> DIF (PI) emulation doesn't work when a target uses async I/O, because
> DIF metadata is saved in a separate file, and it is another non-trivial
> task how to synchronize writing in two files, so that a following read
> operation always returns a consisten metadata for a specified block.
There literally is no way to do that, even without aio. The file
DIF implementation should probably regarded as an early bringup /
prototype tool, not something really usable.
> +static void cmd_rw_aio_do_completion(struct target_core_file_cmd *cmd)
> +{
> + if (!atomic_dec_and_test(&cmd->ref))
> + return;
There is no need for reference counting. If the read_iter/write iter
method returns -EIOCBQUEUED the completion callback needs to complete
the I/O and free the structure, else the method caller.
> + if (!(fd_dev->fbd_flags & FDBD_HAS_BUFFERED_IO_WCE))
> + aio_cmd->iocb.ki_flags |= IOCB_DIRECT;
aio without IOCB_DIRECT doesn't make any sense. But the WCE flag
really has nothing to do with buffers vs direct I/O anyway.
> + if (is_write)
> + ret = call_write_iter(file, &aio_cmd->iocb, &iter);
> + else
> + ret = call_read_iter(file, &aio_cmd->iocb, &iter);
Please call the methods directly instead of through the wrappers.
> +
> static int fd_do_rw(struct se_cmd *cmd, struct file *fd,
> u32 block_size, struct scatterlist *sgl,
> u32 sgl_nents, u32 data_length, int is_write)
> @@ -536,6 +626,7 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> struct file *pfile = fd_dev->fd_prot_file;
> sense_reason_t rc;
> int ret = 0;
> + int aio = fd_dev->fbd_flags & FDBD_HAS_ASYNC_IO;
> /*
> * We are currently limited by the number of iovecs (2048) per
> * single vfs_[writev,readv] call.
> @@ -550,7 +641,11 @@ fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
> * Call vectorized fileio functions to map struct scatterlist
> * physical memory addresses to struct iovec virtual memory.
> */
> - if (data_direction == DMA_FROM_DEVICE) {
> + if (aio) {
fd_execute_rw shares basically no code with the aio case. I'd rather
have a very high level wrapper here:
static sense_reason_t
fd_execute_rw(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
enum dma_data_direction data_direction)
{
if (FD_DEV(cmd->se_dev)->fbd_flags & FDBD_HAS_ASYNC_IO)
return fd_execute_rw_aio(cmd, sgl, sgl_nents, dma_direction);
return fd_execute_rw_buffered(cmd, sgl, sgl_nents, dma_direction);
}
and keep the code separate.
