jbd2: Fix oops in jbd2_journal_file_inode()

Commit 0713ed0c added
jbd2_journal_file_inode() call into ext4_block_zero_page_range().
However that function gets called from truncate path and thus inode
needn't have jinode attached - that happens in ext4_file_open() but
the file needn't be ever open since mount. Calling
jbd2_journal_file_inode() without jinode attached results in the oops.

We fix the problem by attaching jinode to inode also in ext4_truncate()
and ext4_punch_hole() when we are going to zero out partial blocks.
Reported-by: majianpeng <majianpeng@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -2086,6 +2086,7 @@ extern int  ext4_sync_inode(handle_t *, struct inode *);
 extern void ext4_dirty_inode(struct inode *, int);
 extern int ext4_change_inode_journal_flag(struct inode *, int);
 extern int ext4_get_inode_loc(struct inode *, struct ext4_iloc *);
+extern int ext4_inode_attach_jinode(struct inode *inode);
 extern int ext4_can_truncate(struct inode *inode);
 extern void ext4_truncate(struct inode *);
 extern int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length);

fs/ext4/file.c

@@ -219,7 +219,6 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 {
 	struct super_block *sb = inode->i_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	struct ext4_inode_info *ei = EXT4_I(inode);
 	struct vfsmount *mnt = filp->f_path.mnt;
 	struct path path;
 	char buf[64], *cp;
@@ -259,22 +258,10 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 	 * Set up the jbd2_inode if we are opening the inode for
 	 * writing and the journal is present
 	 */
-	if (sbi->s_journal && !ei->jinode && (filp->f_mode & FMODE_WRITE)) {
-		struct jbd2_inode *jinode = jbd2_alloc_inode(GFP_KERNEL);
-
-		spin_lock(&inode->i_lock);
-		if (!ei->jinode) {
-			if (!jinode) {
-				spin_unlock(&inode->i_lock);
-				return -ENOMEM;
-			}
-			ei->jinode = jinode;
-			jbd2_journal_init_jbd_inode(ei->jinode, inode);
-			jinode = NULL;
-		}
-		spin_unlock(&inode->i_lock);
-		if (unlikely(jinode != NULL))
-			jbd2_free_inode(jinode);
+	if (filp->f_mode & FMODE_WRITE) {
+		int ret = ext4_inode_attach_jinode(inode);
+		if (ret < 0)
+			return ret;
 	}
 	return dquot_file_open(inode, filp);
 }

fs/ext4/inode.c

@@ -3533,6 +3533,18 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 		   offset;
 	}
 
+	if (offset & (sb->s_blocksize - 1) ||
+	    (offset + length) & (sb->s_blocksize - 1)) {
+		/*
+		 * Attach jinode to inode for jbd2 if we do any zeroing of
+		 * partial block
+		 */
+		ret = ext4_inode_attach_jinode(inode);
+		if (ret < 0)
+			goto out_mutex;
+
+	}
+
 	first_block_offset = round_up(offset, sb->s_blocksize);
 	last_block_offset = round_down((offset + length), sb->s_blocksize) - 1;
 
@@ -3601,6 +3613,31 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)
 	return ret;
 }
 
+int ext4_inode_attach_jinode(struct inode *inode)
+{
+	struct ext4_inode_info *ei = EXT4_I(inode);
+	struct jbd2_inode *jinode;
+
+	if (ei->jinode || !EXT4_SB(inode->i_sb)->s_journal)
+		return 0;
+
+	jinode = jbd2_alloc_inode(GFP_KERNEL);
+	spin_lock(&inode->i_lock);
+	if (!ei->jinode) {
+		if (!jinode) {
+			spin_unlock(&inode->i_lock);
+			return -ENOMEM;
+		}
+		ei->jinode = jinode;
+		jbd2_journal_init_jbd_inode(ei->jinode, inode);
+		jinode = NULL;
+	}
+	spin_unlock(&inode->i_lock);
+	if (unlikely(jinode != NULL))
+		jbd2_free_inode(jinode);
+	return 0;
+}
+
 /*
  * ext4_truncate()
  *
@@ -3661,6 +3698,12 @@ void ext4_truncate(struct inode *inode)
 			return;
 	}
 
+	/* If we zero-out tail of the page, we have to create jinode for jbd2 */
+	if (inode->i_size & (inode->i_sb->s_blocksize - 1)) {
+		if (ext4_inode_attach_jinode(inode) < 0)
+			return;
+	}
+
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
 		credits = ext4_writepage_trans_blocks(inode);
 	else