aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorNeil Brown <neilb@suse.de>2007-08-23 02:13:17 +0200
committerAdrian Bunk <bunk@stusta.de>2007-08-23 02:13:17 +0200
commit646edb4b5b9c472944af7d6016722fa4895f3bca (patch)
treee49c1e9a944febe6b445651233adc70b20731168
parent4d5eb09cab94fac8cfb767617a4799220f1874ab (diff)
downloadlinux-linaro-stable-646edb4b5b9c472944af7d6016722fa4895f3bca.tar.gz
md: avoid possible BUG_ON in md bitmap handling
md/bitmap tracks how many active write requests are pending on blocks associated with each bit in the bitmap, so that it knows when it can clear the bit (when count hits zero). The counter has 14 bits of space, so if there are ever more than 16383, we cannot cope. Currently the code just calles BUG_ON as "all" drivers have request queue limits much smaller than this. However is seems that some don't. Apparently some multipath configurations can allow more than 16383 concurrent write requests. So, in this unlikely situation, instead of calling BUG_ON we now wait for the count to drop down a bit. This requires a new wait_queue_head, some waiting code, and a wakeup call. Tested by limiting the counter to 20 instead of 16383 (writes go a lot slower in that case...). Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Adrian Bunk <bunk@kernel.org>
-rw-r--r--drivers/md/bitmap.c22
-rw-r--r--include/linux/raid/bitmap.h2
2 files changed, 23 insertions, 1 deletions
diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 2150693145fc..b7d9759be604 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1266,6 +1266,22 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
return 0;
}
+ if (unlikely((*bmc & COUNTER_MAX) == COUNTER_MAX)) {
+ DEFINE_WAIT(__wait);
+ /* note that it is safe to do the prepare_to_wait
+ * after the test as long as we do it before dropping
+ * the spinlock.
+ */
+ prepare_to_wait(&bitmap->overflow_wait, &__wait,
+ TASK_UNINTERRUPTIBLE);
+ spin_unlock_irq(&bitmap->lock);
+ bitmap->mddev->queue
+ ->unplug_fn(bitmap->mddev->queue);
+ schedule();
+ finish_wait(&bitmap->overflow_wait, &__wait);
+ continue;
+ }
+
switch(*bmc) {
case 0:
bitmap_file_set_bit(bitmap, offset);
@@ -1275,7 +1291,7 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
case 1:
*bmc = 2;
}
- if ((*bmc & COUNTER_MAX) == COUNTER_MAX) BUG();
+
(*bmc)++;
spin_unlock_irq(&bitmap->lock);
@@ -1313,6 +1329,9 @@ void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long secto
if (!success && ! (*bmc & NEEDED_MASK))
*bmc |= NEEDED_MASK;
+ if ((*bmc & COUNTER_MAX) == COUNTER_MAX)
+ wake_up(&bitmap->overflow_wait);
+
(*bmc)--;
if (*bmc <= 2) {
set_page_attr(bitmap,
@@ -1525,6 +1544,7 @@ int bitmap_create(mddev_t *mddev)
return -ENOMEM;
spin_lock_init(&bitmap->lock);
+ init_waitqueue_head(&bitmap->overflow_wait);
bitmap->mddev = mddev;
spin_lock_init(&bitmap->write_lock);
diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index 48e2d93d23fb..a9b7629b0e23 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -253,6 +253,8 @@ struct bitmap {
wait_queue_head_t write_wait;
struct list_head complete_pages;
mempool_t *write_pool;
+
+ wait_queue_head_t overflow_wait;
};
/* the bitmap API */