drbd: track details of bitmap IO

Track start and submit time of bitmap operations, and
add pending bitmap IO contexts to a new pending_bitmap_io list.

Signed-off-by: Philipp Reisner <[e-mail]>
Signed-off-by: Lars Ellenberg <[e-mail]>

drivers/block/drbd/drbd_bitmap.c

···
 	spin_unlock_irq(&b->bm_lock);
 }
 
-struct bm_aio_ctx {
-	struct drbd_device *device;
-	atomic_t in_flight;
-	unsigned int done;
-	unsigned flags;
-#define BM_AIO_COPY_PAGES	1
-#define BM_AIO_WRITE_HINTED	2
-#define BM_WRITE_ALL_PAGES	4
-	int error;
-	struct kref kref;
-};
-
-static void bm_aio_ctx_destroy(struct kref *kref)
+static void drbd_bm_aio_ctx_destroy(struct kref *kref)
 {
-	struct bm_aio_ctx *ctx = container_of(kref, struct bm_aio_ctx, kref);
+	struct drbd_bm_aio_ctx *ctx = container_of(kref, struct drbd_bm_aio_ctx, kref);
+	unsigned long flags;
 
+	spin_lock_irqsave(&ctx->device->resource->req_lock, flags);
+	list_del(&ctx->list);
+	spin_unlock_irqrestore(&ctx->device->resource->req_lock, flags);
 	put_ldev(ctx->device);
 	kfree(ctx);
 }
···
 /* bv_page may be a copy, or may be the original */
 static void bm_async_io_complete(struct bio *bio, int error)
 {
-	struct bm_aio_ctx *ctx = bio->bi_private;
+	struct drbd_bm_aio_ctx *ctx = bio->bi_private;
 	struct drbd_device *device = ctx->device;
 	struct drbd_bitmap *b = device->bitmap;
 	unsigned int idx = bm_page_to_idx(bio->bi_io_vec[0].bv_page);
···
 	if (atomic_dec_and_test(&ctx->in_flight)) {
 		ctx->done = 1;
 		wake_up(&device->misc_wait);
-		kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+		kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 	}
 }
 
-static void bm_page_io_async(struct bm_aio_ctx *ctx, int page_nr, int rw) __must_hold(local)
+static void bm_page_io_async(struct drbd_bm_aio_ctx *ctx, int page_nr) __must_hold(local)
 {
 	struct bio *bio = bio_alloc_drbd(GFP_NOIO);
 	struct drbd_device *device = ctx->device;
 	struct drbd_bitmap *b = device->bitmap;
 	struct page *page;
 	unsigned int len;
+	unsigned int rw = (ctx->flags & BM_AIO_READ) ? READ : WRITE;
 
 	sector_t on_disk_sector =
 		device->ldev->md.md_offset + device->ldev->md.bm_offset;
···
 /*
  * bm_rw: read/write the whole bitmap from/to its on disk location.
  */
-static int bm_rw(struct drbd_device *device, int rw, unsigned flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
+static int bm_rw(struct drbd_device *device, const unsigned int flags, unsigned lazy_writeout_upper_idx) __must_hold(local)
 {
-	struct bm_aio_ctx *ctx;
+	struct drbd_bm_aio_ctx *ctx;
 	struct drbd_bitmap *b = device->bitmap;
 	int num_pages, i, count = 0;
 	unsigned long now;
···
 	 * as we submit copies of pages anyways.
 	 */
 
-	ctx = kmalloc(sizeof(struct bm_aio_ctx), GFP_NOIO);
+	ctx = kmalloc(sizeof(struct drbd_bm_aio_ctx), GFP_NOIO);
 	if (!ctx)
 		return -ENOMEM;
 
-	*ctx = (struct bm_aio_ctx) {
+	*ctx = (struct drbd_bm_aio_ctx) {
 		.device = device,
+		.start_jif = jiffies,
 		.in_flight = ATOMIC_INIT(1),
 		.done = 0,
 		.flags = flags,
···
 		.kref = { ATOMIC_INIT(2) },
 	};
 
-	if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in bm_aio_ctx_destroy() */
+	if (!get_ldev_if_state(device, D_ATTACHING)) {  /* put is in drbd_bm_aio_ctx_destroy() */
 		drbd_err(device, "ASSERT FAILED: get_ldev_if_state() == 1 in bm_rw()\n");
 		kfree(ctx);
 		return -ENODEV;
···
 	/* Here D_ATTACHING is sufficient since drbd_bm_read() is called only from
 	   drbd_adm_attach(), after device->ldev was assigned. */
 
-	if (!ctx->flags)
+	if (0 == (ctx->flags & ~BM_AIO_READ))
 		WARN_ON(!(BM_LOCKED_MASK & b->bm_flags));
+
+	spin_lock_irq(&device->resource->req_lock);
+	list_add_tail(&ctx->list, &device->pending_bitmap_io);
+	spin_unlock_irq(&device->resource->req_lock);
 
 	num_pages = b->bm_number_of_pages;
 
···
 		/* ignore completely unchanged pages */
 		if (lazy_writeout_upper_idx && i == lazy_writeout_upper_idx)
 			break;
-		if (rw & WRITE) {
+		if (!(flags & BM_AIO_READ)) {
 			if ((flags & BM_AIO_WRITE_HINTED) &&
 			    !test_and_clear_bit(BM_PAGE_HINT_WRITEOUT,
 				    &page_private(b->bm_pages[i])))
 				continue;
 
-			if (!(flags & BM_WRITE_ALL_PAGES) &&
+			if (!(flags & BM_AIO_WRITE_ALL_PAGES) &&
 			    bm_test_page_unchanged(b->bm_pages[i])) {
 				dynamic_drbd_dbg(device, "skipped bm write for idx %u\n", i);
 				continue;
···
 			}
 		}
 		atomic_inc(&ctx->in_flight);
-		bm_page_io_async(ctx, i, rw);
+		bm_page_io_async(ctx, i);
 		++count;
 		cond_resched();
 	}
···
 	if (!atomic_dec_and_test(&ctx->in_flight))
 		wait_until_done_or_force_detached(device, device->ldev, &ctx->done);
 	else
-		kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+		kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 
 	/* summary for global bitmap IO */
 	if (flags == 0)
 		drbd_info(device, "bitmap %s of %u pages took %lu jiffies\n",
-			 rw == WRITE ? "WRITE" : "READ",
+			 (flags & BM_AIO_READ) ? "READ" : "WRITE",
 			 count, jiffies - now);
 
 	if (ctx->error) {
···
 		err = -EIO; /* Disk timeout/force-detach during IO... */
 
 	now = jiffies;
-	if (rw == READ) {
+	if (flags & BM_AIO_READ) {
 		b->bm_set = bm_count_bits(b);
 		drbd_info(device, "recounting of set bits took additional %lu jiffies\n",
 		     jiffies - now);
 	}
 	now = b->bm_set;
 
-	if (flags == 0)
+	if ((flags & ~BM_AIO_READ) == 0)
 		drbd_info(device, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
 		     ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
 
-	kref_put(&ctx->kref, &bm_aio_ctx_destroy);
+	kref_put(&ctx->kref, &drbd_bm_aio_ctx_destroy);
 	return err;
 }
 
···
  */
 int drbd_bm_read(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, READ, 0, 0);
+	return bm_rw(device, BM_AIO_READ, 0);
 }
 
 /**
···
  */
 int drbd_bm_write(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, 0, 0);
+	return bm_rw(device, 0, 0);
 }
 
 /**
···
  */
 int drbd_bm_write_all(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_WRITE_ALL_PAGES, 0);
+	return bm_rw(device, BM_AIO_WRITE_ALL_PAGES, 0);
 }
 
 /**
···
  */
 int drbd_bm_write_copy_pages(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_AIO_COPY_PAGES, 0);
+	return bm_rw(device, BM_AIO_COPY_PAGES, 0);
 }
 
 /**
···
  */
 int drbd_bm_write_hinted(struct drbd_device *device) __must_hold(local)
 {
-	return bm_rw(device, WRITE, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
+	return bm_rw(device, BM_AIO_WRITE_HINTED | BM_AIO_COPY_PAGES, 0);
 }
 
 /* NOTE

drivers/block/drbd/drbd_int.h

···
 struct drbd_device {
 	struct drbd_resource *resource;
 	struct list_head peer_devices;
+	struct list_head pending_bitmap_io;
 	int vnr;			/* volume number within the connection */
 	struct kref kref;
 
···
 	/* any requests that would block in drbd_make_request()
 	 * are deferred to this single-threaded work queue */
 	struct submit_worker submit;
+};
+
+struct drbd_bm_aio_ctx {
+	struct drbd_device *device;
+	struct list_head list; /* on device->pending_bitmap_io */;
+	unsigned long start_jif;
+	atomic_t in_flight;
+	unsigned int done;
+	unsigned flags;
+#define BM_AIO_COPY_PAGES	1
+#define BM_AIO_WRITE_HINTED	2
+#define BM_AIO_WRITE_ALL_PAGES	4
+#define BM_AIO_READ		8
+	int error;
+	struct kref kref;
 };
 
 struct drbd_config_context {

drivers/block/drbd/drbd_main.c

···
 	kref_get(&device->kref);
 
 	INIT_LIST_HEAD(&device->peer_devices);
+	INIT_LIST_HEAD(&device->pending_bitmap_io);
 	for_each_connection(connection, resource) {
 		peer_device = kzalloc(sizeof(struct drbd_peer_device), GFP_KERNEL);
 		if (!peer_device)