Commit bbab37dd authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Al Viro

block: Add support for DAX reads/writes to block devices

If a block device supports the ->direct_access methods, bypass the normal
DIO path and use DAX to go straight to memcpy() instead of allocating
a DIO and a BIO.

Includes support for the DIO_SKIP_DIO_COUNT flag in DAX, as is done in
Signed-off-by: default avatarMatthew Wilcox <>
Signed-off-by: default avatarAl Viro <>
parent 872eb127
......@@ -151,6 +151,9 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
struct file *file = iocb->ki_filp;
struct inode *inode = file->f_mapping->host;
if (IS_DAX(inode))
return dax_do_io(iocb, inode, iter, offset, blkdev_get_block,
return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
blkdev_get_block, NULL, NULL,
......@@ -1173,6 +1176,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
bdev->bd_disk = disk;
bdev->bd_queue = disk->queue;
bdev->bd_contains = bdev;
bdev->bd_inode->i_flags = disk->fops->direct_access ? S_DAX : 0;
if (!partno) {
ret = -ENXIO;
bdev->bd_part = disk_get_part(disk, partno);
......@@ -209,7 +209,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
/* Protects against truncate */
if (!(flags & DIO_SKIP_DIO_COUNT))
retval = dax_io(inode, iter, pos, end, get_block, &bh);
......@@ -219,7 +220,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
if ((retval > 0) && end_io)
end_io(iocb, pos, retval, bh.b_private);
if (!(flags & DIO_SKIP_DIO_COUNT))
return retval;
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