udf: Convert in-ICB files to use udf_direct_IO()

Switching address_space_operations while a file is used is difficult to
do in a race-free way. To be able to use single address_space_operations
in UDF, make in-ICB files use udf_direct_IO().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/file.c

@@ -76,12 +76,6 @@ static int udf_adinicb_write_begin(struct file *file,
 	return 0;
 }
 
-static ssize_t udf_adinicb_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
-{
-	/* Fallback to buffered I/O. */
-	return 0;
-}
-
 static int udf_adinicb_write_end(struct file *file, struct address_space *mapping,
 				 loff_t pos, unsigned len, unsigned copied,
 				 struct page *page, void *fsdata)
@@ -103,7 +97,7 @@ const struct address_space_operations udf_adinicb_aops = {
 	.writepages	= udf_writepages,
 	.write_begin	= udf_adinicb_write_begin,
 	.write_end	= udf_adinicb_write_end,
-	.direct_IO	= udf_adinicb_direct_IO,
+	.direct_IO	= udf_direct_IO,
 };
 
 static vm_fault_t udf_page_mkwrite(struct vm_fault *vmf)

fs/udf/inode.c

@@ -243,14 +243,17 @@ static int udf_write_begin(struct file *file, struct address_space *mapping,
 	return ret;
 }
 
-static ssize_t udf_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+ssize_t udf_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
 	struct address_space *mapping = file->f_mapping;
 	struct inode *inode = mapping->host;
 	size_t count = iov_iter_count(iter);
 	ssize_t ret;
 
+	/* Fallback to buffered IO for in-ICB files */
+	if (UDF_I(inode)->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB)
+		return 0;
 	ret = blockdev_direct_IO(iocb, inode, iter, udf_get_block);
 	if (unlikely(ret < 0 && iov_iter_rw(iter) == WRITE))
 		udf_write_failed(mapping, iocb->ki_pos + count);

fs/udf/udfdecl.h

@@ -161,6 +161,7 @@ extern void udf_evict_inode(struct inode *);
 extern int udf_write_inode(struct inode *, struct writeback_control *wbc);
 int udf_read_folio(struct file *file, struct folio *folio);
 int udf_writepages(struct address_space *mapping, struct writeback_control *wbc);
+ssize_t udf_direct_IO(struct kiocb *iocb, struct iov_iter *iter);
 extern int8_t inode_bmap(struct inode *, sector_t, struct extent_position *,
 			 struct kernel_lb_addr *, uint32_t *, sector_t *);
 int udf_get_block(struct inode *, sector_t, struct buffer_head *, int);