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dm: enhance internal suspend and resume interface 

Rename dm_internal_{suspend,resume} to dm_internal_{suspend,resume}_fast
-- dm-stats will continue using these methods to avoid all the extra
suspend/resume logic that is not needed in order to quickly flush IO.

Introduce dm_internal_suspend_noflush() variant that actually calls the
mapped_device's target callbacks -- otherwise target-specific hooks are
avoided (e.g. dm-thin's thin_presuspend and thin_postsuspend).  Common
code between dm_internal_{suspend_noflush,resume} and
dm_{suspend,resume} was factored out as __dm_{suspend,resume}.

Update dm_internal_{suspend_noflush,resume} to always take and release
the mapped_device's suspend_lock.  Also update dm_{suspend,resume} to be
aware of potential for DM_INTERNAL_SUSPEND_FLAG to be set and respond
accordingly by interruptibly waiting for the DM_INTERNAL_SUSPEND_FLAG to
be cleared.  Add lockdep annotation to dm_suspend() and dm_resume().

The existing DM_SUSPEND_FLAG remains unchanged.
DM_INTERNAL_SUSPEND_FLAG is set by dm_internal_suspend_noflush() and
cleared by dm_internal_resume().

Both DM_SUSPEND_FLAG and DM_INTERNAL_SUSPEND_FLAG may be set if a device
was already suspended when dm_internal_suspend_noflush() was called --
this can be thought of as a "nested suspend".  A "nested suspend" can
occur with legacy userspace dm-thin code that might suspend all active
thin volumes before suspending the pool for resize.

But otherwise, in the normal dm-thin-pool suspend case moving forward:
the thin-pool will have DM_SUSPEND_FLAG set and all active thins from
that thin-pool will have DM_INTERNAL_SUSPEND_FLAG set.

Also add DM_INTERNAL_SUSPEND_FLAG to status report.  This new
DM_INTERNAL_SUSPEND_FLAG state is being reported to assist with
debugging (e.g. 'dmsetup info' will report an internally suspended
device accordingly).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
This commit is contained in:
Mike Snitzer 2014-10-28 18:34:52 -04:00
parent 80e96c5484
commit ffcc393641
5 changed files with 193 additions and 59 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/md/dm-ioctl.c
View File

@ -684,11 +684,14 @@ static void __dev_status(struct mapped_device *md, struct dm_ioctl *param)
int srcu_idx;
param->flags &= ~(DM_SUSPEND_FLAG | DM_READONLY_FLAG |
DM_ACTIVE_PRESENT_FLAG);
DM_ACTIVE_PRESENT_FLAG | DM_INTERNAL_SUSPEND_FLAG);
if (dm_suspended_md(md))
param->flags |= DM_SUSPEND_FLAG;
if (dm_suspended_internally_md(md))
param->flags |= DM_INTERNAL_SUSPEND_FLAG;
if (dm_test_deferred_remove_flag(md))
param->flags |= DM_DEFERRED_REMOVE;

2
drivers/md/dm-stats.c
View File

@ -824,7 +824,7 @@ static int message_stats_create(struct mapped_device *md,
return 1;
id = dm_stats_create(dm_get_stats(md), start, end, step, program_id, aux_data,
dm_internal_suspend, dm_internal_resume, md);
dm_internal_suspend_fast, dm_internal_resume_fast, md);
if (id < 0)
return id;

231
drivers/md/dm.c
View File

@ -19,6 +19,7 @@
#include <linux/idr.h>
#include <linux/hdreg.h>
#include <linux/delay.h>
#include <linux/wait.h>
#include <trace/events/block.h>
@ -117,6 +118,7 @@ EXPORT_SYMBOL_GPL(dm_get_rq_mapinfo);
#define DMF_NOFLUSH_SUSPENDING 5
#define DMF_MERGE_IS_OPTIONAL 6
#define DMF_DEFERRED_REMOVE 7
#define DMF_SUSPENDED_INTERNALLY 8
/*
* A dummy definition to make RCU happy.
@ -2718,36 +2720,18 @@ static void unlock_fs(struct mapped_device *md)
}
/*
* We need to be able to change a mapping table under a mounted
* filesystem. For example we might want to move some data in
* the background. Before the table can be swapped with
* dm_bind_table, dm_suspend must be called to flush any in
* flight bios and ensure that any further io gets deferred.
*/
/*
* Suspend mechanism in request-based dm.
* If __dm_suspend returns 0, the device is completely quiescent
* now. There is no request-processing activity. All new requests
* are being added to md->deferred list.
*
* 1. Flush all I/Os by lock_fs() if needed.
* 2. Stop dispatching any I/O by stopping the request_queue.
* 3. Wait for all in-flight I/Os to be completed or requeued.
*
* To abort suspend, start the request_queue.
* Caller must hold md->suspend_lock
*/
int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
unsigned suspend_flags, int interruptible)
{
struct dm_table *map = NULL;
int r = 0;
int do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG ? 1 : 0;
int noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG ? 1 : 0;
mutex_lock(&md->suspend_lock);
if (dm_suspended_md(md)) {
r = -EINVAL;
goto out_unlock;
}
map = rcu_dereference(md->map);
bool do_lockfs = suspend_flags & DM_SUSPEND_LOCKFS_FLAG;
bool noflush = suspend_flags & DM_SUSPEND_NOFLUSH_FLAG;
int r;
/*
* DMF_NOFLUSH_SUSPENDING must be set before presuspend.
@ -2772,7 +2756,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
r = lock_fs(md);
if (r) {
dm_table_presuspend_undo_targets(map);
goto out_unlock;
return r;
}
}
@ -2806,7 +2790,7 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
* We call dm_wait_for_completion to wait for all existing requests
* to finish.
*/
r = dm_wait_for_completion(md, TASK_INTERRUPTIBLE);
r = dm_wait_for_completion(md, interruptible);
if (noflush)
clear_bit(DMF_NOFLUSH_SUSPENDING, &md->flags);
@ -2822,14 +2806,55 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
unlock_fs(md);
dm_table_presuspend_undo_targets(map);
goto out_unlock; /* pushback list is already flushed, so skip flush */
/* pushback list is already flushed, so skip flush */
}
/*
* If dm_wait_for_completion returned 0, the device is completely
* quiescent now. There is no request-processing activity. All new
* requests are being added to md->deferred list.
*/
return r;
}
/*
* We need to be able to change a mapping table under a mounted
* filesystem. For example we might want to move some data in
* the background. Before the table can be swapped with
* dm_bind_table, dm_suspend must be called to flush any in
* flight bios and ensure that any further io gets deferred.
*/
/*
* Suspend mechanism in request-based dm.
*
* 1. Flush all I/Os by lock_fs() if needed.
* 2. Stop dispatching any I/O by stopping the request_queue.
* 3. Wait for all in-flight I/Os to be completed or requeued.
*
* To abort suspend, start the request_queue.
*/
int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
{
struct dm_table *map = NULL;
int r = 0;
retry:
mutex_lock_nested(&md->suspend_lock, SINGLE_DEPTH_NESTING);
if (dm_suspended_md(md)) {
r = -EINVAL;
goto out_unlock;
}
if (dm_suspended_internally_md(md)) {
/* already internally suspended, wait for internal resume */
mutex_unlock(&md->suspend_lock);
r = wait_on_bit(&md->flags, DMF_SUSPENDED_INTERNALLY, TASK_INTERRUPTIBLE);
if (r)
return r;
goto retry;
}
map = rcu_dereference(md->map);
r = __dm_suspend(md, map, suspend_flags, TASK_INTERRUPTIBLE);
if (r)
goto out_unlock;
set_bit(DMF_SUSPENDED, &md->flags);
@ -2840,22 +2865,13 @@ out_unlock:
return r;
}
int dm_resume(struct mapped_device *md)
static int __dm_resume(struct mapped_device *md, struct dm_table *map)
{
int r = -EINVAL;
struct dm_table *map = NULL;
mutex_lock(&md->suspend_lock);
if (!dm_suspended_md(md))
goto out;
map = rcu_dereference(md->map);
if (!map || !dm_table_get_size(map))
goto out;
r = dm_table_resume_targets(map);
if (r)
goto out;
if (map) {
int r = dm_table_resume_targets(map);
if (r)
return r;
}
dm_queue_flush(md);
@ -2869,6 +2885,37 @@ int dm_resume(struct mapped_device *md)
unlock_fs(md);
return 0;
}
int dm_resume(struct mapped_device *md)
{
int r = -EINVAL;
struct dm_table *map = NULL;
retry:
mutex_lock_nested(&md->suspend_lock, SINGLE_DEPTH_NESTING);
if (!dm_suspended_md(md))
goto out;
if (dm_suspended_internally_md(md)) {
/* already internally suspended, wait for internal resume */
mutex_unlock(&md->suspend_lock);
r = wait_on_bit(&md->flags, DMF_SUSPENDED_INTERNALLY, TASK_INTERRUPTIBLE);
if (r)
return r;
goto retry;
}
map = rcu_dereference(md->map);
if (!map || !dm_table_get_size(map))
goto out;
r = __dm_resume(md, map);
if (r)
goto out;
clear_bit(DMF_SUSPENDED, &md->flags);
r = 0;
@ -2882,15 +2929,80 @@ out:
* Internal suspend/resume works like userspace-driven suspend. It waits
* until all bios finish and prevents issuing new bios to the target drivers.
* It may be used only from the kernel.
*
* Internal suspend holds md->suspend_lock, which prevents interaction with
* userspace-driven suspend.
*/
void dm_internal_suspend(struct mapped_device *md)
static void __dm_internal_suspend(struct mapped_device *md, unsigned suspend_flags)
{
struct dm_table *map = NULL;
if (dm_suspended_internally_md(md))
return; /* nested internal suspend */
if (dm_suspended_md(md)) {
set_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
return; /* nest suspend */
}
map = rcu_dereference(md->map);
/*
* Using TASK_UNINTERRUPTIBLE because only NOFLUSH internal suspend is
* supported. Properly supporting a TASK_INTERRUPTIBLE internal suspend
* would require changing .presuspend to return an error -- avoid this
* until there is a need for more elaborate variants of internal suspend.
*/
(void) __dm_suspend(md, map, suspend_flags, TASK_UNINTERRUPTIBLE);
set_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
dm_table_postsuspend_targets(map);
}
static void __dm_internal_resume(struct mapped_device *md)
{
if (!dm_suspended_internally_md(md))
return; /* resume from nested internal suspend */
if (dm_suspended_md(md))
goto done; /* resume from nested suspend */
/*
* NOTE: existing callers don't need to call dm_table_resume_targets
* (which may fail -- so best to avoid it for now by passing NULL map)
*/
(void) __dm_resume(md, NULL);
done:
clear_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
smp_mb__after_atomic();
wake_up_bit(&md->flags, DMF_SUSPENDED_INTERNALLY);
}
void dm_internal_suspend_noflush(struct mapped_device *md)
{
mutex_lock(&md->suspend_lock);
if (dm_suspended_md(md))
__dm_internal_suspend(md, DM_SUSPEND_NOFLUSH_FLAG);
mutex_unlock(&md->suspend_lock);
}
EXPORT_SYMBOL_GPL(dm_internal_suspend_noflush);
void dm_internal_resume(struct mapped_device *md)
{
mutex_lock(&md->suspend_lock);
__dm_internal_resume(md);
mutex_unlock(&md->suspend_lock);
}
EXPORT_SYMBOL_GPL(dm_internal_resume);
/*
* Fast variants of internal suspend/resume hold md->suspend_lock,
* which prevents interaction with userspace-driven suspend.
*/
void dm_internal_suspend_fast(struct mapped_device *md)
{
mutex_lock(&md->suspend_lock);
if (dm_suspended_md(md) || dm_suspended_internally_md(md))
return;
set_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags);
@ -2899,9 +3011,9 @@ void dm_internal_suspend(struct mapped_device *md)
dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
}
void dm_internal_resume(struct mapped_device *md)
void dm_internal_resume_fast(struct mapped_device *md)
{
if (dm_suspended_md(md))
if (dm_suspended_md(md) || dm_suspended_internally_md(md))
goto done;
dm_queue_flush(md);
@ -2987,6 +3099,11 @@ int dm_suspended_md(struct mapped_device *md)
return test_bit(DMF_SUSPENDED, &md->flags);
}
int dm_suspended_internally_md(struct mapped_device *md)
{
return test_bit(DMF_SUSPENDED_INTERNALLY, &md->flags);
}
int dm_test_deferred_remove_flag(struct mapped_device *md)
{
return test_bit(DMF_DEFERRED_REMOVE, &md->flags);

9
drivers/md/dm.h
View File

@ -129,6 +129,15 @@ int dm_deleting_md(struct mapped_device *md);
*/
int dm_suspended_md(struct mapped_device *md);
/*
* Internal suspend and resume methods.
*/
int dm_suspended_internally_md(struct mapped_device *md);
void dm_internal_suspend_fast(struct mapped_device *md);
void dm_internal_resume_fast(struct mapped_device *md);
void dm_internal_suspend_noflush(struct mapped_device *md);
void dm_internal_resume(struct mapped_device *md);
/*
* Test if the device is scheduled for deferred remove.
*/

5
include/uapi/linux/dm-ioctl.h
View File

@ -352,4 +352,9 @@ enum {
*/
#define DM_DEFERRED_REMOVE (1 << 17) /* In/Out */
/*
* If set, the device is suspended internally.
*/
#define DM_INTERNAL_SUSPEND_FLAG (1 << 18) /* Out */
#endif /* _LINUX_DM_IOCTL_H */