[PATCH v3 04/12] block/cgroup: Split blkg_conf_exit()

[Bart Van Assche <bvanassche@acm.org>]

Split blkg_conf_exit() into blkg_conf_unprep() and blkg_conf_close_bdev()
because blkg_conf_exit() is not compatible with the Clang thread-safety
annotations. Remove blkg_conf_exit(). Rename blkg_conf_exit_frozen() into
blkg_conf_close_bdev_frozen(). Add thread-safety annotations to the new
functions.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 block/bfq-cgroup.c    |  9 ++++--
 block/blk-cgroup.c    | 58 ++++++++++++++++++-------------------
 block/blk-cgroup.h    | 15 +++++++---
 block/blk-iocost.c    | 67 +++++++++++++++++++++----------------------
 block/blk-iolatency.c | 19 ++++++------
 block/blk-throttle.c  | 34 +++++++++++++---------
 6 files changed, 108 insertions(+), 94 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 38396df9dce7..5d40279d6c9d 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -1053,11 +1053,11 @@ static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto out;
+		return ret;
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_bfq, &ctx);
 	if (ret)
-		goto out;
+		goto close_bdev;
 
 	if (sscanf(ctx.body, "%llu", &v) == 1) {
 		/* require "default" on dfl */
@@ -1078,8 +1078,11 @@ static ssize_t bfq_io_set_device_weight(struct kernfs_open_file *of,
 		bfq_group_set_weight(bfqg, bfqg->entity.weight, v);
 		ret = 0;
 	}
+
 out:
-	blkg_conf_exit(&ctx);
+	blkg_conf_unprep(&ctx);
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
 	return ret ?: nbytes;
 }
 
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index a8d95d51b866..86513c54c217 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -755,7 +755,7 @@ EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
  *
  * Initialize @ctx which can be used to parse blkg config input string @input.
  * Once initialized, @ctx can be used with blkg_conf_open_bdev() and
- * blkg_conf_prep(), and must be cleaned up with blkg_conf_exit().
+ * blkg_conf_prep().
  */
 void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input)
 {
@@ -817,8 +817,8 @@ EXPORT_SYMBOL_GPL(blkg_conf_open_bdev);
  * ensures the correct locking order between freeze queue and q->rq_qos_mutex.
  *
  * This function returns negative error on failure. On success it returns
- * memflags which must be saved and later passed to blkg_conf_exit_frozen
- * for restoring the memalloc scope.
+ * memflags which must be saved and later passed to
+ * blkg_conf_close_bdev_frozen() for restoring the memalloc scope.
  */
 unsigned long __must_check blkg_conf_open_bdev_frozen(struct blkg_conf_ctx *ctx)
 {
@@ -858,11 +858,10 @@ unsigned long __must_check blkg_conf_open_bdev_frozen(struct blkg_conf_ctx *ctx)
  *
  * blkg_conf_open_bdev() must be called on @ctx beforehand. On success, this
  * function returns with queue lock held and must be followed by
- * blkg_conf_exit().
+ * blkg_conf_close_bdev().
  */
 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		   struct blkg_conf_ctx *ctx)
-	__acquires(&bdev->bd_queue->queue_lock)
 {
 	struct gendisk *disk;
 	struct request_queue *q;
@@ -968,42 +967,41 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 EXPORT_SYMBOL_GPL(blkg_conf_prep);
 
 /**
- * blkg_conf_exit - clean up per-blkg config update
+ * blkg_conf_unprep - counterpart of blkg_conf_prep()
  * @ctx: blkg_conf_ctx initialized with blkg_conf_init()
- *
- * Clean up after per-blkg config update. This function must be called on all
- * blkg_conf_ctx's initialized with blkg_conf_init().
  */
-void blkg_conf_exit(struct blkg_conf_ctx *ctx)
-	__releases(&ctx->bdev->bd_queue->queue_lock)
-	__releases(&ctx->bdev->bd_queue->rq_qos_mutex)
+void blkg_conf_unprep(struct blkg_conf_ctx *ctx)
 {
-	if (ctx->blkg) {
-		spin_unlock_irq(&bdev_get_queue(ctx->bdev)->queue_lock);
-		ctx->blkg = NULL;
-	}
+	WARN_ON_ONCE(!ctx->blkg);
+	spin_unlock_irq(&ctx->bdev->bd_disk->queue->queue_lock);
+	ctx->blkg = NULL;
+}
+EXPORT_SYMBOL_GPL(blkg_conf_unprep);
 
-	if (ctx->bdev) {
-		mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex);
-		blkdev_put_no_open(ctx->bdev);
-		ctx->body = NULL;
-		ctx->bdev = NULL;
-	}
+/**
+ * blkg_conf_close_bdev - counterpart of blkg_conf_open_bdev()
+ * @ctx: blkg_conf_ctx initialized with blkg_conf_init()
+ */
+void blkg_conf_close_bdev(struct blkg_conf_ctx *ctx)
+{
+	mutex_unlock(&ctx->bdev->bd_queue->rq_qos_mutex);
+	blkdev_put_no_open(ctx->bdev);
+	ctx->body = NULL;
+	ctx->bdev = NULL;
 }
-EXPORT_SYMBOL_GPL(blkg_conf_exit);
+EXPORT_SYMBOL_GPL(blkg_conf_close_bdev);
 
 /*
- * Similar to blkg_conf_exit, but also unfreezes the queue. Should be used
+ * Similar to blkg_close_bdev, but also unfreezes the queue. Should be used
  * when blkg_conf_open_bdev_frozen is used to open the bdev.
  */
-void blkg_conf_exit_frozen(struct blkg_conf_ctx *ctx, unsigned long memflags)
+void blkg_conf_close_bdev_frozen(struct blkg_conf_ctx *ctx,
+				 unsigned long memflags)
 {
-	if (ctx->bdev) {
-		struct request_queue *q = ctx->bdev->bd_queue;
+	struct request_queue *q = ctx->bdev->bd_queue;
 
-		blkg_conf_exit(ctx);
-		blk_mq_unfreeze_queue(q, memflags);
-	}
+	blkg_conf_close_bdev(ctx);
+	blk_mq_unfreeze_queue(q, memflags);
 }
 
 static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1cce3294634d..f0a3af520c55 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -218,12 +218,19 @@ struct blkg_conf_ctx {
 };
 
 void blkg_conf_init(struct blkg_conf_ctx *ctx, char *input);
-int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx);
+int blkg_conf_open_bdev(struct blkg_conf_ctx *ctx)
+	__cond_acquires(0, &ctx->bdev->bd_queue->rq_qos_mutex);
 unsigned long blkg_conf_open_bdev_frozen(struct blkg_conf_ctx *ctx);
 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
-		   struct blkg_conf_ctx *ctx);
-void blkg_conf_exit(struct blkg_conf_ctx *ctx);
-void blkg_conf_exit_frozen(struct blkg_conf_ctx *ctx, unsigned long memflags);
+		   struct blkg_conf_ctx *ctx)
+	__cond_acquires(0, &ctx->bdev->bd_disk->queue->queue_lock);
+void blkg_conf_unprep(struct blkg_conf_ctx *ctx)
+	__releases(ctx->bdev->bd_disk->queue->queue_lock);
+void blkg_conf_close_bdev(struct blkg_conf_ctx *ctx)
+	__releases(&ctx->bdev->bd_queue->rq_qos_mutex);
+void blkg_conf_close_bdev_frozen(struct blkg_conf_ctx *ctx,
+				 unsigned long memflags)
+	__releases(&ctx->bdev->bd_queue->rq_qos_mutex);
 
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index b34f820dedcc..e611dd63d712 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3142,21 +3142,23 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto err;
+		return ret;
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, &ctx);
 	if (ret)
-		goto err;
+		goto close_bdev;
 
 	iocg = blkg_to_iocg(ctx.blkg);
 
+	ret = -EINVAL;
+
 	if (!strncmp(ctx.body, "default", 7)) {
 		v = 0;
 	} else {
 		if (!sscanf(ctx.body, "%u", &v))
-			goto einval;
+			goto unprep;
 		if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
-			goto einval;
+			goto unprep;
 	}
 
 	spin_lock(&iocg->ioc->lock);
@@ -3165,14 +3167,15 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
 	weight_updated(iocg, &now);
 	spin_unlock(&iocg->ioc->lock);
 
-	blkg_conf_exit(&ctx);
-	return nbytes;
+	ret = 0;
 
-einval:
-	ret = -EINVAL;
-err:
-	blkg_conf_exit(&ctx);
-	return ret;
+unprep:
+	blkg_conf_unprep(&ctx);
+
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
+
+	return ret ? ret : nbytes;
 }
 
 static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
@@ -3241,10 +3244,8 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
 	blkg_conf_init(&ctx, input);
 
 	memflags = blkg_conf_open_bdev_frozen(&ctx);
-	if (IS_ERR_VALUE(memflags)) {
-		ret = memflags;
-		goto err;
-	}
+	if (IS_ERR_VALUE(memflags))
+		return memflags;
 
 	body = ctx.body;
 	disk = ctx.bdev->bd_disk;
@@ -3361,14 +3362,14 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
 
 	blk_mq_unquiesce_queue(disk->queue);
 
-	blkg_conf_exit_frozen(&ctx, memflags);
+	blkg_conf_close_bdev_frozen(&ctx, memflags);
 	return nbytes;
 einval:
 	spin_unlock_irq(&ioc->lock);
 	blk_mq_unquiesce_queue(disk->queue);
 	ret = -EINVAL;
 err:
-	blkg_conf_exit_frozen(&ctx, memflags);
+	blkg_conf_close_bdev_frozen(&ctx, memflags);
 	return ret;
 }
 
@@ -3434,20 +3435,20 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto err;
+		return ret;
 
 	body = ctx.body;
 	q = bdev_get_queue(ctx.bdev);
 	if (!queue_is_mq(q)) {
 		ret = -EOPNOTSUPP;
-		goto err;
+		goto close_bdev;
 	}
 
 	ioc = q_to_ioc(q);
 	if (!ioc) {
 		ret = blk_iocost_init(ctx.bdev->bd_disk);
 		if (ret)
-			goto err;
+			goto close_bdev;
 		ioc = q_to_ioc(q);
 	}
 
@@ -3458,6 +3459,8 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 	memcpy(u, ioc->params.i_lcoefs, sizeof(u));
 	user = ioc->user_cost_model;
 
+	ret = -EINVAL;
+
 	while ((p = strsep(&body, " \t\n"))) {
 		substring_t args[MAX_OPT_ARGS];
 		char buf[32];
@@ -3475,20 +3478,20 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 			else if (!strcmp(buf, "user"))
 				user = true;
 			else
-				goto einval;
+				goto unlock;
 			continue;
 		case COST_MODEL:
 			match_strlcpy(buf, &args[0], sizeof(buf));
 			if (strcmp(buf, "linear"))
-				goto einval;
+				goto unlock;
 			continue;
 		}
 
 		tok = match_token(p, i_lcoef_tokens, args);
 		if (tok == NR_I_LCOEFS)
-			goto einval;
+			goto unlock;
 		if (match_u64(&args[0], &v))
-			goto einval;
+			goto unlock;
 		u[tok] = v;
 		user = true;
 	}
@@ -3500,24 +3503,18 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 		ioc->user_cost_model = false;
 	}
 	ioc_refresh_params(ioc, true);
-	spin_unlock_irq(&ioc->lock);
 
-	blk_mq_unquiesce_queue(q);
-	blk_mq_unfreeze_queue(q, memflags);
-
-	blkg_conf_exit(&ctx);
-	return nbytes;
+	ret = 0;
 
-einval:
+unlock:
 	spin_unlock_irq(&ioc->lock);
 
 	blk_mq_unquiesce_queue(q);
 	blk_mq_unfreeze_queue(q, memflags);
 
-	ret = -EINVAL;
-err:
-	blkg_conf_exit(&ctx);
-	return ret;
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
+	return ret ? ret : nbytes;
 }
 
 static struct cftype ioc_files[] = {
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 53e8dd2dfa8a..1aaee6fb0f59 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -840,7 +840,7 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto out;
+		return ret;
 
 	/*
 	 * blk_iolatency_init() may fail after rq_qos_add() succeeds which can
@@ -850,11 +850,11 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
 	if (!iolat_rq_qos(ctx.bdev->bd_queue))
 		ret = blk_iolatency_init(ctx.bdev->bd_disk);
 	if (ret)
-		goto out;
+		goto close_bdev;
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, &ctx);
 	if (ret)
-		goto out;
+		goto close_bdev;
 
 	iolat = blkg_to_lat(ctx.blkg);
 	p = ctx.body;
@@ -865,7 +865,7 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
 		char val[21];	/* 18446744073709551616 */
 
 		if (sscanf(tok, "%15[^=]=%20s", key, val) != 2)
-			goto out;
+			goto unprep;
 
 		if (!strcmp(key, "target")) {
 			u64 v;
@@ -875,9 +875,9 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
 			else if (sscanf(val, "%llu", &v) == 1)
 				lat_val = v * NSEC_PER_USEC;
 			else
-				goto out;
+				goto unprep;
 		} else {
-			goto out;
+			goto unprep;
 		}
 	}
 
@@ -889,8 +889,11 @@ static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
 	if (oldval != iolat->min_lat_nsec)
 		iolatency_clear_scaling(blkg);
 	ret = 0;
-out:
-	blkg_conf_exit(&ctx);
+
+unprep:
+	blkg_conf_unprep(&ctx);
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
 	return ret ?: nbytes;
 }
 
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 97188a795848..11b571246f45 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1353,21 +1353,21 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto out_finish;
+		return ret;
 
 	if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
 		ret = blk_throtl_init(ctx.bdev->bd_disk);
 		if (ret)
-			goto out_finish;
+			goto close_bdev;
 	}
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
 	if (ret)
-		goto out_finish;
+		goto close_bdev;
 
 	ret = -EINVAL;
 	if (sscanf(ctx.body, "%llu", &v) != 1)
-		goto out_finish;
+		goto unprep;
 	if (!v)
 		v = U64_MAX;
 
@@ -1381,8 +1381,12 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
 
 	tg_conf_updated(tg, false);
 	ret = 0;
-out_finish:
-	blkg_conf_exit(&ctx);
+
+unprep:
+	blkg_conf_unprep(&ctx);
+
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
 	return ret ?: nbytes;
 }
 
@@ -1537,17 +1541,17 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 
 	ret = blkg_conf_open_bdev(&ctx);
 	if (ret)
-		goto out_finish;
+		return ret;
 
 	if (!blk_throtl_activated(ctx.bdev->bd_queue)) {
 		ret = blk_throtl_init(ctx.bdev->bd_disk);
 		if (ret)
-			goto out_finish;
+			goto close_bdev;
 	}
 
 	ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, &ctx);
 	if (ret)
-		goto out_finish;
+		goto close_bdev;
 
 	tg = blkg_to_tg(ctx.blkg);
 	tg_update_carryover(tg);
@@ -1573,11 +1577,11 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		p = tok;
 		strsep(&p, "=");
 		if (!p || (sscanf(p, "%llu", &val) != 1 && strcmp(p, "max")))
-			goto out_finish;
+			goto unprep;
 
 		ret = -ERANGE;
 		if (!val)
-			goto out_finish;
+			goto unprep;
 
 		ret = -EINVAL;
 		if (!strcmp(tok, "rbps"))
@@ -1589,7 +1593,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 		else if (!strcmp(tok, "wiops"))
 			v[3] = min_t(u64, val, UINT_MAX);
 		else
-			goto out_finish;
+			goto unprep;
 	}
 
 	tg->bps[READ] = v[0];
@@ -1599,8 +1603,10 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
 
 	tg_conf_updated(tg, false);
 	ret = 0;
-out_finish:
-	blkg_conf_exit(&ctx);
+unprep:
+	blkg_conf_unprep(&ctx);
+close_bdev:
+	blkg_conf_close_bdev(&ctx);
 	return ret ?: nbytes;
 }