block: Change direct_access calling convention
In order to support accesses to larger chunks of memory, pass in a
'size' parameter (counted in bytes), and return the amount available at
that address.
Add a new helper function, bdev_direct_access(), to handle common
functionality including partition handling, checking the length requested
is positive, checking for the sector being page-aligned, and checking
the length of the request does not pass the end of the partition.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index b48c41b..f314c2c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -429,6 +429,46 @@
}
EXPORT_SYMBOL_GPL(bdev_write_page);
+/**
+ * bdev_direct_access() - Get the address for directly-accessibly memory
+ * @bdev: The device containing the memory
+ * @sector: The offset within the device
+ * @addr: Where to put the address of the memory
+ * @pfn: The Page Frame Number for the memory
+ * @size: The number of bytes requested
+ *
+ * If a block device is made up of directly addressable memory, this function
+ * will tell the caller the PFN and the address of the memory. The address
+ * may be directly dereferenced within the kernel without the need to call
+ * ioremap(), kmap() or similar. The PFN is suitable for inserting into
+ * page tables.
+ *
+ * Return: negative errno if an error occurs, otherwise the number of bytes
+ * accessible at this address.
+ */
+long bdev_direct_access(struct block_device *bdev, sector_t sector,
+ void **addr, unsigned long *pfn, long size)
+{
+ long avail;
+ const struct block_device_operations *ops = bdev->bd_disk->fops;
+
+ if (size < 0)
+ return size;
+ if (!ops->direct_access)
+ return -EOPNOTSUPP;
+ if ((sector + DIV_ROUND_UP(size, 512)) >
+ part_nr_sects_read(bdev->bd_part))
+ return -ERANGE;
+ sector += get_start_sect(bdev);
+ if (sector % (PAGE_SIZE / 512))
+ return -EINVAL;
+ avail = ops->direct_access(bdev, sector, addr, pfn, size);
+ if (!avail)
+ return -ERANGE;
+ return min(avail, size);
+}
+EXPORT_SYMBOL_GPL(bdev_direct_access);
+
/*
* pseudo-fs
*/