linux-kernel - [PATCH 2/2] mm: make it clear that gfp reclaim modifiers are valid only for sleepable allocations

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Date:   Fri,  3 Apr 2020 10:35:43 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Neil Brown <neilb@...e.de>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH 2/2] mm: make it clear that gfp reclaim modifiers are valid only for sleepable allocations

From: Michal Hocko <mhocko@...e.com>

While it might be really clear to MM developers that gfp reclaim
modifiers are applicable only to sleepable allocations (those with
__GFP_DIRECT_RECLAIM) it seems that actual users of the API are not
always sure. Make it explicit that they are not applicable for
GFP_NOWAIT or GFP_ATOMIC allocations which are the most commonly used
non-sleepable allocation masks.

Acked-by: Paul E. McKenney <paulmck@...nel.org>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 include/linux/gfp.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index e3ab1c0d9140..8040fa944cd8 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -127,6 +127,8 @@ struct vm_area_struct;
  *
  * Reclaim modifiers
  * ~~~~~~~~~~~~~~~~~
+ * Please note that all the following flags are only applicable to sleepable
+ * allocations (e.g. %GFP_NOWAIT and %GFP_ATOMIC will ignore them).
  *
  * %__GFP_IO can start physical IO.
  *
-- 
2.25.1