If an oom killed thread calls mempool_alloc(), it is possible that it'll
loop forever if there are no elements on the freelist since
__GFP_NOMEMALLOC prevents it from accessing needed memory reserves in
oom conditions.
Only set __GFP_NOMEMALLOC if there are elements on the freelist. If
there are no free elements, allow allocations without the bit set so
that memory reserves can be accessed if needed.
Additionally, using mempool_alloc() with __GFP_NOMEMALLOC is not
supported since the implementation can loop forever without accessing
memory reserves when needed.
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When removing an element from the mempool, mark it as unpoisoned in KASAN
before verifying its contents for SLUB/SLAB debugging. Otherwise KASAN
will flag the reads checking the element use-after-free writes as
use-after-free reads.
Signed-off-by: Matthew Dawson <matthew@mjdsystems.ca>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
__GFP_WAIT has been used to identify atomic context in callers that hold
spinlocks or are in interrupts. They are expected to be high priority and
have access one of two watermarks lower than "min" which can be referred
to as the "atomic reserve". __GFP_HIGH users get access to the first
lower watermark and can be called the "high priority reserve".
Over time, callers had a requirement to not block when fallback options
were available. Some have abused __GFP_WAIT leading to a situation where
an optimisitic allocation with a fallback option can access atomic
reserves.
This patch uses __GFP_ATOMIC to identify callers that are truely atomic,
cannot sleep and have no alternative. High priority users continue to use
__GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and
are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify
callers that want to wake kswapd for background reclaim. __GFP_WAIT is
redefined as a caller that is willing to enter direct reclaim and wake
kswapd for background reclaim.
This patch then converts a number of sites
o __GFP_ATOMIC is used by callers that are high priority and have memory
pools for those requests. GFP_ATOMIC uses this flag.
o Callers that have a limited mempool to guarantee forward progress clear
__GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall
into this category where kswapd will still be woken but atomic reserves
are not used as there is a one-entry mempool to guarantee progress.
o Callers that are checking if they are non-blocking should use the
helper gfpflags_allow_blocking() where possible. This is because
checking for __GFP_WAIT as was done historically now can trigger false
positives. Some exceptions like dm-crypt.c exist where the code intent
is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to
flag manipulations.
o Callers that built their own GFP flags instead of starting with GFP_KERNEL
and friends now also need to specify __GFP_KSWAPD_RECLAIM.
The first key hazard to watch out for is callers that removed __GFP_WAIT
and was depending on access to atomic reserves for inconspicuous reasons.
In some cases it may be appropriate for them to use __GFP_HIGH.
The second key hazard is callers that assembled their own combination of
GFP flags instead of starting with something like GFP_KERNEL. They may
now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless
if it's missed in most cases as other activity will wake kswapd.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vitaly Wool <vitalywool@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mempool_destroy() does not tolerate a NULL mempool_t pointer argument and
performs a NULL-pointer dereference. This requires additional attention
and effort from developers/reviewers and forces all mempool_destroy()
callers to do a NULL check
if (pool)
mempool_destroy(pool);
Or, otherwise, be invalid mempool_destroy() users.
Tweak mempool_destroy() and NULL-check the pointer there.
Proposed by Andrew Morton.
Link: https://lkml.org/lkml/2015/6/8/583
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mempools keep allocated objects in reserved for situations when ordinary
allocation may not be possible to satisfy. These objects shouldn't be
accessed before they leave the pool.
This patch poison elements when get into the pool and unpoison when they
leave it. This will let KASan to detect use-after-free of mempool's
elements.
Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Tested-by: David Rientjes <rientjes@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dmitry Chernenkov <drcheren@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Mempools keep elements in a reserved pool for contexts in which allocation
may not be possible. When an element is allocated from the reserved pool,
its memory contents is the same as when it was added to the reserved pool.
Because of this, elements lack any free poisoning to detect use-after-free
errors.
This patch adds free poisoning for elements backed by the slab allocator.
This is possible because the mempool layer knows the object size of each
element.
When an element is added to the reserved pool, it is poisoned with
POISON_FREE. When it is removed from the reserved pool, the contents are
checked for POISON_FREE. If there is a mismatch, a warning is emitted to
the kernel log.
This is only effective for configs with CONFIG_DEBUG_SLAB or
CONFIG_SLUB_DEBUG_ON.
[fabio.estevam@freescale.com: use '%zu' for printing 'size_t' variable]
[arnd@arndb.de: add missing include]
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All occurrences of mempools based on slab caches with object constructors
have been removed from the tree, so disallow creating them.
We can only dereference mem->ctor in mm/mempool.c without including
mm/slab.h in include/linux/mempool.h. So simply note the restriction,
just like the comment restricting usage of __GFP_ZERO, and warn on kernels
with CONFIG_DEBUG_VM() if such a mempool is allocated from.
We don't want to incur this check on every element allocation, so use
VM_BUG_ON().
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sebastian Ott <sebott@linux.vnet.ibm.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Allocating a large number of elements in atomic context could quickly
deplete memory reserves, so just disallow atomic resizing entirely.
Nothing currently uses mempool_resize() with anything other than
GFP_KERNEL, so convert existing callers to drop the gfp_mask.
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Steffen Maier <maier@linux.vnet.ibm.com> [zfcp]
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Steve French <sfrench@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When mempool_alloc() returns an existing pool object, kmemleak_alloc()
is no longer called and the stack trace corresponds to the original
object allocation. This patch updates the kmemleak allocation stack
trace for such objects to make it more useful for debugging.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Memory obtained via mempool_alloc is not always zeroed even when
called with __GFP_ZERO. Add a note and VM_BUG_ON statement to make
that clear.
[akpm@linux-foundation.org: use VM_WARN_ON_ONCE]
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add unlikely and likely hints to the function mempool_free. It lays out
the code in such a way that the common path is executed straighforward and
saves a cache line.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mempool_create_node() currently assumes %GFP_KERNEL. Its only user,
blk_init_free_list(), is about to be updated to use other allocation
flags - add @gfp_mask argument to the function.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
mempool modifies gfp_mask so that the backing allocator doesn't try too
hard or trigger warning message when there's pool to fall back on. In
addition, for the first try, it removes __GFP_WAIT and IO, so that it
doesn't trigger reclaim or wait when allocation can be fulfilled from
pool; however, when that allocation fails and pool is empty too, it waits
for the pool to be replenished before retrying.
Allocation which could have succeeded after a bit of reclaim has to wait
on the reserved items and it's not like mempool doesn't retry with
__GFP_WAIT and IO. It just does that *after* someone returns an element,
pointlessly delaying things.
Fix it by retrying immediately if the first round of allocation attempts
w/o __GFP_WAIT and IO fails.
[akpm@linux-foundation.org: shorten the lock hold time]
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mempool_destroy() is a thin wrapper around free_pool(). The only thing it
adds is BUG_ON(pool->curr_nr != pool->min_nr). The intention seems to be
to enforce that all allocated elements are freed; however, the BUG_ON()
can't achieve that (it doesn't know anything about objects above min_nr)
and incorrect as mempool_resize() is allowed to leave the pool extended
but not filled. Furthermore, panicking is way worse than any memory leak
and there are better debug tools to track memory leaks.
Drop the BUG_ON() from mempool_destory() and as that leaves the function
identical to free_pool(), replace it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mempool_alloc/free() use undocumented smp_mb()'s. The code is slightly
broken and misleading.
The lockless part is in mempool_free(). It wants to determine whether the
item being freed needs to be returned to the pool or backing allocator
without grabbing pool->lock. Two things need to be guaranteed for correct
operation.
1. pool->curr_nr + #allocated should never dip below pool->min_nr.
2. Waiters shouldn't be left dangling.
For #1, The only necessary condition is that curr_nr visible at free is
from after the allocation of the element being freed (details in the
comment). For most cases, this is true without any barrier but there can
be fringe cases where the allocated pointer is passed to the freeing task
without going through memory barriers. To cover this case, wmb is
necessary before returning from allocation and rmb is necessary before
reading curr_nr. IOW,
ALLOCATING TASK FREEING TASK
update pool state after alloc;
wmb();
pass pointer to freeing task;
read pointer;
rmb();
read pool state to free;
The current code doesn't have wmb after pool update during allocation and
may theoretically, on machines where unlock doesn't behave as full wmb,
lead to pool depletion and deadlock. smp_wmb() needs to be added after
successful allocation from reserved elements and smp_mb() in
mempool_free() can be replaced with smp_rmb().
For #2, the waiter needs to add itself to waitqueue and then check the
wait condition and the waker needs to update the wait condition and then
wake up. Because waitqueue operations always go through full spinlock
synchronization, there is no need for extra memory barriers.
Furthermore, mempool_alloc() is already holding pool->lock when it decides
that it needs to wait. There is no reason to do unlock - add waitqueue -
test condition again. It can simply add itself to waitqueue while holding
pool->lock and then unlock and sleep.
This patch adds smp_wmb() after successful allocation from reserved pool,
replaces smp_mb() in mempool_free() with smp_rmb() and extend pool->lock
over waitqueue addition. More importantly, it explains what memory
barriers do and how the lockless testing is correct.
-v2: Oleg pointed out that unlock doesn't imply wmb. Added explicit
smp_wmb() after successful allocation from reserved pool and
updated comments accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The files changed within are only using the EXPORT_SYMBOL
macro variants. They are not using core modular infrastructure
and hence don't need module.h but only the export.h header.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
The kzalloc mempool zeros items when they are initially allocated, but
does not rezero used items that are returned to the pool. Consequently
mempool_alloc()s may return non-zeroed memory.
Since there are/were only two in-tree users for
mempool_create_kzalloc_pool(), and 'fixing' this in a way that will
re-zero used (but not new) items before first use is non-trivial, just
remove it.
Signed-off-by: Sage Weil <sage@newdream.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
clean up type-casting twice. "size_t" is typedef as "unsigned long" in
64-bit system, and "unsigned int" in 32-bit system, and the intermediate
cast to 'long' is pointless.
Signed-off-by: Figo.zhang <figo1802@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kmalloc_node() and kmem_cache_alloc_node() were not available in a zeroing
variant in the past. But with __GFP_ZERO it is possible now to do zeroing
while allocating.
Use __GFP_ZERO to remove the explicit clearing of memory via memset whereever
we can.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
A variety of (mostly) innocuous fixes to the embedded kernel-doc content in
source files, including:
* make multi-line initial descriptions single line
* denote some function names, constants and structs as such
* change erroneous opening '/*' to '/**' in a few places
* reword some text for clarity
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch works around a complex dm-related deadlock/livelock down in the
mempool allocator.
Alasdair said:
Several dm targets suffer from this.
Mempools are not yet used correctly everywhere in device-mapper: they can
get shared when devices are stacked, and some targets share them across
multiple instances. I made fixing this one of the prerequisites for this
patch:
md-dm-reduce-stack-usage-with-stacked-block-devices.patch
which in some cases makes people more likely to hit the problem.
There's been some progress on this recently with (unfinished) dm-crypt
patches at:
http://www.kernel.org/pub/linux/kernel/people/agk/patches/2.6/editing/
(dm-crypt-move-io-to-workqueue.patch plus dependencies)
and:
I've no problems with a temporary workaround like that, but Milan Broz (a
new Redhat developer in the Czech Republic) has started reviewing all the
mempool usage in device-mapper so I'm expecting we'll soon have a proper fix
for this associated problems. [He's back from holiday at the start of next
week.]
For now, this sad-but-safe little patch will allow the machine to recover.
[akpm@osdl.org: rewrote changelog]
Cc: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Alexander Potapenko
David Rientjes
Matthew Dawson
Mel Gorman
Sergey Senozhatsky
Andrey Ryabinin
Catalin Marinas
Sebastian Ott
Mikulas Patocka
Joe Perches
Tejun Heo
Paul Gortmaker
Sage Weil
Figo.zhang
Simon Arlott
Christoph Lameter
Rusty Russell
Robert P. J. Day
Pavel Mironchik