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Commit 9256a478 authored by Dan Magenheimer's avatar Dan Magenheimer Committed by Greg Kroah-Hartman
Browse files

zcache: fix deadlock condition 



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: default avatarDan Magenheimer <dan.magenheimer@oracle.com>
Acked-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent c5b1247b

drivers/staging/zcache/zcache-main.c

+3 −4
Original line number Diff line number Diff line
@@ -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++;