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

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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
do_blockdev_direct_IO().

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Matthew Wilcox 2015-07-03 10:40:42 -04:00 committed by Al Viro
parent 872eb127e3
commit bbab37ddc2
2 changed files with 8 additions and 2 deletions
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4
fs/block_dev.c
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@ -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,
NULL, DIO_SKIP_DIO_COUNT);
return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
blkdev_get_block, NULL, NULL,
DIO_SKIP_DIO_COUNT);
@ -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);

6
fs/dax.c
View File

@ -209,7 +209,8 @@ ssize_t dax_do_io(struct kiocb *iocb, struct inode *inode,
}
/* Protects against truncate */
inode_dio_begin(inode);
if (!(flags & DIO_SKIP_DIO_COUNT))
inode_dio_begin(inode);
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);
inode_dio_end(inode);
if (!(flags & DIO_SKIP_DIO_COUNT))
inode_dio_end(inode);
out:
return retval;
}