md/raid5: close race between STRIPE_BIT_DELAY and batching.
When we add a write to a stripe we need to make sure the bitmap
bit is set. While doing that the stripe is not locked so it could
be added to a batch after which further changes to STRIPE_BIT_DELAY
and ->bm_seq are ineffective.
So we need to hold off adding to a stripe until bitmap_startwrite has
completed at least once, and we need to avoid further changes to
STRIPE_BIT_DELAY once the stripe has been added to a batch.
If a bitmap_startwrite() completes after the stripe was added to a
batch, it will not have set the bit, only incremented a counter, so no
extra delay of the stripe is needed.
Reported-by: Shaohua Li <shli@kernel.org>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 7dc0dd8..01cdb9f 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -337,6 +337,9 @@
STRIPE_ON_RELEASE_LIST,
STRIPE_BATCH_READY,
STRIPE_BATCH_ERR,
+ STRIPE_BITMAP_PENDING, /* Being added to bitmap, don't add
+ * to batch yet.
+ */
};
#define STRIPE_EXPAND_SYNC_FLAG \