Commit 5a023cdb authored by Dan Williams's avatar Dan Williams
Browse files

block: enable dax for raw block devices 



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 <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
Reviewed-by: default avatarJan Kara <jack@suse.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent 4ebb16ca

block/ioctl.c

+61 −0
Original line number Diff line number Diff line
@@ -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:

fs/block_dev.c

+95 −8
Original line number Diff line number Diff line
@@ -1235,8 +1235,11 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) 
				}

			}



			if (!ret)

			if (!ret) {

				bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);

				if (!blkdev_dax_capable(bdev))

					bdev->bd_inode->i_flags &= ~S_DAX;

			}



			/*

			 * If the device is invalidated, rescan partition
@@ -1250,6 +1253,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) 
				else if (ret == -ENOMEDIUM)

					invalidate_partitions(disk, bdev);

			}



			if (ret)

				goto out_clear;

		} else {
@@ -1270,12 +1274,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) 
				goto out_clear;

			}

			bd_set_size(bdev, (loff_t)bdev->bd_part->nr_sects << 9);

			/*

			 * 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)))

			if (!blkdev_dax_capable(bdev))

				bdev->bd_inode->i_flags &= ~S_DAX;

		}

	} else {
@@ -1713,13 +1712,101 @@ static const struct address_space_operations def_blk_aops = { 
	.is_dirty_writeback = buffer_check_dirty_writeback,

};



#ifdef CONFIG_FS_DAX

/*

 * In the raw block case we do not need to contend with truncation nor

 * unwritten file extents.  Without those concerns there is no need for

 * additional locking beyond the mmap_sem context that these routines

 * are already executing under.

 *

 * Note, there is no protection if the block device is dynamically

 * resized (partition grow/shrink) during a fault. A stable block device

 * size is already not enforced in the blkdev_direct_IO path.

 *

 * For DAX, it is the responsibility of the block device driver to

 * ensure the whole-disk device size is stable while requests are in

 * flight.

 *

 * Finally, unlike the filemap_page_mkwrite() case there is no

 * filesystem superblock to sync against freezing.  We still include a

 * pfn_mkwrite callback for dax drivers to receive write fault

 * notifications.

 */

static int blkdev_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf)

{

	return __dax_fault(vma, vmf, blkdev_get_block, NULL);

}



static int blkdev_dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,

		pmd_t *pmd, unsigned int flags)

{

	return __dax_pmd_fault(vma, addr, pmd, flags, blkdev_get_block, NULL);

}



static void blkdev_vm_open(struct vm_area_struct *vma)

{

	struct inode *bd_inode = bdev_file_inode(vma->vm_file);

	struct block_device *bdev = I_BDEV(bd_inode);



	mutex_lock(&bd_inode->i_mutex);

	bdev->bd_map_count++;

	mutex_unlock(&bd_inode->i_mutex);

}



static void blkdev_vm_close(struct vm_area_struct *vma)

{

	struct inode *bd_inode = bdev_file_inode(vma->vm_file);

	struct block_device *bdev = I_BDEV(bd_inode);



	mutex_lock(&bd_inode->i_mutex);

	bdev->bd_map_count--;

	mutex_unlock(&bd_inode->i_mutex);

}



static const struct vm_operations_struct blkdev_dax_vm_ops = {

	.open		= blkdev_vm_open,

	.close		= blkdev_vm_close,

	.fault		= blkdev_dax_fault,

	.pmd_fault	= blkdev_dax_pmd_fault,

	.pfn_mkwrite	= blkdev_dax_fault,

};



static const struct vm_operations_struct blkdev_default_vm_ops = {

	.open		= blkdev_vm_open,

	.close		= blkdev_vm_close,

	.fault		= filemap_fault,

	.map_pages	= filemap_map_pages,

};



static int blkdev_mmap(struct file *file, struct vm_area_struct *vma)

{

	struct inode *bd_inode = bdev_file_inode(file);

	struct block_device *bdev = I_BDEV(bd_inode);



	file_accessed(file);

	mutex_lock(&bd_inode->i_mutex);

	bdev->bd_map_count++;

	if (IS_DAX(bd_inode)) {

		vma->vm_ops = &blkdev_dax_vm_ops;

		vma->vm_flags |= VM_MIXEDMAP | VM_HUGEPAGE;

	} else {

		vma->vm_ops = &blkdev_default_vm_ops;

	}

	mutex_unlock(&bd_inode->i_mutex);



	return 0;

}

#else

#define blkdev_mmap generic_file_mmap

#endif



const struct file_operations def_blk_fops = {

	.open		= blkdev_open,

	.release	= blkdev_close,

	.llseek		= block_llseek,

	.read_iter	= blkdev_read_iter,

	.write_iter	= blkdev_write_iter,

	.mmap		= generic_file_mmap,

	.mmap		= blkdev_mmap,

	.fsync		= blkdev_fsync,

	.unlocked_ioctl	= block_ioctl,

#ifdef CONFIG_COMPAT

include/linux/fs.h

+11 −0
Original line number Diff line number Diff line
@@ -482,6 +482,9 @@ struct block_device { 
	int			bd_fsfreeze_count;

	/* Mutex for freeze */

	struct mutex		bd_fsfreeze_mutex;

#ifdef CONFIG_FS_DAX

	int			bd_map_count;

#endif

};



/*
@@ -2264,6 +2267,14 @@ extern struct super_block *freeze_bdev(struct block_device *); 
extern void emergency_thaw_all(void);

extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);

extern int fsync_bdev(struct block_device *);

#ifdef CONFIG_FS_DAX

extern bool blkdev_dax_capable(struct block_device *bdev);

#else

static inline bool blkdev_dax_capable(struct block_device *bdev)

{

	return false;

}

#endif



extern struct super_block *blockdev_superblock;

include/uapi/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -152,6 +152,8 @@ struct inodes_stat_t { 
#define BLKSECDISCARD _IO(0x12,125)

#define BLKROTATIONAL _IO(0x12,126)

#define BLKZEROOUT _IO(0x12,127)

#define BLKDAXSET _IO(0x12,128)

#define BLKDAXGET _IO(0x12,129)



#define BMAP_IOCTL 1		/* obsolete - kept for compatibility */

#define FIBMAP	   _IO(0x00,1)	/* bmap access */

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