mm/mremap_pages: save a few cycles in get_dev_pagemap()

Use 'percpu_ref_tryget_live_rcu()' instead of 'percpu_ref_tryget_live()'
to save a few cycles when it is known that the rcu lock is already
taken/released.

Link: https://lkml.kernel.org/r/9ef1562a1975371360f3e263856e9f1c5749b656.1662136782.git.christophe.jaillet@wanadoo.frSigned-off-by: NChristophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

mm/memremap.c

@@ -454,7 +454,7 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
 	/* fall back to slow path lookup */
 	rcu_read_lock();
 	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
-	if (pgmap && !percpu_ref_tryget_live(&pgmap->ref))
+	if (pgmap && !percpu_ref_tryget_live_rcu(&pgmap->ref))
 		pgmap = NULL;
 	rcu_read_unlock();