[PATCH 1/4] io_uring/kbuf: get rid of lower BGID lists - Linux-stable-mirror

3 Apr 2024

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
---
 include/linux/io_uring_types.h |  1 -
 io_uring/io_uring.c            |  2 -
 io_uring/kbuf.c                | 70 ++++------------------------------
 3 files changed, 8 insertions(+), 65 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index e24893625085..05df0e399d7c 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -294,7 +294,6 @@ struct io_ring_ctx {
struct io_submit_state	submit_state;
-		struct io_buffer_list	*io_bl;
    	struct xarray		io_bl_xa;
struct io_hash_table	cancel_table_locked;
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index d1defb99b89e..bc730f59265f 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -351,7 +351,6 @@ 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;
@@ -2932,7 +2931,6 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
    io_napi_free(ctx);
    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 693c26da4ee1..8bf0121f00af 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));
 }
@@ -208,24 +198,6 @@ 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
  */
@@ -300,13 +272,6 @@ 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);
@@ -489,12 +454,6 @@ 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);
@@ -507,14 +466,9 @@ 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;
    	}
    }
@@ -679,12 +633,6 @@ 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 */
@@ -734,10 +682,8 @@ 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;
 }
@@ -771,7 +717,7 @@ 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;
-- 
2.43.0



    