[PATCH 06/19] drbd: Fix locking across all resources

From: Philipp Reisner
Date: Thu Jul 30 2015 - 07:32:15 EST

From: Andreas Gruenbacher <agruen@xxxxxxxxxx>

Instead of using a rwlock for synchronizing state changes across
resources, take the request locks of all resources for global state
changes. Use resources_mutex to serialize global state changes.

This means that taking the request lock of a resource is now enough to
prevent changes of that resource. (Previously, a read lock on the
global state lock was needed as well.)

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_int.h | 18 ++-------
drivers/block/drbd/drbd_main.c | 24 +++++++++++-
drivers/block/drbd/drbd_nl.c | 45 +++++++++++----------
drivers/block/drbd/drbd_state.c | 14 +++----
drivers/block/drbd/drbd_state.h | 6 +--
drivers/block/drbd/drbd_worker.c | 85 ++++++++++++++++++----------------------
6 files changed, 99 insertions(+), 93 deletions(-)

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 443ae18..a990b8e 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -292,6 +292,9 @@ struct drbd_device_work {

extern int drbd_wait_misc(struct drbd_device *, struct drbd_interval *);

+extern void lock_all_resources(void);
+extern void unlock_all_resources(void);
+
struct drbd_request {
struct drbd_work w;
struct drbd_device *device;
@@ -1418,7 +1421,7 @@ extern struct bio_set *drbd_md_io_bio_set;
/* to allocate from that set */
extern struct bio *bio_alloc_drbd(gfp_t gfp_mask);

-extern rwlock_t global_state_lock;
+extern struct mutex resources_mutex;

extern int conn_lowest_minor(struct drbd_connection *connection);
extern enum drbd_ret_code drbd_create_device(struct drbd_config_context *adm_ctx, unsigned int minor);
@@ -1688,19 +1691,6 @@ static inline int drbd_peer_req_has_active_page(struct drbd_peer_request *peer_r
return 0;
}

-static inline enum drbd_state_rv
-_drbd_set_state(struct drbd_device *device, union drbd_state ns,
- enum chg_state_flags flags, struct completion *done)
-{
- enum drbd_state_rv rv;
-
- read_lock(&global_state_lock);
- rv = __drbd_set_state(device, ns, flags, done);
- read_unlock(&global_state_lock);
-
- return rv;
-}
-
static inline union drbd_state drbd_read_state(struct drbd_device *device)
{
struct drbd_resource *resource = device->resource;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index f21f46f..81a8679 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -117,6 +117,7 @@ module_param_string(usermode_helper, usermode_helper, sizeof(usermode_helper), 0
*/
struct idr drbd_devices;
struct list_head drbd_resources;
+struct mutex resources_mutex;

struct kmem_cache *drbd_request_cache;
struct kmem_cache *drbd_ee_cache; /* peer requests */
@@ -2924,7 +2925,7 @@ static int __init drbd_init(void)
drbd_proc = NULL; /* play safe for drbd_cleanup */
idr_init(&drbd_devices);

- rwlock_init(&global_state_lock);
+ mutex_init(&resources_mutex);
INIT_LIST_HEAD(&drbd_resources);

err = drbd_genl_register();
@@ -3747,6 +3748,27 @@ int drbd_wait_misc(struct drbd_device *device, struct drbd_interval *i)
return 0;
}

+void lock_all_resources(void)
+{
+ struct drbd_resource *resource;
+ int __maybe_unused i = 0;
+
+ mutex_lock(&resources_mutex);
+ local_irq_disable();
+ for_each_resource(resource, &drbd_resources)
+ spin_lock_nested(&resource->req_lock, i++);
+}
+
+void unlock_all_resources(void)
+{
+ struct drbd_resource *resource;
+
+ for_each_resource(resource, &drbd_resources)
+ spin_unlock(&resource->req_lock);
+ local_irq_enable();
+ mutex_unlock(&resources_mutex);
+}
+
#ifdef CONFIG_DRBD_FAULT_INJECTION
/* Fault insertion support including random number generator shamelessly
* stolen from kernel/rcutorture.c */
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 186dc9e..7bca1bc 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1389,13 +1389,13 @@ int drbd_adm_disk_opts(struct sk_buff *skb, struct genl_info *info)
goto fail_unlock;
}

- write_lock_irq(&global_state_lock);
+ lock_all_resources();
retcode = drbd_resync_after_valid(device, new_disk_conf->resync_after);
if (retcode == NO_ERROR) {
rcu_assign_pointer(device->ldev->disk_conf, new_disk_conf);
drbd_resync_after_changed(device);
}
- write_unlock_irq(&global_state_lock);
+ unlock_all_resources();

if (retcode != NO_ERROR)
goto fail_unlock;
@@ -1539,18 +1539,13 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
goto fail;
}

- write_lock_irq(&global_state_lock);
- retcode = drbd_resync_after_valid(device, new_disk_conf->resync_after);
- if (retcode != NO_ERROR)
- goto fail_unlock;
-
rcu_read_lock();
nc = rcu_dereference(connection->net_conf);
if (nc) {
if (new_disk_conf->fencing == FP_STONITH && nc->wire_protocol == DRBD_PROT_A) {
rcu_read_unlock();
retcode = ERR_STONITH_AND_PROT_A;
- goto fail_unlock;
+ goto fail;
}
}
rcu_read_unlock();
@@ -1561,7 +1556,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
drbd_err(device, "open(\"%s\") failed with %ld\n", new_disk_conf->backing_dev,
PTR_ERR(bdev));
retcode = ERR_OPEN_DISK;
- goto fail_unlock;
+ goto fail;
}
nbc->backing_bdev = bdev;

@@ -1581,7 +1576,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
drbd_err(device, "open(\"%s\") failed with %ld\n", new_disk_conf->meta_dev,
PTR_ERR(bdev));
retcode = ERR_OPEN_MD_DISK;
- goto fail_unlock;
+ goto fail;
}
nbc->md_bdev = bdev;

@@ -1589,7 +1584,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
(new_disk_conf->meta_dev_idx == DRBD_MD_INDEX_INTERNAL ||
new_disk_conf->meta_dev_idx == DRBD_MD_INDEX_FLEX_INT)) {
retcode = ERR_MD_IDX_INVALID;
- goto fail_unlock;
+ goto fail;
}

resync_lru = lc_create("resync", drbd_bm_ext_cache,
@@ -1597,14 +1592,14 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
offsetof(struct bm_extent, lce));
if (!resync_lru) {
retcode = ERR_NOMEM;
- goto fail_unlock;
+ goto fail;
}

/* Read our meta data super block early.
* This also sets other on-disk offsets. */
retcode = drbd_md_read(device, nbc);
if (retcode != NO_ERROR)
- goto fail_unlock;
+ goto fail;

if (new_disk_conf->al_extents < DRBD_AL_EXTENTS_MIN)
new_disk_conf->al_extents = DRBD_AL_EXTENTS_MIN;
@@ -1616,7 +1611,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
(unsigned long long) drbd_get_max_capacity(nbc),
(unsigned long long) new_disk_conf->disk_size);
retcode = ERR_DISK_TOO_SMALL;
- goto fail_unlock;
+ goto fail;
}

if (new_disk_conf->meta_dev_idx < 0) {
@@ -1633,7 +1628,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
drbd_warn(device, "refusing attach: md-device too small, "
"at least %llu sectors needed for this meta-disk type\n",
(unsigned long long) min_md_device_sectors);
- goto fail_unlock;
+ goto fail;
}

/* Make sure the new disk is big enough
@@ -1641,7 +1636,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
if (drbd_get_max_capacity(nbc) <
drbd_get_capacity(device->this_bdev)) {
retcode = ERR_DISK_TOO_SMALL;
- goto fail_unlock;
+ goto fail;
}

nbc->known_size = drbd_get_capacity(nbc->backing_bdev);
@@ -1671,7 +1666,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
retcode = rv; /* FIXME: Type mismatch. */
drbd_resume_io(device);
if (rv < SS_SUCCESS)
- goto fail_unlock;
+ goto fail;

if (!get_ldev_if_state(device, D_ATTACHING))
goto force_diskless;
@@ -1706,6 +1701,13 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
goto force_diskless_dec;
}

+ lock_all_resources();
+ retcode = drbd_resync_after_valid(device, new_disk_conf->resync_after);
+ if (retcode != NO_ERROR) {
+ unlock_all_resources();
+ goto force_diskless_dec;
+ }
+
/* Reset the "barriers don't work" bits here, then force meta data to
* be written, to ensure we determine if barriers are supported. */
if (new_disk_conf->md_flushes)
@@ -1728,6 +1730,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)

drbd_resync_after_changed(device);
drbd_bump_write_ordering(device->resource, device->ldev, WO_BDEV_FLUSH);
+ unlock_all_resources();

if (drbd_md_test_flag(device->ldev, MDF_CRASHED_PRIMARY))
set_bit(CRASHED_PRIMARY, &device->flags);
@@ -1850,8 +1853,6 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
if (rv < SS_SUCCESS)
goto force_diskless_dec;

- write_unlock(&global_state_lock);
-
mod_timer(&device->request_timer, jiffies + HZ);

if (device->state.role == R_PRIMARY)
@@ -1874,8 +1875,6 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
force_diskless:
drbd_force_state(device, NS(disk, D_DISKLESS));
drbd_md_sync(device);
- fail_unlock:
- write_unlock_irq(&global_state_lock);
fail:
conn_reconfig_done(connection);
if (nbc) {
@@ -3453,8 +3452,10 @@ int drbd_adm_new_resource(struct sk_buff *skb, struct genl_info *info)
}

/* not yet safe for genl_family.parallel_ops */
+ mutex_lock(&resources_mutex);
if (!conn_create(adm_ctx.resource_name, &res_opts))
retcode = ERR_NOMEM;
+ mutex_unlock(&resources_mutex);
out:
drbd_adm_finish(&adm_ctx, info, retcode);
return 0;
@@ -3545,7 +3546,9 @@ static int adm_del_resource(struct drbd_resource *resource)
if (!idr_is_empty(&resource->devices))
return ERR_RES_IN_USE;

+ mutex_lock(&resources_mutex);
list_del_rcu(&resource->resources);
+ mutex_unlock(&resources_mutex);
/* Make sure all threads have actually stopped: state handling only
* does drbd_thread_stop_nowait(). */
list_for_each_entry(connection, &resource->connections, connections)
diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index 2d7dd26..535ae47 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -937,7 +937,7 @@ void drbd_resume_al(struct drbd_device *device)
drbd_info(device, "Resumed AL updates\n");
}

-/* helper for __drbd_set_state */
+/* helper for _drbd_set_state */
static void set_ov_position(struct drbd_device *device, enum drbd_conns cs)
{
if (first_peer_device(device)->connection->agreed_pro_version < 90)
@@ -965,17 +965,17 @@ static void set_ov_position(struct drbd_device *device, enum drbd_conns cs)
}

/**
- * __drbd_set_state() - Set a new DRBD state
+ * _drbd_set_state() - Set a new DRBD state
* @device: DRBD device.
* @ns: new state.
* @flags: Flags
* @done: Optional completion, that will get completed after the after_state_ch() finished
*
- * Caller needs to hold req_lock, and global_state_lock. Do not call directly.
+ * Caller needs to hold req_lock. Do not call directly.
*/
enum drbd_state_rv
-__drbd_set_state(struct drbd_device *device, union drbd_state ns,
- enum chg_state_flags flags, struct completion *done)
+_drbd_set_state(struct drbd_device *device, union drbd_state ns,
+ enum chg_state_flags flags, struct completion *done)
{
struct drbd_peer_device *peer_device = first_peer_device(device);
struct drbd_connection *connection = peer_device ? peer_device->connection : NULL;
@@ -1444,7 +1444,7 @@ static void after_state_ch(struct drbd_device *device, union drbd_state os,
if (os.disk != D_FAILED && ns.disk == D_FAILED) {
enum drbd_io_error_p eh = EP_PASS_ON;
int was_io_error = 0;
- /* corresponding get_ldev was in __drbd_set_state, to serialize
+ /* corresponding get_ldev was in _drbd_set_state, to serialize
* our cleanup here with the transition to D_DISKLESS.
* But is is still not save to dreference ldev here, since
* we might come from an failed Attach before ldev was set. */
@@ -1759,7 +1759,7 @@ conn_set_state(struct drbd_connection *connection, union drbd_state mask, union
if (flags & CS_IGN_OUTD_FAIL && ns.disk == D_OUTDATED && os.disk < D_OUTDATED)
ns.disk = os.disk;

- rv = __drbd_set_state(device, ns, flags, NULL);
+ rv = _drbd_set_state(device, ns, flags, NULL);
if (rv < SS_SUCCESS)
BUG();

diff --git a/drivers/block/drbd/drbd_state.h b/drivers/block/drbd/drbd_state.h
index 7f53c40..bd98953 100644
--- a/drivers/block/drbd/drbd_state.h
+++ b/drivers/block/drbd/drbd_state.h
@@ -122,9 +122,9 @@ extern enum drbd_state_rv
_drbd_request_state_holding_state_mutex(struct drbd_device *, union drbd_state,
union drbd_state, enum chg_state_flags);

-extern enum drbd_state_rv __drbd_set_state(struct drbd_device *, union drbd_state,
- enum chg_state_flags,
- struct completion *done);
+extern enum drbd_state_rv _drbd_set_state(struct drbd_device *, union drbd_state,
+ enum chg_state_flags,
+ struct completion *done);
extern void print_st_err(struct drbd_device *, union drbd_state,
union drbd_state, int);

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index d0fae55..ef70e1f 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -55,13 +55,6 @@ static int make_resync_request(struct drbd_device *, int);
*
*/

-
-/* About the global_state_lock
- Each state transition on an device holds a read lock. In case we have
- to evaluate the resync after dependencies, we grab a write lock, because
- we need stable states on all devices for that. */
-rwlock_t global_state_lock;
-
/* used for synchronous meta data and bitmap IO
* submitted by drbd_md_sync_page_io()
*/
@@ -1478,70 +1471,73 @@ static int _drbd_may_sync_now(struct drbd_device *device)
}

/**
- * _drbd_pause_after() - Pause resync on all devices that may not resync now
+ * drbd_pause_after() - Pause resync on all devices that may not resync now
* @device: DRBD device.
*
* Called from process context only (admin command and after_state_ch).
*/
-static int _drbd_pause_after(struct drbd_device *device)
+static bool drbd_pause_after(struct drbd_device *device)
{
+ bool changed = false;
struct drbd_device *odev;
- int i, rv = 0;
+ int i;

rcu_read_lock();
idr_for_each_entry(&drbd_devices, odev, i) {
if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
continue;
- if (!_drbd_may_sync_now(odev))
- rv |= (__drbd_set_state(_NS(odev, aftr_isp, 1), CS_HARD, NULL)
- != SS_NOTHING_TO_DO);
+ if (!_drbd_may_sync_now(odev) &&
+ _drbd_set_state(_NS(odev, aftr_isp, 1),
+ CS_HARD, NULL) != SS_NOTHING_TO_DO)
+ changed = true;
}
rcu_read_unlock();

- return rv;
+ return changed;
}

/**
- * _drbd_resume_next() - Resume resync on all devices that may resync now
+ * drbd_resume_next() - Resume resync on all devices that may resync now
* @device: DRBD device.
*
* Called from process context only (admin command and worker).
*/
-static int _drbd_resume_next(struct drbd_device *device)
+static bool drbd_resume_next(struct drbd_device *device)
{
+ bool changed = false;
struct drbd_device *odev;
- int i, rv = 0;
+ int i;

rcu_read_lock();
idr_for_each_entry(&drbd_devices, odev, i) {
if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
continue;
if (odev->state.aftr_isp) {
- if (_drbd_may_sync_now(odev))
- rv |= (__drbd_set_state(_NS(odev, aftr_isp, 0),
- CS_HARD, NULL)
- != SS_NOTHING_TO_DO) ;
+ if (_drbd_may_sync_now(odev) &&
+ _drbd_set_state(_NS(odev, aftr_isp, 0),
+ CS_HARD, NULL) != SS_NOTHING_TO_DO)
+ changed = true;
}
}
rcu_read_unlock();
- return rv;
+ return changed;
}

void resume_next_sg(struct drbd_device *device)
{
- write_lock_irq(&global_state_lock);
- _drbd_resume_next(device);
- write_unlock_irq(&global_state_lock);
+ lock_all_resources();
+ drbd_resume_next(device);
+ unlock_all_resources();
}

void suspend_other_sg(struct drbd_device *device)
{
- write_lock_irq(&global_state_lock);
- _drbd_pause_after(device);
- write_unlock_irq(&global_state_lock);
+ lock_all_resources();
+ drbd_pause_after(device);
+ unlock_all_resources();
}

-/* caller must hold global_state_lock */
+/* caller must lock_all_resources() */
enum drbd_ret_code drbd_resync_after_valid(struct drbd_device *device, int o_minor)
{
struct drbd_device *odev;
@@ -1579,15 +1575,15 @@ enum drbd_ret_code drbd_resync_after_valid(struct drbd_device *device, int o_min
}
}

-/* caller must hold global_state_lock */
+/* caller must lock_all_resources() */
void drbd_resync_after_changed(struct drbd_device *device)
{
- int changes;
+ int changed;

do {
- changes = _drbd_pause_after(device);
- changes |= _drbd_resume_next(device);
- } while (changes);
+ changed = drbd_pause_after(device);
+ changed |= drbd_resume_next(device);
+ } while (changed);
}

void drbd_rs_controller_reset(struct drbd_device *device)
@@ -1707,19 +1703,14 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
} else {
mutex_lock(device->state_mutex);
}
- clear_bit(B_RS_H_DONE, &device->flags);

- /* req_lock: serialize with drbd_send_and_submit() and others
- * global_state_lock: for stable sync-after dependencies */
- spin_lock_irq(&device->resource->req_lock);
- write_lock(&global_state_lock);
+ lock_all_resources();
+ clear_bit(B_RS_H_DONE, &device->flags);
/* Did some connection breakage or IO error race with us? */
if (device->state.conn < C_CONNECTED
|| !get_ldev_if_state(device, D_NEGOTIATING)) {
- write_unlock(&global_state_lock);
- spin_unlock_irq(&device->resource->req_lock);
- mutex_unlock(device->state_mutex);
- return;
+ unlock_all_resources();
+ goto out;
}

ns = drbd_read_state(device);
@@ -1733,7 +1724,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
else /* side == C_SYNC_SOURCE */
ns.pdsk = D_INCONSISTENT;

- r = __drbd_set_state(device, ns, CS_VERBOSE, NULL);
+ r = _drbd_set_state(device, ns, CS_VERBOSE, NULL);
ns = drbd_read_state(device);

if (ns.conn < C_CONNECTED)
@@ -1754,7 +1745,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
device->rs_mark_left[i] = tw;
device->rs_mark_time[i] = now;
}
- _drbd_pause_after(device);
+ drbd_pause_after(device);
/* Forget potentially stale cached per resync extent bit-counts.
* Open coded drbd_rs_cancel_all(device), we already have IRQs
* disabled, and know the disk state is ok. */
@@ -1764,8 +1755,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
device->resync_wenr = LC_FREE;
spin_unlock(&device->al_lock);
}
- write_unlock(&global_state_lock);
- spin_unlock_irq(&device->resource->req_lock);
+ unlock_all_resources();

if (r == SS_SUCCESS) {
wake_up(&device->al_wait); /* for lc_reset() above */
@@ -1829,6 +1819,7 @@ void drbd_start_resync(struct drbd_device *device, enum drbd_conns side)
drbd_md_sync(device);
}
put_ldev(device);
+out:
mutex_unlock(device->state_mutex);
}

--
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/