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  1. 12 Apr, 2017 33 commits
  3. 08 Apr, 2017 7 commits
    • Greg Kroah-Hartman's avatar
      Linux 4.9.21 · 37feaf80
      Greg Kroah-Hartman authored
      37feaf80
    • Keith Busch's avatar
      nvme/pci: Disable on removal when disconnected · 02b23e05
      Keith Busch authored 
      commit 6db28eda upstream.

If the device is not present, the driver should disable the queues
immediately. Prior to this, the driver was relying on the watchdog timer
to kill the queues if requests were outstanding to the device, and that
just delays removal up to one second.
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      02b23e05
    • Keith Busch's avatar
      nvme/core: Fix race kicking freed request_queue · a5e39a7f
      Keith Busch authored 
      commit f33447b9 upstream.

If a namespace has already been marked dead, we don't want to kick the
request_queue again since we may have just freed it from another thread.
Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
Reviewed-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      a5e39a7f
    • Jason A. Donenfeld's avatar
      padata: avoid race in reordering · eb8c62a3
      Jason A. Donenfeld authored 
      commit de5540d0 upstream.

Under extremely heavy uses of padata, crashes occur, and with list
debugging turned on, this happens instead:

[87487.298728] WARNING: CPU: 1 PID: 882 at lib/list_debug.c:33
__list_add+0xae/0x130
[87487.301868] list_add corruption. prev->next should be next
(ffffb17abfc043d0), but was ffff8dba70872c80. (prev=ffff8dba70872b00).
[87487.339011]  [<ffffffff9a53d075>] dump_stack+0x68/0xa3
[87487.342198]  [<ffffffff99e119a1>] ? console_unlock+0x281/0x6d0
[87487.345364]  [<ffffffff99d6b91f>] __warn+0xff/0x140
[87487.348513]  [<ffffffff99d6b9aa>] warn_slowpath_fmt+0x4a/0x50
[87487.351659]  [<ffffffff9a58b5de>] __list_add+0xae/0x130
[87487.354772]  [<ffffffff9add5094>] ? _raw_spin_lock+0x64/0x70
[87487.357915]  [<ffffffff99eefd66>] padata_reorder+0x1e6/0x420
[87487.361084]  [<ffffffff99ef0055>] padata_do_serial+0xa5/0x120

padata_reorder calls list_add_tail with the list to which its adding
locked, which seems correct:

spin_lock(&squeue->serial.lock);
list_add_tail(&padata->list, &squeue->serial.list);
spin_unlock(&squeue->serial.lock);

This therefore leaves only place where such inconsistency could occur:
if padata->list is added at the same time on two different threads.
This pdata pointer comes from the function call to
padata_get_next(pd), which has in it the following block:

next_queue = per_cpu_ptr(pd->pqueue, cpu);
padata = NULL;
reorder = &next_queue->reorder;
if (!list_empty(&reorder->list)) {
       padata = list_entry(reorder->list.next,
                           struct padata_priv, list);
       spin_lock(&reorder->lock);
       list_del_init(&padata->list);
       atomic_dec(&pd->reorder_objects);
       spin_unlock(&reorder->lock);

       pd->processed++;

       goto out;
}
out:
return padata;

I strongly suspect that the problem here is that two threads can race
on reorder list. Even though the deletion is locked, call to
list_entry is not locked, which means it's feasible that two threads
pick up the same padata object and subsequently call list_add_tail on
them at the same time. The fix is thus be hoist that lock outside of
that block.
Signed-off-by: default avatarJason A. Donenfeld <Jason@zx2c4.com>
Acked-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      eb8c62a3
    • NeilBrown's avatar
      blk: Ensure users for current->bio_list can see the full list. · 5959cded
      NeilBrown authored 
      commit f5fe1b51 upstream.

Commit 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
changed current->bio_list so that it did not contain *all* of the
queued bios, but only those submitted by the currently running
make_request_fn.

There are two places which walk the list and requeue selected bios,
and others that check if the list is empty.  These are no longer
correct.

So redefine current->bio_list to point to an array of two lists, which
contain all queued bios, and adjust various code to test or walk both
lists.
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Fixes: 79bd9959 ("blk: improve order of bio handling in generic_make_request()")
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Cc: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      5959cded
    • NeilBrown's avatar
      blk: improve order of bio handling in generic_make_request() · d5986e00
      NeilBrown authored 
      commit 79bd9959 upstream.

To avoid recursion on the kernel stack when stacked block devices
are in use, generic_make_request() will, when called recursively,
queue new requests for later handling.  They will be handled when the
make_request_fn for the current bio completes.

If any bios are submitted by a make_request_fn, these will ultimately
be handled seqeuntially.  If the handling of one of those generates
further requests, they will be added to the end of the queue.

This strict first-in-first-out behaviour can lead to deadlocks in
various ways, normally because a request might need to wait for a
previous request to the same device to complete.  This can happen when
they share a mempool, and can happen due to interdependencies
particular to the device.  Both md and dm have examples where this happens.

These deadlocks can be erradicated by more selective ordering of bios.
Specifically by handling them in depth-first order.  That is: when the
handling of one bio generates one or more further bios, they are
handled immediately after the parent, before any siblings of the
parent.  That way, when generic_make_request() calls make_request_fn
for some particular device, we can be certain that all previously
submited requests for that device have been completely handled and are
not waiting for anything in the queue of requests maintained in
generic_make_request().

An easy way to achieve this would be to use a last-in-first-out stack
instead of a queue.  However this will change the order of consecutive
bios submitted by a make_request_fn, which could have unexpected consequences.
Instead we take a slightly more complex approach.
A fresh queue is created for each call to a make_request_fn.  After it completes,
any bios for a different device are placed on the front of the main queue, followed
by any bios for the same device, followed by all bios that were already on
the queue before the make_request_fn was called.
This provides the depth-first approach without reordering bios on the same level.

This, by itself, it not enough to remove all deadlocks.  It just makes
it possible for drivers to take the extra step required themselves.

To avoid deadlocks, drivers must never risk waiting for a request
after submitting one to generic_make_request.  This includes never
allocing from a mempool twice in the one call to a make_request_fn.

A common pattern in drivers is to call bio_split() in a loop, handling
the first part and then looping around to possibly split the next part.
Instead, a driver that finds it needs to split a bio should queue
(with generic_make_request) the second part, handle the first part,
and then return.  The new code in generic_make_request will ensure the
requests to underlying bios are processed first, then the second bio
that was split off.  If it splits again, the same process happens.  In
each case one bio will be completely handled before the next one is attempted.

With this is place, it should be possible to disable the
punt_bios_to_recover() recovery thread for many block devices, and
eventually it may be possible to remove it completely.

Ref: http://www.spinics.net/lists/raid/msg54680.htmlTested-by: default avatarJinpu Wang <jinpu.wang@profitbricks.com>
Inspired-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
Cc: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      d5986e00
    • Johannes Weiner's avatar
      mm: workingset: fix premature shadow node shrinking with cgroups · e3a55294
      Johannes Weiner authored 
      commit 0cefabda upstream.

Commit 0a6b76dd ("mm: workingset: make shadow node shrinker memcg
aware") enabled cgroup-awareness in the shadow node shrinker, but forgot
to also enable cgroup-awareness in the list_lru the shadow nodes sit on.

Consequently, all shadow nodes are sitting on a global (per-NUMA node)
list, while the shrinker applies the limits according to the amount of
cache in the cgroup its shrinking.  The result is excessive pressure on
the shadow nodes from cgroups that have very little cache.

Enable memcg-mode on the shadow node LRUs, such that per-cgroup limits
are applied to per-cgroup lists.

Fixes: 0a6b76dd ("mm: workingset: make shadow node shrinker memcg aware")
Link: http://lkml.kernel.org/r/20170322005320.8165-1-hannes@cmpxchg.orgSigned-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarVladimir Davydov <vdavydov@tarantool.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      e3a55294
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