[patch 099/262] mm/vmalloc: be more explicit about supported gfp flags

Andrew Morton
2021-11-05T20:39:53Z

From: Michal Hocko <mhocko@suse.com>
Subject: mm/vmalloc: be more explicit about supported gfp flags

The core of the vmalloc allocator __vmalloc_area_node doesn't say anything
about gfp mask argument. Not all gfp flags are supported though. Be more
explicit about constraints.

Link: https://lkml.kernel.org/r/20211020082545.4830-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/vmalloc.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

--- a/mm/vmalloc.c~mm-vmalloc-be-more-explicit-about-supported-gfp-flags
+++ a/mm/vmalloc.c
@@ -2983,8 +2983,16 @@ fail:
* @caller: caller's return address
*
* Allocate enough pages to cover @size from the page level
- * allocator with @gfp_mask flags. Map them into contiguous
- * kernel virtual space, using a pagetable protection of @prot.
+ * allocator with @gfp_mask flags. Please note that the full set of gfp
+ * flags are not supported. GFP_KERNEL would be a preferred allocation mode
+ * but GFP_NOFS and GFP_NOIO are supported as well. 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 (aka
+ * __GFP_NORETRY and __GFP_RETRY_MAYFAIL are not supported).
+ * __GFP_NOWARN can be used to suppress error messages about failures.
+ *
+ * Map them into contiguous kernel virtual space, using a pagetable
+ * protection of @prot.
*
* Return: the address of the area or %NULL on failure
*/
_