Re: [PATCH 1/2] io_uring: set ctx sq/cq entry count earlier

[Stefano Garzarella <sgarzare@redhat.com>]

On Wed, Aug 05, 2020 at 01:02:23PM -0600, Jens Axboe wrote:
> If we hit an earlier error path in io_uring_create(), then we will have
> accounted memory, but not set ctx->{sq,cq}_entries yet. Then when the
> ring is torn down in error, we use those values to unaccount the memory.
> 
> Ensure we set the ctx entries before we're able to hit a potential error
> path.
> 
> Cc: stable@vger.kernel.org
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  fs/io_uring.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 8f96566603f3..0d857f7ca507 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -8193,6 +8193,10 @@ static int io_allocate_scq_urings(struct io_ring_ctx *ctx,
>  	struct io_rings *rings;
>  	size_t size, sq_array_offset;
>  
> +	/* make sure these are sane, as we already accounted them */
> +	ctx->sq_entries = p->sq_entries;
> +	ctx->cq_entries = p->cq_entries;
> +
>  	size = rings_size(p->sq_entries, p->cq_entries, &sq_array_offset);
>  	if (size == SIZE_MAX)
>  		return -EOVERFLOW;
> @@ -8209,8 +8213,6 @@ static int io_allocate_scq_urings(struct io_ring_ctx *ctx,
>  	rings->cq_ring_entries = p->cq_entries;
>  	ctx->sq_mask = rings->sq_ring_mask;
>  	ctx->cq_mask = rings->cq_ring_mask;
> -	ctx->sq_entries = rings->sq_ring_entries;
> -	ctx->cq_entries = rings->cq_ring_entries;
>  
>  	size = array_size(sizeof(struct io_uring_sqe), p->sq_entries);
>  	if (size == SIZE_MAX) {
> -- 
> 2.28.0
> 

While reviewing I was asking if we should move io_account_mem() before
io_allocate_scq_urings(), then I saw the second patch :-)

LGTM:

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Thanks,
Stefano