On Tue, May 6, 2025 at 1:26 AM Vlastimil Babka <vbabka@xxxxxxx> wrote: > > On 5/1/25 05:27, Alexei Starovoitov wrote: > > From: Alexei Starovoitov <ast@xxxxxxxxxx> > > > > 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. > > > > Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> > > > @@ -7378,20 +7378,21 @@ 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. > > Should we explain that the "ENOMEM" doesn't necessarily mean the system is > out of memory, but also that the calling context might be simply unlucky > (preempted someone with the lock) and retrying in the same context can't > help it? Technically correct, but it opens the door for "retry" thinking: "I called it and got unlucky, maybe I should retry once.. I promise I won't loop forever". So I really think the doc should say "ENOMEM. no reason to retry" like above.
