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zcache: fix deadlock condition

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I discovered this deadlock condition awhile ago working on RAMster
but it affects zcache as well.  The list spinlock must be
locked prior to the page spinlock and released after.  As
a result, the page copy must also be done while the locks are held.

Applies to 3.2.  Konrad, please push (via GregKH?)...
this is definitely a bug fix so need not be pushed during
a -rc0 window.

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Dan Magenheimer 2012-01-25 14:32:51 -08:00 committed by Greg Kroah-Hartman
parent c5b1247bd1
commit 9256a4789b
1 changed files with 3 additions and 4 deletions
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7
drivers/staging/zcache/zcache-main.c
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@ -358,8 +358,8 @@ static struct zbud_hdr *zbud_create(uint16_t client_id, uint16_t pool_id,
if (unlikely(zbpg == NULL))
goto out;
/* ok, have a page, now compress the data before taking locks */
spin_lock(&zbpg->lock);
spin_lock(&zbud_budlists_spinlock);
spin_lock(&zbpg->lock);
list_add_tail(&zbpg->bud_list, &zbud_unbuddied[nchunks].list);
zbud_unbuddied[nchunks].count++;
zh = &zbpg->buddy[0];
@ -389,12 +389,11 @@ init_zh:
zh->oid = *oid;
zh->pool_id = pool_id;
zh->client_id = client_id;
/* can wait to copy the data until the list locks are dropped */
spin_unlock(&zbud_budlists_spinlock);
to = zbud_data(zh, size);
memcpy(to, cdata, size);
spin_unlock(&zbpg->lock);
spin_unlock(&zbud_budlists_spinlock);
zbud_cumul_chunk_counts[nchunks]++;
atomic_inc(&zcache_zbud_curr_zpages);
zcache_zbud_cumul_zpages++;