Commit c22198e7 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

direct-io: remove random prefetches 



Randomly poking into block device internals for manual prefetches isn't
exactly a very maintainable thing to do.  And none of the performance
critical direct I/O implementations still use this library function
anyway, so just drop it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarDamien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220415045258.199825-28-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 44abff2c

fs/direct-io.c

+4 −28
Original line number Diff line number Diff line
@@ -1115,8 +1115,7 @@ static inline int drop_refcount(struct dio *dio) 
 * individual fields and will generate much worse code. This is important

 * for the whole file.

 */

static inline ssize_t

do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,

ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,

		struct block_device *bdev, struct iov_iter *iter,

		get_block_t get_block, dio_iodone_t end_io,

		dio_submit_t submit_io, int flags)
@@ -1334,29 +1333,6 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, 
	kmem_cache_free(dio_cache, dio);

	return retval;

}



ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,

			     struct block_device *bdev, struct iov_iter *iter,

			     get_block_t get_block,

			     dio_iodone_t end_io, dio_submit_t submit_io,

			     int flags)

{

	/*

	 * The block device state is needed in the end to finally

	 * submit everything.  Since it's likely to be cache cold

	 * prefetch it here as first thing to hide some of the

	 * latency.

	 *

	 * Attempt to prefetch the pieces we likely need later.

	 */

	prefetch(&bdev->bd_disk->part_tbl);

	prefetch(bdev->bd_disk->queue);

	prefetch((char *)bdev->bd_disk->queue + SMP_CACHE_BYTES);



	return do_blockdev_direct_IO(iocb, inode, bdev, iter, get_block,

				     end_io, submit_io, flags);

}



EXPORT_SYMBOL(__blockdev_direct_IO);



static __init int dio_init(void)