ocfs2: Handle quota file corruption more gracefully

ocfs2_read_virt_blocks() does BUG when we try to read a block from a file
beyond its end. Since this can happen due to filesystem corruption, it
is not really an appropriate answer. Make ocfs2_read_quota_block() check
the condition and handle it by calling ocfs2_error() and returning EIO.

[ Modified to print ip_blkno in the error - Joel ]
Reported-by: Tristan Ye <tristan.ye@oracle.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

fs/ocfs2/quota_global.c

@@ -23,6 +23,7 @@
 #include "sysfile.h"
 #include "dlmglue.h"
 #include "uptodate.h"
+#include "super.h"
 #include "quota.h"
 
 static struct workqueue_struct *ocfs2_quota_wq = NULL;
@@ -114,6 +115,15 @@ int ocfs2_read_quota_block(struct inode *inode, u64 v_block,
 	int rc = 0;
 	struct buffer_head *tmp = *bh;
 
+	if (i_size_read(inode) >> inode->i_sb->s_blocksize_bits <= v_block) {
+		ocfs2_error(inode->i_sb,
+			    "Quota file %llu is probably corrupted! Requested "
+			    "to read block %Lu but file has size only %Lu\n",
+			    (unsigned long long)OCFS2_I(inode)->ip_blkno,
+			    (unsigned long long)v_block,
+			    (unsigned long long)i_size_read(inode));
+		return -EIO;
+	}
 	rc = ocfs2_read_virt_blocks(inode, v_block, 1, &tmp, 0,
 				    ocfs2_validate_quota_block);
 	if (rc)