[PATCH 27/27] direct-io: remove random prefetches

Christoph Hellwig
2022-04-09T05:19:51Z

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/direct-io.c | 32 ++++----------------------------
1 file changed, 4 insertions(+), 28 deletions(-)

diff --git a/fs/direct-io.c b/fs/direct-io.c
index aef06e607b405..840752006f601 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -1115,11 +1115,10 @@ 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,
- 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)
+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)
{
unsigned i_blkbits = READ_ONCE(inode->i_blkbits);
unsigned blkbits = i_blkbits;
@@ -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)
--
2.30.2