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[3.8.y.z,extended,stable] Patch "mm: fix sleeping function warning from __put_anon_vma" has been added to staging queue

Message ID 1405977699-1761-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa July 21, 2014, 9:21 p.m. UTC 
This is a note to let you know that I have just added a patch titled

    mm: fix sleeping function warning from __put_anon_vma

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.27.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From e53a9dc40593565652269422edf0c2ca4308983d Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Wed, 4 Jun 2014 16:05:33 -0700
Subject: mm: fix sleeping function warning from __put_anon_vma

commit 7f39dda9d86fb4f4f17af0de170decf125726f8c upstream.

Trinity reports BUG:

  sleeping function called from invalid context at kernel/locking/rwsem.c:47
  in_atomic(): 0, irqs_disabled(): 0, pid: 5787, name: trinity-c27

__might_sleep < down_write < __put_anon_vma < page_get_anon_vma <
migrate_pages < compact_zone < compact_zone_order < try_to_compact_pages ..

Right, since conversion to mutex then rwsem, we should not put_anon_vma()
from inside an rcu_read_lock()ed section: fix the two places that did so.
And add might_sleep() to anon_vma_free(), as suggested by Peter Zijlstra.

Fixes: 88c22088bf23 ("mm: optimize page_lock_anon_vma() fast-path")
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 mm/rmap.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--
1.9.1
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Patch

diff --git a/mm/rmap.c b/mm/rmap.c
index 770320b..f350f9f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -103,6 +103,7 @@  static inline void anon_vma_free(struct anon_vma *anon_vma)
 	 * LOCK should suffice since the actual taking of the lock must
 	 * happen _before_ what follows.
 	 */
+	might_sleep();
 	if (rwsem_is_locked(&anon_vma->root->rwsem)) {
 		anon_vma_lock_write(anon_vma);
 		anon_vma_unlock_write(anon_vma);
@@ -426,8 +427,9 @@  struct anon_vma *page_get_anon_vma(struct page *page)
 	 * above cannot corrupt).
 	 */
 	if (!page_mapped(page)) {
+		rcu_read_unlock();
 		put_anon_vma(anon_vma);
-		anon_vma = NULL;
+		return NULL;
 	}
 out:
 	rcu_read_unlock();
@@ -477,9 +479,9 @@  struct anon_vma *page_lock_anon_vma_read(struct page *page)
 	}

 	if (!page_mapped(page)) {
+		rcu_read_unlock();
 		put_anon_vma(anon_vma);
-		anon_vma = NULL;
-		goto out;
+		return NULL;
 	}

 	/* we pinned the anon_vma, its safe to sleep */