Add [pre|post]suspend functions to the exception store API.
These will become important for future exception stores. Current
exception store implementations will not alter metadata after
a 'commit_exception' completes. However, future stores may do
journaling or other actions. They might return from 'commit_exception'
when the request hits the journal, but continue flushing after.
This could be bad, because we expect them to not do anything once
a 'suspend' is issued. Adding these functions to the API allows
them to finish what they are doing and conform to device-mapper
requirements. (The above was just one example... Cluster-aware
exception stores will also require the notification of when they
need to suspend their activity.)

RFC-by: Jonathan Brassow <jbrassow@redhat.com>

Index: linux-2.6/drivers/md/dm-exception-store.h
================================================== =================
--- linux-2.6.orig/drivers/md/dm-exception-store.h
+++ linux-2.6/drivers/md/dm-exception-store.h
@@ -32,6 +32,8 @@ struct dm_exception_store_type {
void (*dtr) (struct dm_exception_store *store);

int (*resume) (struct dm_exception_store *store);
+ void (*presuspend) (struct dm_exception_store *store);
+ void (*postsuspend) (struct dm_exception_store *store);

/*
* Find somewhere to store the next exception.
Index: linux-2.6/drivers/md/dm-snap.c
================================================== =================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -1006,6 +1006,22 @@ static void snapshot_resume(struct dm_ta
up_write(&s->lock);
}

+static void snapshot_presuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ if(s->store->type->presuspend)
+ s->store->type->presuspend(s->store);
+}
+
+static void snapshot_postsuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ if (s->store->type->postsuspend)
+ s->store->type->postsuspend(s->store);
+}
+
static int snapshot_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
@@ -1285,6 +1301,8 @@ static struct target_type snapshot_targe
.map = snapshot_map,
.end_io = snapshot_end_io,
.resume = snapshot_resume,
+ .presuspend = snapshot_presuspend,
+ .postsuspend = snapshot_postsuspend,
.status = snapshot_status,
};



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Add [pre|post]suspend functions to the exception store API.
These will become important for future exception stores. Current
exception store implementations will not alter metadata after
a 'commit_exception' completes. However, future stores may do
journaling or other actions. They might return from 'commit_exception'
when the request hits the journal, but continue flushing after.
This could be bad, because we expect them to not do anything once
a 'suspend' is issued. Adding these functions to the API allows
them to finish what they are doing and conform to device-mapper
requirements. (The above was just one example... Cluster-aware
exception stores will also require the notification of when they
need to suspend their activity.)

RFC-by: Jonathan Brassow <jbrassow@redhat.com>

Index: linux-2.6/drivers/md/dm-exception-store.h
================================================== =================
--- linux-2.6.orig/drivers/md/dm-exception-store.h
+++ linux-2.6/drivers/md/dm-exception-store.h
@@ -32,6 +32,8 @@ struct dm_exception_store_type {
void (*dtr) (struct dm_exception_store *store);

int (*resume) (struct dm_exception_store *store);
+ void (*presuspend) (struct dm_exception_store *store);
+ void (*postsuspend) (struct dm_exception_store *store);

/*
* Find somewhere to store the next exception.
Index: linux-2.6/drivers/md/dm-snap.c
================================================== =================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -1001,6 +1001,22 @@ static void snapshot_resume(struct dm_ta
up_write(&s->lock);
}

+static void snapshot_presuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ if(s->store->type->presuspend)
+ s->store->type->presuspend(s->store);
+}
+
+static void snapshot_postsuspend(struct dm_target *ti)
+{
+ struct dm_snapshot *s = ti->private;
+
+ if (s->store->type->postsuspend)
+ s->store->type->postsuspend(s->store);
+}
+
static int snapshot_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
@@ -1280,6 +1296,8 @@ static struct target_type snapshot_targe
.map = snapshot_map,
.end_io = snapshot_end_io,
.resume = snapshot_resume,
+ .presuspend = snapshot_presuspend,
+ .postsuspend = snapshot_postsuspend,
.status = snapshot_status,
};


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