> On Aug 27, 2021, at 3:14 AM, NeilBrown <neilb@xxxxxxx> wrote:
>
> Subject: [PATCH] SUNRPC: don't pause on incomplete allocation
>
> alloc_pages_bulk_array() attempts to allocate at least one page based on
> the provided pages, and then opportunistically allocates more if that
> can be done without dropping the spinlock.
>
> So if it returns fewer than requested, that could just mean that it
> needed to drop the lock. In that case, try again immediately.
>
> Only pause for a time if no progress could be made.
The case I was worried about was "no pages available on the
pcplist", in which case, alloc_pages_bulk_array() resorts
to calling __alloc_pages() and returns only one new page.
"No progess" would mean even __alloc_pages() failed.
So this patch would behave essentially like the
pre-alloc_pages_bulk_array() code: call alloc_page() for
each empty struct_page in the array without pausing. That
seems correct to me.
I would add
Fixes: f6e70aab9dfe ("SUNRPC: refresh rq_pages using a bulk page allocator")
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
> net/sunrpc/svc_xprt.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
> index d66a8e44a1ae..99268dd95519 100644
> --- a/net/sunrpc/svc_xprt.c
> +++ b/net/sunrpc/svc_xprt.c
> @@ -662,7 +662,7 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
> {
> struct svc_serv *serv = rqstp->rq_server;
> struct xdr_buf *arg = &rqstp->rq_arg;
> - unsigned long pages, filled;
> + unsigned long pages, filled, prev;
>
> pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
> if (pages > RPCSVC_MAXPAGES) {
> @@ -672,11 +672,14 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
> pages = RPCSVC_MAXPAGES;
> }
>
> - for (;;) {
> + for (prev = 0;; prev = filled) {
> filled = alloc_pages_bulk_array(GFP_KERNEL, pages,
> rqstp->rq_pages);
> if (filled == pages)
> break;
> + if (filled > prev)
> + /* Made progress, don't sleep yet */
> + continue;
>
> set_current_state(TASK_INTERRUPTIBLE);
> if (signalled() || kthread_should_stop()) {
--
Chuck Lever
