Re: [Virtio-fs] [PATCH v3 2/3] dax: Add a wakeup mode parameter to put_unlocked_entry()

Greg Kurz
2021-04-20T07:34:28Z

On Mon, 19 Apr 2021 17:36:35 -0400
Vivek Goyal <vgoyal@redhat.com> wrote:

> As of now put_unlocked_entry() always wakes up next waiter. In next
> patches we want to wake up all waiters at one callsite. Hence, add a
> parameter to the function.
>
> This patch does not introduce any change of behavior.
>
> Suggested-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
> fs/dax.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 00978d0838b1..f19d76a6a493 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -275,11 +275,12 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry)
> finish_wait(wq, &ewait.wait);
> }
>
> -static void put_unlocked_entry(struct xa_state *xas, void *entry)
> +static void put_unlocked_entry(struct xa_state *xas, void *entry,
> + enum dax_entry_wake_mode mode)
> {
> /* If we were the only waiter woken, wake the next one */

With this change, the comment is no longer accurate since the
function can now wake all waiters if passed mode == WAKE_ALL.
Also, it paraphrases the code which is simple enough, so I'd
simply drop it.

This is minor though and it shouldn't prevent this fix to go
forward.

Reviewed-by: Greg Kurz <groug@kaod.org>

> if (entry && !dax_is_conflict(entry))
> - dax_wake_entry(xas, entry, WAKE_NEXT);
> + dax_wake_entry(xas, entry, mode);
> }
>
> /*
> @@ -633,7 +634,7 @@ struct page *dax_layout_busy_page_range(struct address_space *mapping,
> entry = get_unlocked_entry(&xas, 0);
> if (entry)
> page = dax_busy_page(entry);
> - put_unlocked_entry(&xas, entry);
> + put_unlocked_entry(&xas, entry, WAKE_NEXT);
> if (page)
> break;
> if (++scanned % XA_CHECK_SCHED)
> @@ -675,7 +676,7 @@ static int __dax_invalidate_entry(struct address_space *mapping,
> mapping->nrexceptional--;
> ret = 1;
> out:
> - put_unlocked_entry(&xas, entry);
> + put_unlocked_entry(&xas, entry, WAKE_NEXT);
> xas_unlock_irq(&xas);
> return ret;
> }
> @@ -954,7 +955,7 @@ static int dax_writeback_one(struct xa_state *xas, struct dax_device *dax_dev,
> return ret;
>
> put_unlocked:
> - put_unlocked_entry(xas, entry);
> + put_unlocked_entry(xas, entry, WAKE_NEXT);
> return ret;
> }
>
> @@ -1695,7 +1696,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order)
> /* Did we race with someone splitting entry or so? */
> if (!entry || dax_is_conflict(entry) ||
> (order == 0 && !dax_is_pte_entry(entry))) {
> - put_unlocked_entry(&xas, entry);
> + put_unlocked_entry(&xas, entry, WAKE_NEXT);
> xas_unlock_irq(&xas);
> trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf,
> VM_FAULT_NOPAGE);