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Commit 10f6d992 authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Philipp Reisner
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drbd: don't BUG_ON, if bio_add_page of a single page to an empty bio fails 



Just deal with it more gracefully, if we fail to add even a single page
to an empty bio. We used to BUG_ON() there, but it has been observed in
some Xen deployment, so we need to handle that case more robustly now.

Signed-off-by: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
parent 039312b6

drivers/block/drbd/drbd_receiver.c

+30 −15
Original line number Diff line number Diff line
@@ -1073,6 +1073,16 @@ void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo) 
 * @mdev:	DRBD device.

 * @e:		epoch entry

 * @rw:		flag field, see bio->bi_rw

 *

 * May spread the pages to multiple bios,

 * depending on bio_add_page restrictions.

 *

 * Returns 0 if all bios have been submitted,

 * -ENOMEM if we could not allocate enough bios,

 * -ENOSPC (any better suggestion?) if we have not been able to bio_add_page a

 *  single page to an empty bio (which should never happen and likely indicates

 *  that the lower level IO stack is in some way broken). This has been observed

 *  on certain Xen deployments.

 */

/* TODO allocate from our own bio_set. */

int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e,
@@ -1085,6 +1095,7 @@ int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, 
	unsigned ds = e->size;

	unsigned n_bios = 0;

	unsigned nr_pages = (ds + PAGE_SIZE -1) >> PAGE_SHIFT;

	int err = -ENOMEM;



	/* In most cases, we will only need one bio.  But in case the lower

	 * level restrictions happen to be different at this offset on this
@@ -1110,8 +1121,17 @@ int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, 
	page_chain_for_each(page) {

		unsigned len = min_t(unsigned, ds, PAGE_SIZE);

		if (!bio_add_page(bio, page, len, 0)) {

			/* a single page must always be possible! */

			BUG_ON(bio->bi_vcnt == 0);

			/* A single page must always be possible!

			 * But in case it fails anyways,

			 * we deal with it, and complain (below). */

			if (bio->bi_vcnt == 0) {

				dev_err(DEV,

					"bio_add_page failed for len=%u, "

					"bi_vcnt=0 (bi_sector=%llu)\n",

					len, (unsigned long long)bio->bi_sector);

				err = -ENOSPC;

				goto fail;

			}

			goto next_bio;

		}

		ds -= len;
@@ -1137,7 +1157,7 @@ int drbd_submit_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, 
		bios = bios->bi_next;

		bio_put(bio);

	}

	return -ENOMEM;

	return err;

}



static int receive_Barrier(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned int data_size)
@@ -1436,9 +1456,8 @@ static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_si 
	if (drbd_submit_ee(mdev, e, WRITE, DRBD_FAULT_RS_WR) == 0)

		return true;



	/* drbd_submit_ee currently fails for one reason only:

	 * not being able to allocate enough bios.

	 * Is dropping the connection going to help? */

	/* don't care for the reason here */

	dev_err(DEV, "submit failed, triggering re-connect\n");

	spin_lock_irq(&mdev->req_lock);

	list_del(&e->w.list);

	spin_unlock_irq(&mdev->req_lock);
@@ -1837,9 +1856,8 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned 
	if (drbd_submit_ee(mdev, e, rw, DRBD_FAULT_DT_WR) == 0)

		return true;



	/* drbd_submit_ee currently fails for one reason only:

	 * not being able to allocate enough bios.

	 * Is dropping the connection going to help? */

	/* don't care for the reason here */

	dev_err(DEV, "submit failed, triggering re-connect\n");

	spin_lock_irq(&mdev->req_lock);

	list_del(&e->w.list);

	hlist_del_init(&e->colision);
@@ -1848,9 +1866,7 @@ static int receive_Data(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned 
		drbd_al_complete_io(mdev, e->sector);



out_interrupted:

	/* yes, the epoch_size now is imbalanced.

	 * but we drop the connection anyways, so we don't have a chance to

	 * receive a barrier... atomic_inc(&mdev->epoch_size); */

	drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + EV_CLEANUP);

	put_ldev(mdev);

	drbd_free_ee(mdev, e);

	return false;
@@ -2096,9 +2112,8 @@ static int receive_DataRequest(struct drbd_conf *mdev, enum drbd_packets cmd, un 
	if (drbd_submit_ee(mdev, e, READ, fault_type) == 0)

		return true;



	/* drbd_submit_ee currently fails for one reason only:

	 * not being able to allocate enough bios.

	 * Is dropping the connection going to help? */

	/* don't care for the reason here */

	dev_err(DEV, "submit failed, triggering re-connect\n");

	spin_lock_irq(&mdev->req_lock);

	list_del(&e->w.list);

	spin_unlock_irq(&mdev->req_lock);

drivers/block/drbd/drbd_worker.c

+4 −3
Original line number Diff line number Diff line
@@ -369,9 +369,10 @@ static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size) 
	if (drbd_submit_ee(mdev, e, READ, DRBD_FAULT_RS_RD) == 0)

		return 0;



	/* drbd_submit_ee currently fails for one reason only:

	 * not being able to allocate enough bios.

	 * Is dropping the connection going to help? */

	/* If it failed because of ENOMEM, retry should help.  If it failed

	 * because bio_add_page failed (probably broken lower level driver),

	 * retry may or may not help.

	 * If it does not, you may need to force disconnect. */

	spin_lock_irq(&mdev->req_lock);

	list_del(&e->w.list);

	spin_unlock_irq(&mdev->req_lock);