io_uring/kbuf: get rid of lower BGID lists

commit 09ab7eff38202159271534d2f5ad45526168f2a5 upstream.

Just rely on the xarray for any kind of bgid. This simplifies things, and
it really doesn't bring us much, if anything.

Cc: stable@vger.kernel.org # v6.4+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 8 insertions, 64 deletions

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index adf944bb5a2f..ea7d9ed6405c 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -353,7 +353,6 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 err:
 	kfree(ctx->cancel_table.hbs);
 	kfree(ctx->cancel_table_locked.hbs);
-	kfree(ctx->io_bl);
 	xa_destroy(&ctx->io_bl_xa);
 	kfree(ctx);
 	return NULL;
@@ -2906,7 +2905,6 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 		io_wq_put_hash(ctx->hash_map);
 	kfree(ctx->cancel_table.hbs);
 	kfree(ctx->cancel_table_locked.hbs);
-	kfree(ctx->io_bl);
 	xa_destroy(&ctx->io_bl_xa);
 	kfree(ctx);
 }
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 18df5a9d2f5e..d6346144cbb6 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -17,8 +17,6 @@
 
 #define IO_BUFFER_LIST_BUF_PER_PAGE (PAGE_SIZE / sizeof(struct io_uring_buf))
 
-#define BGID_ARRAY	64
-
 /* BIDs are addressed by a 16-bit field in a CQE */
 #define MAX_BIDS_PER_BGID (1 << 16)
 
@@ -40,13 +38,9 @@ struct io_buf_free {
 	int				inuse;
 };
 
-static struct io_buffer_list *__io_buffer_get_list(struct io_ring_ctx *ctx,
-						   struct io_buffer_list *bl,
-						   unsigned int bgid)
+static inline struct io_buffer_list *__io_buffer_get_list(struct io_ring_ctx *ctx,
+							  unsigned int bgid)
 {
-	if (bl && bgid < BGID_ARRAY)
-		return &bl[bgid];
-
 	return xa_load(&ctx->io_bl_xa, bgid);
 }
 
@@ -55,7 +49,7 @@ static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
 {
 	lockdep_assert_held(&ctx->uring_lock);
 
-	return __io_buffer_get_list(ctx, ctx->io_bl, bgid);
+	return __io_buffer_get_list(ctx, bgid);
 }
 
 static int io_buffer_add_list(struct io_ring_ctx *ctx,
@@ -68,10 +62,6 @@ static int io_buffer_add_list(struct io_ring_ctx *ctx,
 	 */
 	bl->bgid = bgid;
 	smp_store_release(&bl->is_ready, 1);
-
-	if (bgid < BGID_ARRAY)
-		return 0;
-
 	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
 }
 
@@ -217,24 +207,6 @@ void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
 	return ret;
 }
 
-static __cold int io_init_bl_list(struct io_ring_ctx *ctx)
-{
-	struct io_buffer_list *bl;
-	int i;
-
-	bl = kcalloc(BGID_ARRAY, sizeof(struct io_buffer_list), GFP_KERNEL);
-	if (!bl)
-		return -ENOMEM;
-
-	for (i = 0; i < BGID_ARRAY; i++) {
-		INIT_LIST_HEAD(&bl[i].buf_list);
-		bl[i].bgid = i;
-	}
-
-	smp_store_release(&ctx->io_bl, bl);
-	return 0;
-}
-
 /*
  * Mark the given mapped range as free for reuse
  */
@@ -309,13 +281,6 @@ void io_destroy_buffers(struct io_ring_ctx *ctx)
 	struct list_head *item, *tmp;
 	struct io_buffer *buf;
 	unsigned long index;
-	int i;
-
-	for (i = 0; i < BGID_ARRAY; i++) {
-		if (!ctx->io_bl)
-			break;
-		__io_remove_buffers(ctx, &ctx->io_bl[i], -1U);
-	}
 
 	xa_for_each(&ctx->io_bl_xa, index, bl) {
 		xa_erase(&ctx->io_bl_xa, bl->bgid);
@@ -498,12 +463,6 @@ int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
 
 	io_ring_submit_lock(ctx, issue_flags);
 
-	if (unlikely(p->bgid < BGID_ARRAY && !ctx->io_bl)) {
-		ret = io_init_bl_list(ctx);
-		if (ret)
-			goto err;
-	}
-
 	bl = io_buffer_get_list(ctx, p->bgid);
 	if (unlikely(!bl)) {
 		bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
@@ -516,14 +475,9 @@ int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
 		if (ret) {
 			/*
 			 * Doesn't need rcu free as it was never visible, but
-			 * let's keep it consistent throughout. Also can't
-			 * be a lower indexed array group, as adding one
-			 * where lookup failed cannot happen.
+			 * let's keep it consistent throughout.
 			 */
-			if (p->bgid >= BGID_ARRAY)
-				kfree_rcu(bl, rcu);
-			else
-				WARN_ON_ONCE(1);
+			kfree_rcu(bl, rcu);
 			goto err;
 		}
 	}
@@ -688,12 +642,6 @@ int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 	if (reg.ring_entries >= 65536)
 		return -EINVAL;
 
-	if (unlikely(reg.bgid < BGID_ARRAY && !ctx->io_bl)) {
-		int ret = io_init_bl_list(ctx);
-		if (ret)
-			return ret;
-	}
-
 	bl = io_buffer_get_list(ctx, reg.bgid);
 	if (bl) {
 		/* if mapped buffer ring OR classic exists, don't allow */
@@ -743,10 +691,8 @@ int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 		return -EINVAL;
 
 	__io_remove_buffers(ctx, bl, -1U);
-	if (bl->bgid >= BGID_ARRAY) {
-		xa_erase(&ctx->io_bl_xa, bl->bgid);
-		kfree_rcu(bl, rcu);
-	}
+	xa_erase(&ctx->io_bl_xa, bl->bgid);
+	kfree_rcu(bl, rcu);
 	return 0;
 }
 
@@ -780,7 +726,7 @@ void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid)
 {
 	struct io_buffer_list *bl;
 
-	bl = __io_buffer_get_list(ctx, smp_load_acquire(&ctx->io_bl), bgid);
+	bl = __io_buffer_get_list(ctx, bgid);
 
 	if (!bl || !bl->is_mmap)
 		return NULL;