mm: rename try_alloc_pages() to alloc_pages_nolock()

The "try_" prefix is confusing, since it made people believe that
try_alloc_pages() is analogous to spin_trylock() and NULL return means
EAGAIN.  This is not the case.  If it returns NULL there is no reason to
call it again.  It will most likely return NULL again.  Hence rename it to
alloc_pages_nolock() to make it symmetrical to free_pages_nolock() and
document that NULL means ENOMEM.

Link: https://lkml.kernel.org/r/20250517003446.60260-1-alexei.starovoitov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Harry Yoo <harry.yoo@oracle.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 7 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 4ee55edf1ad7..dbafa7c69a6a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5070,7 +5070,7 @@ EXPORT_SYMBOL(__free_pages);
 
 /*
  * Can be called while holding raw_spin_lock or from IRQ and NMI for any
- * page type (not only those that came from try_alloc_pages)
+ * page type (not only those that came from alloc_pages_nolock)
  */
 void free_pages_nolock(struct page *page, unsigned int order)
 {
@@ -7311,20 +7311,21 @@ static bool __free_unaccepted(struct page *page)
 #endif /* CONFIG_UNACCEPTED_MEMORY */
 
 /**
- * try_alloc_pages - opportunistic reentrant allocation from any context
+ * alloc_pages_nolock - opportunistic reentrant allocation from any context
  * @nid: node to allocate from
  * @order: allocation order size
  *
  * Allocates pages of a given order from the given node. This is safe to
  * call from any context (from atomic, NMI, and also reentrant
- * allocator -> tracepoint -> try_alloc_pages_noprof).
+ * allocator -> tracepoint -> alloc_pages_nolock_noprof).
  * Allocation is best effort and to be expected to fail easily so nobody should
  * rely on the success. Failures are not reported via warn_alloc().
  * See always fail conditions below.
  *
- * Return: allocated page or NULL on failure.
+ * Return: allocated page or NULL on failure. NULL does not mean EBUSY or EAGAIN.
+ * It means ENOMEM. There is no reason to call it again and expect !NULL.
  */
-struct page *try_alloc_pages_noprof(int nid, unsigned int order)
+struct page *alloc_pages_nolock_noprof(int nid, unsigned int order)
 {
 	/*
 	 * Do not specify __GFP_DIRECT_RECLAIM, since direct claim is not allowed.
@@ -7333,7 +7334,7 @@ struct page *try_alloc_pages_noprof(int nid, unsigned int order)
 	 *
 	 * These two are the conditions for gfpflags_allow_spinning() being true.
 	 *
-	 * Specify __GFP_NOWARN since failing try_alloc_pages() is not a reason
+	 * Specify __GFP_NOWARN since failing alloc_pages_nolock() is not a reason
 	 * to warn. Also warn would trigger printk() which is unsafe from
 	 * various contexts. We cannot use printk_deferred_enter() to mitigate,
 	 * since the running context is unknown.
@@ -7343,7 +7344,7 @@ struct page *try_alloc_pages_noprof(int nid, unsigned int order)
 	 * BPF use cases.
 	 *
 	 * Though __GFP_NOMEMALLOC is not checked in the code path below,
-	 * specify it here to highlight that try_alloc_pages()
+	 * specify it here to highlight that alloc_pages_nolock()
 	 * doesn't want to deplete reserves.
 	 */
 	gfp_t alloc_gfp = __GFP_NOWARN | __GFP_ZERO | __GFP_NOMEMALLOC