ext4: dax: keep orphan list before truncate overflow allocated blocks

Any extending write for ext4 requires the inode to be placed on the
orphan list before the actual write. In addition, the inode can be
actually removed from the orphan list only after all writes are
completed. Otherwise we'd leave allocated blocks beyond i_disksize if we
could not copy all the data into allocated block and e2fsck would
complain.

Currently, direct IO and buffered IO comply with this logic(buffered
IO will truncate all overflow allocated blocks that has not been
written successfully, and direct IO will truncate all allocated blocks
when error occurs). However, dax write break this since dax write will
remove the inode from the orphan list by calling
ext4_handle_inode_extension unconditionally during extending write.

We add a argument to help determine does we do a fully write, and for
the case not fully write, we leave the inode on the orphan list, and the
latter ext4_inode_extension_cleanup will help us truncate the overflow
allocated blocks, and then remove the inode from the orphan list.

Signed-off-by: yangerkun <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: yangerkun

fs/ext4/file.c

@@ -306,7 +306,7 @@ static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
 }
 
 static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
-					   ssize_t count)
+					   ssize_t written, ssize_t count)
 {
 	handle_t *handle;
 
@@ -315,19 +315,19 @@ static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 
-	if (ext4_update_inode_size(inode, offset + count)) {
+	if (ext4_update_inode_size(inode, offset + written)) {
 		int ret = ext4_mark_inode_dirty(handle, inode);
 		if (unlikely(ret)) {
 			ext4_journal_stop(handle);
 			return ret;
 		}
 	}
 
-	if (inode->i_nlink)
+	if ((written == count) && inode->i_nlink)
 		ext4_orphan_del(handle, inode);
 	ext4_journal_stop(handle);
 
-	return count;
+	return written;
 }
 
 /*
@@ -393,7 +393,7 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
 	if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize) &&
 	    pos + size <= i_size_read(inode))
 		return size;
-	return ext4_handle_inode_extension(inode, pos, size);
+	return ext4_handle_inode_extension(inode, pos, size, size);
 }
 
 static const struct iomap_dio_ops ext4_dio_write_ops = {
@@ -669,7 +669,7 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
 
 	if (extend) {
-		ret = ext4_handle_inode_extension(inode, offset, ret);
+		ret = ext4_handle_inode_extension(inode, offset, ret, count);
 		ext4_inode_extension_cleanup(inode, ret < (ssize_t)count);
 	}
 out: