ext4: move inode extension check out from ext4_iomap_alloc()

Lift the inode extension/orphan list handling code out from
ext4_iomap_alloc() and apply it within the ext4_dax_write_iter().
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Link: https://lore.kernel.org/r/fd5c84db25d5d0da87d97ed4c36fd844f57da759.1572949325.git.mbobrowski@mbobrowski.orgSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/file.c

@@ -323,6 +323,8 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t ret;
 	size_t count;
 	loff_t offset;
+	handle_t *handle;
+	bool extend = false;
 	struct inode *inode = file_inode(iocb->ki_filp);
 
 	if (!inode_trylock(inode)) {
@@ -342,7 +344,27 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 	offset = iocb->ki_pos;
 	count = iov_iter_count(from);
+
+	if (offset + count > EXT4_I(inode)->i_disksize) {
+		handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
+		if (IS_ERR(handle)) {
+			ret = PTR_ERR(handle);
+			goto out;
+		}
+
+		ret = ext4_orphan_add(handle, inode);
+		if (ret) {
+			ext4_journal_stop(handle);
+			goto out;
+		}
+
+		extend = true;
+		ext4_journal_stop(handle);
+	}
+
 	ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);
+
+	if (extend)
 		ret = ext4_handle_inode_extension(inode, offset, ret, count);
 out:
 	inode_unlock(inode);

fs/ext4/inode.c

@@ -3494,7 +3494,6 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
 			    unsigned int flags)
 {
 	handle_t *handle;
-	u8 blkbits = inode->i_blkbits;
 	int ret, dio_credits, retries = 0;
 
 	/*
@@ -3517,28 +3516,7 @@ static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
 		return PTR_ERR(handle);
 
 	ret = ext4_map_blocks(handle, inode, map, EXT4_GET_BLOCKS_CREATE_ZERO);
-	if (ret < 0)
-		goto journal_stop;
-
-	/*
-	 * If we've allocated blocks beyond EOF, we need to ensure that they're
-	 * truncated if we crash before updating the inode size metadata within
-	 * ext4_iomap_end(). For faults, we don't need to do that (and cannot
-	 * due to orphan list operations needing an inode_lock()). If we happen
-	 * to instantiate blocks beyond EOF, it is because we race with a
-	 * truncate operation, which already has added the inode onto the
-	 * orphan list.
-	 */
-	if (!(flags & IOMAP_FAULT) && map->m_lblk + map->m_len >
-	    (i_size_read(inode) + (1 << blkbits) - 1) >> blkbits) {
-		int err;
-
-		err = ext4_orphan_add(handle, inode);
-		if (err < 0)
-			ret = err;
-	}
 
-journal_stop:
 	ext4_journal_stop(handle);
 	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
 		goto retry;