Re: [PATCH v3 09/10] mm/vmalloc: Update __vmalloc_node_range() documentation

[Uladzislau Rezki <urezki@gmail.com>]

On Mon, Oct 06, 2025 at 09:17:44PM +0800, Baoquan He wrote:
> On 10/06/25 at 12:06pm, Uladzislau Rezki wrote:
> > On Sat, Oct 04, 2025 at 01:02:02PM +0800, Baoquan He wrote:
> > > On 10/04/25 at 12:11pm, Baoquan He wrote:
> > > > On 10/01/25 at 09:26pm, Uladzislau Rezki (Sony) wrote:
> > > > > __vmalloc() function now supports non-blocking flags such as
> > > > > GFP_ATOMIC and GFP_NOWAIT. Update the documentation accordingly.
> > > > > 
> > > > > Acked-by: Michal Hocko <mhocko@suse.com>
> > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > > > > ---
> > > > >  mm/vmalloc.c | 21 +++++++++++----------
> > > > >  1 file changed, 11 insertions(+), 10 deletions(-)
> > > > > 
> > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > > > > index d7e7049e01f8..2b45cd4ce119 100644
> > > > > --- a/mm/vmalloc.c
> > > > > +++ b/mm/vmalloc.c
> > > > > @@ -3881,19 +3881,20 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> > > > >   * @caller:		  caller's return address
> > > > >   *
> > > > >   * Allocate enough pages to cover @size from the page level
> > > > > - * allocator with @gfp_mask flags. Please note that the full set of gfp
> > > > > - * flags are not supported. GFP_KERNEL, GFP_NOFS and GFP_NOIO are all
> > > > > - * supported.
> > > > > - * Zone modifiers are not supported. From the reclaim modifiers
> > > > > - * __GFP_DIRECT_RECLAIM is required (aka GFP_NOWAIT is not supported)
> > > > > - * and only __GFP_NOFAIL is supported (i.e. __GFP_NORETRY and
> > > > > - * __GFP_RETRY_MAYFAIL are not supported).
> > > > > + * allocator with @gfp_mask flags and map them into contiguous
> > > > > + * virtual range with protection @prot.
> > > > >   *
> > > > > - * __GFP_NOWARN can be used to suppress failures messages.
> > > > > + * Supported GFP classes: %GFP_KERNEL, %GFP_ATOMIC, %GFP_NOWAIT,
> > > > > + * %GFP_NOFS and %GFP_NOIO. Zone modifiers are not supported.
> > > > > + * Please note %GFP_ATOMIC and %GFP_NOWAIT are supported only
> > > > > + * by __vmalloc().
> > > > > +
> > > > > + * Retry modifiers: only %__GFP_NOFAIL is supported; %__GFP_NORETRY
> > > > > + * and %__GFP_RETRY_MAYFAIL are not supported.
> > > > 
> > > > Do we need to update the documentation of __vmalloc_node_noprof()
> > > > accordingly? I see it has below description about "Retry modifiers"
> > > > where gfp_mask is passed down to __vmalloc_node_range_noprof() directly
> > > > but have different description. Not sure if I missed anything.
> > > > 
> > > > ===
> > > >  * Retry modifiers: only %__GFP_NOFAIL is supported; %__GFP_NORETRY
> > > >  * and %__GFP_RETRY_MAYFAIL are not supported.
> > > > ===
> > > 
> > > Sorry, I copied the wrong sentences. Below is copied from documentation
> > > of __vmalloc_node_noprof().
> > > ====
> > >  * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_RETRY_MAYFAIL
> > >  * and __GFP_NOFAIL are not supported
> > > ====
> > > 
> > > 
> > > > 
> > > > >   *
> > > > > - * Map them into contiguous kernel virtual space, using a pagetable
> > > > > - * protection of @prot.
> > > > > + * %__GFP_NOWARN can be used to suppress failure messages.
> > > > >   *
> > > > > + * Can not be called from interrupt nor NMI contexts.
> > > > >   * Return: the address of the area or %NULL on failure
> > > > >   */
> > > > >  void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,
> > > > > -- 
> > > > > 2.47.3
> > > > > 
> > > > 
> > > 
> > We need. But i am not sure it should be fully copy-pasted from the
> > __vmalloc_node_range_noprof(). At least __GFP_NOFAIL is supported
> > and thus stating that it is not - is wrong.
> > 
> > It has to be fixed but not by this series because when __GFP_NOFAIL
> > support was introduced the doc. should have to be updated accordingly.
> 
> Maybe just remove the documentation for __vmalloc_node_noprof() since
> it's only a wrapper of __vmalloc_node_range_noprof()? Surely this should
> be done in another standalone patch later.
> 
Like below?

<snip>
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 9a63c91c6150..7ff81a38dcb8 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4027,12 +4027,8 @@ void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,
  * Allocate enough pages to cover @size from the page level allocator with
  * @gfp_mask flags.  Map them into contiguous kernel virtual space.
  *
- * Reclaim modifiers in @gfp_mask - __GFP_NORETRY, __GFP_RETRY_MAYFAIL
- * and __GFP_NOFAIL are not supported
- *
- * Any use of gfp flags outside of GFP_KERNEL should be consulted
- * with mm people.
- *
+ * For detailed information about supported GFP flags and retry modifiers,
+ * see the __vmalloc_node_range_noprof() function description.
  * Return: pointer to the allocated memory or %NULL on error
  */
 void *__vmalloc_node_noprof(unsigned long size, unsigned long align,
<snip>

--
Uladzislau Rezki