linux-toradex.git/block/blk-throttle.c, branch v4.0

blk-throttle: check stats_cpu before reading it from sysfs

2015-02-21T06:11:58+00:00

When reading blkio.throttle.io_serviced in a recently created blkio
cgroup, it's possible to race against the creation of a throttle policy,
which delays the allocation of stats_cpu.

Like other functions in the throttle code, just checking for a NULL
stats_cpu prevents the following oops caused by that race.

[ 1117.285199] Unable to handle kernel paging request for data at address 0x7fb4d0020
[ 1117.285252] Faulting instruction address: 0xc0000000003efa2c
[ 1137.733921] Oops: Kernel access of bad area, sig: 11 [#1]
[ 1137.733945] SMP NR_CPUS=2048 NUMA PowerNV
[ 1137.734025] Modules linked in: bridge stp llc kvm_hv kvm binfmt_misc autofs4
[ 1137.734102] CPU: 3 PID: 5302 Comm: blkcgroup Not tainted 3.19.0 #5
[ 1137.734132] task: c000000f1d188b00 ti: c000000f1d210000 task.ti: c000000f1d210000
[ 1137.734167] NIP: c0000000003efa2c LR: c0000000003ef9f0 CTR: c0000000003ef980
[ 1137.734202] REGS: c000000f1d213500 TRAP: 0300   Not tainted  (3.19.0)
[ 1137.734230] MSR: 9000000000009032   CR: 42008884  XER: 20000000
[ 1137.734325] CFAR: 0000000000008458 DAR: 00000007fb4d0020 DSISR: 40000000 SOFTE: 0
GPR00: c0000000003ed3a0 c000000f1d213780 c000000000c59538 0000000000000000
GPR04: 0000000000000800 0000000000000000 0000000000000000 0000000000000000
GPR08: ffffffffffffffff 00000007fb4d0020 00000007fb4d0000 c000000000780808
GPR12: 0000000022000888 c00000000fdc0d80 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 000001003e120200 c000000f1d5b0cc0 0000000000000200 0000000000000000
GPR24: 0000000000000001 c000000000c269e0 0000000000000020 c000000f1d5b0c80
GPR28: c000000000ca3a08 c000000000ca3dec c000000f1c667e00 c000000f1d213850
[ 1137.734886] NIP [c0000000003efa2c] .tg_prfill_cpu_rwstat+0xac/0x180
[ 1137.734915] LR [c0000000003ef9f0] .tg_prfill_cpu_rwstat+0x70/0x180
[ 1137.734943] Call Trace:
[ 1137.734952] [c000000f1d213780] [d000000005560520] 0xd000000005560520 (unreliable)
[ 1137.734996] [c000000f1d2138a0] [c0000000003ed3a0] .blkcg_print_blkgs+0xe0/0x1a0
[ 1137.735039] [c000000f1d213960] [c0000000003efb50] .tg_print_cpu_rwstat+0x50/0x70
[ 1137.735082] [c000000f1d2139e0] [c000000000104b48] .cgroup_seqfile_show+0x58/0x150
[ 1137.735125] [c000000f1d213a70] [c0000000002749dc] .kernfs_seq_show+0x3c/0x50
[ 1137.735161] [c000000f1d213ae0] [c000000000218630] .seq_read+0xe0/0x510
[ 1137.735197] [c000000f1d213bd0] [c000000000275b04] .kernfs_fop_read+0x164/0x200
[ 1137.735240] [c000000f1d213c80] [c0000000001eb8e0] .__vfs_read+0x30/0x80
[ 1137.735276] [c000000f1d213cf0] [c0000000001eb9c4] .vfs_read+0x94/0x1b0
[ 1137.735312] [c000000f1d213d90] [c0000000001ebb38] .SyS_read+0x58/0x100
[ 1137.735349] [c000000f1d213e30] [c000000000009218] syscall_exit+0x0/0x98
[ 1137.735383] Instruction dump:
[ 1137.735405] 7c6307b4 7f891800 409d00b8 60000000 60420000 3d420004 392a63b0 786a1f24
[ 1137.735471] 7d49502a e93e01c8 7d495214 7d2ad214 <7cead02a> e9090008 e9490010 e9290018

And here is one code that allows to easily reproduce this, although this
has first been found by running docker.

void run(pid_t pid)
{
	int n;
	int status;
	int fd;
	char *buffer;
	buffer = memalign(BUFFER_ALIGN, BUFFER_SIZE);
	n = snprintf(buffer, BUFFER_SIZE, "%d\n", pid);
	fd = open(CGPATH "/test/tasks", O_WRONLY);
	write(fd, buffer, n);
	close(fd);
	if (fork() > 0) {
		fd = open("/dev/sda", O_RDONLY | O_DIRECT);
		read(fd, buffer, 512);
		close(fd);
		wait(&status);
	} else {
		fd = open(CGPATH "/test/blkio.throttle.io_serviced", O_RDONLY);
		n = read(fd, buffer, BUFFER_SIZE);
		close(fd);
	}
	free(buffer);
	exit(0);
}

void test(void)
{
	int status;
	mkdir(CGPATH "/test", 0666);
	if (fork() > 0)
		wait(&status);
	else
		run(getpid());
	rmdir(CGPATH "/test");
}

int main(int argc, char **argv)
{
	int i;
	for (i = 0; i < NR_TESTS; i++)
		test();
	return 0;
}

Reported-by: Ricardo Marin Matinata 
Signed-off-by: Thadeu Lima de Souza Cascardo 
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe

cgroup: remove sane_behavior support on non-default hierarchies

2014-07-09T14:08:08+00:00

sane_behavior has been used as a development vehicle for the default
unified hierarchy.  Now that the default hierarchy is in place, the
flag became redundant and confusing as its usage is allowed on all
hierarchies.  There are gonna be either the default hierarchy or
legacy ones.  Let's make that clear by removing sane_behavior support
on non-default hierarchies.

This patch replaces cgroup_sane_behavior() with cgroup_on_dfl().  The
comment on top of CGRP_ROOT_SANE_BEHAVIOR is moved to on top of
cgroup_on_dfl() with sane_behavior specific part dropped.

On the default and legacy hierarchies w/o sane_behavior, this
shouldn't cause any behavior differences.

Signed-off-by: Tejun Heo 
Acked-by: Vivek Goyal 
Acked-by: Li Zefan 
Cc: Johannes Weiner 
Cc: Michal Hocko

Merge branch 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

2014-06-09T22:03:33+00:00

Pull cgroup updates from Tejun Heo:
 "A lot of activities on cgroup side.  Heavy restructuring including
  locking simplification took place to improve the code base and enable
  implementation of the unified hierarchy, which currently exists behind
  a __DEVEL__ mount option.  The core support is mostly complete but
  individual controllers need further work.  To explain the design and
  rationales of the the unified hierarchy

        Documentation/cgroups/unified-hierarchy.txt

  is added.

  Another notable change is css (cgroup_subsys_state - what each
  controller uses to identify and interact with a cgroup) iteration
  update.  This is part of continuing updates on css object lifetime and
  visibility.  cgroup started with reference count draining on removal
  way back and is now reaching a point where csses behave and are
  iterated like normal refcnted objects albeit with some complexities to
  allow distinguishing the state where they're being deleted.  The css
  iteration update isn't taken advantage of yet but is planned to be
  used to simplify memcg significantly"

* 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits)
  cgroup: disallow disabled controllers on the default hierarchy
  cgroup: don't destroy the default root
  cgroup: disallow debug controller on the default hierarchy
  cgroup: clean up MAINTAINERS entries
  cgroup: implement css_tryget()
  device_cgroup: use css_has_online_children() instead of has_children()
  cgroup: convert cgroup_has_live_children() into css_has_online_children()
  cgroup: use CSS_ONLINE instead of CGRP_DEAD
  cgroup: iterate cgroup_subsys_states directly
  cgroup: introduce CSS_RELEASED and reduce css iteration fallback window
  cgroup: move cgroup->serial_nr into cgroup_subsys_state
  cgroup: link all cgroup_subsys_states in their sibling lists
  cgroup: move cgroup->sibling and ->children into cgroup_subsys_state
  cgroup: remove cgroup->parent
  device_cgroup: remove direct access to cgroup->children
  memcg: update memcg_has_children() to use css_next_child()
  memcg: remove tasks/children test from mem_cgroup_force_empty()
  cgroup: remove css_parent()
  cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css
  cgroup: use cgroup->self.refcnt for cgroup refcnting
  ...

cgroup: replace cftype->write_string() with cftype->write()

2014-05-13T16:16:21+00:00

Convert all cftype->write_string() users to the new cftype->write()
which maps directly to kernfs write operation and has full access to
kernfs and cgroup contexts.  The conversions are mostly mechanical.

* @css and @cft are accessed using of_css() and of_cft() accessors
  respectively instead of being specified as arguments.

* Should return @nbytes on success instead of 0.

* @buf is not trimmed automatically.  Trim if necessary.  Note that
  blkcg and netprio don't need this as the parsers already handle
  whitespaces.

cftype->write_string() has no user left after the conversions and
removed.

While at it, remove unnecessary local variable @p in
cgroup_subtree_control_write() and stale comment about
CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c.

This patch doesn't introduce any visible behavior changes.

v2: netprio was missing from conversion.  Converted.

Signed-off-by: Tejun Heo 
Acked-by: Aristeu Rozanski 
Acked-by: Vivek Goyal 
Acked-by: Li Zefan 
Cc: Jens Axboe 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: Neil Horman 
Cc: "David S. Miller"

block/blk-throttle.c: fix return of 0/1 with return type bool

2014-05-02T17:38:03+00:00

Fix 4 coccinelle warnings.

Cc: Jens Axboe 
Cc: Andrew Morton 
Signed-off-by: Fabian Frederick 
Signed-off-by: Jens Axboe

block/blk-throttle.c: add static to blk_throtl_dispatch_work_fn

2014-04-22T01:30:28+00:00

blk_throtl_dispatch_work_fn is only used in blk-throttle.c

Cc: Jens Axboe 
Cc: Andrew Morton 
Signed-off-by: Fabian Frederick 
Signed-off-by: Jens Axboe

cgroup: drop const from @buffer of cftype->write_string()

2014-03-19T14:23:54+00:00

cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer.  The
only thing const achieves is unnecessarily complicating parsing of the
buffer.  Drop const from @buffer.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan 
Cc: Peter Zijlstra 
Cc: Paul Mackerras 
Cc: Ingo Molnar 
Cc: Arnaldo Carvalho de Melo 
Cc: Daniel Borkmann 
Cc: Michal Hocko                                            
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: KAMEZAWA Hiroyuki

cgroup: update the meaning of cftype->max_write_len

2014-02-11T16:52:48+00:00

cftype->max_write_len is used to extend the maximum size of writes.
It's interpreted in such a way that the actual maximum size is one
less than the specified value.  The default size is defined by
CGROUP_LOCAL_BUFFER_SIZE.  Its interpretation is quite confusing - its
value is decremented by 1 and then compared for equality with max
size, which means that the actual default size is
CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars.

There's no point in having a limit that low.  Update its definition so
that it means the actual string length sans termination and anything
below PAGE_SIZE-1 is treated as PAGE_SIZE-1.

.max_write_len for "release_agent" is updated to PATH_MAX-1 and
cgroup_release_agent_write() is updated so that the redundant strlen()
check is removed and it uses strlcpy() instead of strcpy().
.max_write_len initializations in blk-throttle.c and cfq-iosched.c are
no longer necessary and removed.  The one in cpuset is kept unchanged
as it's an approximated value to begin with.

This will also make transition to kernfs smoother.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan

Merge branch 'for-3.14/core' of git://git.kernel.dk/linux-block

2014-01-30T19:19:05+00:00

Pull core block IO changes from Jens Axboe:
 "The major piece in here is the immutable bio_ve series from Kent, the
  rest is fairly minor.  It was supposed to go in last round, but
  various issues pushed it to this release instead.  The pull request
  contains:

   - Various smaller blk-mq fixes from different folks.  Nothing major
     here, just minor fixes and cleanups.

   - Fix for a memory leak in the error path in the block ioctl code
     from Christian Engelmayer.

   - Header export fix from CaiZhiyong.

   - Finally the immutable biovec changes from Kent Overstreet.  This
     enables some nice future work on making arbitrarily sized bios
     possible, and splitting more efficient.  Related fixes to immutable
     bio_vecs:

        - dm-cache immutable fixup from Mike Snitzer.
        - btrfs immutable fixup from Muthu Kumar.

  - bio-integrity fix from Nic Bellinger, which is also going to stable"

* 'for-3.14/core' of git://git.kernel.dk/linux-block: (44 commits)
  xtensa: fixup simdisk driver to work with immutable bio_vecs
  block/blk-mq-cpu.c: use hotcpu_notifier()
  blk-mq: for_each_* macro correctness
  block: Fix memory leak in rw_copy_check_uvector() handling
  bio-integrity: Fix bio_integrity_verify segment start bug
  block: remove unrelated header files and export symbol
  blk-mq: uses page->list incorrectly
  blk-mq: use __smp_call_function_single directly
  btrfs: fix missing increment of bi_remaining
  Revert "block: Warn and free bio if bi_end_io is not set"
  block: Warn and free bio if bi_end_io is not set
  blk-mq: fix initializing request's start time
  block: blk-mq: don't export blk_mq_free_queue()
  block: blk-mq: make blk_sync_queue support mq
  block: blk-mq: support draining mq queue
  dm cache: increment bi_remaining when bi_end_io is restored
  block: fixup for generic bio chaining
  block: Really silence spurious compiler warnings
  block: Silence spurious compiler warnings
  block: Kill bio_pair_split()
  ...

cgroup: replace cftype->read_seq_string() with cftype->seq_show()

2013-12-05T17:28:04+00:00

In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs.  This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.

The conversions are mechanical.  As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively.  In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.

This patch does not introduce any behavior changes.

Signed-off-by: Tejun Heo 
Acked-by: Aristeu Rozanski 
Acked-by: Vivek Goyal 
Acked-by: Michal Hocko 
Acked-by: Daniel Wagner 
Acked-by: Li Zefan 
Cc: Jens Axboe 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Johannes Weiner 
Cc: Balbir Singh 
Cc: KAMEZAWA Hiroyuki 
Cc: Neil Horman