linux-ext4 - [PATCH] ext4: add inode to ordered data list when extending file without block allocation

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Date:   Thu, 4 Apr 2019 17:29:52 +0800
From:   "zhangyi (F)" <yi.zhang@...wei.com>
To:     <linux-ext4@...r.kernel.org>
CC:     <tytso@....edu>, <jack@...e.cz>, <adilger.kernel@...ger.ca>,
        <yi.zhang@...wei.com>, <miaoxie@...wei.com>
Subject: [PATCH] ext4: add inode to ordered data list when extending file without block allocation

Currently we capture a NULL data exposure problem after a crash or
poweroff when append writing a file in the data=ordered mode. The
problem is that we were not add inode to the transaction's order data
list when updating i_disksize without new block allocation no matter
the delay allocated block feature is enabled or not.

write                           jbd2                    writeback
append write in allocated block
mark buffer dirty
update i_disksize
mark inode dirty
                          commit transaction
                          write inode
                          (data exposure after a crash)
                                                    write dirty buffer

It's fine in the case of new block allocation because we do this job in
ext4_map_blocks(). To fix this problem, this patch add inode to current
transaction's order data list after new data is copied and needing
update i_disksize in the case of no block allocation.

Fixes: 06bd3c36a733ac ("ext4: fix data exposure after a crash")
Fixes: f3b59291a69d0b ("ext4: remove calls to ext4_jbd2_file_inode() from delalloc write path")
Signed-off-by: zhangyi (F) <yi.zhang@...wei.com>
---
 fs/ext4/inode.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b32a57b..5cfa066 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1419,6 +1419,16 @@ static int ext4_write_end(struct file *file,
 	if (i_size_changed || inline_data)
 		ext4_mark_inode_dirty(handle, inode);
 
+	/*
+	 * Updating i_disksize when extending file without block
+	 * allocation, the newly written data where should be visible
+	 * after transaction commit must be on transaction's ordered
+	 * data list.
+	 */
+	if (copied && (i_size_changed & 0x2) &&
+	    ext4_should_order_data(inode))
+		ext4_jbd2_inode_add_write(handle, inode);
+
 	if (pos + len > inode->i_size && ext4_can_truncate(inode))
 		/* if we have allocated more blocks and copied
 		 * less. We will have blocks allocated outside
@@ -3185,6 +3195,15 @@ static int ext4_da_write_end(struct file *file,
 			 * bu greater than i_disksize.(hint delalloc)
 			 */
 			ext4_mark_inode_dirty(handle, inode);
+
+			/*
+			 * Updating i_disksize when extending file without
+			 * block allocation, the newly written data where
+			 * should be visible after transaction commit must
+			 * be on transaction's ordered data list.
+			 */
+			if (ext4_should_order_data(inode))
+				ext4_jbd2_inode_add_write(handle, inode);
 		}
 	}
 
-- 
2.7.4