Commit 2d96afc8 authored by Toshi Kani's avatar Toshi Kani Committed by Vishal Verma
Browse files

block: Add bdev_dax_supported() for dax mount checks 



DAX imposes additional requirements to a device.  Add
bdev_dax_supported() which performs all the precondition checks
necessary for filesystem to mount the device with dax option.

Also add a new check to verify if a partition is aligned by 4KB.
When a partition is unaligned, any dax read/write access fails,
except for metadata update.

Signed-off-by: default avatarToshi Kani <toshi.kani@hpe.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@fb.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Boaz Harrosh <boaz@plexistor.com>
Signed-off-by: default avatarVishal Verma <vishal.l.verma@intel.com>
parent 2af3a815

fs/block_dev.c

+45 −0
Original line number Diff line number Diff line
@@ -509,6 +509,51 @@ long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax) 
}

EXPORT_SYMBOL_GPL(bdev_direct_access);



/**

 * bdev_dax_supported() - Check if the device supports dax for filesystem

 * @sb: The superblock of the device

 * @blocksize: The block size of the device

 *

 * This is a library function for filesystems to check if the block device

 * can be mounted with dax option.

 *

 * Return: negative errno if unsupported, 0 if supported.

 */

int bdev_dax_supported(struct super_block *sb, int blocksize)

{

	struct blk_dax_ctl dax = {

		.sector = 0,

		.size = PAGE_SIZE,

	};

	int err;



	if (blocksize != PAGE_SIZE) {

		vfs_msg(sb, KERN_ERR, "error: unsupported blocksize for dax");

		return -EINVAL;

	}



	err = bdev_direct_access(sb->s_bdev, &dax);

	if (err < 0) {

		switch (err) {

		case -EOPNOTSUPP:

			vfs_msg(sb, KERN_ERR,

				"error: device does not support dax");

			break;

		case -EINVAL:

			vfs_msg(sb, KERN_ERR,

				"error: unaligned partition for dax");

			break;

		default:

			vfs_msg(sb, KERN_ERR,

				"error: dax access failed (%d)", err);

		}

		return err;

	}



	return 0;

}

EXPORT_SYMBOL_GPL(bdev_dax_supported);



/*

 * pseudo-fs

 */

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -1688,6 +1688,7 @@ extern int bdev_read_page(struct block_device *, sector_t, struct page *); 
extern int bdev_write_page(struct block_device *, sector_t, struct page *,

						struct writeback_control *);

extern long bdev_direct_access(struct block_device *, struct blk_dax_ctl *);

extern int bdev_dax_supported(struct super_block *, int);

#else /* CONFIG_BLOCK */



struct block_device;

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