_write(struct file *filp,
 				size_t count,
 				loff_t *ppos)
 {
+	char lvb_buf[DLM_LVB_LEN];
 	int bytes_left;
-	char *lvb_buf;
 	struct inode *inode = file_inode(filp);
 
 	mlog(0, "inode %lu, count = %zu, *ppos = %llu\n",
 		inode->i_ino, count, *ppos);
 
-	if (*ppos >= i_size_read(inode))
+	if (*ppos >= DLM_LVB_LEN)
 		return -ENOSPC;
 
 	/* don't write past the lvb */
-	if (count > i_size_read(inode) - *ppos)
-		count = i_size_read(inode) - *ppos;
+	if (count > DLM_LVB_LEN - *ppos)
+		count = DLM_LVB_LEN - *ppos;
 
 	if (!count)
 		return 0;
 
-	lvb_buf = kmalloc(count, GFP_NOFS);
-	if (!lvb_buf)
-		return -ENOMEM;
-
 	bytes_left = copy_from_user(lvb_buf, buf, count);
 	count -= bytes_left;
 	if (count)
 		user_dlm_write_lvb(inode, lvb_buf, count);
 
-	kfree(lvb_buf);
-
 	*ppos = *ppos + count;
 	mlog(0, "wrote %zu bytes\n", count);
 	return count;

fs/ocfs2/dlmfs/userdlm.c

@@ -547,24 +547,20 @@ void user_dlm_write_lvb(struct inode *inode,
 	spin_unlock(&lockres->l_lock);
 }
 
-ssize_t user_dlm_read_lvb(struct inode *inode,
-			  char *val,
-			  unsigned int len)
+bool user_dlm_read_lvb(struct inode *inode, char *val)
 {
 	struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
 	char *lvb;
-	ssize_t ret = len;
-
-	BUG_ON(len > DLM_LVB_LEN);
+	bool ret = true;
 
 	spin_lock(&lockres->l_lock);
 
 	BUG_ON(lockres->l_level < DLM_LOCK_PR);
 	if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)) {
 		lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
-		memcpy(val, lvb, len);
+		memcpy(val, lvb, DLM_LVB_LEN);
 	} else
-		ret = 0;
+		ret = false;
 
 	spin_unlock(&lockres->l_lock);
 	return ret;

fs/ocfs2/dlmfs/userdlm.h

@@ -66,9 +66,7 @@ void user_dlm_cluster_unlock(struct user_lock_res *lockres,
 void user_dlm_write_lvb(struct inode *inode,
 			const char *val,
 			unsigned int len);
-ssize_t user_dlm_read_lvb(struct inode *inode,
-			  char *val,
-			  unsigned int len);
+bool user_dlm_read_lvb(struct inode *inode, char *val);
 struct ocfs2_cluster_connection *user_dlm_register(const struct qstr *name);
 void user_dlm_unregister(struct ocfs2_cluster_connection *conn);
 void user_dlm_set_locking_protocol(void);