On 07/30/2014 07:03 PM, Boaz Harrosh wrote:
<>

quoted

+long bdev_direct_access(struct block_device *bdev, sector_t sector,
+			void **addr, unsigned long *pfn, long size)
+{
+	const struct block_device_operations *ops = bdev->bd_disk->fops;
+	if (!ops->direct_access)
+		return -EOPNOTSUPP;

You need to check alignment on PAGE_SIZE since this API requires it, do
to pfn defined to a page_number.

(Unless you want to define another output-param like page_offset.
 but this exercise can be left to the caller)

You also need to check against the partition boundary. so something like:

+ 	if (sector & (PAGE_SECTORS-1))
+ 		return -EINVAL;
+	if (unlikely(sector + size > part_nr_sects_read(bdev->bd_part)))

Off course I was wrong here size is in bytes not in sectors. Which points
out that maybe this API needs to be in sectors.

[Actually it needs to be in pages both size and offset, because of return of
pfn, but its your call.]

Anyway my code above needs to be fixed with
	(size + 512 -1) / 512

Thanks
Boaz

+ 		return -ERANGE;

Then perhaps you can remove that check from drivers

quoted

+	return ops->direct_access(bdev, sector + get_start_sect(bdev), addr,
+					pfn, size);
+}
+EXPORT_SYMBOL_GPL(bdev_direct_access);

<>


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