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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 07-08-2008, 04:49 PM
Milan Broz
 
Default dm co wait for barrier in process in suspend

Implement waiting for barrier in dm_suspend request.

suspend_lock cannot be used inside barrier processing,
because there can be generated new barrier request during suspend
process (e.g. in lock_fs() call).

Add wait for for ongoing barrier to finish before suspending.

There are two status bits used:
DMF_BLOCK_IO -> all ios are queued
DMF_BARRIER -> device is processing barrier (always include BLOCK_IO too).

Suspend call simply waits till DMF_BARRIER disappear and immediatelly
and switch to BLOCK_IO to prevent another barrier to start.

Signed-off-by: Milan Broz <mbroz@redhat.com>

---
drivers/md/dm.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++-------
1 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1a65389..d7b2a17 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1452,6 +1452,13 @@ static void __flush_deferred_io(struct mapped_device *md, int barrier_flag)
while ((c = bio_list_pop(&md->deferred))) {
barrier = bio_barrier(c);

+ /* FIXME: is this possible here? */
+ /* New barrier and no flag */
+ if (barrier && !test_bit(DMF_BARRIER, &md->flags)) {
+ __submit_barrier(md, c);
+ return;
+ }
+
if (__split_bio(md, c))
bio_io_error(c);

@@ -1591,6 +1598,47 @@ static void unlock_fs(struct mapped_device *md)
clear_bit(DMF_FROZEN, &md->flags);
}

+static int _blockio_if_not_in_barrier(struct mapped_device *md)
+{
+ int in_barrier;
+
+ down_write(&md->io_lock);
+ smp_mb();
+ in_barrier = test_bit(DMF_BARRIER, &md->flags);
+ if (!in_barrier)
+ set_bit(DMF_BLOCK_IO, &md->flags);
+ up_write(&md->io_lock);
+
+ return !in_barrier;
+}
+
+static int dm_wait_blockio(struct mapped_device *md)
+{
+ int r = 0;
+
+ while (1) {
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (_blockio_if_not_in_barrier(md))
+ break;
+
+ if (signal_pending(current)) {
+ r = -EINTR;
+ break;
+ }
+
+ /*
+ * We cannot use io_schedule here
+ * all io can be already processed.
+ * FIXME: starvation here?
+ */
+ schedule_timeout(HZ/100);
+ }
+ set_current_state(TASK_RUNNING);
+
+ 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
@@ -1613,12 +1661,6 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)
goto out_unlock;
}

- /* FIXME: temporary, it must not fail here */
- if (test_bit(DMF_BARRIER, &md->flags)) {
- r = -EBUSY;
- goto out_unlock;
- }
-
map = dm_get_table(md);

/*
@@ -1653,10 +1695,13 @@ int dm_suspend(struct mapped_device *md, unsigned suspend_flags)

/*
* First we set the BLOCK_IO flag so no more ios will be mapped.
+ * But wait for possible ongoing barrier to finish first.
*/
- down_write(&md->io_lock);
- set_bit(DMF_BLOCK_IO, &md->flags);
+ r = dm_wait_blockio(md);
+ if (r)
+ goto out;

+ down_write(&md->io_lock);
add_wait_queue(&md->wait, &wait);
up_write(&md->io_lock);



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