io_uring: introduce a struct for hash table

Instead of passing around a pointer to hash buckets, add a bit of type
safety and wrap it into a structure.

Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/d65bc3faba537ec2aca9eabf334394936d44bd28.1655371007.git.asml.silence@gmail.com
Reviewed-by: Hao Xu <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

io_uring/cancel.c

@@ -193,12 +193,12 @@ int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags)
 	return IOU_OK;
 }
 
-void init_hash_table(struct io_hash_bucket *hash_table, unsigned size)
+void init_hash_table(struct io_hash_table *table, unsigned size)
 {
 	unsigned int i;
 
 	for (i = 0; i < size; i++) {
-		spin_lock_init(&hash_table[i].lock);
-		INIT_HLIST_HEAD(&hash_table[i].list);
+		spin_lock_init(&table->hbs[i].lock);
+		INIT_HLIST_HEAD(&table->hbs[i].list);
 	}
 }

io_uring/cancel.h

@@ -4,9 +4,4 @@ int io_async_cancel_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags);
 
 int io_try_cancel(struct io_kiocb *req, struct io_cancel_data *cd);
-void init_hash_table(struct io_hash_bucket *hash_table, unsigned size);
-
-struct io_hash_bucket {
-	spinlock_t		lock;
-	struct hlist_head	list;
-} ____cacheline_aligned_in_smp;
+void init_hash_table(struct io_hash_table *table, unsigned size);

io_uring/fdinfo.c

@@ -158,8 +158,8 @@ static __cold void __io_uring_show_fdinfo(struct io_ring_ctx *ctx,
 		mutex_unlock(&ctx->uring_lock);
 
 	seq_puts(m, "PollList:\n");
-	for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
-		struct io_hash_bucket *hb = &ctx->cancel_hash[i];
+	for (i = 0; i < (1U << ctx->cancel_table.hash_bits); i++) {
+		struct io_hash_bucket *hb = &ctx->cancel_table.hbs[i];
 		struct io_kiocb *req;
 
 		spin_lock(&hb->lock);

io_uring/io_uring.c

@@ -241,11 +241,23 @@ static __cold void io_fallback_req_func(struct work_struct *work)
 	percpu_ref_put(&ctx->refs);
 }
 
+static int io_alloc_hash_table(struct io_hash_table *table, unsigned bits)
+{
+	unsigned hash_buckets = 1U << bits;
+	size_t hash_size = hash_buckets * sizeof(table->hbs[0]);
+
+	table->hbs = kmalloc(hash_size, GFP_KERNEL);
+	if (!table->hbs)
+		return -ENOMEM;
+
+	table->hash_bits = bits;
+	init_hash_table(table, hash_buckets);
+	return 0;
+}
+
 static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 {
 	struct io_ring_ctx *ctx;
-	unsigned hash_buckets;
-	size_t hash_size;
 	int hash_bits;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
@@ -261,16 +273,9 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	 */
 	hash_bits = ilog2(p->cq_entries) - 5;
 	hash_bits = clamp(hash_bits, 1, 8);
-	hash_buckets = 1U << hash_bits;
-	hash_size = hash_buckets * sizeof(struct io_hash_bucket);
-
-	ctx->cancel_hash_bits = hash_bits;
-	ctx->cancel_hash = kmalloc(hash_size, GFP_KERNEL);
-	if (!ctx->cancel_hash)
+	if (io_alloc_hash_table(&ctx->cancel_table, hash_bits))
 		goto err;
 
-	init_hash_table(ctx->cancel_hash, hash_buckets);
-
 	ctx->dummy_ubuf = kzalloc(sizeof(*ctx->dummy_ubuf), GFP_KERNEL);
 	if (!ctx->dummy_ubuf)
 		goto err;
@@ -311,7 +316,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	return ctx;
 err:
 	kfree(ctx->dummy_ubuf);
-	kfree(ctx->cancel_hash);
+	kfree(ctx->cancel_table.hbs);
 	kfree(ctx->io_bl);
 	xa_destroy(&ctx->io_bl_xa);
 	kfree(ctx);
@@ -2487,7 +2492,7 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	io_req_caches_free(ctx);
 	if (ctx->hash_map)
 		io_wq_put_hash(ctx->hash_map);
-	kfree(ctx->cancel_hash);
+	kfree(ctx->cancel_table.hbs);
 	kfree(ctx->dummy_ubuf);
 	kfree(ctx->io_bl);
 	xa_destroy(&ctx->io_bl_xa);

io_uring/io_uring_types.h

@@ -9,6 +9,16 @@
 #include "io-wq.h"
 #include "filetable.h"
 
+struct io_hash_bucket {
+	spinlock_t		lock;
+	struct hlist_head	list;
+} ____cacheline_aligned_in_smp;
+
+struct io_hash_table {
+	struct io_hash_bucket	*hbs;
+	unsigned		hash_bits;
+};
+
 struct io_uring {
 	u32 head ____cacheline_aligned_in_smp;
 	u32 tail ____cacheline_aligned_in_smp;
@@ -224,8 +234,7 @@ struct io_ring_ctx {
 		 * manipulate the list, hence no extra locking is needed there.
 		 */
 		struct io_wq_work_list	iopoll_list;
-		struct io_hash_bucket	*cancel_hash;
-		unsigned		cancel_hash_bits;
+		struct io_hash_table	cancel_table;
 		bool			poll_multi_queue;
 
 		struct list_head	io_buffers_comp;

io_uring/poll.c

@@ -73,9 +73,9 @@ static struct io_poll *io_poll_get_single(struct io_kiocb *req)
 
 static void io_poll_req_insert(struct io_kiocb *req)
 {
-	struct io_ring_ctx *ctx = req->ctx;
-	u32 index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits);
-	struct io_hash_bucket *hb = &ctx->cancel_hash[index];
+	struct io_hash_table *table = &req->ctx->cancel_table;
+	u32 index = hash_long(req->cqe.user_data, table->hash_bits);
+	struct io_hash_bucket *hb = &table->hbs[index];
 
 	spin_lock(&hb->lock);
 	hlist_add_head(&req->hash_node, &hb->list);
@@ -84,8 +84,9 @@ static void io_poll_req_insert(struct io_kiocb *req)
 
 static void io_poll_req_delete(struct io_kiocb *req, struct io_ring_ctx *ctx)
 {
-	u32 index = hash_long(req->cqe.user_data, ctx->cancel_hash_bits);
-	spinlock_t *lock = &ctx->cancel_hash[index].lock;
+	struct io_hash_table *table = &req->ctx->cancel_table;
+	u32 index = hash_long(req->cqe.user_data, table->hash_bits);
+	spinlock_t *lock = &table->hbs[index].lock;
 
 	spin_lock(lock);
 	hash_del(&req->hash_node);
@@ -539,13 +540,15 @@ int io_arm_poll_handler(struct io_kiocb *req, unsigned issue_flags)
 __cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk,
 			       bool cancel_all)
 {
+	struct io_hash_table *table = &ctx->cancel_table;
+	unsigned nr_buckets = 1U << table->hash_bits;
 	struct hlist_node *tmp;
 	struct io_kiocb *req;
 	bool found = false;
 	int i;
 
-	for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
-		struct io_hash_bucket *hb = &ctx->cancel_hash[i];
+	for (i = 0; i < nr_buckets; i++) {
+		struct io_hash_bucket *hb = &table->hbs[i];
 
 		spin_lock(&hb->lock);
 		hlist_for_each_entry_safe(req, tmp, &hb->list, hash_node) {
@@ -562,12 +565,12 @@ __cold bool io_poll_remove_all(struct io_ring_ctx *ctx, struct task_struct *tsk,
 
 static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
 				     struct io_cancel_data *cd,
-				     struct io_hash_bucket hash_table[],
+				     struct io_hash_table *table,
 				     struct io_hash_bucket **out_bucket)
 {
 	struct io_kiocb *req;
-	u32 index = hash_long(cd->data, ctx->cancel_hash_bits);
-	struct io_hash_bucket *hb = &hash_table[index];
+	u32 index = hash_long(cd->data, table->hash_bits);
+	struct io_hash_bucket *hb = &table->hbs[index];
 
 	*out_bucket = NULL;
 
@@ -591,16 +594,17 @@ static struct io_kiocb *io_poll_find(struct io_ring_ctx *ctx, bool poll_only,
 
 static struct io_kiocb *io_poll_file_find(struct io_ring_ctx *ctx,
 					  struct io_cancel_data *cd,
-					  struct io_hash_bucket hash_table[],
+					  struct io_hash_table *table,
 					  struct io_hash_bucket **out_bucket)
 {
+	unsigned nr_buckets = 1U << table->hash_bits;
 	struct io_kiocb *req;
 	int i;
 
 	*out_bucket = NULL;
 
-	for (i = 0; i < (1U << ctx->cancel_hash_bits); i++) {
-		struct io_hash_bucket *hb = &hash_table[i];
+	for (i = 0; i < nr_buckets; i++) {
+		struct io_hash_bucket *hb = &table->hbs[i];
 
 		spin_lock(&hb->lock);
 		hlist_for_each_entry(req, &hb->list, hash_node) {
@@ -628,15 +632,15 @@ static bool io_poll_disarm(struct io_kiocb *req)
 }
 
 static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
-			    struct io_hash_bucket hash_table[])
+			    struct io_hash_table *table)
 {
 	struct io_hash_bucket *bucket;
 	struct io_kiocb *req;
 
 	if (cd->flags & (IORING_ASYNC_CANCEL_FD|IORING_ASYNC_CANCEL_ANY))
-		req = io_poll_file_find(ctx, cd, ctx->cancel_hash, &bucket);
+		req = io_poll_file_find(ctx, cd, table, &bucket);
 	else
-		req = io_poll_find(ctx, false, cd, ctx->cancel_hash, &bucket);
+		req = io_poll_find(ctx, false, cd, table, &bucket);
 
 	if (req)
 		io_poll_cancel_req(req);
@@ -647,7 +651,7 @@ static int __io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
 
 int io_poll_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd)
 {
-	return __io_poll_cancel(ctx, cd, ctx->cancel_hash);
+	return __io_poll_cancel(ctx, cd, &ctx->cancel_table);
 }
 
 static __poll_t io_poll_parse_events(const struct io_uring_sqe *sqe,
@@ -745,7 +749,7 @@ int io_poll_remove(struct io_kiocb *req, unsigned int issue_flags)
 	int ret2, ret = 0;
 	bool locked;
 
-	preq = io_poll_find(ctx, true, &cd, ctx->cancel_hash, &bucket);
+	preq = io_poll_find(ctx, true, &cd, &ctx->cancel_table, &bucket);
 	if (preq)
 		ret2 = io_poll_disarm(preq);
 	if (bucket)