Merge branches 'consolidate.2019.04.09a', 'doc.2019.03.26b', 'fixes.2019.03.26b', 'srcu.2019.03.26b', 'stall.2019.03.26b' and 'torture.2019.03.26b' into HEAD
The RCU flavors have been consolidated, so this commit replaces mentions
of the now-obsolete synchronize_sched() function with synchronize_rcu().
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jonathan Corbet <corbet@lwn.net> Cc: <linux-doc@vger.kernel.org> Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
The scripting must supply the CONFIG_INITRAMFS_SOURCE Kconfig option
so that kbuild can find the desired initrd, but the configcheck.sh
script gets confused by this option because it takes a string instead
of the expected y/n/m. This causes checkconfig.sh to complain about
CONFIG_INITRAMFS_SOURCE in the torture-test output (though not in the
summary). As more people use rcutorture, the resulting confusion is
an increasing concern.
This commit therefore suppresses this false-positive warning by filtering
CONFIG_INITRAMFS_SOURCE from within the checkconfig.sh script.
Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Thu, 21 Mar 2019 20:30:01 +0000 (13:30 -0700)]
locktorture: NULL cxt.lwsa and cxt.lrsa to allow bad-arg detection
Currently, lock_torture_cleanup() uses the values of cxt.lwsa and cxt.lrsa
to detect bad parameters that prevented locktorture from initializing,
let alone running. In this case, lock_torture_cleanup() does no cleanup
aside from invoking torture_cleanup_begin() and torture_cleanup_end(),
as required to permit future torture tests to run. However, this
heuristic fails if the run with bad parameters was preceded by a previous
run that actually ran: In this case, both cxt.lwsa and cxt.lrsa will
remain non-zero, which means that the current lock_torture_cleanup()
invocation will be unable to detect the fact that it should skip cleanup,
which can result in charming outcomes such as double frees.
This commit therefore NULLs out both cxt.lwsa and cxt.lrsa at the end
of any run that actually ran.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: Josh Triplett <josh@joshtriplett.org>
Paul E. McKenney [Thu, 21 Mar 2019 17:26:41 +0000 (10:26 -0700)]
rcuperf: Fix cleanup path for invalid perf_type strings
If the specified rcuperf.perf_type is not in the rcu_perf_init()
function's perf_ops[] array, rcuperf prints some console messages and
then invokes rcu_perf_cleanup() to set state so that a future torture
test can run. However, rcu_perf_cleanup() also attempts to end the
test that didn't actually start, and in doing so relies on the value
of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.
This commit therefore sets the value of cur_ops to NULL in this case and
inserts a check near the beginning of rcu_perf_cleanup(), thus avoiding
relying on an irrelevant cur_ops value.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Thu, 21 Mar 2019 16:27:28 +0000 (09:27 -0700)]
rcutorture: Fix cleanup path for invalid torture_type strings
If the specified rcutorture.torture_type is not in the rcu_torture_init()
function's torture_ops[] array, rcutorture prints some console messages
and then invokes rcu_torture_cleanup() to set state so that a future
torture test can run. However, rcu_torture_cleanup() also attempts to
end the test that didn't actually start, and in doing so relies on the
value of cur_ops, a value that is not particularly relevant in this case.
This can result in confusing output or even follow-on failures due to
attempts to use facilities that have not been properly initialized.
This commit therefore sets the value of cur_ops to NULL in this case
and inserts a check near the beginning of rcu_torture_cleanup(),
thus avoiding relying on an irrelevant cur_ops value.
Reported-by: kernel test robot <rong.a.chen@intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Neeraj Upadhyay [Fri, 8 Mar 2019 19:10:45 +0000 (00:40 +0530)]
rcutorture: Fix expected forward progress duration in OOM notifier
The rcutorture_oom_notify() function has a misplaced close parenthesis
that results in increasingly long delays in rcu_fwd_progress_check()'s
checking for various RCU forward-progress problems. This commit therefore
puts the parenthesis in the right place.
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Thu, 28 Feb 2019 23:59:43 +0000 (15:59 -0800)]
rcutorture: Remove ->ext_irq_conflict field
Back when there was a separate RCU-bh flavor, the ->ext_irq_conflict
field was used to prevent executing local_bh_enable() while interrupts
were disabled. However, there is no longer an RCU-bh flavor, so this
commit removes the no-longer-needed ->ext_irq_conflict field.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Thu, 28 Feb 2019 23:06:13 +0000 (15:06 -0800)]
rcutorture: Make rcutorture_extend_mask() comment match the code
The code actually rarely uses more than one type of RCU read-side
protection, as is actually desired given that we need some reasonable
probability of preempting RCU read-side critical sections, which cannot
happen with multiple types of protection. This comment therefore adjusts
the comment.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Wed, 23 Jan 2019 03:23:00 +0000 (19:23 -0800)]
torture: Don't try to offline the last CPU
If there is only one online CPU, it doesn't make sense to try to offline
it, as any such attempt is guaranteed to fail. This commit therefore
check for this condition and refuses to attempt the nonsensical.
Reported-by: Su Yue <suy.fnst@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-By: Su Yue <suy.fnst@cn.fujitsu.com>
Neeraj Upadhyay [Fri, 8 Mar 2019 19:57:48 +0000 (11:57 -0800)]
rcu: Fix nohz status in stall warning
The Documentation/RCU/stallwarn.txt file says that stall warnings
print "D" if dyntick-idle processing is enabled, but the code in
print_cpu_stall_fast_no_hz() prints "." instead. This commit therefore
reverses the sense of the test to make the code match the documentation.
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Tue, 15 Jan 2019 15:01:33 +0000 (07:01 -0800)]
rcu: Move forward-progress checkers into tree_stall.h
This commit further consolidates stall-warning functionality by moving
forward-progress checkers into kernel/rcu/tree_stall.h, updating a
comment or two while in the area. More specifically, this commit moves
show_rcu_gp_kthreads(), rcu_check_gp_start_stall(), rcu_fwd_progress_check(),
sysrq_rcu, sysrq_show_rcu(), sysrq_rcudump_op, and rcu_sysrq_init() from
kernel/rcu/tree.c to kernel/rcu/tree_stall.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Mon, 14 Jan 2019 18:19:20 +0000 (10:19 -0800)]
rcu: Move irq-disabled stall-warning checking to tree_stall.h
The rcu_iw_handler() function's sole purpose in life is to indicate
whether a stalled CPU had interrupts disabled, so it belongs in
kernel/rcu/tree_stall.h. This commit therefore makes that move,
clarifying its header comment while in the area.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 17:35:44 +0000 (09:35 -0800)]
rcu: Organize functions in tree_stall.h
This commit does only code movement, removal of now-unneeded forward
declarations, and addition of comments. It organizes the functions
that implement RCU CPU stall warnings for normal grace periods into
three categories:
1. Control of RCU CPU stall warnings, including computing timeouts.
2. Interaction of stall warnings with grace periods.
3. Actual printing of the RCU CPU stall-warning messages.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 05:05:17 +0000 (21:05 -0800)]
rcu: Move FAST_NO_HZ stall-warning code to tree_stall.h
This commit further consolidates the stall-warning code by moving
print_cpu_stall_info() and its helper functions along with
zero_cpu_stall_ticks() to kernel/rcu/tree_stall.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 04:58:58 +0000 (20:58 -0800)]
rcu: Inline RCU stall-warning info helper functions
The print_cpu_stall_info_begin() and print_cpu_stall_info_end() print a
single character each onto the console, and are a holdover from a time
when RCU CPU stall warning messages could be abbreviated using a long-gone
Kconfig option. This commit therefore adds these single characters to
already-printed strings in the calling functions, and then eliminates
both print_cpu_stall_info_begin() and print_cpu_stall_info_end().
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 04:51:49 +0000 (20:51 -0800)]
rcu: Move rcu_print_task_exp_stall() to tree_exp.h
Because expedited CPU stall warnings are contained within the
kernel/rcu/tree_exp.h file, rcu_print_task_exp_stall() should live
there too. This commit carries out the required code motion.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
The rcu_print_detail_task_stall(), rcu_print_task_stall_begin(), and
rcu_print_task_stall_end() functions were defined to allow long-gone
Kconfig options to provide an abbreviated RCU CPU stall warning printout.
This commit saves a few lines of code by inlining them into their sole
callers.
While in the area, a useless call of rcu_print_detail_task_stall_rnp()
on the root rcu_node structure was eliminated. If there is only one
rcu_node structure, its tasks get printed twice, but if there are more,
the root rcu_node structure is guaranteed to have an empty list of blocked
tasks, hence the uselessness. (Long ago, root rcu_node structures with
non-empty ->blkd_tasks lists could happen, but no longer.)
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 00:57:41 +0000 (16:57 -0800)]
rcu: Move RCU CPU stall-warning code out of tree.c
This commit completes the process of consolidating the code for RCU CPU
stall warnings for normal grace periods by moving the remaining such
code from kernel/rcu/tree.c to kernel/rcu/tree_stall.h.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 00:34:47 +0000 (16:34 -0800)]
rcu: Move RCU CPU stall-warning code out of tree_plugin.h
The RCU CPU stall-warning code for normal grace periods is currently
scattered across two files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired. Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit continues this process by moving stall-warning code from
kernel/rcu/tree_plugin.c to a new kernel/rcu/tree_stall.h file.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Sat, 12 Jan 2019 00:10:57 +0000 (16:10 -0800)]
rcu: Move RCU CPU stall-warning code out of update.c
The RCU CPU stall-warning code for normal grace periods is currently
scattered across three files, due to earlier Tiny RCU support for RCU
CPU stall warnings and for old Kconfig options that have long since
been retired. Given that it is hard for the lead RCU maintainer to
find relevant stall-warning code, it would be good to consolidate it.
This commit starts this process by moving stall-warning code from
kernel/rcu/update.c to a new kernel/rcu/tree_stall.h file.
Note that the definitions of rcu_cpu_stall_suppress and
rcu_cpu_stall_timeout must remain in kernel/rcu/update.h to provide
compatibility for kernel boot parameter lists.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Wed, 13 Feb 2019 21:54:37 +0000 (13:54 -0800)]
srcu: Remove cleanup_srcu_struct_quiesced()
The cleanup_srcu_struct_quiesced() function was added because NVME
used WQ_MEM_RECLAIM workqueues and SRCU did not, which meant that
NVME workqueues waiting on SRCU workqueues could result in deadlocks
during low-memory conditions. However, SRCU now also has WQ_MEM_RECLAIM
workqueues, so there is no longer a potential for deadlock. Furthermore,
it turns out to be extremely hard to use cleanup_srcu_struct_quiesced()
correctly due to the fact that SRCU callback invocation accesses the
srcu_struct structure's per-CPU data area just after callbacks are
invoked. Therefore, the usual practice of using srcu_barrier() to wait
for callbacks to be invoked before invoking cleanup_srcu_struct_quiesced()
fails because SRCU's callback-invocation workqueue handler might be
delayed, which can result in cleanup_srcu_struct_quiesced() being invoked
(and thus freeing the per-CPU data) before the SRCU's callback-invocation
workqueue handler is finished using that per-CPU data. Nor is this a
theoretical problem: KASAN emitted use-after-free warnings because of
this problem on actual runs.
In short, NVME can now safely invoke cleanup_srcu_struct(), which
avoids the use-after-free scenario. And cleanup_srcu_struct_quiesced()
is quite difficult to use safely. This commit therefore removes
cleanup_srcu_struct_quiesced(), switching its sole user back to
cleanup_srcu_struct(). This effectively reverts the following pair
of commits:
Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Tested-by: Bart Van Assche <bvanassche@acm.org>
Paul E. McKenney [Tue, 12 Feb 2019 18:44:33 +0000 (10:44 -0800)]
srcu: Check for in-flight callbacks in _cleanup_srcu_struct()
If someone fails to drain the corresponding SRCU callbacks (for
example, by failing to invoke srcu_barrier()) before invoking either
cleanup_srcu_struct() or cleanup_srcu_struct_quiesced(), the resulting
diagnostic is an ambiguous use-after-free diagnostic, and even then
only if you are running something like KASAN. This commit therefore
improves SRCU diagnostics by adding checks for in-flight callbacks at
_cleanup_srcu_struct() time.
Note that these diagnostics can still be defeated, for example, by
invoking call_srcu() concurrently with cleanup_srcu_struct(). Which is
a really bad idea, but sometimes all too easy to do. But even then,
these diagnostics have at least some probability of catching the problem.
Reported-by: Sagi Grimberg <sagi@grimberg.me> Reported-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Bart Van Assche <bvanassche@acm.org>
Paul E. McKenney [Tue, 26 Mar 2019 17:22:22 +0000 (10:22 -0700)]
rcu: Correct READ_ONCE()/WRITE_ONCE() for ->rcu_read_unlock_special
The task_struct structure's ->rcu_read_unlock_special field is only ever
read or written by the owning task, but it is accessed both at process
and interrupt levels. It may therefore be accessed using plain reads
and writes while interrupts are disabled, but must be accessed using
READ_ONCE() and WRITE_ONCE() or better otherwise. This commit makes a
few adjustments to align with this discipline.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Zhouyi Zhou [Wed, 20 Mar 2019 03:33:00 +0000 (03:33 +0000)]
rcu: Fix force_qs_rnp() header comment
Previously, threads blocked on offlining CPUS were migrated to the
root rcu_node structure, thus requiring RCU priority boosting on this
structure. However, since commit d19fb8d1f3f6 ("rcu: Don't migrate
blocked tasks even if all corresponding CPUs offline"), RCU does not
migrate blocked tasks. Consequently, RCU no longer does RCU priority
boosting on the root rcu_node structure as of commit 1be0085b515e ("rcu:
Don't initiate RCU priority boosting on root rcu_node").
This commit therefore brings comments for the force_qs_rnp() function's
header comment in line with this new no-root-boosting reality.
Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
[ paulmck: Also remove obsolete comment on suppressing new grace periods. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Neeraj Upadhyay [Mon, 11 Mar 2019 11:58:03 +0000 (17:28 +0530)]
rcu: Do a single rhp->func read in rcu_head_after_call_rcu()
The rcu_head_after_call_rcu() function reads the rhp->func pointer twice,
which can result in a false-positive WARN_ON_ONCE() if the callback
were passed to call_rcu() between the two reads. Although racing
rcu_head_after_call_rcu() with call_rcu() is to be a dubious use case
(the return value is not reliable in that case), intermittent and
irreproducible warnings are also quite dubious. This commit therefore
uses a single READ_ONCE() to pick up the value of rhp->func once, then
tests that value twice, thus guaranteeing consistent processing within
rcu_head_after_call_rcu()().
Neverthless, racing rcu_head_after_call_rcu() with call_rcu() is still
a dubious use case.
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
[ paulmck: Add blank line after declaration per checkpatch.pl. ] Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Neeraj Upadhyay [Mon, 11 Mar 2019 09:46:11 +0000 (15:16 +0530)]
rcu: Default jiffies_to_sched_qs to jiffies_till_sched_qs
The current code only calls adjust_jiffies_till_sched_qs() if
jiffies_till_sched_qs is left at its default value, so when the
jiffies_till_sched_qs kernel-boot parameter actually is specified,
jiffies_to_sched_qs will be left with the value zero, which
will result in useless slowdowns of cond_resched(). This commit
therefore changes rcu_init_geometry() to unconditionally invoke
adjust_jiffies_till_sched_qs(), which ensures that jiffies_to_sched_qs
will be initialized in all cases, thus maintaining good cond_resched()
performance.
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Neeraj Upadhyay [Fri, 8 Mar 2019 09:46:18 +0000 (15:16 +0530)]
rcu: Fix self-wakeups for grace-period kthread
The current rcu_gp_kthread_wake() function uses in_interrupt()
and thus does a self-wakeup from all interrupt contexts, including
the pointless case where the GP kthread happens to be running with
bottom halves disabled, along with the impossible case where the GP
kthread is running within an NMI handler (you are not supposed to invoke
rcu_gp_kthread_wake() from within an NMI handler. This commit therefore
replaces the in_interrupt() with in_irq(), so that the self-wakeups
happen only from handlers for hardware interrupts and softirqs.
This also makes the code match the comment.
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
rcu: Report error for bad rcu_nocbs= parameter values
This commit prints a console message when cpulist_parse() reports a
bad list of CPUs, and sets all CPUs' bits in that case. The reason for
setting all CPUs' bits is that this is the safe(r) choice for real-time
workloads, which would normally be the ones using the rcu_nocbs= kernel
boot parameter. Either way, later RCU console log messages list the
actual set of CPUs whose RCU callbacks will be offloaded.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Currently, the rcu_nocbs= kernel boot parameter requires that a specific
list of CPUs be specified, and has no way to say "all of them".
As noted by user RavFX in a comment to Phoronix topic 1002538, this
is an inconvenient side effect of the removal of the RCU_NOCB_CPU_ALL
Kconfig option. This commit therefore enables the rcu_nocbs= kernel boot
parameter to be given the string "all", as in "rcu_nocbs=all" to specify
that all CPUs on the system are to have their RCU callbacks offloaded.
Another approach would be to make cpulist_parse() check for "all", but
there are uses of cpulist_parse() that do other checking, which could
conflict with an "all". This commit therefore focuses on the specific
use of cpulist_parse() in rcu_nocb_setup().
Just a note to other people who would like changes to Linux-kernel RCU:
If you send your requests to me directly, they might get fixed somewhat
faster. RavFX's comment was posted on January 22, 2018 and I first saw
it on March 5, 2019. And the only reason that I found it -at- -all- was
that I was looking for projects using RCU, and my search engine showed
me that Phoronix comment quite by accident. Your choice, though! ;-)
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Akira Yokosawa [Sat, 2 Mar 2019 08:25:19 +0000 (17:25 +0900)]
rcu: Move common code out of if-else block
As the result of recent addition of "rdp->core_needs_qs = false;" in
the "if" block, now both branches of the if-else have the same
assignment.
Factor it out and reduce line count.
Signed-off-by: Akira Yokosawa <akiyks@gmail.com> Cc: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Liu Song [Thu, 21 Feb 2019 14:13:27 +0000 (22:13 +0800)]
rcu: Set rcutree.kthread_prio sysfs access to read-only
The rcutree.kthread_prio kernel-boot parameter is used to set the
priority for boost (rcub), per-CPU (rcuc), and grace-period (rcu_preempt
or rcu_sched) kthreads. It is also used by rcutorture to check whether
it is possible to meaningfully test RCU priority boosting. However,
all of these cases will either ignore or be confused by any post-boot
changes to rcutree.kthread_prio.
Note that the user really can change the priorities of all of these
kthreads using chrt, given sufficient privileges. Therefore, the
read-write nature of sysfs access to rcutree.kthread_prio is thus at
best an attractive nuisance.
This commit therefore changes sysfs access to rcutree.kthread_prio to
be read-only.
Signed-off-by: Liu Song <liu.song11@zte.com.cn> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Mon, 11 Feb 2019 15:21:29 +0000 (07:21 -0800)]
rcu: Make exit_rcu() handle non-preempted RCU readers
The purpose of exit_rcu() is to handle cases where buggy code causes a
task to exit within an RCU read-side critical section. It currently
does that in the case where said RCU read-side critical section was
preempted at least once, but fails to handle cases where preemption did
not occur. This case needs to be handled because otherwise the final
context switch away from the exiting task will incorrectly behave as if
task exit were instead a preemption of an RCU read-side critical section,
and will therefore queue the exiting task. The exiting task will have
exited, and thus won't ever execute rcu_read_unlock(), which means that
it will remain queued forever, blocking all subsequent grace periods,
and eventually resulting in OOM.
Although this is arguably better than letting grace periods proceed
and having a later rcu_read_unlock() access the now-freed task
structure that once belonged to the exiting tasks, it would obviously
be better to correctly handle this case. This commit therefore sets
->rcu_read_lock_nesting to 1 in that case, so that the subsequence call
to __rcu_read_unlock() causes the exiting task to exit its dangling RCU
read-side critical section.
Note that deferred quiescent states need not be considered. The reason
is that removing the task from the ->blkd_tasks[] list in the call to
rcu_preempt_deferred_qs() handles the per-task component of any deferred
quiescent state, and all other components of any deferred quiescent state
are associated with the CPU, which isn't going anywhere until some later
CPU-hotplug operation, which will report any remaining deferred quiescent
states from within the rcu_report_dead() function.
Note also that negative values of ->rcu_read_lock_nesting need not be
considered. First, these won't show up in exit_rcu() unless there is
a serious bug in RCU, and second, setting ->rcu_read_lock_nesting sets
the state so that the RCU read-side critical section will be exited
normally.
Again, this code has no effect unless there has been some prior bug
that prevents a task from leaving an RCU read-side critical section
before exiting. Furthermore, there have been no reports of the bug
fixed by this commit appearing in production. This commit is therefore
absolutely -not- recommended for backporting to -stable.
Reported-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in> Reported-by: BHARATH Y MOURYA <bharathm@iisc.ac.in> Reported-by: Aravinda Prasad <aravinda@iisc.ac.in> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: ABHISHEK DUBEY <dabhishek@iisc.ac.in>
Cyrill Gorcunov [Thu, 24 Jan 2019 18:14:37 +0000 (21:14 +0300)]
rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twice
The rcu_qs is disabling IRQs by self so no need to do the same in raise_softirq
but instead we can save some cycles using raise_softirq_irqoff directly.
CC: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
rcu: Avoid unnecessary softirq when system is idle
When there are no callbacks pending on an idle system, I noticed that
RCU softirq is continuously firing. During this the cpu_no_qs is set to
false, and core_needs_qs is set to true indefinitely. This causes
rcu_process_callbacks to be repeatedly called, even though the node
corresponding to the CPU has that CPU's mask bit cleared and the system
is idle. I believe the race is when such mask clearing is done during
idle CPU scan of the quiescent state forcing stage in the kthread
instead of the softirq. Since the rnp mask is cleared, but the flags on
the CPU's rdp are not cleared, the CPU thinks it still needs to report
to core RCU.
Cure this by clearing the core_needs_qs flag when the CPU detects that
its node is already updated which will avoid the unwanted softirq raises
to the benefit of real-time systems.
Test: Ran rcutorture for various tree RCU configs.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Paul E. McKenney [Thu, 10 Jan 2019 23:30:15 +0000 (15:30 -0800)]
rcu: Unconditionally expedite during suspend/hibernate
The rcu_pm_notify() function refuses to switch to/from expedited grace
periods on systems with more than 256 CPUs due to the serialized
initialization of expedited grace periods. However, expedited grace
periods are now initialized in parallel, removing this concern.
This commit therefore removes the checks from rcu_pm_notify(), so that
expedited grace periods are used unconditionally during suspend/resume
and hibernate/wake operations.
As always, real-time workloads wishing to completely avoid expedited
grace periods can use the rcupdate.rcu_normal= kernel parameter.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Tycho Andersen [Tue, 29 Jan 2019 22:05:46 +0000 (15:05 -0700)]
doc: Repair some whitespace damage
A diagram in whatisRCU.txt has space character before tabs. This commit
therefore makes this diagram consistent with elsewhere in the document:
Use one leading tab, followed by spaces for any additional whitespace
required.
Signed-off-by: Tycho Andersen <tycho@tycho.ws> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
doc: Remove obsolete RCU update functions from RCU documentation
Now that synchronize_rcu_bh, synchronize_rcu_bh_expedited, call_rcu_bh,
rcu_barrier_bh, synchronize_sched, synchronize_sched_expedited,
call_rcu_sched, rcu_barrier_sched, get_state_synchronize_sched,
and cond_synchronize_sched are obsolete, let's remove them from the
documentation aside from a small historical section.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Peter Zijlstra [Mon, 11 Feb 2019 17:09:43 +0000 (18:09 +0100)]
Documentation/atomic_t: Clarify signed vs unsigned
Clarify the whole signed vs unsigned issue for atomic_t.
There has been enough confusion on this topic to warrant a few explicit
words I feel.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Will Deacon <will.deacon@arm.com> Acked-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Currently, herdtools version information appears no fewer than three
times in the LKMM source, which is difficult to maintain. This commit
therefore places the required version in one place, namely the
tools/memory-model/README file.
Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Alan Stern <stern@rowland.harvard.edu>
This commit checks that the return value of srcu_read_lock() is passed
to the matching srcu_read_unlock(), where "matching" is determined by
nesting. This check operates as follows:
1. srcu_read_lock() creates an integer token, which is stored into
the generated events.
2. srcu_read_unlock() records its second (token) argument into the
generated event.
3. A new herd primitive 'different-values' filters out pairs of events
with identical values from the relation passed as its argument.
4. The bell file applies the above primitive to the (srcu)
read-side-critical-section relation 'srcu-rscs' and flags non-empty
results.
BEWARE: Works only with herd version 7.51+6 and onwards.
Signed-off-by: Luc Maranget <Luc.Maranget@inria.fr> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
[ paulmck: Apply Andrea Parri's off-list feedback. ] Acked-by: Alan Stern <stern@rowland.harvard.edu>
Alan Stern [Tue, 11 Dec 2018 16:38:53 +0000 (11:38 -0500)]
tools/memory-model: Update Documentation/explanation.txt to include SRCU support
The recent commit adding support for SRCU to the Linux Kernel Memory
Model ended up changing the names and meanings of several relations.
This patch updates the explanation.txt documentation file to reflect
those changes.
It also revises the statement of the RCU Guarantee to a more accurate
form, and it adds a short paragraph mentioning the new support for SRCU.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Cc: Akira Yokosawa <akiyks@gmail.com> Cc: Andrea Parri <andrea.parri@amarulasolutions.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Daniel Lustig <dlustig@nvidia.com> Cc: David Howells <dhowells@redhat.com> Cc: Jade Alglave <j.alglave@ucl.ac.uk> Cc: Luc Maranget <luc.maranget@inria.fr> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: "Paul E. McKenney" <paulmck@linux.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Paul E. McKenney [Mon, 26 Nov 2018 22:26:43 +0000 (14:26 -0800)]
tools/memory-model: Update README for addition of SRCU
This commit updates the section on LKMM limitations to no longer say
that SRCU is not modeled, but instead describe how LKMM's modeling of
SRCU departs from the Linux-kernel implementation.
TL;DR: There is no known valid use case that cares about the Linux
kernel's ability to have partially overlapping SRCU read-side critical
sections.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Acked-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Alan Stern [Thu, 15 Nov 2018 16:20:37 +0000 (11:20 -0500)]
tools/memory-model: Add SRCU support
Add support for SRCU. Herd creates srcu events and linux-kernel.def
associates them with three possible annotations (srcu-lock,
srcu-unlock, and sync-srcu) corresponding to the API routines
srcu_read_lock(), srcu_read_unlock(), and synchronize_srcu().
The linux-kernel.bell file now declares the annotations
and determines matching lock/unlock pairs delimiting SRCU read-side
critical sections, and it also checks for synchronize_srcu() calls
inside an RCU critical section (which would generate a "sleeping in
atomic context" error in real kernel code). The linux-kernel.cat file
now adds SRCU-induced ordering, analogous to the existing RCU-induced
ordering, to the gp and rcu-fence relations.
Curiously enough, these small changes to the model's .cat code are all
that is needed to describe SRCU.
Portions of this patch (linux-kernel.def and the first hunk in
linux-kernel.bell) were written by Luc Maranget.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> CC: Luc Maranget <luc.maranget@inria.fr> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Alan Stern [Thu, 15 Nov 2018 16:19:58 +0000 (11:19 -0500)]
tools/memory-model: Refactor some RCU relations
In preparation for adding support for SRCU, refactor the definitions
of rcu-fence, rcu-rscsi, rcu-link, and rb by moving the po and po?
terms from the first two to the second two. An rcu-gp relation is
added; it is equivalent to gp with the po and po? terms removed.
This is necessary because for SRCU, we will have to use the loc
relation to check that the terms at the start and end of each disjunct
in the definition of rcu-fence refer to the same srcu_struct
location. If these terms are hidden behind po and po?, there's no way
to carry out this check.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Alan Stern [Thu, 15 Nov 2018 16:19:44 +0000 (11:19 -0500)]
tools/memory-model: Rename some RCU relations
In preparation for adding support for SRCU, rename "crit" to
"rcu-rscs", rename "rscs" to "rcu-rscsi", and remove the restriction
to only the outermost level of nesting.
The name change is needed for disambiguating RCU read-side critical
sections from SRCU read-side critical sections. Adding the "i" at the
end of "rcu-rscsi" emphasizes that the relation is inverted; it links
rcu_read_unlock() events to their corresponding preceding
rcu_read_lock() events.
The restriction to outermost nesting levels was never essential; it
was included mostly to show that it could be done. Rather than add
equivalent unnecessary code for SRCU lock nesting, it seemed better to
remove the existing code.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com> Tested-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Linus Torvalds [Sun, 17 Mar 2019 16:10:56 +0000 (09:10 -0700)]
Merge tag '9p-for-5.1' of git://github.com/martinetd/linux
Pull 9p updates from Dominique Martinet:
"Here is a 9p update for 5.1; there honestly hasn't been much.
Two fixes (leak on invalid mount argument and possible deadlock on
i_size update on 32bit smp) and a fall-through warning cleanup"
* tag '9p-for-5.1' of git://github.com/martinetd/linux:
9p/net: fix memory leak in p9_client_create
9p: use inode->i_lock to protect i_size_write() under 32-bit
9p: mark expected switch fall-through
Masahiro Yamada [Sun, 17 Mar 2019 02:01:09 +0000 (11:01 +0900)]
kbuild: force all architectures except um to include mandatory-y
Currently, every arch/*/include/uapi/asm/Kbuild explicitly includes
the common Kbuild.asm file. Factor out the duplicated include directives
to scripts/Makefile.asm-generic so that no architecture would opt out
of the mandatory-y mechanism.
um is not forced to include mandatory-y since it is a very exceptional
case which does not support UAPI.
The commit was fine but is no longer needed as of commit 3a2429e1faf4
("kbuild: change if_changed_rule for multi-line recipe"). Let's go
back to using ";" to be consistent.
Douglas Anderson [Thu, 14 Mar 2019 23:41:59 +0000 (16:41 -0700)]
kbuild: Make NOSTDINC_FLAGS a simply expanded variable
During a simple no-op (nothing changed) build I saw 39 invocations of
the C compiler with the argument "-print-file-name=include". We don't
need to call the C compiler 39 times for this--one time will suffice.
Let's change NOSTDINC_FLAGS to a simply expanded variable to avoid
this since there doesn't appear to be any reason it should be
recursively expanded.
On my build this shaved ~400 ms off my "no-op" build.
Note that the recursive expansion seems to date back to the (really
old) commit e8f5bdb02ce0 ("[PATCH] Makefile include path ordering").
It's a little unclear to me if the point of that patch was to switch
the variable to be recursively expanded (which it did) or to avoid
directly assigning to NOSTDINC_FLAGS (AKA to switch to +=) because
someone else (out of tree?) was setting it. I presume later since if
the only goal was to switch to recursive expansion the patch would
have just removed the ":".
Signed-off-by: Douglas Anderson <dianders@chromium.org> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> -b, --build directory [format-specific-parameters]
> Build a source package (--build since dpkg 1.17.14).
> <...>
>
> dpkg-source will build the source package with the first
> format found in this ordered list: the format indicated
> with the --format command line option, the format
> indicated in debian/source/format, “1.0”. The fallback
> to “1.0” is deprecated and will be removed at some point
> in the future, you should always document the desired
> source format in debian/source/format. See section
> SOURCE PACKAGE FORMATS for an extensive description of
> the various source package formats.
Thus it would be more foolproof to explicitly use 1.0 (as we always
did) than to rely on dpkg-source's defaults.
* In a similar vein, debian/rules is not made executable by mkdebian,
and dpkg-source warns about that but still silently fixes the file.
Let's be explicit once again.
Wen Yang [Fri, 15 Feb 2019 07:55:19 +0000 (15:55 +0800)]
coccinelle: semantic code search for missing put_device()
The of_find_device_by_node() takes a reference to the underlying device
structure, we should release that reference.
The implementation of this semantic code search is:
In a function, for a local variable returned by calling
of_find_device_by_node(),
a, if it is released by a function such as
put_device()/of_dev_put()/platform_device_put() after the last use,
it is considered that there is no reference leak;
b, if it is passed back to the caller via
dev_get_drvdata()/platform_get_drvdata()/get_device(), etc., the
reference will be released in other functions, and the current function
also considers that there is no reference leak;
c, for the rest of the situation, the current function should release the
reference by calling put_device, this code search will report the
corresponding error message.
By using this semantic code search, we have found some object reference leaks,
such as:
commit 11907e9d3533 ("ASoC: fsl-asoc-card: fix object reference leaks in
fsl_asoc_card_probe")
commit a12085d13997 ("mtd: rawnand: atmel: fix possible object reference leak")
commit 11493f26856a ("mtd: rawnand: jz4780: fix possible object reference leak")
There are still dozens of reference leaks in the current kernel code.
Further, for the case of b, the object returned to other functions may also
have a reference leak, we will continue to develop other cocci scripts to
further check the reference leak.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn> Reviewed-by: Julia Lawall <Julia.Lawall@lip6.fr> Reviewed-by: Markus Elfring <Markus.Elfring@web.de> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Linus Torvalds [Sat, 16 Mar 2019 20:47:14 +0000 (13:47 -0700)]
Merge tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux
Pull pidfd system call from Christian Brauner:
"This introduces the ability to use file descriptors from /proc/<pid>/
as stable handles on struct pid. Even if a pid is recycled the handle
will not change. For a start these fds can be used to send signals to
the processes they refer to.
With the ability to use /proc/<pid> fds as stable handles on struct
pid we can fix a long-standing issue where after a process has exited
its pid can be reused by another process. If a caller sends a signal
to a reused pid it will end up signaling the wrong process.
With this patchset we enable a variety of use cases. One obvious
example is that we can now safely delegate an important part of
process management - sending signals - to processes other than the
parent of a given process by sending file descriptors around via scm
rights and not fearing that the given process will have been recycled
in the meantime. It also allows for easy testing whether a given
process is still alive or not by sending signal 0 to a pidfd which is
quite handy.
There has been some interest in this feature e.g. from systems
management (systemd, glibc) and container managers. I have requested
and gotten comments from glibc to make sure that this syscall is
suitable for their needs as well. In the future I expect it to take on
most other pid-based signal syscalls. But such features are left for
the future once they are needed.
This has been sitting in linux-next for quite a while and has not
caused any issues. It comes with selftests which verify basic
functionality and also test that a recycled pid cannot be signaled via
a pidfd.
Jon has written about a prior version of this patchset. It should
cover the basic functionality since not a lot has changed since then:
https://lwn.net/Articles/773459/
The commit message for the syscall itself is extensively documenting
the syscall, including it's functionality and extensibility"
* tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
selftests: add tests for pidfd_send_signal()
signal: add pidfd_send_signal() syscall
Linus Torvalds [Sat, 16 Mar 2019 20:05:32 +0000 (13:05 -0700)]
Merge tag 'devdax-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull device-dax updates from Dan Williams:
"New device-dax infrastructure to allow persistent memory and other
"reserved" / performance differentiated memories, to be assigned to
the core-mm as "System RAM".
Some users want to use persistent memory as additional volatile
memory. They are willing to cope with potential performance
differences, for example between DRAM and 3D Xpoint, and want to use
typical Linux memory management apis rather than a userspace memory
allocator layered over an mmap() of a dax file. The administration
model is to decide how much Persistent Memory (pmem) to use as System
RAM, create a device-dax-mode namespace of that size, and then assign
it to the core-mm. The rationale for device-dax is that it is a
generic memory-mapping driver that can be layered over any "special
purpose" memory, not just pmem. On subsequent boots udev rules can be
used to restore the memory assignment.
One implication of using pmem as RAM is that mlock() no longer keeps
data off persistent media. For this reason it is recommended to enable
NVDIMM Security (previously merged for 5.0) to encrypt pmem contents
at rest. We considered making this recommendation an actively enforced
requirement, but in the end decided to leave it as a distribution /
administrator policy to allow for emulation and test environments that
lack security capable NVDIMMs.
Summary:
- Replace the /sys/class/dax device model with /sys/bus/dax, and
include a compat driver so distributions can opt-in to the new ABI.
- Allow for an alternative driver for the device-dax address-range
- Introduce the 'kmem' driver to hotplug / assign a device-dax
address-range to the core-mm.
- Arrange for the device-dax target-node to be onlined so that the
newly added memory range can be uniquely referenced by numa apis"
NOTE! I'm not entirely happy with the whole "PMEM as RAM" model because
we currently have special - and very annoying rules in the kernel about
accessing PMEM only with the "MC safe" accessors, because machine checks
inside the regular repeat string copy functions can be fatal in some
(not described) circumstances.
And apparently the PMEM modules can cause that a lot more than regular
RAM. The argument is that this happens because PMEM doesn't necessarily
get scrubbed at boot like RAM does, but that is planned to be added for
the user space tooling.
Quoting Dan from another email:
"The exposure can be reduced in the volatile-RAM case by scanning for
and clearing errors before it is onlined as RAM. The userspace tooling
for that can be in place before v5.1-final. There's also runtime
notifications of errors via acpi_nfit_uc_error_notify() from
background scrubbers on the DIMM devices. With that mechanism the
kernel could proactively clear newly discovered poison in the volatile
case, but that would be additional development more suitable for v5.2.
I understand the concern, and the need to highlight this issue by
tapping the brakes on feature development, but I don't see PMEM as RAM
making the situation worse when the exposure is also there via DAX in
the PMEM case. Volatile-RAM is arguably a safer use case since it's
possible to repair pages where the persistent case needs active
application coordination"
* tag 'devdax-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
device-dax: "Hotplug" persistent memory for use like normal RAM
mm/resource: Let walk_system_ram_range() search child resources
mm/memory-hotplug: Allow memory resources to be children
mm/resource: Move HMM pr_debug() deeper into resource code
mm/resource: Return real error codes from walk failures
device-dax: Add a 'modalias' attribute to DAX 'bus' devices
device-dax: Add a 'target_node' attribute
device-dax: Auto-bind device after successful new_id
acpi/nfit, device-dax: Identify differentiated memory with a unique numa-node
device-dax: Add /sys/class/dax backwards compatibility
device-dax: Add support for a dax override driver
device-dax: Move resource pinning+mapping into the common driver
device-dax: Introduce bus + driver model
device-dax: Start defining a dax bus model
device-dax: Remove multi-resource infrastructure
device-dax: Kill dax_region base
device-dax: Kill dax_region ida
Linus Torvalds [Sat, 16 Mar 2019 19:51:50 +0000 (12:51 -0700)]
Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
Pull more SCSI updates from James Bottomley:
"This is the final round of mostly small fixes and performance
improvements to our initial submit.
The main regression fix is the ia64 simscsi build failure which was
missed in the serial number elimination conversion"
* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (24 commits)
scsi: ia64: simscsi: use request tag instead of serial_number
scsi: aacraid: Fix performance issue on logical drives
scsi: lpfc: Fix error codes in lpfc_sli4_pci_mem_setup()
scsi: libiscsi: Hold back_lock when calling iscsi_complete_task
scsi: hisi_sas: Change SERDES_CFG init value to increase reliability of HiLink
scsi: hisi_sas: Send HARD RESET to clear the previous affiliation of STP target port
scsi: hisi_sas: Set PHY linkrate when disconnected
scsi: hisi_sas: print PHY RX errors count for later revision of v3 hw
scsi: hisi_sas: Fix a timeout race of driver internal and SMP IO
scsi: hisi_sas: Change return variable type in phy_up_v3_hw()
scsi: qla2xxx: check for kstrtol() failure
scsi: lpfc: fix 32-bit format string warning
scsi: lpfc: fix unused variable warning
scsi: target: tcmu: Switch to bitmap_zalloc()
scsi: libiscsi: fall back to sendmsg for slab pages
scsi: qla2xxx: avoid printf format warning
scsi: lpfc: resolve static checker warning in lpfc_sli4_hba_unset
scsi: lpfc: Correct __lpfc_sli_issue_iocb_s4 lockdep check
scsi: ufs: hisi: fix ufs_hba_variant_ops passing
scsi: qla2xxx: Fix panic in qla_dfs_tgt_counters_show
...
Linus Torvalds [Sat, 16 Mar 2019 19:36:39 +0000 (12:36 -0700)]
Merge tag 'for-5.1/block-post-20190315' of git://git.kernel.dk/linux-block
Pull more block layer changes from Jens Axboe:
"This is a collection of both stragglers, and fixes that came in after
I finalized the initial pull. This contains:
- An MD pull request from Song, with a few minor fixes
- Set of NVMe patches via Christoph
- Pull request from Konrad, with a few fixes for xen/blkback
- pblk fix IO calculation fix (Javier)
- Segment calculation fix for pass-through (Ming)
- Fallthrough annotation for blkcg (Mathieu)"
* tag 'for-5.1/block-post-20190315' of git://git.kernel.dk/linux-block: (25 commits)
blkcg: annotate implicit fall through
nvme-tcp: support C2HData with SUCCESS flag
nvmet: ignore EOPNOTSUPP for discard
nvme: add proper write zeroes setup for the multipath device
nvme: add proper discard setup for the multipath device
nvme: remove nvme_ns_config_oncs
nvme: disable Write Zeroes for qemu controllers
nvmet-fc: bring Disconnect into compliance with FC-NVME spec
nvmet-fc: fix issues with targetport assoc_list list walking
nvme-fc: reject reconnect if io queue count is reduced to zero
nvme-fc: fix numa_node when dev is null
nvme-fc: use nr_phys_segments to determine existence of sgl
nvme-loop: init nvmet_ctrl fatal_err_work when allocate
nvme: update comment to make the code easier to read
nvme: put ns_head ref if namespace fails allocation
nvme-trace: fix cdw10 buffer overrun
nvme: don't warn on block content change effects
nvme: add get-feature to admin cmds tracer
md: Fix failed allocation of md_register_thread
It's wrong to add len to sector_nr in raid10 reshape twice
...
Linus Torvalds [Sat, 16 Mar 2019 19:28:18 +0000 (12:28 -0700)]
Merge tag 'nfs-for-5.1-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs
Pull NFS client bugfixes from Trond Myklebust:
"Highlights include:
Bugfixes:
- Fix an Oops in SUNRPC back channel tracepoints
- Fix a SUNRPC client regression when handling oversized replies
- Fix the minimal size for SUNRPC reply buffer allocation
- rpc_decode_header() must always return a non-zero value on error
- Fix a typo in pnfs_update_layout()
Cleanup:
- Remove redundant check for the reply length in call_decode()"
* tag 'nfs-for-5.1-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
SUNRPC: Remove redundant check for the reply length in call_decode()
SUNRPC: Handle the SYSTEM_ERR rpc error
SUNRPC: rpc_decode_header() must always return a non-zero value on error
SUNRPC: Use the ENOTCONN error on socket disconnect
SUNRPC: Fix the minimal size for reply buffer allocation
SUNRPC: Fix a client regression when handling oversized replies
pNFS: Fix a typo in pnfs_update_layout
fix null pointer deref in tracepoints in back channel
Linus Torvalds [Sat, 16 Mar 2019 17:45:17 +0000 (10:45 -0700)]
Merge tag 'powerpc-5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fixes from Michael Ellerman:
"One fix to prevent runtime allocation of 16GB pages when running in a
VM (as opposed to bare metal), because it doesn't work.
A small fix to our recently added KCOV support to exempt some more
code from being instrumented.
Plus a few minor build fixes, a small dead code removal and a
defconfig update.
Thanks to: Alexey Kardashevskiy, Aneesh Kumar K.V, Christophe Leroy,
Jason Yan, Joel Stanley, Mahesh Salgaonkar, Mathieu Malaterre"
* tag 'powerpc-5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/64s: Include <asm/nmi.h> header file to fix a warning
powerpc/powernv: Fix compile without CONFIG_TRACEPOINTS
powerpc/mm: Disable kcov for SLB routines
powerpc: remove dead code in head_fsl_booke.S
powerpc/configs: Sync skiroot defconfig
powerpc/hugetlb: Don't do runtime allocation of 16G pages in LPAR configuration
Linus Torvalds [Sat, 16 Mar 2019 01:52:12 +0000 (18:52 -0700)]
Merge tag '5.1-rc-smb3' of git://git.samba.org/sfrench/cifs-2.6
Pull more smb3 updates from Steve French:
"Various tracing and debugging improvements, crediting fixes, some
cleanup, and important fallocate fix (fixes three xfstests) and lock
fix.
Summary:
- Various additional dynamic tracing tracepoints
- Debugging improvements (including ability to query the server via
SMB3 fsctl from userspace tools which can help with stats and
debugging)
- One minor performance improvement (root directory inode caching)
- Crediting (SMB3 flow control) fixes
- Some cleanup (docs and to mknod)
- Important fixes: one to smb3 implementation of fallocate zero range
(which fixes three xfstests) and a POSIX lock fix"
* tag '5.1-rc-smb3' of git://git.samba.org/sfrench/cifs-2.6: (22 commits)
CIFS: fix POSIX lock leak and invalid ptr deref
SMB3: Allow SMB3 FSCTL queries to be sent to server from tools
cifs: fix incorrect handling of smb2_set_sparse() return in smb3_simple_falloc
smb2: fix typo in definition of a few error flags
CIFS: make mknod() an smb_version_op
cifs: minor documentation updates
cifs: remove unused value pointed out by Coverity
SMB3: passthru query info doesn't check for SMB3 FSCTL passthru
smb3: add dynamic tracepoints for simple fallocate and zero range
cifs: fix smb3_zero_range so it can expand the file-size when required
cifs: add SMB2_ioctl_init/free helpers to be used with compounding
smb3: Add dynamic trace points for various compounded smb3 ops
cifs: cache FILE_ALL_INFO for the shared root handle
smb3: display volume serial number for shares in /proc/fs/cifs/DebugData
cifs: simplify how we handle credits in compound_send_recv()
smb3: add dynamic tracepoint for timeout waiting for credits
smb3: display security information in /proc/fs/cifs/DebugData more accurately
cifs: add a timeout argument to wait_for_free_credits
cifs: prevent starvation in wait_for_free_credits for multi-credit requests
cifs: wait_for_free_credits() make it possible to wait for >=1 credits
...
Linus Torvalds [Fri, 15 Mar 2019 22:07:32 +0000 (15:07 -0700)]
Merge branch 'for-linus-5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml
Pull UML updates from Richard Weinberger:
"Bugfix for the UML block device driver"
* 'for-linus-5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
um: Fix for a possible OOPS in ubd initialization
um: Remove duplicated include from vector_user.c
Linus Torvalds [Fri, 15 Mar 2019 22:00:28 +0000 (15:00 -0700)]
Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull KVM updates from Paolo Bonzini:
"ARM:
- some cleanups
- direct physical timer assignment
- cache sanitization for 32-bit guests
s390:
- interrupt cleanup
- introduction of the Guest Information Block
- preparation for processor subfunctions in cpu models
PPC:
- bug fixes and improvements, especially related to machine checks
and protection keys
x86:
- many, many cleanups, including removing a bunch of MMU code for
unnecessary optimizations
- AVIC fixes
Generic:
- memcg accounting"
* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (147 commits)
kvm: vmx: fix formatting of a comment
KVM: doc: Document the life cycle of a VM and its resources
MAINTAINERS: Add KVM selftests to existing KVM entry
Revert "KVM/MMU: Flush tlb directly in the kvm_zap_gfn_range()"
KVM: PPC: Book3S: Add count cache flush parameters to kvmppc_get_cpu_char()
KVM: PPC: Fix compilation when KVM is not enabled
KVM: Minor cleanups for kvm_main.c
KVM: s390: add debug logging for cpu model subfunctions
KVM: s390: implement subfunction processor calls
arm64: KVM: Fix architecturally invalid reset value for FPEXC32_EL2
KVM: arm/arm64: Remove unused timer variable
KVM: PPC: Book3S: Improve KVM reference counting
KVM: PPC: Book3S HV: Fix build failure without IOMMU support
Revert "KVM: Eliminate extra function calls in kvm_get_dirty_log_protect()"
x86: kvmguest: use TSC clocksource if invariant TSC is exposed
KVM: Never start grow vCPU halt_poll_ns from value below halt_poll_ns_grow_start
KVM: Expose the initial start value in grow_halt_poll_ns() as a module parameter
KVM: grow_halt_poll_ns() should never shrink vCPU halt_poll_ns
KVM: x86/mmu: Consolidate kvm_mmu_zap_all() and kvm_mmu_zap_mmio_sptes()
KVM: x86/mmu: WARN if zapping a MMIO spte results in zapping children
...
Linus Torvalds [Fri, 15 Mar 2019 21:47:02 +0000 (14:47 -0700)]
Merge tag 'trace-v5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes and cleanups from Steven Rostedt:
"This contains a series of last minute clean ups, small fixes and error
checks"
* tag 'trace-v5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing/probe: Verify alloc_trace_*probe() result
tracing/probe: Check event/group naming rule at parsing
tracing/probe: Check the size of argument name and body
tracing/probe: Check event name length correctly
tracing/probe: Check maxactive error cases
tracing: kdb: Fix ftdump to not sleep
trace/probes: Remove kernel doc style from non kernel doc comment
tracing/probes: Make reserved_field_names static
Linus Torvalds [Fri, 15 Mar 2019 21:37:46 +0000 (14:37 -0700)]
Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm
Pull ARM updates from Russell King:
- An improvement from Ard Biesheuvel, who noted that the identity map
setup was taking a long time due to flush_cache_louis().
- Update a comment about dma_ops from Wolfram Sang.
- Remove use of "-p" with ld, where this flag has been a no-op since
2004.
- Remove the printing of the virtual memory layout, which is no longer
useful since we hide pointers.
- Correct SCU help text.
- Remove legacy TWD registration method.
- Add pgprot_device() implementation for mapping PCI sysfs resource
files.
- Initialise PFN limits earlier for kmemleak.
- Fix argument count to match macro definition (affects clang builds)
- Use unified assembler language almost everywhere for clang, and other
clang improvements (from Stefan Agner, Nathan Chancellor).
- Support security extension for noMMU and other noMMU cleanups (from
Vladimir Murzin).
- Remove unnecessary SMP bringup code (which was incorrectly copy'n'
pasted from the ARM platform implementations) and remove it from the
arch code to discourge further copys of it appearing.
- Add Cortex A9 erratum preventing kexec working on some SoCs.
- AMBA bus identification updates from Mike Leach.
- More use of raw spinlocks to avoid -RT kernel issues (from Yang Shi
and Sebastian Andrzej Siewior).
- MCPM hyp/svc mode mismatch fixes from Marek Szyprowski.
* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm: (32 commits)
ARM: 8849/1: NOMMU: Fix encodings for PMSAv8's PRBAR4/PRLAR4
ARM: 8848/1: virt: Align GIC version check with arm64 counterpart
ARM: 8847/1: pm: fix HYP/SVC mode mismatch when MCPM is used
ARM: 8845/1: use unified assembler in c files
ARM: 8844/1: use unified assembler in assembly files
ARM: 8843/1: use unified assembler in headers
ARM: 8841/1: use unified assembler in macros
ARM: 8840/1: use a raw_spinlock_t in unwind
ARM: 8839/1: kprobe: make patch_lock a raw_spinlock_t
ARM: 8837/1: coresight: etmv4: Update ID register table to add UCI support
ARM: 8836/1: drivers: amba: Update component matching to use the CoreSight UCI values.
ARM: 8838/1: drivers: amba: Updates to component identification for driver matching.
ARM: 8833/1: Ensure that NEON code always compiles with Clang
ARM: avoid Cortex-A9 livelock on tight dmb loops
ARM: smp: remove arch-provided "pen_release"
ARM: actions: remove boot_lock and pen_release
ARM: oxnas: remove CPU hotplug implementation
ARM: qcom: remove unnecessary boot_lock
ARM: 8832/1: NOMMU: Limit visibility for CONFIG_FLASH_{MEM_BASE,SIZE}
ARM: 8831/1: NOMMU: pmsa-v8: remove unneeded semicolon
...
Linus Torvalds [Fri, 15 Mar 2019 21:32:59 +0000 (14:32 -0700)]
Merge tag 'ntb-5.1' of git://github.com/jonmason/ntb
Pull NTB updates from Jon Mason:
- fixes for switchtec debugability and mapping table entries
- NTB transport improvements
- a reworking of the peer_db_addr for better abstraction
* tag 'ntb-5.1' of git://github.com/jonmason/ntb:
NTB: add new parameter to peer_db_addr() db_bit and db_data
NTB: ntb_transport: Ensure the destination buffer is mapped for TX DMA
NTB: ntb_transport: Free MWs in ntb_transport_link_cleanup()
ntb_hw_switchtec: Added support of >=4G memory windows
ntb_hw_switchtec: NT req id mapping table register entry number should be 512
ntb_hw_switchtec: debug print 64bit aligned crosslink BAR Numbers
Linus Torvalds [Fri, 15 Mar 2019 21:22:59 +0000 (14:22 -0700)]
Merge tag 'fbdev-v5.1' of git://github.com/bzolnier/linux
Pull fbdev updates from Bartlomiej Zolnierkiewicz:
"Just a couple of small fixes and cleanups:
- fix memory access if logo is bigger than the screen (Manfred
Schlaegl)
- silence fbcon logo on 'quiet' boots (Prarit Bhargava)
- use kvmalloc() for scrollback buffer in fbcon (Konstantin Khorenko)
- misc fixes (Colin Ian King, YueHaibing, Matteo Croce, Mathieu
Malaterre, Anders Roxell, Arnd Bergmann)
- misc cleanups (Rob Herring, Lubomir Rintel, Greg Kroah-Hartman,
Jani Nikula, Michal Vokáč)"
* tag 'fbdev-v5.1' of git://github.com/bzolnier/linux:
fbdev: mbx: fix a misspelled variable name
fbdev: omap2: fix warnings in dss core
video: fbdev: Fix potential NULL pointer dereference
fbcon: Silence fbcon logo on 'quiet' boots
printk: Export console_printk
ARM: dts: imx28-cfa10036: Fix the reset gpio signal polarity
video: ssd1307fb: Do not hard code active-low reset sequence
dt-bindings: display: ssd1307fb: Remove reset-active-low from examples
fbdev: fbmem: fix memory access if logo is bigger than the screen
video/fbdev: refactor video= cmdline parsing
fbdev: mbx: fix up debugfs file creation
fbdev: omap2: no need to check return value of debugfs_create functions
video: fbdev: geode: remove ifdef OLPC noise
video: offb: annotate implicit fall throughs
omapfb: fix typo
fbdev: Use of_node_name_eq for node name comparisons
fbcon: use kvmalloc() for scrollback buffer
fbdev: chipsfb: remove set but not used variable 'size'
fbdev/via: fix spelling mistake "Expandsion" -> "Expansion"
Linus Torvalds [Fri, 15 Mar 2019 21:16:28 +0000 (14:16 -0700)]
Merge branch 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux
Pull i2c fixes from Wolfram Sang:
"A set of driver bugfixes and an improvement for a core helper"
* 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
i2c: i2c-designware-platdrv: Always use a dynamic adapter number
i2c: i2c-designware-platdrv: Cleanup setting of the adapter number
i2c: add extra check to safe DMA buffer helper
i2c: i2c-stm32f7: Fix SDADEL minimum formula
i2c: rcar: explain the lockless design
i2c: rcar: fix concurrency issue related to ICDMAER
i2c: sis630: correct format strings
i2c: mediatek: modify threshold passed to i2c_get_dma_safe_msg_buf()
Linus Torvalds [Fri, 15 Mar 2019 21:05:00 +0000 (14:05 -0700)]
Merge tag 'sound-fix-5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound
Pull sound fixes from Takashi Iwai:
"Some cleaning after the first batch; mostly about HD-audio quirks but
also some NULL dereference fixes in corner cases and a random build
error fix, too"
* tag 'sound-fix-5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
ALSA: hda/realtek - Add support headset mode for New DELL WYSE NB
ALSA: hda/realtek - Add support headset mode for DELL WYSE AIO
ALSA: hda/realtek: merge alc_fixup_headset_jack to alc295_fixup_chromebook
ALSA: pcm: Fix function name in kernel-doc comment
ALSA: hda: hdmi - add Icelake support
ALSA: hda - add more quirks for HP Z2 G4 and HP Z240
ALSA: hda/realtek - Fixed Headset Mic JD not stable
ALSA: hda/realtek: Enable headset MIC of Acer TravelMate X514-51T with ALC255
ALSA: hda/tegra: avoid build error without CONFIG_PM
ALSA: usx2y: Fix potential NULL pointer dereference
ALSA: hda: Avoid NULL pointer dereference at snd_hdac_stream_start()
Linus Torvalds [Fri, 15 Mar 2019 20:58:35 +0000 (13:58 -0700)]
Merge tag 'drm-next-2019-03-15' of git://anongit.freedesktop.org/drm/drm
Pull drm fixes and updates from Dave Airlie:
"A few various fixes pulls and one late etnaviv pull but it was nearly
all fixes anyways.
etnaviv:
- late next pull
- mmu mapping fix
- build non-ARM arches
- misc fixes
i915:
- HDCP state handling fix
- shrinker interaction fix
- atomic state leak fix
qxl:
- kick out framebuffers early fix
amdgpu:
- Powerplay fixes
- DC fixes
- BACO turned off for now on vega20
- Locking fix
- KFD MQD fix
- gfx9 golden register updates"
* tag 'drm-next-2019-03-15' of git://anongit.freedesktop.org/drm/drm: (43 commits)
drm/amdgpu: Update gc golden setting for vega family
drm/amd/powerplay: correct power reading on fiji
drm/amd/powerplay: set max fan target temperature as 105C
drm/i915: Relax mmap VMA check
drm/i915: Fix atomic state leak when resetting HDMI link
drm/i915: Acquire breadcrumb ref before cancelling
drm/i915/selftests: Always free spinner on __sseu_prepare error
drm/i915: Reacquire priolist cache after dropping the engine lock
drm/i915: Protect i915_active iterators from the shrinker
drm/i915: HDCP state handling in ddi_update_pipe
drm/qxl: remove conflicting framebuffers earlier
drm/fb-helper: call vga_remove_vgacon automatically.
drm: move i915_kick_out_vgacon to vgaarb
drm/amd/display: don't call dm_pp_ function from an fpu block
drm: add __user attribute to ptr_to_compat()
drm/amdgpu: clear PDs/PTs only after initializing them
drm/amd/display: Pass app_tf by value rather than by reference
Revert "drm/amdgpu: use BACO reset on vega20 if platform support"
drm/amd/powerplay: show the right override pcie parameters
drm/amd/powerplay: honor the OD settings
...
Linus Torvalds [Fri, 15 Mar 2019 20:55:30 +0000 (13:55 -0700)]
Merge tag 'xfs-5.1-merge-5' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux
Pull xfs cleanups from Darrick Wong:
"Here's a few more cleanups that trickled in for the merge window.
It's all fixes for static checker complaints and slowly unwinding
typedef usage. The four patches here have gone through a few days
worth of fstest runs with no new problems observed.
Summary:
- Fix some clang/smatch/sparse warnings about uninitialized
variables.
- Clean up some typedef usage"
* tag 'xfs-5.1-merge-5' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: clean up xfs_dir2_leaf_addname
xfs: zero initialize highstale and lowstale in xfs_dir2_leaf_addname
xfs: clean up xfs_dir2_leafn_add
xfs: Zero initialize highstale and lowstale in xfs_dir2_leafn_add
Linus Torvalds [Fri, 15 Mar 2019 20:42:53 +0000 (13:42 -0700)]
Merge tag 'f2fs-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs
Pull f2fs updates from Jaegeuk Kim:
"We've continued mainly to fix bugs in this round, as f2fs has been
shipped in more devices. Especially, we've focused on stabilizing
checkpoint=disable feature, and provided some interfaces for QA.
Enhancements:
- expose FS_NOCOW_FL for pin_file
- run discard jobs at unmount time with timeout
- tune discarding thread to avoid idling which consumes power
- some checking codes to address vulnerabilities
- give random value to i_generation
- shutdown with more flags for QA
Bug fixes:
- clean up stale objects when mount is failed along with
checkpoint=disable
- fix system being stuck due to wrong count by atomic writes
- handle some corrupted disk cases
- fix a deadlock in f2fs_read_inline_dir
We've also added some minor build error fixes and clean-up patches"
* tag 'f2fs-for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (53 commits)
f2fs: set pin_file under CAP_SYS_ADMIN
f2fs: fix to avoid deadlock in f2fs_read_inline_dir()
f2fs: fix to adapt small inline xattr space in __find_inline_xattr()
f2fs: fix to do sanity check with inode.i_inline_xattr_size
f2fs: give some messages for inline_xattr_size
f2fs: don't trigger read IO for beyond EOF page
f2fs: fix to add refcount once page is tagged PG_private
f2fs: remove wrong comment in f2fs_invalidate_page()
f2fs: fix to use kvfree instead of kzfree
f2fs: print more parameters in trace_f2fs_map_blocks
f2fs: trace f2fs_ioc_shutdown
f2fs: fix to avoid deadlock of atomic file operations
f2fs: fix to dirty inode for i_mode recovery
f2fs: give random value to i_generation
f2fs: no need to take page lock in readdir
f2fs: fix to update iostat correctly in IPU path
f2fs: fix encrypted page memory leak
f2fs: make fault injection covering __submit_flush_wait()
f2fs: fix to retry fill_super only if recovery failed
f2fs: silence VM_WARN_ON_ONCE in mempool_alloc
...
Linus Torvalds [Fri, 15 Mar 2019 19:00:45 +0000 (12:00 -0700)]
Merge branch 'akpm' (rest of patches from Andrew)
Merge the left-over patches from Andrew Morton.
This merges the remaining two patches from Andrew's pile of "little bit
more MM". I mulled it over, and we emailed back and forth with Josef,
and he pointed out where I was wrong.
Rule #51 of kernel maintenance: when somebody makes it clear that they
know the code better than you did, stop arguing and just apply the damn
patch.
Add a third patch by me to add a comment for the case that I had thought
was buggy and Josef corrected me on.
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
filemap: add a comment about FAULT_FLAG_RETRY_NOWAIT behavior
filemap: drop the mmap_sem for all blocking operations
filemap: kill page_cache_read usage in filemap_fault
Linus Torvalds [Fri, 15 Mar 2019 18:26:07 +0000 (11:26 -0700)]
filemap: add a comment about FAULT_FLAG_RETRY_NOWAIT behavior
I thought Josef Bacik's patch to drop the mmap_sem was buggy, because
when looking at the error cases, there was one case where we returned
VM_FAULT_RETRY without actually dropping the mmap_sem.
Josef had to explain to me (using small words) that yes, that's actually
what we're supposed to do, and his patch was correct. Which not only
convinced me he knew what he was doing and I should stop arguing with
him, but also that I should add a comment to the case I was confused
about.
Patiently-pointed-out-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
KVM: doc: Document the life cycle of a VM and its resources
The series to add memcg accounting to KVM allocations[1] states:
There are many KVM kernel memory allocations which are tied to the
life of the VM process and should be charged to the VM process's
cgroup.
While it is correct to account KVM kernel allocations to the cgroup of
the process that created the VM, it's technically incorrect to state
that the KVM kernel memory allocations are tied to the life of the VM
process. This is because the VM itself, i.e. struct kvm, is not tied to
the life of the process which created it, rather it is tied to the life
of its associated file descriptor. In other words, kvm_destroy_vm() is
not invoked until fput() decrements its associated file's refcount to
zero. A simple example is to fork() in Qemu and have the child sleep
indefinitely; kvm_destroy_vm() isn't called until Qemu closes its file
descriptor *and* the rogue child is killed.
The allocations are guaranteed to be *accounted* to the process which
created the VM, but only because KVM's per-{VM,vCPU} ioctls reject the
ioctl() with -EIO if kvm->mm != current->mm. I.e. the child can keep
the VM "alive" but can't do anything useful with its reference.
Note that because 'struct kvm' also holds a reference to the mm_struct
of its owner, the above behavior also applies to userspace allocations.
Given that mucking with a VM's file descriptor can lead to subtle and
undesirable behavior, e.g. memcg charges persisting after a VM is shut
down, explicitly document a VM's lifecycle and its impact on the VM's
resources.
Alternatively, KVM could aggressively free resources when the creating
process exits, e.g. via mmu_notifier->release(). However, mmu_notifier
isn't guaranteed to be available, and freeing resources when the creator
exits is likely to be error prone and fragile as KVM would need to
ensure that it only freed resources that are truly out of reach. In
practice, the existing behavior shouldn't be problematic as a properly
configured system will prevent a child process from being moved out of
the appropriate cgroup hierarchy, i.e. prevent hiding the process from
the OOM killer, and will prevent an unprivileged user from being able to
to hold a reference to struct kvm via another method, e.g. debugfs.
Josef Bacik [Wed, 13 Mar 2019 18:44:22 +0000 (11:44 -0700)]
filemap: drop the mmap_sem for all blocking operations
Currently we only drop the mmap_sem if there is contention on the page
lock. The idea is that we issue readahead and then go to lock the page
while it is under IO and we want to not hold the mmap_sem during the IO.
The problem with this is the assumption that the readahead does anything.
In the case that the box is under extreme memory or IO pressure we may end
up not reading anything at all for readahead, which means we will end up
reading in the page under the mmap_sem.
Even if the readahead does something, it could get throttled because of io
pressure on the system and the process is in a lower priority cgroup.
Holding the mmap_sem while doing IO is problematic because it can cause
system-wide priority inversions. Consider some large company that does a
lot of web traffic. This large company has load balancing logic in it's
core web server, cause some engineer thought this was a brilliant plan.
This load balancing logic gets statistics from /proc about the system,
which trip over processes mmap_sem for various reasons. Now the web
server application is in a protected cgroup, but these other processes may
not be, and if they are being throttled while their mmap_sem is held we'll
stall, and cause this nice death spiral.
Instead rework filemap fault path to drop the mmap sem at any point that
we may do IO or block for an extended period of time. This includes while
issuing readahead, locking the page, or needing to call ->readpage because
readahead did not occur. Then once we have a fully uptodate page we can
return with VM_FAULT_RETRY and come back again to find our nicely in-cache
page that was gotten outside of the mmap_sem.
This patch also adds a new helper for locking the page with the mmap_sem
dropped. This doesn't make sense currently as generally speaking if the
page is already locked it'll have been read in (unless there was an error)
before it was unlocked. However a forthcoming patchset will change this
with the ability to abort read-ahead bio's if necessary, making it more
likely that we could contend for a page lock and still have a not uptodate
page. This allows us to deal with this case by grabbing the lock and
issuing the IO without the mmap_sem held, and then returning
VM_FAULT_RETRY to come back around.
[josef@toxicpanda.com: v6] Link: http://lkml.kernel.org/r/20181212152757.10017-1-josef@toxicpanda.com
[kirill@shutemov.name: fix race in filemap_fault()] Link: http://lkml.kernel.org/r/20181228235106.okk3oastsnpxusxs@kshutemo-mobl1
[akpm@linux-foundation.org: coding style fixes] Link: http://lkml.kernel.org/r/20181211173801.29535-4-josef@toxicpanda.com Signed-off-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Jan Kara <jack@suse.cz> Tested-by: syzbot+b437b5a429d680cf2217@syzkaller.appspotmail.com Cc: Dave Chinner <david@fromorbit.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Josef Bacik [Wed, 13 Mar 2019 18:44:14 +0000 (11:44 -0700)]
filemap: kill page_cache_read usage in filemap_fault
Patch series "drop the mmap_sem when doing IO in the fault path", v6.
Now that we have proper isolation in place with cgroups2 we have started
going through and fixing the various priority inversions. Most are all
gone now, but this one is sort of weird since it's not necessarily a
priority inversion that happens within the kernel, but rather because of
something userspace does.
We have giant applications that we want to protect, and parts of these
giant applications do things like watch the system state to determine how
healthy the box is for load balancing and such. This involves running
'ps' or other such utilities. These utilities will often walk
/proc/<pid>/whatever, and these files can sometimes need to
down_read(&task->mmap_sem). Not usually a big deal, but we noticed when
we are stress testing that sometimes our protected application has latency
spikes trying to get the mmap_sem for tasks that are in lower priority
cgroups.
This is because any down_write() on a semaphore essentially turns it into
a mutex, so even if we currently have it held for reading, any new readers
will not be allowed on to keep from starving the writer. This is fine,
except a lower priority task could be stuck doing IO because it has been
throttled to the point that its IO is taking much longer than normal. But
because a higher priority group depends on this completing it is now stuck
behind lower priority work.
In order to avoid this particular priority inversion we want to use the
existing retry mechanism to stop from holding the mmap_sem at all if we
are going to do IO. This already exists in the read case sort of, but
needed to be extended for more than just grabbing the page lock. With
io.latency we throttle at submit_bio() time, so the readahead stuff can
block and even page_cache_read can block, so all these paths need to have
the mmap_sem dropped.
The other big thing is ->page_mkwrite. btrfs is particularly shitty here
because we have to reserve space for the dirty page, which can be a very
expensive operation. We use the same retry method as the read path, and
simply cache the page and verify the page is still setup properly the next
pass through ->page_mkwrite().
I've tested these patches with xfstests and there are no regressions.
This patch (of 3):
If we do not have a page at filemap_fault time we'll do this weird forced
page_cache_read thing to populate the page, and then drop it again and
loop around and find it. This makes for 2 ways we can read a page in
filemap_fault, and it's not really needed. Instead add a FGP_FOR_MMAP
flag so that pagecache_get_page() will return a unlocked page that's in
pagecache. Then use the normal page locking and readpage logic already in
filemap_fault. This simplifies the no page in page cache case
significantly.
[akpm@linux-foundation.org: fix comment text]
[josef@toxicpanda.com: don't unlock null page in FGP_FOR_MMAP case] Link: http://lkml.kernel.org/r/20190312201742.22935-1-josef@toxicpanda.com Link: http://lkml.kernel.org/r/20181211173801.29535-2-josef@toxicpanda.com Signed-off-by: Josef Bacik <josef@toxicpanda.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Tejun Heo <tj@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Rik van Riel <riel@redhat.com> Cc: "Kirill A. Shutemov" <kirill@shutemov.name> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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