From: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
To: Alasdair Kergon <agk@redhat.com>,
device-mapper development <dm-devel@redhat.com>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] 2.6.12-rc6: fix rh_dec()/rh_inc() race in dm-raid1.c
Date: Thu, 16 Jun 2005 18:51:41 -0400 [thread overview]
Message-ID: <42B2027D.7040807@ce.jp.nec.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 947 bytes --]
Hello,
Attached patch fixes the another bug in dm-raid1.c that
the dirty region may stay in or be moved to clean list
and freed while in use.
It happens as follows:
CPU0 CPU1
------------------------------------------------------------------------------
rh_dec()
if (atomic_dec_and_test(pending))
<the region is still marked dirty>
rh_inc()
if the region is clean
mark the region dirty
and remove from clean list
mark the region clean
and move to clean list
atomic_inc(pending)
At this stage, the region is in clean list and
will be mistakenly reclaimed by rh_update_states() later.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
[-- Attachment #2: dm-raid1-race2.patch --]
[-- Type: text/x-patch, Size: 1071 bytes --]
--- kernel/drivers/md/dm-raid1.c.orig 2005-06-16 07:13:50.610325768 -0400
+++ kernel/drivers/md/dm-raid1.c 2005-06-16 10:34:12.510719112 -0400
@@ -375,16 +380,18 @@ static void rh_inc(struct region_hash *r
read_lock(&rh->hash_lock);
reg = __rh_find(rh, region);
+
+ atomic_inc(®->pending);
+
+ spin_lock_irq(&rh->region_lock);
if (reg->state == RH_CLEAN) {
rh->log->type->mark_region(rh->log, reg->key);
- spin_lock_irq(&rh->region_lock);
reg->state = RH_DIRTY;
list_del_init(®->list); /* take off the clean list */
- spin_unlock_irq(&rh->region_lock);
}
+ spin_unlock_irq(&rh->region_lock);
- atomic_inc(®->pending);
read_unlock(&rh->hash_lock);
}
@@ -408,6 +414,10 @@ static void rh_dec(struct region_hash *r
if (atomic_dec_and_test(®->pending)) {
spin_lock_irqsave(&rh->region_lock, flags);
+ if (atomic_read(®->pending)) { /* check race */
+ spin_unlock_irqrestore(&rh->region_lock, flags);
+ return;
+ }
if (reg->state == RH_RECOVERING) {
list_add_tail(®->list, &rh->quiesced_regions);
} else {
WARNING: multiple messages have this Message-ID (diff)
From: "Jun'ichi Nomura" <j-nomura@ce.jp.nec.com>
To: Alasdair Kergon <agk@redhat.com>,
device-mapper development <dm-devel@redhat.com>
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH] 2.6.12-rc6: fix rh_dec()/rh_inc() race in dm-raid1.c
Date: Thu, 16 Jun 2005 18:51:41 -0400 [thread overview]
Message-ID: <42B2027D.7040807@ce.jp.nec.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 947 bytes --]
Hello,
Attached patch fixes the another bug in dm-raid1.c that
the dirty region may stay in or be moved to clean list
and freed while in use.
It happens as follows:
CPU0 CPU1
------------------------------------------------------------------------------
rh_dec()
if (atomic_dec_and_test(pending))
<the region is still marked dirty>
rh_inc()
if the region is clean
mark the region dirty
and remove from clean list
mark the region clean
and move to clean list
atomic_inc(pending)
At this stage, the region is in clean list and
will be mistakenly reclaimed by rh_update_states() later.
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
[-- Attachment #2: dm-raid1-race2.patch --]
[-- Type: text/x-patch, Size: 1071 bytes --]
--- kernel/drivers/md/dm-raid1.c.orig 2005-06-16 07:13:50.610325768 -0400
+++ kernel/drivers/md/dm-raid1.c 2005-06-16 10:34:12.510719112 -0400
@@ -375,16 +380,18 @@ static void rh_inc(struct region_hash *r
read_lock(&rh->hash_lock);
reg = __rh_find(rh, region);
+
+ atomic_inc(®->pending);
+
+ spin_lock_irq(&rh->region_lock);
if (reg->state == RH_CLEAN) {
rh->log->type->mark_region(rh->log, reg->key);
- spin_lock_irq(&rh->region_lock);
reg->state = RH_DIRTY;
list_del_init(®->list); /* take off the clean list */
- spin_unlock_irq(&rh->region_lock);
}
+ spin_unlock_irq(&rh->region_lock);
- atomic_inc(®->pending);
read_unlock(&rh->hash_lock);
}
@@ -408,6 +414,10 @@ static void rh_dec(struct region_hash *r
if (atomic_dec_and_test(®->pending)) {
spin_lock_irqsave(&rh->region_lock, flags);
+ if (atomic_read(®->pending)) { /* check race */
+ spin_unlock_irqrestore(&rh->region_lock, flags);
+ return;
+ }
if (reg->state == RH_RECOVERING) {
list_add_tail(®->list, &rh->quiesced_regions);
} else {
[-- Attachment #3: Type: text/plain, Size: 0 bytes --]
next reply other threads:[~2005-06-16 22:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-16 22:51 Jun'ichi Nomura [this message]
2005-06-16 22:51 ` [PATCH] 2.6.12-rc6: fix rh_dec()/rh_inc() race in dm-raid1.c Jun'ichi Nomura
2005-06-24 15:19 ` Jonathan E Brassow
2005-06-24 15:45 ` Jun'ichi Nomura
2005-06-27 17:34 ` Jun'ichi Nomura
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