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block: Change direct_access calling convention

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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>
This commit is contained in:
Matthew Wilcox 2015-01-07 18:05:34 +02:00 • committed by Jens Axboe
parent c761d96b07
commit dd22f551ac
7 changed files with 86 additions and 58 deletions
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40
fs/block_dev.c
View file

@ -429,6 +429,46 @@ int bdev_write_page(struct block_device *bdev, sector_t sector,
}
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
*/