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block: Add bdev_dax_supported() for dax mount checks

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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: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Christoph 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: Vishal Verma <vishal.l.verma@intel.com>
This commit is contained in:
Toshi Kani 2016-05-10 10:23:53 -06:00 committed by Vishal Verma
parent 2af3a8159c
commit 2d96afc8f7
2 changed files with 46 additions and 0 deletions
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45
fs/block_dev.c
View File

@ -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
*/

1
include/linux/blkdev.h
View File

@ -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;