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block: enable dax for raw block devices

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If an application wants exclusive access to all of the persistent memory
provided by an NVDIMM namespace it can use this raw-block-dax facility
to forgo establishing a filesystem.  This capability is targeted
primarily to hypervisors wanting to provision persistent memory for
guests.  It can be disabled / enabled dynamically via the new BLKDAXSET
ioctl.

Cc: Jeff Moyer <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Ross Zwisler <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
This commit is contained in:
Dan Williams 2015-11-30 10:20:29 -08:00
commit 5a023cdba5
4 changed files with 169 additions and 8 deletions
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61
block/ioctl.c
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@ -406,6 +406,62 @@ static inline int is_unrecognized_ioctl(int ret)
ret == -ENOIOCTLCMD;
}
#ifdef CONFIG_FS_DAX
bool blkdev_dax_capable(struct block_device *bdev)
{
struct gendisk *disk = bdev->bd_disk;
if (!disk->fops->direct_access)
return false;
/*
* If the partition is not aligned on a page boundary, we can't
* do dax I/O to it.
*/
if ((bdev->bd_part->start_sect % (PAGE_SIZE / 512))
|| (bdev->bd_part->nr_sects % (PAGE_SIZE / 512)))
return false;
return true;
}
static int blkdev_daxset(struct block_device *bdev, unsigned long argp)
{
unsigned long arg;
int rc = 0;
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
if (get_user(arg, (int __user *)(argp)))
return -EFAULT;
arg = !!arg;
if (arg == !!(bdev->bd_inode->i_flags & S_DAX))
return 0;
if (arg)
arg = S_DAX;
if (arg && !blkdev_dax_capable(bdev))
return -ENOTTY;
mutex_lock(&bdev->bd_inode->i_mutex);
if (bdev->bd_map_count == 0)
inode_set_flags(bdev->bd_inode, arg, S_DAX);
else
rc = -EBUSY;
mutex_unlock(&bdev->bd_inode->i_mutex);
return rc;
}
#else
static int blkdev_daxset(struct block_device *bdev, int arg)
{
if (arg)
return -ENOTTY;
return 0;
}
#endif
static int blkdev_flushbuf(struct block_device *bdev, fmode_t mode,
unsigned cmd, unsigned long arg)
{
@ -568,6 +624,11 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
case BLKTRACESETUP:
case BLKTRACETEARDOWN:
return blk_trace_ioctl(bdev, cmd, argp);
case BLKDAXSET:
return blkdev_daxset(bdev, arg);
case BLKDAXGET:
return put_int(arg, !!(bdev->bd_inode->i_flags & S_DAX));
break;
case IOC_PR_REGISTER:
return blkdev_pr_register(bdev, argp);
case IOC_PR_RESERVE: