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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: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20220415045258.199825-28-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-04-15 06:52:58 +02:00 committed by Jens Axboe
parent 44abff2c0b
commit c22198e78d
1 changed files with 4 additions and 28 deletions
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32
fs/direct-io.c
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@ -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)