linux-stable.git/drivers/staging/zcache, branch v3.3.6

staging: zcache: avoid AB-BA deadlock condition

2012-04-02T17:31:31+00:00

commit cfbc6a92212e74b07aa76c9e2f20c542e36077fb upstream.

Commit 9256a47 fixed a deadlock condition, being sure that the buddy
list spinlock is always taken before the page spinlock.

However in zbud_free_and_delist() locking order is the opposite
(page lock -> list lock).

Possible unsafe locking scenario (reported by lockdep):

        CPU0                    CPU1
        ----                    ----
   lock(&(&zbpg->lock)->rlock);
                                lock(zbud_budlists_spinlock);
                                lock(&(&zbpg->lock)->rlock);
   lock(zbud_budlists_spinlock);

Fix by grabbing the locks in opposite order in zbud_free_and_delist().

Signed-off-by: Andrea Righi 
Signed-off-by: Greg Kroah-Hartman

staging: zcache: fix serialization bug in zv stats

2012-02-08T22:14:14+00:00

In a multithreaded workload, the zv_curr_dist_counts
and zv_cumul_dist_counts statistics are being corrupted
because the increments and decrements in zv_create
and zv_free are not atomic.

This patch converts these statistics and their corresponding
increments/decrements/reads to atomic operations.

Signed-off-by: Seth Jennings 
Acked-by: Dan Magenheimer 
Signed-off-by: Greg Kroah-Hartman

zcache: Set SWIZ_BITS to 8 to reduce tmem bucket lock contention.

2012-02-08T22:14:12+00:00

SWIZ_BITS > 8 results in a much larger number of "tmem_obj"
allocations, likely one per page-placed-in-frontswap.  The
tmem_obj is not huge (roughly 100 bytes), but it is large
enough to add a not-insignificant memory overhead to zcache.

The SWIZ_BITS=8  will get roughly the same lock contention
without the space wastage.

The effect of SWIZ_BITS can be thought of as "2^SWIZ_BITS is
the number of unique oids that be generated" (This concept is
limited to frontswap's use of tmem).

Acked-by: Seth Jennings 
Signed-off-by: Konrad Rzeszutek Wilk 
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

zcache: fix deadlock condition

2012-02-08T22:14:12+00:00

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 
Acked-by: Konrad Rzeszutek Wilk 
Cc: stable 
Signed-off-by: Greg Kroah-Hartman

Staging: zcache: Fix calls to obsolete function

2011-11-27T02:13:55+00:00

Function "strict_strtol" replaced by "kstrtol" as suggested by the checkpatch script

Signed-off-by: Bernhard Heinloth 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'staging-next' into Linux 3.1

2011-10-25T07:18:11+00:00

This was done to resolve a conflict in the
drivers/staging/comedi/drivers/ni_labpc.c file that resolved a build
bugfix in Linus's tree with a "better" bugfix that was in the
staging-next tree that resolved the issue in a more complete manner.

Signed-off-by: Greg Kroah-Hartman

staging: zcache: remove zcache_direct_reclaim_lock

2011-10-17T22:24:11+00:00

zcache_do_preload() currently does a spin_trylock() on the
zcache_direct_reclaim_lock. Holding this lock intends to prevent
shrink_zcache_memory() from evicting zbud pages as a result
of a preload.

However, it also prevents two threads from
executing zcache_do_preload() at the same time.  The first
thread will obtain the lock and the second thread's spin_trylock()
will fail (an aborted preload) causing the page to be either lost
(cleancache) or pushed out to the swap device (frontswap). It
also doesn't ensure that the call to shrink_zcache_memory() is
on the same thread as the call to zcache_do_preload().

Additional, there is no need for this mechanism because all
zcache_do_preload() calls that come down from cleancache already
have PF_MEMALLOC set in the process flags which prevents
direct reclaim in the memory manager. If the zcache_do_preload()
call is done from the frontswap path, we _want_ reclaim to be
done (which it isn't right now).

This patch removes the zcache_direct_reclaim_lock and related
statistics in zcache.

Based on v3.1-rc8

Signed-off-by: Seth Jennings 
Reviewed-by: Dave Hansen 
Acked-by: Dan Magenheimer 
Signed-off-by: Greg Kroah-Hartman

staging: zcache: reduce tmem bucket lock contention

2011-10-12T15:29:03+00:00

tmem uses hash buckets each with their own rbtree and lock to
quickly lookup tmem objects.  tmem has TMEM_HASH_BUCKETS (256)
buckets per pool.  However, because of the way the tmem_oid is
generated for frontswap pages, only 16 unique tmem_oids are being
generated, resulting in only 16 of the 256 buckets being used.
This cause high lock contention for the per bucket locks.

This patch changes SWIZ_BITS to include more bits of the offset.
The result is that all 256 hash buckets are potentially used resulting in a
95% drop in hash bucket lock contention.

Signed-off-by: Seth Jennings 
Acked-by: Dan Magenheimer 
Signed-off-by: Greg Kroah-Hartman

staging: zcache: fix crash on cpu remove

2011-10-11T16:02:49+00:00

In the case that a cpu is taken offline before zcache_do_preload() is
ever called on the cpu, the per-cpu zcache_preloads structure will
be uninitialized.  In the CPU_DEAD case for zcache_cpu_notifier(),
kp->obj is not checked before calling kmem_cache_free() on it.
If it is NULL, a crash results.

This patch ensures that both kp->obj and kp->page are not NULL before
calling the respective free functions. In practice, just checking
one or the other should be sufficient since they are assigned together
in zcache_do_preload(), but I check both for safety.

Signed-off-by: Seth Jennings 
Acked-by: Dave Hansen 
Signed-off-by: Greg Kroah-Hartman

staging: zcache: fix cleancache crash

2011-09-20T21:17:13+00:00

After commit c5f5c4db3938 ("staging: zcache: fix crash on high memory
swap") cleancache crashes on the first successful get.  This was caused
by a remaining virt_to_page() call in zcache_pampd_get_data_and_free()
that only gets run in the cleancache path.

The patch converts the virt_to_page() to struct page casting like was
done for other instances in c5f5c4db3938.

Signed-off-by: Seth Jennings 
Tested-By: Valdis Kletnieks 
Acked-by: Dan Magenheimer 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Linus Torvalds