Tejun Heo [Wed, 14 May 2014 13:15:01 +0000 (09:15 -0400)]
cgroup: move cgroup->sibling unlinking to cgroup_put()
Move cgroup->sibling unlinking from cgroup_destroy_css_killed() to
cgroup_put(). This is later but still before the RCU grace period, so
it doesn't break css_next_child() although there now is a larger
window in which a dead cgroup is visible during css iteration. As css
iteration always could have included offline csses, this doesn't
affect correctness; however, it does make css_next_child() fall back
to reiterting mode more often. This also makes cgroup_put() directly
take cgroup_mutex, which limits where it can be called from. These
are not immediately problematic and will be dealt with later.
This change enables simplification of cgroup destruction path.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Wed, 14 May 2014 13:15:01 +0000 (09:15 -0400)]
cgroup: move check_for_release(parent) call to the end of cgroup_destroy_locked()
Currently, check_for_release() on the parent of a destroyed cgroup is
invoked from cgroup_destroy_css_killed(). This is because this is
where the destroyed cgroup can be removed from the parent's children
list. check_for_release() tests the emptiness of the list directly,
so invoking it before removing the cgroup from the list makes it think
that the parent still has children even when it no longer does.
This patch updates check_for_release() to use
cgroup_has_live_children() instead of directly testing ->children
emptiness and moves check_for_release(parent) earlier to the end of
cgroup_destroy_locked(). As cgroup_has_live_children() ignores
cgroups marked DEAD, check_for_release() functions correctly as long
as it's called after asserting DEAD.
This makes release notification slightly more timely and more
importantly enables further simplification of cgroup destruction path.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Wed, 14 May 2014 13:15:00 +0000 (09:15 -0400)]
cgroup: rename cgroup->dummy_css to ->self and move it to the top
cgroup->dummy_css is used as the placeholder css when performing css
oriended operations on the cgroup. We're gonna shift more cgroup
management to this css. Let's rename it to ->self and move it to the
top.
This is pure rename and field relocation.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Wed, 14 May 2014 13:15:00 +0000 (09:15 -0400)]
cgroup: use restart_syscall() for mount retries
cgroup_mount() uses dumb delay-and-retry logic to wait for cgroup_root
which is being destroyed. The retry currently loops inside
cgroup_mount() proper. This patch makes it return with
restart_syscall() instead so that retry travels out to userland
boundary.
This slightly simplifies the logic and more importantly makes the
retry logic behave better when the wait for some reason becomes
lengthy or infinite by allowing the operation to be suspended or
terminated from userland.
v2: The original patch forgot to free memory allocated for @opts.
Fixed. Caught by Li Zefan.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:23 +0000 (12:19 -0400)]
cgroup: remove cgroup_tree_mutex
cgroup_tree_mutex was introduced to work around the circular
dependency between cgroup_mutex and kernfs active protection - some
kernfs file and directory operations needed cgroup_mutex putting
cgroup_mutex under active protection but cgroup also needs to be able
to access cgroup hierarchies and cftypes to determine which
kernfs_nodes need to be removed. cgroup_tree_mutex nested above both
cgroup_mutex and kernfs active protection and used to protect the
hierarchy and cftypes. While this worked, it added a lot of double
lockings and was generally cumbersome.
kernfs provides a mechanism to opt out of active protection and cgroup
was already using it for removal and subtree_control. There's no
reason to mix both methods of avoiding circular locking dependency and
the preceding cgroup_kn_lock_live() changes applied it to all relevant
cgroup kernfs operations making it unnecessary to nest cgroup_mutex
under kernfs active protection. The previous patch reversed the
original lock ordering and put cgroup_mutex above kernfs active
protection.
After these changes, all cgroup_tree_mutex usages are now accompanied
by cgroup_mutex making the former completely redundant. This patch
removes cgroup_tree_mutex and all its usages.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:23 +0000 (12:19 -0400)]
cgroup: nest kernfs active protection under cgroup_mutex
After the recent cgroup_kn_lock_live() changes, cgroup_mutex is no
longer nested below kernfs active protection. The two don't have any
relationship now.
This patch nests kernfs active protection under cgroup_mutex. All
cftype operations now require both cgroup_tree_mutex and cgroup_mutex,
temporary cgroup_mutex releases over kernfs operations are removed,
and cgroup_add/rm_cftypes() grab both mutexes.
This makes cgroup_tree_mutex redundant, which will be removed by the
next patch.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:23 +0000 (12:19 -0400)]
cgroup: use cgroup_kn_lock_live() in other cgroup kernfs methods
Make __cgroup_procs_write() and cgroup_release_agent_write() use
cgroup_kn_lock_live() and cgroup_kn_unlock() instead of
cgroup_lock_live_group(). This puts the operations under both
cgroup_tree_mutex and cgroup_mutex protection without circular
dependency from kernfs active protection. Also, this means that
cgroup_mutex is no longer nested below kernfs active protection.
There is no longer any place where the two locks interact.
This leaves cgroup_lock_live_group() without any user. Removed.
This will help simplifying cgroup locking.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:22 +0000 (12:19 -0400)]
cgroup: factor out cgroup_kn_lock_live() and cgroup_kn_unlock()
cgroup_mkdir(), cgroup_rmdir() and cgroup_subtree_control_write()
share the logic to break active protection so that they can grab
cgroup_tree_mutex which nests above active protection and/or remove
self. Factor out this logic into cgroup_kn_lock_live() and
cgroup_kn_unlock().
This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:22 +0000 (12:19 -0400)]
cgroup: move cgroup->kn->priv clearing to cgroup_rmdir()
The ->priv field of a cgroup directory kernfs_node points back to the
cgroup. This field is RCU cleared in cgroup_destroy_locked() for
non-kernfs accesses from css_tryget_from_dir() and
cgroupstats_build().
As these are only applicable to cgroups which finished creation
successfully and fully initialized cgroups are always removed by
cgroup_rmdir(), this can be safely moved to the end of cgroup_rmdir().
This will help simplifying cgroup locking and shouldn't introduce any
behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:22 +0000 (12:19 -0400)]
cgroup: grab cgroup_mutex earlier in cgroup_subtree_control_write()
Move cgroup_lock_live_group() invocation upwards to right below
cgroup_tree_mutex in cgroup_subtree_control_write(). This is to help
the planned locking simplification.
This doesn't make any userland-visible behavioral changes.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:22 +0000 (12:19 -0400)]
cgroup: collapse cgroup_create() into croup_mkdir()
cgroup_mkdir() is the sole user of cgroup_create(). Let's collapse
the latter into the former. This will help simplifying locking.
While at it, remove now stale comment about inode locking.
This patch doesn't introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:19:22 +0000 (12:19 -0400)]
cgroup: reorganize cgroup_create()
Reorganize cgroup_create() so that all paths share unlock out path.
* All err_* labels are renamed to out_* as they're now shared by both
success and failure paths.
* @err renamed to @ret for the similar reason as above and so that
it's more consistent with other functions.
* cgroup memory allocation moved after locking so that freeing failed
cgroup happens before unlocking. While this moves more code inside
critical section, memory allocations inside cgroup locking are
already pretty common and this is unlikely to make any noticeable
difference.
* While at it, replace a stray @parent->root dereference with @root.
This reorganization will help simplifying locking.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:16:22 +0000 (12:16 -0400)]
cgroup: remove cgroup->control_kn
Now that cgroup_subtree_control_write() has access to the associated
kernfs_open_file and thus the kernfs_node, there's no need to cache it
in cgroup->control_kn on creation. Remove cgroup->control_kn and use
@of->kn directly.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:16:22 +0000 (12:16 -0400)]
cgroup: convert "tasks" and "cgroup.procs" handle to use cftype->write()
cgroup_tasks_write() and cgroup_procs_write() are currently using
cftype->write_u64(). This patch converts them to use cftype->write()
instead. This allows access to the associated kernfs_open_file which
will be necessary to implement the planned kernfs active protection
manipulation for these files.
This shifts buffer parsing to attach_task_by_pid() and makes it return
@nbytes on success. Let's rename it to __cgroup_procs_write() to
clearly indicate that this is a write handler implementation.
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:16:21 +0000 (12:16 -0400)]
cgroup: replace cftype->trigger() with cftype->write()
cftype->trigger() is pointless. It's trivial to ignore the input
buffer from a regular ->write() operation. Convert all ->trigger()
users to ->write() and remove ->trigger().
This patch doesn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz>
Tejun Heo [Tue, 13 May 2014 16:16:21 +0000 (12:16 -0400)]
cgroup: replace cftype->write_string() with cftype->write()
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 <tj@kernel.org> Acked-by: Aristeu Rozanski <arozansk@redhat.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: "David S. Miller" <davem@davemloft.net>
Tejun Heo [Tue, 13 May 2014 16:16:21 +0000 (12:16 -0400)]
cgroup: implement cftype->write()
During the recent conversion to kernfs, cftype's seq_file operations
are updated so that they are directly mapped to kernfs operations and
thus can fully access the associated kernfs and cgroup contexts;
however, write path hasn't seen similar updates and none of the
existing write operations has access to, for example, the associated
kernfs_open_file.
Let's introduce a new operation cftype->write() which maps directly to
the kernfs write operation and has access to all the arguments and
contexts. This will replace ->write_string() and ->trigger() and ease
manipulation of kernfs active protection from cgroup file operations.
Two accessors - of_cft() and of_css() - are introduced to enable
accessing the associated cgroup context from cftype->write() which
only takes kernfs_open_file for the context information. The
accessors for seq_file operations - seq_cft() and seq_css() - are
rewritten to wrap the of_ accessors.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:11:01 +0000 (12:11 -0400)]
cgroup: rename css_tryget*() to css_tryget_online*()
Unlike the more usual refcnting, what css_tryget() provides is the
distinction between online and offline csses instead of protection
against upping a refcnt which already reached zero. cgroup is
planning to provide actual tryget which fails if the refcnt already
reached zero. Let's rename the existing trygets so that they clearly
indicate that they're onliness.
I thought about keeping the existing names as-are and introducing new
names for the planned actual tryget; however, given that each
controller participates in the synchronization of the online state, it
seems worthwhile to make it explicit that these functions are about
on/offline state.
Rename css_tryget() to css_tryget_online() and css_tryget_from_dir()
to css_tryget_online_from_dir(). This is pure rename.
v2: cgroup_freezer grew new usages of css_tryget(). Update
accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Tejun Heo [Tue, 13 May 2014 16:11:00 +0000 (12:11 -0400)]
cgroup: use release_agent_path_lock in cgroup_release_agent_show()
release_path is now protected by release_agent_path_lock to allow
accessing it without grabbing cgroup_mutex; however,
cgroup_release_agent_show() was still grabbing cgroup_mutex. Let's
convert it to release_agent_path_lock so that we don't have to worry
about this one for the planned locking updates.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:11:00 +0000 (12:11 -0400)]
cgroup: use restart_syscall() for retries after offline waits in cgroup_subtree_control_write()
After waiting for a child to finish offline,
cgroup_subtree_control_write() jumps up to retry from after the input
parsing and active protection breaking. This retry makes the
scheduled locking update - removal of cgroup_tree_mutex - more
difficult. Let's simplify it by returning with restart_syscall() for
retries.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 16:10:59 +0000 (12:10 -0400)]
cgroup: update and fix parsing of "cgroup.subtree_control"
I was confused that strsep() was equivalent to strtok_r() in skipping
over consecutive delimiters. strsep() just splits at the first
occurrence of one of the delimiters which makes the parsing very
inflexible, which makes allowing multiple whitespace chars as
delimters kinda moot. Let's just be consistently strict and require
list of tokens separated by spaces. This is what
Documentation/cgroups/unified-hierarchy.txt describes too.
Also, parsing may access beyond the end of the string if the string
ends with spaces or is zero-length. Make sure it skips zero-length
tokens. Note that this also ensures that the parser doesn't puke on
multiple consecutive spaces.
v2: Add zero-length token skipping.
v3: Added missing space after "==". Spotted by Li.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
c1a71504e971 ("cgroup: don't recycle cgroup id until all csses' have
been destroyed") made cgroup ID persist until a cgroup is released and
add cgroup->subsys[] clearing to css_release() so that css_from_id()
doesn't return a css which has already been released which happens
before cgroup release; however, the right change here was updating
offline_css() to clear cgroup->subsys[] which was done by e32978031016
("cgroup: cgroup->subsys[] should be cleared after the css is
offlined") instead of clearing it from css_release().
We're now clearing cgroup->subsys[] twice. This is okay for
traditional hierarchies as a css's lifetime is the same as its
cgroup's; however, this confuses unified hierarchy and turning on and
off a controller repeatedly using "cgroup.subtree_control" can lead to
an oops like the following which happens because cgroup->subsys[] is
incorrectly cleared asynchronously by css_release().
Tejun Heo [Tue, 13 May 2014 16:10:59 +0000 (12:10 -0400)]
cgroup: fix offlining child waiting in cgroup_subtree_control_write()
cgroup_subtree_control_write() waits for offline to complete
child-by-child before enabling a controller; however, it has a couple
bugs.
* It doesn't initialize the wait_queue_t. This can lead to infinite
hang on the following schedule() among other things.
* It forgets to pin the child before releasing cgroup_tree_mutex and
performing schedule(). The child may already be gone by the time it
wakes up and invokes finish_wait(). Pin the child being waited on.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Tue, 13 May 2014 15:30:04 +0000 (11:30 -0400)]
Merge branch 'for-3.15-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup into for-3.16
Pull to receive e37a06f10994 ("cgroup: fix the retry path of
cgroup_mount()") to avoid unnecessary conflicts with planned
cgroup_tree_mutex removal and also to be able to remove the temp fix
added by 36c38fb7144a ("blkcg: use trylock on blkcg_pol_mutex in
blkcg_reset_stats()") afterwards.
Tejun Heo [Tue, 13 May 2014 15:28:30 +0000 (11:28 -0400)]
cgroup: fix rcu_read_lock() leak in update_if_frozen()
While updating cgroup_freezer locking, 68fafb77d827 ("cgroup_freezer:
replace freezer->lock with freezer_mutex") introduced a bug in
update_if_frozen() where it returns with rcu_read_lock() held. Fix it
by adding rcu_read_unlock() before returning.
Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: kbuild test robot <fengguang.wu@intel.com>
Tejun Heo [Thu, 8 May 2014 01:31:17 +0000 (21:31 -0400)]
cgroup_freezer: replace freezer->lock with freezer_mutex
After 96d365e0b86e ("cgroup: make css_set_lock a rwsem and rename it
to css_set_rwsem"), css task iterators requires sleepable context as
it may block on css_set_rwsem. I missed that cgroup_freezer was
iterating tasks under IRQ-safe spinlock freezer->lock. This leads to
errors like the following on freezer state reads and transitions.
BUG: sleeping function called from invalid context at /work
/os/work/kernel/locking/rwsem.c:20
in_atomic(): 0, irqs_disabled(): 0, pid: 462, name: bash
5 locks held by bash/462:
#0: (sb_writers#7){.+.+.+}, at: [<ffffffff811f0843>] vfs_write+0x1a3/0x1c0
#1: (&of->mutex){+.+.+.}, at: [<ffffffff8126d78b>] kernfs_fop_write+0xbb/0x170
#2: (s_active#70){.+.+.+}, at: [<ffffffff8126d793>] kernfs_fop_write+0xc3/0x170
#3: (freezer_mutex){+.+...}, at: [<ffffffff81135981>] freezer_write+0x61/0x1e0
#4: (rcu_read_lock){......}, at: [<ffffffff81135973>] freezer_write+0x53/0x1e0
Preemption disabled at:[<ffffffff81104404>] console_unlock+0x1e4/0x460
freezer->lock used to be used in hot paths but that time is long gone
and there's no reason for the lock to be IRQ-safe spinlock or even
per-cgroup. In fact, given the fact that a cgroup may contain large
number of tasks, it's not a good idea to iterate over them while
holding IRQ-safe spinlock.
Let's simplify locking by replacing per-cgroup freezer->lock with
global freezer_mutex. This also makes the comments explaining the
intricacies of policy inheritance and the locking around it as the
states are protected by a common mutex.
The conversion is mostly straight-forward. The followings are worth
mentioning.
* freezer_css_online() no longer needs double locking.
* freezer_attach() now performs propagation simply while holding
freezer_mutex. update_if_frozen() race no longer exists and the
comment is removed.
* freezer_fork() now tests whether the task is in root cgroup using
the new task_css_is_root() without doing rcu_read_lock/unlock(). If
not, it grabs freezer_mutex and performs the operation.
* freezer_read() and freezer_change_state() grab freezer_mutex across
the whole operation and pin the css while iterating so that each
descendant processing happens in sleepable context.
Fixes: 96d365e0b86e ("cgroup: make css_set_lock a rwsem and rename it to css_set_rwsem") Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Thu, 8 May 2014 01:31:17 +0000 (21:31 -0400)]
cgroup: introduce task_css_is_root()
Determining the css of a task usually requires RCU read lock as that's
the only thing which keeps the returned css accessible till its
reference is acquired; however, testing whether a task belongs to the
root can be performed without dereferencing the returned css by
comparing the returned pointer against the root one in init_css_set[]
which never changes.
Implement task_css_is_root() which can be invoked in any context.
This will be used by the scheduled cgroup_freezer change.
v2: cgroup no longer supports modular controllers. No need to export
init_css_set. Pointed out by Li.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Fri, 9 May 2014 19:11:53 +0000 (15:11 -0400)]
percpu-refcount: implement percpu_ref_tryget()
Implement percpu_ref_tryget() which fails if the refcnt already
reached zero. Note that this is different from the recently renamed
percpu_ref_tryget_live() which fails if the refcnt has been killed and
is draining the remaining references. percpu_ref_tryget() succeeds on
a killed refcnt as long as its current refcnt is above zero.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Kent Overstreet <kmo@daterainc.com>
Tejun Heo [Fri, 9 May 2014 19:11:53 +0000 (15:11 -0400)]
percpu-refcount: rename percpu_ref_tryget() to percpu_ref_tryget_live()
percpu_ref_tryget() is different from the usual tryget semantics in
that it fails if the refcnt is in its dying stage even if the refcnt
hasn't reached zero yet. We're about to introduce the more
conventional tryget and the current one has only one user. Let's
rename it to percpu_ref_tryget_live() so that it explicitly signifies
the peculiarities of its semantics.
This is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Kent Overstreet <kmo@daterainc.com>
Tejun Heo [Mon, 5 May 2014 16:37:30 +0000 (12:37 -0400)]
blkcg: use trylock on blkcg_pol_mutex in blkcg_reset_stats()
During the recent conversion of cgroup to kernfs, cgroup_tree_mutex
which nests above both the kernfs s_active protection and cgroup_mutex
is added to synchronize cgroup file type operations as cgroup_mutex
needed to be grabbed from some file operations and thus can't be put
above s_active protection.
While this arrangement mostly worked for cgroup, this triggered the
following lockdep warning.
======================================================
[ INFO: possible circular locking dependency detected ] 3.15.0-rc3-next-20140430-sasha-00016-g4e281fa-dirty #429 Tainted: G W
-------------------------------------------------------
trinity-c173/9024 is trying to acquire lock:
(blkcg_pol_mutex){+.+.+.}, at: blkcg_reset_stats (include/linux/spinlock.h:328 block/blk-cgroup.c:455)
but task is already holding lock:
(s_active#89){++++.+}, at: kernfs_fop_write (fs/kernfs/file.c:283)
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
This is a highly unlikely but valid circular dependency between "echo
1 > blkcg.reset_stats" and cfq module [un]loading. cgroup is going
through further locking update which will remove this complication but
for now let's use trylock on blkcg_pol_mutex and retry the file
operation if the trylock fails.
device_cgroup: check if exception removal is allowed
[PATCH v3 1/2] device_cgroup: check if exception removal is allowed
When the device cgroup hierarchy was introduced in bd2953ebbb53 - devcg: propagate local changes down the hierarchy
a specific case was overlooked. Consider the hierarchy bellow:
A default policy: ALLOW, exceptions will deny access
\
B default policy: ALLOW, exceptions will deny access
There's no need to verify when an new exception is added to B because
in this case exceptions will deny access to further devices, which is
always fine. Hierarchy in device cgroup only makes sure B won't have
more access than A.
But when an exception is removed (by writing devices.allow), it isn't
checked if the user is in fact removing an inherited exception from A,
thus giving more access to B.
This shouldn't be allowed and this patch fixes it by making sure to never allow
exceptions in this case to be removed if the exception is partially or fully
present on the parent.
v3: missing '*' in function description
v2: improved log message and formatting fixes
Tejun Heo [Sun, 4 May 2014 19:09:14 +0000 (15:09 -0400)]
cgroup, memcg: implement css->id and convert css_from_id() to use it
Until now, cgroup->id has been used to identify all the associated
csses and css_from_id() takes cgroup ID and returns the matching css
by looking up the cgroup and then dereferencing the css associated
with it; however, now that the lifetimes of cgroup and css are
separate, this is incorrect and breaks on the unified hierarchy when a
controller is disabled and enabled back again before the previous
instance is released.
This patch adds css->id which is a subsystem-unique ID and converts
css_from_id() to look up by the new css->id instead. memcg is the
only user of css_from_id() and also converted to use css->id instead.
For traditional hierarchies, this shouldn't make any functional
difference.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jianyu Zhan <nasa4836@gmail.com> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Sun, 4 May 2014 19:09:14 +0000 (15:09 -0400)]
cgroup: update init_css() into init_and_link_css()
init_css() takes the cgroup the new css belongs to as an argument and
initializes the new css's ->cgroup and ->parent pointers but doesn't
acquire the matching reference counts. After the previous patch,
create_css() puts init_css() and reference acquisition right next to
each other. Let's move reference acquistion into init_css() and
rename the function to init_and_link_css(). This makes sense and is
easier to follow. This makes the root csses to hold a reference on
cgrp_dfl_root.cgrp, which is harmless.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Sun, 4 May 2014 19:09:14 +0000 (15:09 -0400)]
cgroup: use RCU free in create_css() failure path
Currently, when create_css() fails in the middle, the half-initialized
css is freed by invoking cgroup_subsys->css_free() directly. This
patch updates the function so that it invokes RCU free path instead.
As the RCU free path puts the parent css and owning cgroup, their
references are now acquired right after a new css is successfully
allocated.
This doesn't make any visible difference now but is to enable
implementing css->id and RCU protected lookup by such IDs.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Sun, 4 May 2014 19:09:13 +0000 (15:09 -0400)]
cgroup: protect cgroup_root->cgroup_idr with a spinlock
Currently, cgroup_root->cgroup_idr is protected by cgroup_mutex, which
ends up requiring cgroup_put() to be invoked under sleepable context.
This is okay for now but is an unusual requirement and we'll soon add
css->id which will have the same problem but won't be able to simply
grab cgroup_mutex as removal will have to happen from css_release()
which can't sleep.
Introduce cgroup_idr_lock and idr_alloc/replace/remove() wrappers
which protects the idr operations with the lock and use them for
cgroup_root->cgroup_idr. cgroup_put() no longer needs to grab
cgroup_mutex and css_from_id() is updated to always require RCU read
lock instead of either RCU read lock or cgroup_mutex, which doesn't
affect the existing users.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Sun, 4 May 2014 19:09:13 +0000 (15:09 -0400)]
cgroup, memcg: allocate cgroup ID from 1
Currently, cgroup->id is allocated from 0, which is always assigned to
the root cgroup; unfortunately, memcg wants to use ID 0 to indicate
invalid IDs and ends up incrementing all IDs by one.
It's reasonable to reserve 0 for special purposes. This patch updates
cgroup core so that ID 0 is not used and the root cgroups get ID 1.
The ID incrementing is removed form memcg.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo [Sun, 4 May 2014 19:09:13 +0000 (15:09 -0400)]
cgroup: make flags and subsys_masks unsigned int
There's no reason to use atomic bitops for cgroup_subsys_state->flags,
cgroup_root->flags and various subsys_masks. This patch updates those
to use bitwise and/or operations instead and converts them form
unsigned long to unsigned int.
This makes the fields occupy (marginally) smaller space and makes it
clear that they don't require atomicity.
This patch doesn't cause any behavior difference.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Joe Perches [Fri, 25 Apr 2014 22:28:03 +0000 (18:28 -0400)]
cgroup: Use more current logging style
Use pr_fmt and remove embedded prefixes.
Realign modified multi-line statements to open parenthesis.
Convert embedded function name to "%s: ", __func__
Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Tejun Heo <tj@kernel.org>
6612f05b88fa309c9 ("cgroup: unify pidlist and other file handling")
has removed the only user of cgroup_pidlist_seq_operations :
cgroup_pidlist_open().
cgroup: clean up obsolete comment for parse_cgroupfs_options()
1d5be6b287c8efc87 ("cgroup: move module ref handling into
rebind_subsystems()") makes parse_cgroupfs_options() no longer takes
refcounts on subsystems.
And unified hierachy makes parse_cgroupfs_options not need to call
with cgroup_mutex held to protect the cgroup_subsys[].
So this patch removes BUG_ON() and the comment. As the comment
doesn't contain useful information afterwards, the whole comment is
removed.
Unified hierarchy will be the new version of cgroup interface. This
patch adds Documentation/cgroups/unified-hierarchy.txt which describes
the design and rationales of unified hierarchy.
v2: Grammatical updates as per Randy Dunlap's review.
Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Randy Dunlap <rdunlap@infradead.org>
cgroup: implement cgroup.populated for the default hierarchy
cgroup users often need a way to determine when a cgroup's
subhierarchy becomes empty so that it can be cleaned up. cgroup
currently provides release_agent for it; unfortunately, this mechanism
is riddled with issues.
* It delivers events by forking and execing a userland binary
specified as the release_agent. This is a long deprecated method of
notification delivery. It's extremely heavy, slow and cumbersome to
integrate with larger infrastructure.
* There is single monitoring point at the root. There's no way to
delegate management of a subtree.
* The event isn't recursive. It triggers when a cgroup doesn't have
any tasks or child cgroups. Events for internal nodes trigger only
after all children are removed. This again makes it impossible to
delegate management of a subtree.
* Events are filtered from the kernel side. "notify_on_release" file
is used to subscribe to or suppress release event. This is
unnecessarily complicated and probably done this way because event
delivery itself was expensive.
This patch implements interface file "cgroup.populated" which can be
used to monitor whether the cgroup's subhierarchy has tasks in it or
not. Its value is 0 if there is no task in the cgroup and its
descendants; otherwise, 1, and kernfs_notify() notificaiton is
triggers when the value changes, which can be monitored through poll
and [di]notify.
This is a lot ligther and simpler and trivially allows delegating
management of subhierarchy - subhierarchy monitoring can block further
propgation simply by putting itself or another process in the root of
the subhierarchy and monitor events that it's interested in from there
without interfering with monitoring higher in the tree.
v2: Patch description updated as per Serge.
v3: "cgroup.subtree_populated" renamed to "cgroup.populated". The
subtree_ prefix was a bit confusing because
"cgroup.subtree_control" uses it to denote the tree rooted at the
cgroup sans the cgroup itself while the populated state includes
the cgroup itself.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Serge Hallyn <serge.hallyn@ubuntu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Lennart Poettering <lennart@poettering.net>
kernfs: make kernfs_notify() trigger inotify events too
kernfs_notify() is used to indicate either new data is available or
the content of a file has changed. It currently only triggers poll
which may not be the most convenient to monitor especially when there
are a lot to monitor. Let's hook it up to fsnotify too so that the
events can be monitored via inotify too.
fsnotify_modify() requires file * but kernfs_notify() doesn't have any
specific file associated; however, we can walk all super_blocks
associated with a kernfs_root and as kernfs always associate one ino
with inode and one dentry with an inode, it's trivial to look up the
dentry associated with a given kernfs_node. As any active monitor
would pin dentry, just looking up existing dentry is enough. This
patch looks up the dentry associated with the specified kernfs_node
and generates events equivalent to fsnotify_modify().
Note that as fsnotify doesn't provide fsnotify_modify() equivalent
which can be called with dentry, kernfs_notify() directly calls
fsnotify_parent() and fsnotify(). It might be better to add a wrapper
in fsnotify.h instead.
Signed-off-by: Tejun Heo <tj@kernel.org> Cc: John McCutchan <john@johnmccutchan.com> Cc: Robert Love <rlove@rlove.org> Cc: Eric Paris <eparis@parisplace.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Currently, there's no way to find out which super_blocks are
associated with a given kernfs_root. Let's implement it - the planned
inotify extension to kernfs_notify() needs it.
Make kernfs_super_info point back to the super_block and chain it at
kernfs_root->supers.
cgroup: implement dynamic subtree controller enable/disable on the default hierarchy
cgroup is switching away from multiple hierarchies and will use one
unified default hierarchy where controllers can be dynamically enabled
and disabled per subtree. The default hierarchy will serve as the
unified hierarchy to which all controllers are attached and a css on
the default hierarchy would need to also serve the tasks of descendant
cgroups which don't have the controller enabled - ie. the tree may be
collapsed from leaf towards root when viewed from specific
controllers. This has been implemented through effective css in the
previous patches.
This patch finally implements dynamic subtree controller
enable/disable on the default hierarchy via a new knob -
"cgroup.subtree_control" which controls which controllers are enabled
on the child cgroups. Let's assume a hierarchy like the following.
root - A - B - C
\ D
root's "cgroup.subtree_control" determines which controllers are
enabled on A. A's on B. B's on C and D. This coincides with the
fact that controllers on the immediate sub-level are used to
distribute the resources of the parent. In fact, it's natural to
assume that resource control knobs of a child belong to its parent.
Enabling a controller in "cgroup.subtree_control" declares that
distribution of the respective resources of the cgroup will be
controlled. Note that this means that controller enable states are
shared among siblings.
The default hierarchy has an extra restriction - only cgroups which
don't contain any task may have controllers enabled in
"cgroup.subtree_control". Combined with the other properties of the
default hierarchy, this guarantees that, from the view point of
controllers, tasks are only on the leaf cgroups. In other words, only
leaf csses may contain tasks. This rules out situations where child
cgroups compete against internal tasks of the parent, which is a
competition between two different types of entities without any clear
way to determine resource distribution between the two. Different
controllers handle it differently and all the implemented behaviors
are ambiguous, ad-hoc, cumbersome and/or just wrong. Having this
structural constraints imposed from cgroup core removes the burden
from controller implementations and enables showing one consistent
behavior across all controllers.
When a controller is enabled or disabled, css associations for the
controller in the subtrees of each child should be updated. After
enabling, the whole subtree of a child should point to the new css of
the child. After disabling, the whole subtree of a child should point
to the cgroup's css. This is implemented by first updating cgroup
states such that cgroup_e_css() result points to the appropriate css
and then invoking cgroup_update_dfl_csses() which migrates all tasks
in the affected subtrees to the self cgroup on the default hierarchy.
* When read, "cgroup.subtree_control" lists all the currently enabled
controllers on the children of the cgroup.
* White-space separated list of controller names prefixed with either
'+' or '-' can be written to "cgroup.subtree_control". The ones
prefixed with '+' are enabled on the controller and '-' disabled.
* A controller can be enabled iff the parent's
"cgroup.subtree_control" enables it and disabled iff no child's
"cgroup.subtree_control" has it enabled.
* If a cgroup has tasks, no controller can be enabled via
"cgroup.subtree_control". Likewise, if "cgroup.subtree_control" has
some controllers enabled, tasks can't be migrated into the cgroup.
* All controllers which aren't bound on other hierarchies are
automatically associated with the root cgroup of the default
hierarchy. All the controllers which are bound to the default
hierarchy are listed in the read-only file "cgroup.controllers" in
the root directory.
* "cgroup.controllers" in all non-root cgroups is read-only file whose
content is equal to that of "cgroup.subtree_control" of the parent.
This indicates which controllers can be used in the cgroup's
"cgroup.subtree_control".
This is still experimental and there are some holes, one of which is
that ->can_attach() failure during cgroup_update_dfl_csses() may leave
the cgroups in an undefined state. The issues will be addressed by
future patches.
v2: Non-root cgroups now also have "cgroup.controllers".
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
cgroup: prepare migration path for unified hierarchy
Unified hierarchy implementation would require re-migrating tasks onto
the same cgroup on the default hierarchy to reflect updated effective
csses. Update cgroup_migrate_prepare_dst() so that it accepts NULL as
the destination cgrp. When NULL is specified, the destination is
considered to be the cgroup on the default hierarchy associated with
each css_set.
After this change, the identity check in cgroup_migrate_add_src()
isn't sufficient for noop detection as the associated csses may change
without any cgroup association changing. The only way to tell whether
a migration is noop or not is testing whether the source and
destination csets are identical. The noop check in
cgroup_migrate_add_src() is removed and cset identity test is added to
cgroup_migreate_prepare_dst(). If it's detected that source and
destination csets are identical, the cset is removed removed from
@preloaded_csets and all the migration nodes are cleared which makes
cgroup_migrate() ignore the cset.
Also, make the function append the destination css_sets to
@preloaded_list so that destination css_sets always come after source
css_sets.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Because the default root couldn't have any non-root csses attached to
it, rebinding away from it was always allowed; however, the default
hierarchy will soon host the unified hierarchy and have non-root csses
so the rebind restrictions need to be updated accordingly.
Instead of special casing rebinding from the default hierarchy and
then checking whether the source hierarchy has children cgroups, which
implies non-root csses for !dfl hierarchies, simply check whether the
source hierarchy has non-root csses for the subsystem using
css_next_child().
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
To implement the unified hierarchy behavior, we'll need to be able to
determine the associated cgroup on the default hierarchy from css_set.
Let's add css_set->dfl_cgrp so that it can be accessed conveniently
and efficiently.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
cgroup: allow cgroup creation and suppress automatic css creation in the unified hierarchy
Now that effective css handling has been added and iterators updated
accordingly, it's safe to allow cgroup creation in the default
hierarchy. Unblock cgroup creation in the default hierarchy.
As the default hierarchy will implement explicit enabling and
disabling of controllers on each cgroup, suppress automatic css
enabling on cgroup creation.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
cgroup: cgroup->subsys[] should be cleared after the css is offlined
After a css finishes offlining, offline_css() mistakenly performs
RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css) which just sets the
cgroup->subsys[] pointer to the current value. The intention was to
clear it after offline is complete, not reassign the same value.
Update it to assign NULL instead of the current value. This makes
cgroup_css() to return NULL once offline is complete. All the
existing users of the function either can handle NULL return already
or guarantee that the css doesn't get offlined.
While this is a bugfix, as css lifetime is currently tied to the
cgroup it belongs to, this bug doesn't cause any actual problems.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_task_iter iterates tasks associated with a css by
visiting each css_set associated with the owning cgroup and walking
tasks of each of them. This works fine for !unified hierarchies as
each cgroup has its own css for each associated subsystem on the
hierarchy; however, on the planned unified hierarchy, a cgroup may not
have csses associated and its tasks would be considered associated
with the matching css of the nearest ancestor which has the subsystem
enabled.
This means that on the default unified hierarchy, just walking all
tasks associated with a cgroup isn't enough to walk all tasks which
are associated with the specified css. If any of its children doesn't
have the matching css enabled, task iteration should also include all
tasks from the subtree. We already added cgroup->e_csets[] to list
all css_sets effectively associated with a given css and walk css_sets
on that list instead to achieve such iteration.
This patch updates css_task_iter iteration such that it walks css_sets
on cgroup->e_csets[] instead of cgroup->cset_links if iteration is
requested on an non-dummy css. Thanks to the previous iteration
update, this change can be achieved with the addition of
css_task_iter->ss and minimal updates to css_advance_task_iter() and
css_task_iter_start().
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
This patch reorganizes css_task_iter so that adding effective css
support is easier.
* s/->cset_link/->cset_pos/ and s/->task/->task_pos/ for consistency
* ->origin_css is used to determine whether the iteration reached the
last css_set. Replace it with explicit ->cset_head so that
css_advance_task_iter() doesn't have to know the termination
condition directly.
* css_task_iter_next() currently assumes that it's walking list of
cgrp_cset_link and reaches into the current cset through the current
link to determine the termination conditions for task walking. As
this won't always be true for effective css walking, add
->tasks_head and ->mg_tasks_head and use them to control task
walking so that css_task_iter_next() doesn't have to know how
css_sets are being walked.
This patch doesn't make any behavior changes. The iteration logic
stays unchanged after the patch.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
css_next_child() walks the children of the specified css. It does
this by finding the next cgroup and then returning the requested css.
On the default unified hierarchy, a cgroup may not have a css
associated with it even if the hierarchy has the subsystem enabled.
This patch updates css_next_child() so that it skips children without
the requested css associated.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
On the default unified hierarchy, a cgroup may be associated with
csses of its ancestors, which means that a css of a given cgroup may
be associated with css_sets of descendant cgroups. This means that we
can't walk all tasks associated with a css by iterating the css_sets
associated with the cgroup as there are css_sets which are pointing to
the css but linked on the descendants.
This patch adds per-subsystem list heads cgroup->e_csets[]. Any
css_set which is pointing to a css is linked to
css->cgroup->e_csets[$SUBSYS_ID] through
css_set->e_cset_node[$SUBSYS_ID]. The lists are protected by
css_set_rwsem and will allow us to walk all css_sets associated with a
given css so that we can find out all associated tasks.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
In the planned default unified hierarchy, controllers may get
dynamically attached to and detached from a cgroup and a cgroup may
not have csses for all the controllers associated with the hierarchy.
When a cgroup doesn't have its own css for a given controller, the css
of the nearest ancestor with the controller enabled will be used,
which is called the effective css. This patch introduces
cgroup_e_css() and for_each_e_css() to access the effective csses and
convert compare_css_sets(), find_existing_css_set() and
cgroup_migrate() to use the effective csses so that they can handle
cgroups with partial csses correctly.
This means that for two css_sets to be considered identical, they
should have both matching csses and cgroups. compare_css_sets()
already compares both, not for correctness but for optimization. As
this now becomes a matter of correctness, update the comments
accordingly.
For all !default hierarchies, cgroup_e_css() always equals
cgroup_css(), so this patch doesn't change behavior.
While at it, fix incorrect locking comment for for_each_css().
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
cgroup: update cgroup->subsys_mask to ->child_subsys_mask and restore cgroup_root->subsys_mask
944196278d3d ("cgroup: move ->subsys_mask from cgroupfs_root to
cgroup") moved ->subsys_mask from cgroup_root to cgroup to prepare for
the unified hierarhcy; however, it turns out that carrying the
subsys_mask of the children in the parent, instead of itself, is a lot
more natural. This patch restores cgroup_root->subsys_mask and morphs
cgroup->subsys_mask into cgroup->child_subsys_mask.
* Uses of root->cgrp.subsys_mask are restored to root->subsys_mask.
* Remove automatic setting and clearing of cgrp->subsys_mask and
instead just inherit ->child_subsys_mask from the parent during
cgroup creation. Note that this doesn't affect any current
behaviors.
* Undo __kill_css() separation.
Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
cgroup: cgroup_apply_cftypes() shouldn't skip the default hierarhcy
cgroup_apply_cftypes() skip creating or removing files if the
subsystem is attached to the default hierarchy, which led to missing
files in the root of the default hierarchy.
Skipping made sense when the default hierarchy was dummy; however, now
that the default hierarchy is full functional and planned to be used
as the unified hierarchy, it shouldn't be skipped over.
Reported-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
device_cgroup: rework device access check and exception checking
Whenever a device file is opened and checked against current device
cgroup rules, it uses the same function (may_access()) as when a new
exception rule is added by writing devices.{allow,deny}. And in both
cases, the algorithm is the same, doesn't matter the behavior.
First problem is having device access to be considered the same as rule
checking. Consider the following structure:
A (default behavior: allow, exceptions disallow access)
\
B (default behavior: allow, exceptions disallow access)
A new exception is added to B by writing devices.deny:
c 12:34 rw
When checking if that exception is allowed in may_access():
if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) {
if (behavior == DEVCG_DEFAULT_ALLOW) {
/* the exception will deny access to certain devices */
return true;
Which is ok, since B is not getting more privileges than A, it doesn't
matter and the rule is accepted
Now, consider it's a device file open check and the process belongs to
cgroup B. The access will be generated as:
behavior: allow
exception: c 12:34 rw
The very same chunk of code will allow it, even if there's an explicit
exception telling to do otherwise.
c39a2a3018f8 devcg: prepare may_access() for hierarchy support
To solve this problem, the device file open function was split from the
new exception check.
Second problem is how exceptions are processed by may_access(). The
first part of the said function tries to match fully with an existing
exception:
list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
continue;
if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))
continue;
if (ex->major != ~0 && ex->major != refex->major)
continue;
if (ex->minor != ~0 && ex->minor != refex->minor)
continue;
if (refex->access & (~ex->access))
continue;
match = true;
break;
}
That means the new exception should be contained into an existing one to
be considered a match:
New exception Existing match? notes
b 12:34 rwm b 12:34 rwm yes
b 12:34 r b *:34 rw yes
b 12:34 rw b 12:34 w no extra "r"
b *:34 rw b 12:34 rw no too broad "*"
b *:34 rw b *:34 rwm yes
Which is fine in some cases. Consider:
A (default behavior: deny, exceptions allow access)
\
B (default behavior: deny, exceptions allow access)
In this case the full match makes sense, the new exception cannot add
more access than the parent allows
But this doesn't always work, consider:
A (default behavior: allow, exceptions disallow access)
\
B (default behavior: deny, exceptions allow access)
In this case, a new exception in B shouldn't match any of the exceptions
in A, after all you can't allow something that was forbidden by A. But
consider this scenario:
New exception Existing in A match? outcome
b 12:34 rw b 12:34 r no exception is accepted
Because the new exception has "w" as extra, it doesn't match, so it'll
be added to B's exception list.
The same problem can happen during a file access check. Consider a
cgroup with allow as default behavior:
Access Exception match?
b 12:34 rw b 12:34 r no
In this case, the access didn't match any of the exceptions in the
cgroup, which is required since exceptions will disallow access.
To solve this problem, two new functions were created to match an
exception either fully or partially. In the example above, a partial
check will be performed and it'll produce a match since at least
"b 12:34 r" from "b 12:34 rw" access matches.
Merge branch 'fixes' of git://git.infradead.org/users/vkoul/slave-dma
Pull slave-dmaengine fixes from Vinod Koul:
"Back from long weekend here in India and now the time to send fixes
for slave dmaengine.
- Dan's fix of sirf xlate code
- Jean's fix for timberland
- edma fixes by Sekhar for SG handling and Yuan for changing init
call"
* 'fixes' of git://git.infradead.org/users/vkoul/slave-dma:
dma: fix eDMA driver as a subsys_initcall
dmaengine: sirf: off by one in of_dma_sirfsoc_xlate()
platform: Fix timberdale dependencies
dma: edma: fix incorrect SG list handling
Merge tag 'iommu-fixes-v3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu
Pull iommu fixes from Joerg Roedel:
"Fixes for regressions:
- fix wrong IOMMU enumeration causing some SCSI device drivers
initialization failures
- ARM-SMMU fixes for a panic condition and a wrong return value"
* tag 'iommu-fixes-v3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu:
iommu/arm-smmu: fix panic in arm_smmu_alloc_init_pte
iommu/arm-smmu: Return 0 on unmap failure
iommu/vt-d: fix bug in matching PCI devices with DRHD/RMRR descriptors
iommu/vt-d: Fix get_domain_for_dev() handling of upstream PCIe bridges
iommu/vt-d: fix memory leakage caused by commit ea8ea46
Adrien BAK [Fri, 18 Apr 2014 02:00:43 +0000 (11:00 +0900)]
perf tools: Improve error reporting
In the current version, when using perf record, if something goes
wrong in tools/perf/builtin-record.c:375
session = perf_session__new(file, false, NULL);
The error message:
"Not enough memory for reading per file header"
is issued. This error message seems to be outdated and is not very
helpful. This patch proposes to replace this error message by
"Perf session creation failed"
I believe this issue has been brought to lkml:
https://lkml.org/lkml/2014/2/24/458
although this patch only tackles a (small) part of the issue.
Additionnaly, this patch improves error reporting in
tools/perf/util/data.c open_file_write.
Currently, if the call to open fails, the user is unaware of it.
This patch logs the error, before returning the error code to
the caller.
Reported-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Adrien BAK <adrien.bak@metascale.org> Link: http://lkml.kernel.org/r/1397786443.3093.4.camel@beast
[ Reorganize the changelog into paragraphs ]
[ Added empty line after fd declaration in open_file_write ] Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Vladimir Nikulichev <nvs@tbricks.com> Tested-by: Namhyung Kim <namhyung@kernel.org> Reviewed-by: Adrian Hunter <adrian.hunter@intel.com> Link: http://lkml.kernel.org/r/969812.163009436-sendEmail@nvs Signed-off-by: Jiri Olsa <jolsa@redhat.com>
perf kvm: Fix 'Min time' counting in report command
Every event in the perf-kvm has a 'stats' structure, which contains
max/min/average/etc times of handling this event.
The problem is that the 'perf-kvm stat report' command always shows
that 'min time' is 0us for every event. Example:
This happens because the 'stats' structure is not initialized and
stats->min equals to 0. Lets initialize the structure for every
event after its allocation using init_stats() function. This initializes
stats->min to -1 and makes 'Min time' statistics counting work:
Merge branch 'drm-fixes' of git://people.freedesktop.org/~airlied/linux
Pull drm fixes from Dave Airlie:
"Unfortunately this contains no easter eggs, its a bit larger than I'd
like, but I included a patch that just moves code from one file to
another and I'd like to avoid merge conflicts with that later, so it
makes it seem worse than it is,
Otherwise:
- radeon: fixes to use new microcode to stabilise some cards, use
some common displayport code, some runtime pm fixes, pll regression
fixes
- i915: fix for some context oopses, a warn in a used path, backlight
fixes
- nouveau: regression fix
- omap: a bunch of fixes"
* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux: (51 commits)
drm: bochs: drop unused struct fields
drm: bochs: add power management support
drm: cirrus: add power management support
drm: Split out drm_probe_helper.c from drm_crtc_helper.c
drm/plane-helper: Don't fake-implement primary plane disabling
drm/ast: fix value check in cbr_scan2
drm/nouveau/bios: fix a bit shift error introduced by 457e77b
drm/radeon/ci: make sure mc ucode is loaded before checking the size
drm/radeon/si: make sure mc ucode is loaded before checking the size
drm/radeon: improve PLL params if we don't match exactly v2
drm/radeon: memory leak on bo reservation failure. v2
drm/radeon: fix VCE fence command
drm/radeon: re-enable mclk dpm on R7 260X asics
drm/radeon: add support for newer mc ucode on CI (v2)
drm/radeon: add support for newer mc ucode on SI (v2)
drm/radeon: apply more strict limits for PLL params v2
drm/radeon: update CI DPM powertune settings
drm/radeon: fix runpm handling on APUs (v4)
drm/radeon: disable mclk dpm on R7 260X
drm/tegra: Remove gratuitous pad field
...
Dave Airlie [Sat, 19 Apr 2014 01:16:02 +0000 (11:16 +1000)]
Merge branch 'drm-next-3.15-wip' of git://people.freedesktop.org/~deathsimple/linux into drm-next
Some i2c fixes over DisplayPort.
* 'drm-next-3.15-wip' of git://people.freedesktop.org/~deathsimple/linux:
drm/radeon: Improve vramlimit module param documentation
drm/radeon: fix audio pin counts for DCE6+ (v2)
drm/radeon/dp: switch to the common i2c over aux code
drm/dp/i2c: Update comments about common i2c over dp assumptions (v3)
drm/dp/i2c: send bare addresses to properly reset i2c connections (v4)
drm/radeon/dp: handle zero sized i2c over aux transactions (v2)
drm/i915: support address only i2c-over-aux transactions
drm/tegra: dp: Support address-only I2C-over-AUX transactions
1) Fix mlx4_en_netpoll implementation, it needs to schedule a NAPI
context, not synchronize it. From Chris Mason.
2) Ipv4 flow input interface should never be zero, it should be
LOOPBACK_IFINDEX instead. From Cong Wang and Julian Anastasov.
3) Properly configure MAC to PHY connection in mvneta devices, from
Thomas Petazzoni.
4) sys_recv should use SYSCALL_DEFINE. From Jan Glauber.
5) Tunnel driver ioctls do not use the correct namespace, fix from
Nicolas Dichtel.
6) Fix memory leak on seccomp filter attach, from Kees Cook.
7) Fix lockdep warning for nested vlans, from Ding Tianhong.
8) Crashes can happen in SCTP due to how the auth_enable value is
managed, fix from Vlad Yasevich.
9) Wireless fixes from John W Linville and co.
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (45 commits)
net: sctp: cache auth_enable per endpoint
tg3: update rx_jumbo_pending ring param only when jumbo frames are enabled
vlan: Fix lockdep warning when vlan dev handle notification
seccomp: fix memory leak on filter attach
isdn: icn: buffer overflow in icn_command()
ip6_tunnel: use the right netns in ioctl handler
sit: use the right netns in ioctl handler
ip_tunnel: use the right netns in ioctl handler
net: use SYSCALL_DEFINEx for sys_recv
net: mdio-gpio: Add support for separate MDI and MDO gpio pins
net: mdio-gpio: Add support for active low gpio pins
net: mdio-gpio: Use devm_ functions where possible
ipv4, route: pass 0 instead of LOOPBACK_IFINDEX to fib_validate_source()
ipv4, fib: pass LOOPBACK_IFINDEX instead of 0 to flowi4_iif
mlx4_en: don't use napi_synchronize inside mlx4_en_netpoll
net: mvneta: properly configure the MAC <-> PHY connection in all situations
net: phy: add minimal support for QSGMII PHY
sfc:On MCDI timeout, issue an FLR (and mark MCDI to fail-fast)
mwifiex: fix hung task on command timeout
mwifiex: process event before command response
...
Merge branch 'for-next' of git://git.samba.org/sfrench/cifs-2.6
Pull cifs fixes from Steve French:
"A set of 5 small cifs fixes"
* 'for-next' of git://git.samba.org/sfrench/cifs-2.6:
cif: fix dead code
cifs: fix error handling cifs_user_readv
fs: cifs: remove unused variable.
Return correct error on query of xattr on file with empty xattrs
cifs: Wait for writebacks to complete before attempting write.
Merge tag 'char-misc-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull char/misc driver fixes from Greg KH:
"Here are a few driver fixes for char/misc drivers that resolve
reported issues.
All have been in linux-next successfully for a few days"
* tag 'char-misc-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
Drivers: hv: vmbus: Negotiate version 3.0 when running on ws2012r2 hosts
Tools: hv: Handle the case when the target file exists correctly
vme_tsi148: Utilize to_pci_dev() macro
vme_tsi148: Fix PCI address mapping assumption
vme_tsi148: Fix typo in tsi148_slave_get()
w1: avoid recursive device_add
w1: fix netlink refcnt leak on error path
misc: Grammar s/addition/additional/
drivers: mcb: fix memory leak in chameleon_parse_cells() error path
mei: ignore client writing state during cb completion
mei: me: do not load the driver if the FW doesn't support MEI interface
GenWQE: Increase driver version number
GenWQE: Fix multithreading problems
GenWQE: Ensure rc is not returning an uninitialized value
GenWQE: Add wmb before DDCB is started
GenWQE: Enable access to VPD flash area
Merge tag 'driver-core-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core fixes from Greg KH:
"Here are some driver core fixes for 3.15-rc2. Also in here are some
documentation updates, as well as an API removal that had to wait for
after -rc1 due to the cleanups coming into you from multiple developer
trees (this one and the PPC tree.)
All have been in linux next successfully"
* tag 'driver-core-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
drivers/base/dd.c incorrect pr_debug() parameters
Documentation: Update stable address in Chinese and Japanese translations
topology: Fix compilation warning when not in SMP
Chinese: add translation of io_ordering.txt
stable_kernel_rules: spelling/word usage
sysfs, driver-core: remove unused {sysfs|device}_schedule_callback_owner()
kernfs: protect lazy kernfs_iattrs allocation with mutex
fs: Don't return 0 from get_anon_bdev
Merge tag 'staging-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
Pull staging driver fixes from Greg KH:
"Here are a few staging driver fixes for issues that have been reported
for 3.15-rc2.
Also dominating the diffstat for the pull request is the removal of
the rtl8187se driver. It's no longer needed in staging as a "real"
driver for this hardware is now merged in the tree in the "correct"
location in drivers/net/
All of these patches have been tested in linux-next"
* tag 'staging-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
staging: r8188eu: Fix case where ethtype was never obtained and always be checked against 0
staging: r8712u: Fix case where ethtype was never obtained and always be checked against 0
staging: r8188eu: Calling rtw_get_stainfo() with a NULL sta_addr will return NULL
staging: comedi: fix circular locking dependency in comedi_mmap()
staging: r8723au: Add missing initialization of change_inx in sort algorithm
Staging: unisys: use after free in list_for_each()
staging: unisys: use after free in error messages
staging: speakup: fix misuse of kstrtol() in handle_goto()
staging: goldfish: Call free_irq in error path
staging: delete rtl8187se wireless driver
staging: rtl8723au: Fix buffer overflow in rtw_get_wfd_ie()
staging: gs_fpgaboot: remove __TIMESTAMP__ macro
staging: vme: fix memory leak in vme_user_probe()
staging: fpgaboot: clean up Makefile
staging/usbip: fix store_attach() sscanf return value check
staging/usbip: userspace - fix usbipd SIGSEGV from refresh_exported_devices()
staging: rtl8188eu: remove spaces, correct counts to unbreak P2P ioctls
staging/rtl8821ae: Fix OOM handling in _rtl_init_deferred_work()
Merge tag 'tty-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty/serial driver fixes from Greg KH:
"Here are a number of small tty/serial driver fixes for 3.15-rc2. Also
in here are some Documentation file removals for drivers that we
removed a long time ago, no need to keep it around any longer.
All of these have been in linux-next for a bit"
* tag 'tty-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
Revert "serial: 8250, disable "too much work" messages"
serial: amba-pl011: fix regression, causing an Oops on rmmod
tty: Fix help text of SYNCLINK_CS
tty: fix memleak in alloc_pid
ttyprintk: Allow built as a module
ttyprintk: Fix wrong tty_unregister_driver() call in the error path
serial: 8250, disable "too much work" messages
Documentation/serial: Delete obsolete driver documentation
serial: omap: Fix missing pm_runtime_resume handling by simplifying code
serial_core: Fix pm imbalance on unbind
serial: pl011: change Rx burst size to half of trigger level
serial: timberdale: Depend on X86_32
serial: st-asc: Fix SysRq char handling
Revert "serial: clps711x: Give a chance to perform useful tasks during wait loop"
serial_core: Fix conditional start_tx on ring buffer not empty
serial: efm32: use $vendor,$device scheme for compatible string
serial: omap: free the wakeup settings in remove
Merge tag 'usb-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
Pull USB fixes from Greg KH:
"Here are a number of tiny USB fixes and new device ids for 3.15-rc2.
Nothing major, just issues some people have reported.
All of these have been in linux-next"
* tag 'usb-3.15-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
uas: fix deadlocky memory allocations
uas: fix error handling during scsi_scan()
uas: fix GFP_NOIO under spinlock
uwb: adds missing error handling
USB: cdc-acm: Remove Motorola/Telit H24 serial interfaces from ACM driver
USB: ohci-jz4740: FEAT_POWER is a port feature, not a hub feature
USB: ohci-jz4740: Fix uninitialized variable warning
USB: EHCI: tegra: set txfill_tuning
usb: ehci-platform: Return immediately from suspend if ehci_suspend fails
usb: ehci-exynos: Return immediately from suspend if ehci_suspend fails
USB: fix crash during hotplug of PCI USB controller card
USB: cdc-acm: fix double usb_autopm_put_interface() in acm_port_activate()
usb: usb-common: fix typo for usb_state_string
USB: usb_wwan: fix handling of missing bulk endpoints
USB: pl2303: add ids for Hewlett-Packard HP POS pole displays
USB: cp210x: Add 8281 (Nanotec Plug & Drive)
usb: option driver, add support for Telit UE910v2
Revert "USB: serial: add usbid for dell wwan card to sierra.c"
USB: serial: ftdi_sio: add id for Brainboxes serial cards
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
thp: close race between split and zap huge pages
mm: fix new kernel-doc warning in filemap.c
mm: fix CONFIG_DEBUG_VM_RB description
mm: use paravirt friendly ops for NUMA hinting ptes
mips: export flush_icache_range
mm/hugetlb.c: add cond_resched_lock() in return_unused_surplus_pages()
wait: explain the shadowing and type inconsistencies
Shiraz has moved
Documentation/vm/numa_memory_policy.txt: fix wrong document in numa_memory_policy.txt
powerpc/mm: fix ".__node_distance" undefined
kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()
init/Kconfig: move the trusted keyring config option to general setup
vmscan: reclaim_clean_pages_from_list() must use mod_zone_page_state()
Sasha Levin has reported two THP BUGs[1][2]. I believe both of them
have the same root cause. Let's look to them one by one.
The first bug[1] is "kernel BUG at mm/huge_memory.c:1829!". It's
BUG_ON(mapcount != page_mapcount(page)) in __split_huge_page(). From my
testing I see that page_mapcount() is higher than mapcount here.
I think it happens due to race between zap_huge_pmd() and
page_check_address_pmd(). page_check_address_pmd() misses PMD which is
under zap:
CPU0 CPU1
zap_huge_pmd()
pmdp_get_and_clear()
__split_huge_page()
anon_vma_interval_tree_foreach()
__split_huge_page_splitting()
page_check_address_pmd()
mm_find_pmd()
/*
* We check if PMD present without taking ptl: no
* serialization against zap_huge_pmd(). We miss this PMD,
* it's not accounted to 'mapcount' in __split_huge_page().
*/
pmd_present(pmd) == 0
The second bug[2] is "kernel BUG at mm/huge_memory.c:1371!".
It's VM_BUG_ON_PAGE(!PageHead(page), page) in zap_huge_pmd().
This happens in similar way:
CPU0 CPU1
zap_huge_pmd()
pmdp_get_and_clear()
page_remove_rmap(page)
atomic_add_negative(-1, &page->_mapcount)
__split_huge_page()
anon_vma_interval_tree_foreach()
__split_huge_page_splitting()
page_check_address_pmd()
mm_find_pmd()
pmd_present(pmd) == 0 /* The same comment as above */
/*
* No crash this time since we already decremented page->_mapcount in
* zap_huge_pmd().
*/
BUG_ON(mapcount != page_mapcount(page))
/*
* We split the compound page here into small pages without
* serialization against zap_huge_pmd()
*/
__split_huge_page_refcount()
VM_BUG_ON_PAGE(!PageHead(page), page); // CRASH!!!
So my understanding the problem is pmd_present() check in mm_find_pmd()
without taking page table lock.
The bug was introduced by me commit with commit 117b0791ac42. Sorry for
that. :(
Let's open code mm_find_pmd() in page_check_address_pmd() and do the
check under page table lock.
Note that __page_check_address() does the same for PTE entires
if sync != 0.
I've stress tested split and zap code paths for 36+ hours by now and
don't see crashes with the patch applied. Before it took <20 min to
trigger the first bug and few hours for second one (if we ignore
first).
This appears to be a copy/paste error. Update the description to
reflect extra rbtree debug and checks for the config option instead of
duplicating CONFIG_DEBUG_VM.
mm: use paravirt friendly ops for NUMA hinting ptes
David Vrabel identified a regression when using automatic NUMA balancing
under Xen whereby page table entries were getting corrupted due to the
use of native PTE operations. Quoting him
Xen PV guest page tables require that their entries use machine
addresses if the preset bit (_PAGE_PRESENT) is set, and (for
successful migration) non-present PTEs must use pseudo-physical
addresses. This is because on migration MFNs in present PTEs are
translated to PFNs (canonicalised) so they may be translated back
to the new MFN in the destination domain (uncanonicalised).
pte_mknonnuma(), pmd_mknonnuma(), pte_mknuma() and pmd_mknuma()
set and clear the _PAGE_PRESENT bit using pte_set_flags(),
pte_clear_flags(), etc.
In a Xen PV guest, these functions must translate MFNs to PFNs
when clearing _PAGE_PRESENT and translate PFNs to MFNs when setting
_PAGE_PRESENT.
His suggested fix converted p[te|md]_[set|clear]_flags to using
paravirt-friendly ops but this is overkill. He suggested an alternative
of using p[te|md]_modify in the NUMA page table operations but this is
does more work than necessary and would require looking up a VMA for
protections.
This patch modifies the NUMA page table operations to use paravirt
friendly operations to set/clear the flags of interest. Unfortunately
this will take a performance hit when updating the PTEs on
CONFIG_PARAVIRT but I do not see a way around it that does not break
Xen.
Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: David Vrabel <david.vrabel@citrix.com> Tested-by: David Vrabel <david.vrabel@citrix.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Anvin <hpa@zytor.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Steven Noonan <steven@uplinklabs.net> Cc: Rik van Riel <riel@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The lkdtm module performs tests against executable memory ranges, so it
needs to flush the icache for proper behaviors. Other architectures
already export this, so do the same for MIPS.
[akpm@linux-foundation.org: relocate export sites] Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Sanjay Lal <sanjayl@kymasys.com> Cc: John Crispin <blogic@openwrt.org> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/hugetlb.c: add cond_resched_lock() in return_unused_surplus_pages()
soft lockup in freeing gigantic hugepage fixed in commit 55f67141a892 "mm:
hugetlb: fix softlockup when a large number of hugepages are freed." can
happen in return_unused_surplus_pages(), so let's fix it.
Documentation/vm/numa_memory_policy.txt: fix wrong document in numa_memory_policy.txt
In document numa_memory_policy.txt, the following examples for flag
MPOL_F_RELATIVE_NODES are incorrect.
For example, consider a task that is attached to a cpuset with
mems 2-5 that sets an Interleave policy over the same set with
MPOL_F_RELATIVE_NODES. If the cpuset's mems change to 3-7, the
interleave now occurs over nodes 3,5-6. If the cpuset's mems
then change to 0,2-3,5, then the interleave occurs over nodes
0,3,5.
According to the comment of the patch adding flag MPOL_F_RELATIVE_NODES,
the nodemasks the user specifies should be considered relative to the
current task's mems_allowed.
(https://lkml.org/lkml/2008/2/29/428)
And according to numa_memory_policy.txt, if the user's nodemask includes
nodes that are outside the range of the new set of allowed nodes, then
the remap wraps around to the beginning of the nodemask and, if not
already set, sets the node in the mempolicy nodemask.
So in the example, if the user specifies 2-5, for a task whose
mems_allowed is 3-7, the nodemasks should be remapped the third, fourth,
fifth, sixth node in mems_allowed. like the following:
mems_allowed: 3 4 5 6 7
relative index: 0 1 2 3 4
5
So the nodemasks should be remapped to 3,5-7, but not 3,5-6.
And for a task whose mems_allowed is 0,2-3,5, the nodemasks should be
remapped to 0,2-3,5, but not 0,3,5.
mems_allowed: 0 2 3 5
relative index: 0 1 2 3
4 5
Signed-off-by: Tang Chen <tangchen@cn.fujitsu.com> Cc: Randy Dunlap <rdunlap@infradead.org> Acked-by: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>