linux/block/blk-cgroup.c
Gui Jianfeng bcf4dd4342 blk-cgroup: Fix potential deadlock in blk-cgroup
I triggered a lockdep warning as following.

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.33-rc2 #1
-------------------------------------------------------
test_io_control/7357 is trying to acquire lock:
 (blkio_list_lock){+.+...}, at: [<c053a990>] blkiocg_weight_write+0x82/0x9e

but task is already holding lock:
 (&(&blkcg->lock)->rlock){......}, at: [<c053a949>] blkiocg_weight_write+0x3b/0x9e

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&(&blkcg->lock)->rlock){......}:
       [<c04583b7>] validate_chain+0x8bc/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c0692b0a>] _raw_spin_lock_irqsave+0x27/0x5a
       [<c053a4e1>] blkiocg_add_blkio_group+0x1a/0x6d
       [<c053cac7>] cfq_get_queue+0x225/0x3de
       [<c053eec2>] cfq_set_request+0x217/0x42d
       [<c052c8a6>] elv_set_request+0x17/0x26
       [<c0532a0f>] get_request+0x203/0x2c5
       [<c0532ae9>] get_request_wait+0x18/0x10e
       [<c0533470>] __make_request+0x2ba/0x375
       [<c0531985>] generic_make_request+0x28d/0x30f
       [<c0532da7>] submit_bio+0x8a/0x8f
       [<c04d827a>] submit_bh+0xf0/0x10f
       [<c04d91d2>] ll_rw_block+0xc0/0xf9
       [<f86e9705>] ext3_find_entry+0x319/0x544 [ext3]
       [<f86eae58>] ext3_lookup+0x2c/0xb9 [ext3]
       [<c04c3e1b>] do_lookup+0xd3/0x172
       [<c04c56c8>] link_path_walk+0x5fb/0x95c
       [<c04c5a65>] path_walk+0x3c/0x81
       [<c04c5b63>] do_path_lookup+0x21/0x8a
       [<c04c66cc>] do_filp_open+0xf0/0x978
       [<c04c0c7e>] open_exec+0x1b/0xb7
       [<c04c1436>] do_execve+0xbb/0x266
       [<c04081a9>] sys_execve+0x24/0x4a
       [<c04028a2>] ptregs_execve+0x12/0x18

-> #1 (&(&q->__queue_lock)->rlock){..-.-.}:
       [<c04583b7>] validate_chain+0x8bc/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c0692b0a>] _raw_spin_lock_irqsave+0x27/0x5a
       [<c053dd2a>] cfq_unlink_blkio_group+0x17/0x41
       [<c053a6eb>] blkiocg_destroy+0x72/0xc7
       [<c0467df0>] cgroup_diput+0x4a/0xb2
       [<c04ca473>] dentry_iput+0x93/0xb7
       [<c04ca4b3>] d_kill+0x1c/0x36
       [<c04cb5c5>] dput+0xf5/0xfe
       [<c04c6084>] do_rmdir+0x95/0xbe
       [<c04c60ec>] sys_rmdir+0x10/0x12
       [<c04027cc>] sysenter_do_call+0x12/0x32

-> #0 (blkio_list_lock){+.+...}:
       [<c0458117>] validate_chain+0x61c/0xb9c
       [<c0458dba>] __lock_acquire+0x723/0x789
       [<c0458eb0>] lock_acquire+0x90/0xa7
       [<c06929fd>] _raw_spin_lock+0x1e/0x4e
       [<c053a990>] blkiocg_weight_write+0x82/0x9e
       [<c0467f1e>] cgroup_file_write+0xc6/0x1c0
       [<c04bd2f3>] vfs_write+0x8c/0x116
       [<c04bd7c6>] sys_write+0x3b/0x60
       [<c04027cc>] sysenter_do_call+0x12/0x32

other info that might help us debug this:

1 lock held by test_io_control/7357:
 #0:  (&(&blkcg->lock)->rlock){......}, at: [<c053a949>] blkiocg_weight_write+0x3b/0x9e
stack backtrace:
Pid: 7357, comm: test_io_control Not tainted 2.6.33-rc2 #1
Call Trace:
 [<c045754f>] print_circular_bug+0x91/0x9d
 [<c0458117>] validate_chain+0x61c/0xb9c
 [<c0458dba>] __lock_acquire+0x723/0x789
 [<c0458eb0>] lock_acquire+0x90/0xa7
 [<c053a990>] ? blkiocg_weight_write+0x82/0x9e
 [<c06929fd>] _raw_spin_lock+0x1e/0x4e
 [<c053a990>] ? blkiocg_weight_write+0x82/0x9e
 [<c053a990>] blkiocg_weight_write+0x82/0x9e
 [<c0467f1e>] cgroup_file_write+0xc6/0x1c0
 [<c0454df5>] ? trace_hardirqs_off+0xb/0xd
 [<c044d93a>] ? cpu_clock+0x2e/0x44
 [<c050e6ec>] ? security_file_permission+0xf/0x11
 [<c04bcdda>] ? rw_verify_area+0x8a/0xad
 [<c0467e58>] ? cgroup_file_write+0x0/0x1c0
 [<c04bd2f3>] vfs_write+0x8c/0x116
 [<c04bd7c6>] sys_write+0x3b/0x60
 [<c04027cc>] sysenter_do_call+0x12/0x32

To prevent deadlock, we should take locks as following sequence:

blkio_list_lock -> queue_lock ->  blkcg_lock.

The following patch should fix this bug.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-02-01 09:58:54 +01:00

361 lines
9.1 KiB
C

/*
* Common Block IO controller cgroup interface
*
* Based on ideas and code from CFQ, CFS and BFQ:
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
*
* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
* Paolo Valente <paolo.valente@unimore.it>
*
* Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
* Nauman Rafique <nauman@google.com>
*/
#include <linux/ioprio.h>
#include <linux/seq_file.h>
#include <linux/kdev_t.h>
#include <linux/module.h>
#include <linux/err.h>
#include "blk-cgroup.h"
static DEFINE_SPINLOCK(blkio_list_lock);
static LIST_HEAD(blkio_list);
struct blkio_cgroup blkio_root_cgroup = { .weight = 2*BLKIO_WEIGHT_DEFAULT };
EXPORT_SYMBOL_GPL(blkio_root_cgroup);
bool blkiocg_css_tryget(struct blkio_cgroup *blkcg)
{
if (!css_tryget(&blkcg->css))
return false;
return true;
}
EXPORT_SYMBOL_GPL(blkiocg_css_tryget);
void blkiocg_css_put(struct blkio_cgroup *blkcg)
{
css_put(&blkcg->css);
}
EXPORT_SYMBOL_GPL(blkiocg_css_put);
struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
{
return container_of(cgroup_subsys_state(cgroup, blkio_subsys_id),
struct blkio_cgroup, css);
}
EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
unsigned long time, unsigned long sectors)
{
blkg->time += time;
blkg->sectors += sectors;
}
EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_stats);
void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
struct blkio_group *blkg, void *key, dev_t dev)
{
unsigned long flags;
spin_lock_irqsave(&blkcg->lock, flags);
rcu_assign_pointer(blkg->key, key);
blkg->blkcg_id = css_id(&blkcg->css);
hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
spin_unlock_irqrestore(&blkcg->lock, flags);
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* Need to take css reference ? */
cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
#endif
blkg->dev = dev;
}
EXPORT_SYMBOL_GPL(blkiocg_add_blkio_group);
static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
{
hlist_del_init_rcu(&blkg->blkcg_node);
blkg->blkcg_id = 0;
}
/*
* returns 0 if blkio_group was still on cgroup list. Otherwise returns 1
* indicating that blk_group was unhashed by the time we got to it.
*/
int blkiocg_del_blkio_group(struct blkio_group *blkg)
{
struct blkio_cgroup *blkcg;
unsigned long flags;
struct cgroup_subsys_state *css;
int ret = 1;
rcu_read_lock();
css = css_lookup(&blkio_subsys, blkg->blkcg_id);
if (!css)
goto out;
blkcg = container_of(css, struct blkio_cgroup, css);
spin_lock_irqsave(&blkcg->lock, flags);
if (!hlist_unhashed(&blkg->blkcg_node)) {
__blkiocg_del_blkio_group(blkg);
ret = 0;
}
spin_unlock_irqrestore(&blkcg->lock, flags);
out:
rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL_GPL(blkiocg_del_blkio_group);
/* called under rcu_read_lock(). */
struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key)
{
struct blkio_group *blkg;
struct hlist_node *n;
void *__key;
hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {
__key = blkg->key;
if (__key == key)
return blkg;
}
return NULL;
}
EXPORT_SYMBOL_GPL(blkiocg_lookup_group);
#define SHOW_FUNCTION(__VAR) \
static u64 blkiocg_##__VAR##_read(struct cgroup *cgroup, \
struct cftype *cftype) \
{ \
struct blkio_cgroup *blkcg; \
\
blkcg = cgroup_to_blkio_cgroup(cgroup); \
return (u64)blkcg->__VAR; \
}
SHOW_FUNCTION(weight);
#undef SHOW_FUNCTION
static int
blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
{
struct blkio_cgroup *blkcg;
struct blkio_group *blkg;
struct hlist_node *n;
struct blkio_policy_type *blkiop;
if (val < BLKIO_WEIGHT_MIN || val > BLKIO_WEIGHT_MAX)
return -EINVAL;
blkcg = cgroup_to_blkio_cgroup(cgroup);
spin_lock(&blkio_list_lock);
spin_lock_irq(&blkcg->lock);
blkcg->weight = (unsigned int)val;
hlist_for_each_entry(blkg, n, &blkcg->blkg_list, blkcg_node) {
list_for_each_entry(blkiop, &blkio_list, list)
blkiop->ops.blkio_update_group_weight_fn(blkg,
blkcg->weight);
}
spin_unlock_irq(&blkcg->lock);
spin_unlock(&blkio_list_lock);
return 0;
}
#define SHOW_FUNCTION_PER_GROUP(__VAR) \
static int blkiocg_##__VAR##_read(struct cgroup *cgroup, \
struct cftype *cftype, struct seq_file *m) \
{ \
struct blkio_cgroup *blkcg; \
struct blkio_group *blkg; \
struct hlist_node *n; \
\
if (!cgroup_lock_live_group(cgroup)) \
return -ENODEV; \
\
blkcg = cgroup_to_blkio_cgroup(cgroup); \
rcu_read_lock(); \
hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
if (blkg->dev) \
seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev), \
MINOR(blkg->dev), blkg->__VAR); \
} \
rcu_read_unlock(); \
cgroup_unlock(); \
return 0; \
}
SHOW_FUNCTION_PER_GROUP(time);
SHOW_FUNCTION_PER_GROUP(sectors);
#ifdef CONFIG_DEBUG_BLK_CGROUP
SHOW_FUNCTION_PER_GROUP(dequeue);
#endif
#undef SHOW_FUNCTION_PER_GROUP
#ifdef CONFIG_DEBUG_BLK_CGROUP
void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
unsigned long dequeue)
{
blkg->dequeue += dequeue;
}
EXPORT_SYMBOL_GPL(blkiocg_update_blkio_group_dequeue_stats);
#endif
struct cftype blkio_files[] = {
{
.name = "weight",
.read_u64 = blkiocg_weight_read,
.write_u64 = blkiocg_weight_write,
},
{
.name = "time",
.read_seq_string = blkiocg_time_read,
},
{
.name = "sectors",
.read_seq_string = blkiocg_sectors_read,
},
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "dequeue",
.read_seq_string = blkiocg_dequeue_read,
},
#endif
};
static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
return cgroup_add_files(cgroup, subsys, blkio_files,
ARRAY_SIZE(blkio_files));
}
static void blkiocg_destroy(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg = cgroup_to_blkio_cgroup(cgroup);
unsigned long flags;
struct blkio_group *blkg;
void *key;
struct blkio_policy_type *blkiop;
rcu_read_lock();
remove_entry:
spin_lock_irqsave(&blkcg->lock, flags);
if (hlist_empty(&blkcg->blkg_list)) {
spin_unlock_irqrestore(&blkcg->lock, flags);
goto done;
}
blkg = hlist_entry(blkcg->blkg_list.first, struct blkio_group,
blkcg_node);
key = rcu_dereference(blkg->key);
__blkiocg_del_blkio_group(blkg);
spin_unlock_irqrestore(&blkcg->lock, flags);
/*
* This blkio_group is being unlinked as associated cgroup is going
* away. Let all the IO controlling policies know about this event.
*
* Currently this is static call to one io controlling policy. Once
* we have more policies in place, we need some dynamic registration
* of callback function.
*/
spin_lock(&blkio_list_lock);
list_for_each_entry(blkiop, &blkio_list, list)
blkiop->ops.blkio_unlink_group_fn(key, blkg);
spin_unlock(&blkio_list_lock);
goto remove_entry;
done:
free_css_id(&blkio_subsys, &blkcg->css);
rcu_read_unlock();
kfree(blkcg);
}
static struct cgroup_subsys_state *
blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
{
struct blkio_cgroup *blkcg, *parent_blkcg;
if (!cgroup->parent) {
blkcg = &blkio_root_cgroup;
goto done;
}
/* Currently we do not support hierarchy deeper than two level (0,1) */
parent_blkcg = cgroup_to_blkio_cgroup(cgroup->parent);
if (css_depth(&parent_blkcg->css) > 0)
return ERR_PTR(-EINVAL);
blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
if (!blkcg)
return ERR_PTR(-ENOMEM);
blkcg->weight = BLKIO_WEIGHT_DEFAULT;
done:
spin_lock_init(&blkcg->lock);
INIT_HLIST_HEAD(&blkcg->blkg_list);
return &blkcg->css;
}
/*
* We cannot support shared io contexts, as we have no mean to support
* two tasks with the same ioc in two different groups without major rework
* of the main cic data structures. For now we allow a task to change
* its cgroup only if it's the only owner of its ioc.
*/
static int blkiocg_can_attach(struct cgroup_subsys *subsys,
struct cgroup *cgroup, struct task_struct *tsk,
bool threadgroup)
{
struct io_context *ioc;
int ret = 0;
/* task_lock() is needed to avoid races with exit_io_context() */
task_lock(tsk);
ioc = tsk->io_context;
if (ioc && atomic_read(&ioc->nr_tasks) > 1)
ret = -EINVAL;
task_unlock(tsk);
return ret;
}
static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
struct cgroup *prev, struct task_struct *tsk,
bool threadgroup)
{
struct io_context *ioc;
task_lock(tsk);
ioc = tsk->io_context;
if (ioc)
ioc->cgroup_changed = 1;
task_unlock(tsk);
}
struct cgroup_subsys blkio_subsys = {
.name = "blkio",
.create = blkiocg_create,
.can_attach = blkiocg_can_attach,
.attach = blkiocg_attach,
.destroy = blkiocg_destroy,
.populate = blkiocg_populate,
.subsys_id = blkio_subsys_id,
.use_id = 1,
};
void blkio_policy_register(struct blkio_policy_type *blkiop)
{
spin_lock(&blkio_list_lock);
list_add_tail(&blkiop->list, &blkio_list);
spin_unlock(&blkio_list_lock);
}
EXPORT_SYMBOL_GPL(blkio_policy_register);
void blkio_policy_unregister(struct blkio_policy_type *blkiop)
{
spin_lock(&blkio_list_lock);
list_del_init(&blkiop->list);
spin_unlock(&blkio_list_lock);
}
EXPORT_SYMBOL_GPL(blkio_policy_unregister);