On Sun, Dec 20, 2020 at 03:18:05PM +0000, Pavel Begunkov wrote:
> On 20/12/2020 06:50, noah wrote:> From: noah <goldstei...@wustl.edu>
> >
> > This patch makes it so that specify a file descriptor value of -2 will
> > skip updating the corresponding fixed file index.
> >
> > This will allow for users to reduce the number of syscalls necessary
> > to update a sparse file range when using the fixed file option.
>
> Answering the github thread -- it's indeed a simple change, I had it the
> same day you posted the issue. See below it's a bit cleaner. However, I
> want to first review "io_uring: buffer registration enhancements", and
> if it's good, for easier merging/etc I'd rather prefer to let it go
> first (even if partially).
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 941fe9b64fd9..b3ae9d5da17e 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -7847,9 +7847,8 @@ static int __io_sqe_files_update(struct io_ring_ctx
> *ctx,
> if (IS_ERR(ref_node))
> return PTR_ERR(ref_node);
>
> - done = 0;
> fds = u64_to_user_ptr(up->fds);
> - while (nr_args) {
> + for (done = 0; done < nr_args; done++) {
> struct fixed_file_table *table;
> unsigned index;
>
> @@ -7858,7 +7857,10 @@ static int __io_sqe_files_update(struct io_ring_ctx
> *ctx,
> err = -EFAULT;
> break;
> }
> - i = array_index_nospec(up->offset, ctx->nr_user_files);
> + if (fd == IORING_REGISTER_FILES_SKIP)
> + continue;
> +
> + i = array_index_nospec(up->offset + done, ctx->nr_user_files);
> table = &ctx->file_data->table[i >> IORING_FILE_TABLE_SHIFT];
> index = i & IORING_FILE_TABLE_MASK;
> if (table->files[index]) {
> @@ -7896,9 +7898,6 @@ static int __io_sqe_files_update(struct io_ring_ctx
> *ctx,
> break;
> }
> }
> - nr_args--;
> - done++;
> - up->offset++;
> }
>
> if (needs_switch) {
>
> --
> Pavel Begunkov
Ah. Got it.
