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drbd: fix potential access of on-stack wait_queue_head_t after return 

I run into something declaring itself as "spinlock deadlock",
 BUG: spinlock lockup on CPU#1, kjournald/27816, ffff88000ad6bca0
 Pid: 27816, comm: kjournald Tainted: G        W 2.6.34.6 #2
 Call Trace:
  <IRQ>  [<ffffffff811ba0aa>] do_raw_spin_lock+0x11e/0x14d
  [<ffffffff81340fde>] _raw_spin_lock_irqsave+0x6a/0x81
  [<ffffffff8103b694>] ? __wake_up+0x22/0x50
  [<ffffffff8103b694>] __wake_up+0x22/0x50
  [<ffffffffa07ff661>] bm_async_io_complete+0x258/0x299 [drbd]
but the call traces do not fit at all,
all other cpus are cpu_idle.

I think it may be this race:

drbd_bm_write_page
 wait_queue_head_t io_wait;
 atomic_t in_flight;
 bm_async_io
  submit_bio
					bm_async_io_complete
					  if (atomic_dec_and_test(in_flight))
 wait_event(io_wait,
	atomic_read(in_flight) == 0)
 return
					    wake_up(io_wait)

The wake_up now accesses the wait_queue_head_t spinlock, which is no
longer valid, since the stack frame of drbd_bm_write_page has been
clobbered now.

Fix this by using struct completion, which does both the condition test
as well as the wake_up inside its spinlock, so this race cannot happen.

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 2010-12-19 11:29:55 +01:00 committed by Philipp Reisner
parent 06d33e968d
commit 725a97e43e
1 changed files with 22 additions and 16 deletions
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38
drivers/block/drbd/drbd_bitmap.c
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@ -897,7 +897,7 @@ void drbd_bm_clear_all(struct drbd_conf *mdev)
struct bm_aio_ctx {
struct drbd_conf *mdev;
atomic_t in_flight;
wait_queue_head_t io_wait;
struct completion done;
unsigned flags;
#define BM_AIO_COPY_PAGES 1
int error;
@ -948,7 +948,7 @@ static void bm_async_io_complete(struct bio *bio, int error)
bio_put(bio);
if (atomic_dec_and_test(&ctx->in_flight))
wake_up(&ctx->io_wait);
complete(&ctx->done);
}
static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
@ -1009,8 +1009,12 @@ static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must
*/
static int bm_rw(struct drbd_conf *mdev, int rw, unsigned lazy_writeout_upper_idx) __must_hold(local)
{
struct bm_aio_ctx ctx =
{ .flags = lazy_writeout_upper_idx ? BM_AIO_COPY_PAGES : 0 };
struct bm_aio_ctx ctx = {
.mdev = mdev,
.in_flight = ATOMIC_INIT(1),
.done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
.flags = lazy_writeout_upper_idx ? BM_AIO_COPY_PAGES : 0,
};
struct drbd_bitmap *b = mdev->bitmap;
int num_pages, i, count = 0;
unsigned long now;
@ -1031,10 +1035,6 @@ static int bm_rw(struct drbd_conf *mdev, int rw, unsigned lazy_writeout_upper_id
num_pages = b->bm_number_of_pages;
now = jiffies;
ctx.mdev = mdev;
atomic_set(&ctx.in_flight, 1); /* one extra ref */
init_waitqueue_head(&ctx.io_wait);
ctx.error = 0;
/* let the layers below us try to merge these bios... */
for (i = 0; i < num_pages; i++) {
@ -1060,8 +1060,13 @@ static int bm_rw(struct drbd_conf *mdev, int rw, unsigned lazy_writeout_upper_id
cond_resched();
}
atomic_dec(&ctx.in_flight); /* drop the extra ref */
wait_event(ctx.io_wait, atomic_read(&ctx.in_flight) == 0);
/*
* We initialize ctx.in_flight to one to make sure bm_async_io_complete
* will not complete() early, and decrement / test it here. If there
* are still some bios in flight, we need to wait for them here.
*/
if (!atomic_dec_and_test(&ctx.in_flight))
wait_for_completion(&ctx.done);
dev_info(DEV, "bitmap %s of %u pages took %lu jiffies\n",
rw == WRITE ? "WRITE" : "READ",
count, jiffies - now);
@ -1133,19 +1138,20 @@ int drbd_bm_write_lazy(struct drbd_conf *mdev, unsigned upper_idx) __must_hold(l
*/
int drbd_bm_write_page(struct drbd_conf *mdev, unsigned int idx) __must_hold(local)
{
struct bm_aio_ctx ctx = { .flags = BM_AIO_COPY_PAGES, };
struct bm_aio_ctx ctx = {
.mdev = mdev,
.in_flight = ATOMIC_INIT(1),
.done = COMPLETION_INITIALIZER_ONSTACK(ctx.done),
.flags = BM_AIO_COPY_PAGES,
};
if (bm_test_page_unchanged(mdev->bitmap->bm_pages[idx])) {
dynamic_dev_dbg(DEV, "skipped bm page write for idx %u\n", idx);
return 0;
}
ctx.mdev = mdev;
atomic_set(&ctx.in_flight, 1);
init_waitqueue_head(&ctx.io_wait);
bm_page_io_async(&ctx, idx, WRITE_SYNC);
wait_event(ctx.io_wait, atomic_read(&ctx.in_flight) == 0);
wait_for_completion(&ctx.done);
if (ctx.error)
drbd_chk_io_error(mdev, 1, true);