From ceaa762527f41a431b552bc000de4b626d2d8cb7 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Thu, 28 Oct 2021 08:57:09 -0600 Subject: [PATCH] block: move direct_IO into our own read_iter handler Don't call into generic_file_read_iter() if we know it's O_DIRECT, just set it up ourselves and call our own handler. This avoids an indirect call for O_DIRECT. Fall back to filemap_read() if we fail. Signed-off-by: Jens Axboe --- block/fops.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/block/fops.c b/block/fops.c index ad732a3..4d0e220 100644 --- a/block/fops.c +++ b/block/fops.c @@ -566,21 +566,48 @@ static ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to) { struct block_device *bdev = iocb->ki_filp->private_data; loff_t size = bdev_nr_bytes(bdev); + size_t count = iov_iter_count(to); loff_t pos = iocb->ki_pos; size_t shorted = 0; - ssize_t ret; + ssize_t ret = 0; - if (unlikely(pos + iov_iter_count(to) > size)) { + if (unlikely(pos + count > size)) { if (pos >= size) return 0; size -= pos; - if (iov_iter_count(to) > size) { - shorted = iov_iter_count(to) - size; + if (count > size) { + shorted = count - size; iov_iter_truncate(to, size); } } - ret = generic_file_read_iter(iocb, to); + if (iocb->ki_flags & IOCB_DIRECT) { + struct address_space *mapping = iocb->ki_filp->f_mapping; + + if (iocb->ki_flags & IOCB_NOWAIT) { + if (filemap_range_needs_writeback(mapping, iocb->ki_pos, + iocb->ki_pos + count - 1)) + return -EAGAIN; + } else { + ret = filemap_write_and_wait_range(mapping, + iocb->ki_pos, + iocb->ki_pos + count - 1); + if (ret < 0) + return ret; + } + + file_accessed(iocb->ki_filp); + + ret = blkdev_direct_IO(iocb, to); + if (ret >= 0) { + iocb->ki_pos += ret; + count -= ret; + } + if (ret < 0 || !count) + return ret; + } + + ret = filemap_read(iocb, to, ret); if (unlikely(shorted)) iov_iter_reexpand(to, iov_iter_count(to) + shorted); -- 2.7.4