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drbd: report congestion if we are waiting for some userland callback

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If the drbd worker thread is synchronously waiting for some userland
callback, we don't want some casual pageout to block on us.
Have drbd_congested() report congestion in that case.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
This commit is contained in:
Lars Ellenberg 2012-06-14 15:14:06 +02:00 committed by Philipp Reisner
parent 383606e0de
commit c2ba686f35
3 changed files with 29 additions and 0 deletions
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7
drivers/block/drbd/drbd_int.h
View File

@ -850,6 +850,13 @@ enum {
AL_SUSPENDED, /* Activity logging is currently suspended. */
AHEAD_TO_SYNC_SOURCE, /* Ahead -> SyncSource queued */
STATE_SENT, /* Do not change state/UUIDs while this is set */
CALLBACK_PENDING, /* Whether we have a call_usermodehelper(, UMH_WAIT_PROC)
* pending, from drbd worker context.
* If set, bdi_write_congested() returns true,
* so shrink_page_list() would not recurse into,
* and potentially deadlock on, this drbd worker.
*/
};
struct drbd_bitmap; /* opaque for drbd_conf */

16
drivers/block/drbd/drbd_main.c
View File

@ -3553,6 +3553,22 @@ static int drbd_congested(void *congested_data, int bdi_bits)
goto out;
}
if (test_bit(CALLBACK_PENDING, &mdev->flags)) {
r |= (1 << BDI_async_congested);
/* Without good local data, we would need to read from remote,
* and that would need the worker thread as well, which is
* currently blocked waiting for that usermode helper to
* finish.
*/
if (!get_ldev_if_state(mdev, D_UP_TO_DATE))
r |= (1 << BDI_sync_congested);
else
put_ldev(mdev);
r &= bdi_bits;
reason = 'c';
goto out;
}
if (get_ldev(mdev)) {
q = bdev_get_queue(mdev->ldev->backing_bdev);
r = bdi_congested(&q->backing_dev_info, bdi_bits);

6
drivers/block/drbd/drbd_nl.c
View File

@ -147,6 +147,9 @@ int drbd_khelper(struct drbd_conf *mdev, char *cmd)
char *argv[] = {usermode_helper, cmd, mb, NULL };
int ret;
if (current == mdev->worker.task)
set_bit(CALLBACK_PENDING, &mdev->flags);
snprintf(mb, 12, "minor-%d", mdev_to_minor(mdev));
if (get_net_conf(mdev)) {
@ -189,6 +192,9 @@ int drbd_khelper(struct drbd_conf *mdev, char *cmd)
usermode_helper, cmd, mb,
(ret >> 8) & 0xff, ret);
if (current == mdev->worker.task)
clear_bit(CALLBACK_PENDING, &mdev->flags);
if (ret < 0) /* Ignore any ERRNOs we got. */
ret = 0;