erofs: clarify direct I/O support

Currently, only filesystems backed by block devices support direct I/O.

Also remove the unnecessary strict checks that can be supported with iomap.

Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20241115074625.2520728-1-hsiangkao@linux.alibaba.com

Author: hsiangkao

fs/erofs/data.c

@@ -405,22 +405,9 @@ static ssize_t erofs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	if (IS_DAX(inode))
 		return dax_iomap_rw(iocb, to, &erofs_iomap_ops);
 #endif
-	if (iocb->ki_flags & IOCB_DIRECT) {
-		struct block_device *bdev = inode->i_sb->s_bdev;
-		unsigned int blksize_mask;
-
-		if (bdev)
-			blksize_mask = bdev_logical_block_size(bdev) - 1;
-		else
-			blksize_mask = i_blocksize(inode) - 1;
-
-		if ((iocb->ki_pos | iov_iter_count(to) |
-		     iov_iter_alignment(to)) & blksize_mask)
-			return -EINVAL;
-
+	if ((iocb->ki_flags & IOCB_DIRECT) && inode->i_sb->s_bdev)
 		return iomap_dio_rw(iocb, to, &erofs_iomap_ops,
 				    NULL, 0, NULL, 0);
-	}
 	return filemap_read(iocb, to, 0);
 }
 

fs/erofs/inode.c

@@ -318,6 +318,7 @@ int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
 		  unsigned int query_flags)
 {
 	struct inode *const inode = d_inode(path->dentry);
+	struct block_device *bdev = inode->i_sb->s_bdev;
 	bool compressed =
 		erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout);
 
@@ -330,15 +331,14 @@ int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
 	/*
 	 * Return the DIO alignment restrictions if requested.
 	 *
-	 * In EROFS, STATX_DIOALIGN is not supported in ondemand mode and
-	 * compressed files, so in these cases we report no DIO support.
+	 * In EROFS, STATX_DIOALIGN is only supported in bdev-based mode
+	 * and uncompressed inodes, otherwise we report no DIO support.
 	 */
 	if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) {
 		stat->result_mask |= STATX_DIOALIGN;
-		if (!erofs_is_fscache_mode(inode->i_sb) && !compressed) {
-			stat->dio_mem_align =
-				bdev_logical_block_size(inode->i_sb->s_bdev);
-			stat->dio_offset_align = stat->dio_mem_align;
+		if (bdev && !compressed) {
+			stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
+			stat->dio_offset_align = bdev_logical_block_size(bdev);
 		}
 	}
 	generic_fillattr(idmap, request_mask, inode, stat);