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drbd: fix for possible deadlock on IO error during resync 

Scenario:

Something (say, flush-147:0) is in drbd_al_begin_io,
holding a local_cnt, waiting for the resync to make progress.

Disk fails, worker in after_state_ch does drbd_rs_cancel_all,
then waits for local_cnt to drop to zero.

flush-147:0 is woken by drbd_rs_cancel_all, needs to write an AL
transaction, and queues that on the worker.

Deadlock.

Fix: do not wait in the worker, have put_ldev() trigger the
state change D_FAILED -> D_DISKLESS when necessary.
put_ldev() cannot do the state change directly, as it may or may not
already hold various spinlocks. We queue a short work instead.

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 2010-09-14 20:26:27 +02:00 committed by Philipp Reisner
parent 22cc37a943
commit e9e6f3ec53
2 changed files with 56 additions and 24 deletions
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8
drivers/block/drbd/drbd_int.h
View File

@ -852,6 +852,7 @@ enum {
BITMAP_IO, /* suspend application io;
once no more io in flight, start bitmap io */
BITMAP_IO_QUEUED, /* Started bitmap IO */
GO_DISKLESS, /* Disk failed, local_cnt reached zero, we are going diskless */
RESYNC_AFTER_NEG, /* Resync after online grow after the attach&negotiate finished. */
NET_CONGESTED, /* The data socket is congested */
@ -976,6 +977,7 @@ struct drbd_conf {
unsigned int ko_count;
struct drbd_work resync_work,
unplug_work,
go_diskless,
md_sync_work;
struct timer_list resync_timer;
struct timer_list md_sync_timer;
@ -1278,6 +1280,7 @@ extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
extern void drbd_go_diskless(struct drbd_conf *mdev);
/* Meta data layout
@ -2123,8 +2126,11 @@ static inline void put_ldev(struct drbd_conf *mdev)
int i = atomic_dec_return(&mdev->local_cnt);
__release(local);
D_ASSERT(i >= 0);
if (i == 0)
if (i == 0) {
if (mdev->state.disk == D_FAILED)
drbd_go_diskless(mdev);
wake_up(&mdev->misc_wait);
}
}
#ifndef __CHECKER__

72
drivers/block/drbd/drbd_main.c
View File

@ -77,6 +77,7 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused);
static void md_sync_timer_fn(unsigned long data);
static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused);
static int w_go_diskless(struct drbd_conf *mdev, struct drbd_work *w, int unused);
MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
"Lars Ellenberg <lars@linbit.com>");
@ -1363,42 +1364,46 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
os.disk > D_INCONSISTENT && ns.disk == D_INCONSISTENT)
drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL, "set_n_write from invalidate");
/* first half of local IO error */
if (os.disk > D_FAILED && ns.disk == D_FAILED) {
enum drbd_io_error_p eh;
enum drbd_io_error_p eh = EP_PASS_ON;
if (drbd_send_state(mdev))
dev_warn(DEV, "Notified peer that my disk is broken.\n");
else
dev_err(DEV, "Sending state for drbd_io_error() failed\n");
drbd_rs_cancel_all(mdev);
eh = EP_PASS_ON;
if (get_ldev_if_state(mdev, D_FAILED)) {
eh = mdev->ldev->dc.on_io_error;
put_ldev(mdev);
}
drbd_rs_cancel_all(mdev);
/* since get_ldev() only works as long as disk>=D_INCONSISTENT,
and it is D_DISKLESS here, local_cnt can only go down, it can
not increase... It will reach zero */
wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
mdev->rs_total = 0;
mdev->rs_failed = 0;
atomic_set(&mdev->rs_pending_cnt, 0);
spin_lock_irq(&mdev->req_lock);
_drbd_set_state(_NS(mdev, disk, D_DISKLESS), CS_HARD, NULL);
spin_unlock_irq(&mdev->req_lock);
if (eh == EP_CALL_HELPER)
drbd_khelper(mdev, "local-io-error");
}
/* second half of local IO error handling,
* after local_cnt references have reached zero: */
if (os.disk == D_FAILED && ns.disk == D_DISKLESS) {
mdev->rs_total = 0;
mdev->rs_failed = 0;
atomic_set(&mdev->rs_pending_cnt, 0);
}
if (os.disk > D_DISKLESS && ns.disk == D_DISKLESS) {
int c = atomic_read(&mdev->local_cnt);
if (os.disk == D_FAILED) /* && ns.disk == D_DISKLESS*/ {
if (drbd_send_state(mdev))
dev_warn(DEV, "Notified peer that my disk is broken.\n");
else
dev_err(DEV, "Sending state in drbd_io_error() failed\n");
if (drbd_send_state(mdev))
dev_warn(DEV, "Notified peer that I detached my disk.\n");
else
dev_err(DEV, "Sending state for detach failed\n");
if (c != 0) {
dev_err(DEV, "Logic bug, local_cnt=%d, but should be 0\n", c);
wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
}
wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
lc_destroy(mdev->resync);
mdev->resync = NULL;
lc_destroy(mdev->act_log);
@ -2803,11 +2808,13 @@ void drbd_init_set_defaults(struct drbd_conf *mdev)
INIT_LIST_HEAD(&mdev->meta.work.q);
INIT_LIST_HEAD(&mdev->resync_work.list);
INIT_LIST_HEAD(&mdev->unplug_work.list);
INIT_LIST_HEAD(&mdev->go_diskless.list);
INIT_LIST_HEAD(&mdev->md_sync_work.list);
INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
mdev->resync_work.cb = w_resync_inactive;
mdev->unplug_work.cb = w_send_write_hint;
mdev->go_diskless.cb = w_go_diskless;
mdev->md_sync_work.cb = w_md_sync;
mdev->bm_io_work.w.cb = w_bitmap_io;
init_timer(&mdev->resync_timer);
@ -2885,6 +2892,7 @@ void drbd_mdev_cleanup(struct drbd_conf *mdev)
D_ASSERT(list_empty(&mdev->meta.work.q));
D_ASSERT(list_empty(&mdev->resync_work.list));
D_ASSERT(list_empty(&mdev->unplug_work.list));
D_ASSERT(list_empty(&mdev->go_diskless.list));
}
@ -3712,6 +3720,24 @@ static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused)
return 1;
}
static int w_go_diskless(struct drbd_conf *mdev, struct drbd_work *w, int unused)
{
D_ASSERT(mdev->state.disk == D_FAILED);
D_ASSERT(atomic_read(&mdev->local_cnt) == 0);
drbd_force_state(mdev, NS(disk, D_DISKLESS));
clear_bit(GO_DISKLESS, &mdev->flags);
return 1;
}
void drbd_go_diskless(struct drbd_conf *mdev)
{
D_ASSERT(mdev->state.disk == D_FAILED);
if (!test_and_set_bit(GO_DISKLESS, &mdev->flags))
drbd_queue_work_front(&mdev->data.work, &mdev->go_diskless);
}
/**
* drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
* @mdev: DRBD device.