[PATCH v4 2/6] block: Add bdev_dax_supported() for dax mount checks
From: Toshi Kani <hidden>
Date: 2016-05-10 16:23:53
Also in:
linux-fsdevel, lkml, nvdimm
Subsystem:
block layer, filesystems (vfs and infrastructure), the rest · Maintainers:
Jens Axboe, Alexander Viro, Christian Brauner, Linus Torvalds
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 <redacted> 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 <redacted> Cc: Ross Zwisler <redacted> Cc: Christoph Hellwig <hch@infradead.org> Cc: Boaz Harrosh <redacted> --- fs/block_dev.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ include/linux/blkdev.h | 1 + 2 files changed, 46 insertions(+)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7be17c4..db55638 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c@@ -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 */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 78c48ab..71231a5 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h@@ -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;