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: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index a56b107..9e9fc34 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1073,6 +1073,16 @@
* @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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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);
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index ff0eb308..cfd324b 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -369,9 +369,10 @@
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);