linux-kernel - [PATCH] mm: clear __GFP_FS when PF_MEMALLOC

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Message-Id: <1409723694-16047-1-git-send-email-junxiao.bi@oracle.com>
Date:	Wed,  3 Sep 2014 13:54:54 +0800
From:	Junxiao Bi <junxiao.bi@...cle.com>
To:	david@...morbit.com, akpm@...ux-foundation.org
Cc:	xuejiufei@...wei.com, ming.lei@...onical.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH] mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set

commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O during memory allocation")
introduces PF_MEMALLOC_NOIO flag to avoid doing I/O inside memory allocation, __GFP_IO is cleared
when this flag is set, but __GFP_FS implies __GFP_IO, it should also be cleared. Or it may still
run into I/O, like in superblock shrinker.

Signed-off-by: Junxiao Bi <junxiao.bi@...cle.com>
Cc: joyce.xue <xuejiufei@...wei.com>
Cc: Ming Lei <ming.lei@...onical.com>
---
 include/linux/sched.h |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c2c885..2fb2c47 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1936,11 +1936,13 @@ extern void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut,
 #define tsk_used_math(p) ((p)->flags & PF_USED_MATH)
 #define used_math() tsk_used_math(current)
 
-/* __GFP_IO isn't allowed if PF_MEMALLOC_NOIO is set in current->flags */
+/* __GFP_IO isn't allowed if PF_MEMALLOC_NOIO is set in current->flags
+ * __GFP_FS is also cleared as it implies __GFP_IO.
+ */
 static inline gfp_t memalloc_noio_flags(gfp_t flags)
 {
 	if (unlikely(current->flags & PF_MEMALLOC_NOIO))
-		flags &= ~__GFP_IO;
+		flags &= ~(__GFP_IO | __GFP_FS);
 	return flags;
 }
 
-- 
1.7.9.5

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