1 files changed, 486 insertions, 294 deletions

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index 4a6401080c1f..796d131107dd 100644
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -7,6 +7,7 @@
 #include <linux/slab.h>
 #include <linux/namei.h>
 #include <linux/poll.h>
+#include <linux/vmalloc.h>
 #include <linux/io_uring.h>
 
 #include <uapi/linux/io_uring.h>
@@ -14,25 +15,66 @@
 #include "io_uring.h"
 #include "opdef.h"
 #include "kbuf.h"
+#include "memmap.h"
 
-#define IO_BUFFER_LIST_BUF_PER_PAGE (PAGE_SIZE / sizeof(struct io_uring_buf))
+/* BIDs are addressed by a 16-bit field in a CQE */
+#define MAX_BIDS_PER_BGID (1 << 16)
 
-#define BGID_ARRAY	64
+/* Mapped buffer ring, return io_uring_buf from head */
+#define io_ring_head_to_buf(br, head, mask)	&(br)->bufs[(head) & (mask)]
 
 struct io_provide_buf {
 	struct file			*file;
 	__u64				addr;
 	__u32				len;
 	__u32				bgid;
-	__u16				nbufs;
+	__u32				nbufs;
 	__u16				bid;
 };
 
+static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
+{
+	while (len) {
+		struct io_uring_buf *buf;
+		u32 buf_len, this_len;
+
+		buf = io_ring_head_to_buf(bl->buf_ring, bl->head, bl->mask);
+		buf_len = READ_ONCE(buf->len);
+		this_len = min_t(u32, len, buf_len);
+		buf_len -= this_len;
+		/* Stop looping for invalid buffer length of 0 */
+		if (buf_len || !this_len) {
+			WRITE_ONCE(buf->addr, READ_ONCE(buf->addr) + this_len);
+			WRITE_ONCE(buf->len, buf_len);
+			return false;
+		}
+		WRITE_ONCE(buf->len, 0);
+		bl->head++;
+		len -= this_len;
+	}
+	return true;
+}
+
+bool io_kbuf_commit(struct io_kiocb *req,
+		    struct io_buffer_list *bl, int len, int nr)
+{
+	if (unlikely(!(req->flags & REQ_F_BUFFERS_COMMIT)))
+		return true;
+
+	req->flags &= ~REQ_F_BUFFERS_COMMIT;
+
+	if (unlikely(len < 0))
+		return true;
+	if (bl->flags & IOBL_INC)
+		return io_kbuf_inc_commit(bl, len);
+	bl->head += nr;
+	return true;
+}
+
 static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
 							unsigned int bgid)
 {
-	if (ctx->io_bl && bgid < BGID_ARRAY)
-		return &ctx->io_bl[bgid];
+	lockdep_assert_held(&ctx->uring_lock);
 
 	return xa_load(&ctx->io_bl_xa, bgid);
 }
@@ -40,71 +82,41 @@ static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
 static int io_buffer_add_list(struct io_ring_ctx *ctx,
 			      struct io_buffer_list *bl, unsigned int bgid)
 {
+	/*
+	 * Store buffer group ID and finally mark the list as visible.
+	 * The normal lookup doesn't care about the visibility as we're
+	 * always under the ->uring_lock, but lookups from mmap do.
+	 */
 	bl->bgid = bgid;
-	if (bgid < BGID_ARRAY)
-		return 0;
-
+	guard(mutex)(&ctx->mmap_lock);
 	return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
 }
 
-void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
+void io_kbuf_drop_legacy(struct io_kiocb *req)
+{
+	if (WARN_ON_ONCE(!(req->flags & REQ_F_BUFFER_SELECTED)))
+		return;
+	req->flags &= ~REQ_F_BUFFER_SELECTED;
+	kfree(req->kbuf);
+	req->kbuf = NULL;
+}
+
+bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
 	struct io_buffer *buf;
 
-	/*
-	 * For legacy provided buffer mode, don't recycle if we already did
-	 * IO to this buffer. For ring-mapped provided buffer mode, we should
-	 * increment ring->head to explicitly monopolize the buffer to avoid
-	 * multiple use.
-	 */
-	if (req->flags & REQ_F_PARTIAL_IO)
-		return;
-
 	io_ring_submit_lock(ctx, issue_flags);
 
 	buf = req->kbuf;
 	bl = io_buffer_get_list(ctx, buf->bgid);
 	list_add(&buf->list, &bl->buf_list);
+	bl->nbufs++;
 	req->flags &= ~REQ_F_BUFFER_SELECTED;
-	req->buf_index = buf->bgid;
 
 	io_ring_submit_unlock(ctx, issue_flags);
-	return;
-}
-
-unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
-{
-	unsigned int cflags;
-
-	/*
-	 * We can add this buffer back to two lists:
-	 *
-	 * 1) The io_buffers_cache list. This one is protected by the
-	 *    ctx->uring_lock. If we already hold this lock, add back to this
-	 *    list as we can grab it from issue as well.
-	 * 2) The io_buffers_comp list. This one is protected by the
-	 *    ctx->completion_lock.
-	 *
-	 * We migrate buffers from the comp_list to the issue cache list
-	 * when we need one.
-	 */
-	if (req->flags & REQ_F_BUFFER_RING) {
-		/* no buffers to recycle for this case */
-		cflags = __io_put_kbuf_list(req, NULL);
-	} else if (issue_flags & IO_URING_F_UNLOCKED) {
-		struct io_ring_ctx *ctx = req->ctx;
-
-		spin_lock(&ctx->completion_lock);
-		cflags = __io_put_kbuf_list(req, &ctx->io_buffers_comp);
-		spin_unlock(&ctx->completion_lock);
-	} else {
-		lockdep_assert_held(&req->ctx->uring_lock);
-
-		cflags = __io_put_kbuf_list(req, &req->ctx->io_buffers_cache);
-	}
-	return cflags;
+	return true;
 }
 
 static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
@@ -115,8 +127,11 @@ static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
 
 		kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
 		list_del(&kbuf->list);
+		bl->nbufs--;
 		if (*len == 0 || *len > kbuf->len)
 			*len = kbuf->len;
+		if (list_empty(&bl->buf_list))
+			req->flags |= REQ_F_BL_EMPTY;
 		req->flags |= REQ_F_BUFFER_SELECTED;
 		req->kbuf = kbuf;
 		req->buf_index = kbuf->bid;
@@ -125,149 +140,324 @@ static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
 	return NULL;
 }
 
-static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
-					  struct io_buffer_list *bl,
-					  unsigned int issue_flags)
+static int io_provided_buffers_select(struct io_kiocb *req, size_t *len,
+				      struct io_buffer_list *bl,
+				      struct iovec *iov)
+{
+	void __user *buf;
+
+	buf = io_provided_buffer_select(req, len, bl);
+	if (unlikely(!buf))
+		return -ENOBUFS;
+
+	iov[0].iov_base = buf;
+	iov[0].iov_len = *len;
+	return 1;
+}
+
+static bool io_should_commit(struct io_kiocb *req, unsigned int issue_flags)
+{
+	/*
+	* If we came in unlocked, we have no choice but to consume the
+	* buffer here, otherwise nothing ensures that the buffer won't
+	* get used by others. This does mean it'll be pinned until the
+	* IO completes, coming in unlocked means we're being called from
+	* io-wq context and there may be further retries in async hybrid
+	* mode. For the locked case, the caller must call commit when
+	* the transfer completes (or if we get -EAGAIN and must poll of
+	* retry).
+	*/
+	if (issue_flags & IO_URING_F_UNLOCKED)
+		return true;
+
+	/* uring_cmd commits kbuf upfront, no need to auto-commit */
+	if (!io_file_can_poll(req) && req->opcode != IORING_OP_URING_CMD)
+		return true;
+	return false;
+}
+
+static struct io_br_sel io_ring_buffer_select(struct io_kiocb *req, size_t *len,
+					      struct io_buffer_list *bl,
+					      unsigned int issue_flags)
 {
 	struct io_uring_buf_ring *br = bl->buf_ring;
+	__u16 tail, head = bl->head;
+	struct io_br_sel sel = { };
 	struct io_uring_buf *buf;
-	__u16 head = bl->head;
+	u32 buf_len;
+
+	tail = smp_load_acquire(&br->tail);
+	if (unlikely(tail == head))
+		return sel;
+
+	if (head + 1 == tail)
+		req->flags |= REQ_F_BL_EMPTY;
+
+	buf = io_ring_head_to_buf(br, head, bl->mask);
+	buf_len = READ_ONCE(buf->len);
+	if (*len == 0 || *len > buf_len)
+		*len = buf_len;
+	req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
+	req->buf_index = READ_ONCE(buf->bid);
+	sel.buf_list = bl;
+	sel.addr = u64_to_user_ptr(READ_ONCE(buf->addr));
+
+	if (io_should_commit(req, issue_flags)) {
+		io_kbuf_commit(req, sel.buf_list, *len, 1);
+		sel.buf_list = NULL;
+	}
+	return sel;
+}
 
-	if (unlikely(smp_load_acquire(&br->tail) == head))
-		return NULL;
+struct io_br_sel io_buffer_select(struct io_kiocb *req, size_t *len,
+				  unsigned buf_group, unsigned int issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_br_sel sel = { };
+	struct io_buffer_list *bl;
 
-	head &= bl->mask;
-	if (head < IO_BUFFER_LIST_BUF_PER_PAGE) {
-		buf = &br->bufs[head];
-	} else {
-		int off = head & (IO_BUFFER_LIST_BUF_PER_PAGE - 1);
-		int index = head / IO_BUFFER_LIST_BUF_PER_PAGE;
-		buf = page_address(bl->buf_pages[index]);
-		buf += off;
+	io_ring_submit_lock(req->ctx, issue_flags);
+
+	bl = io_buffer_get_list(ctx, buf_group);
+	if (likely(bl)) {
+		if (bl->flags & IOBL_BUF_RING)
+			sel = io_ring_buffer_select(req, len, bl, issue_flags);
+		else
+			sel.addr = io_provided_buffer_select(req, len, bl);
+	}
+	io_ring_submit_unlock(req->ctx, issue_flags);
+	return sel;
+}
+
+/* cap it at a reasonable 256, will be one page even for 4K */
+#define PEEK_MAX_IMPORT		256
+
+static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
+				struct io_buffer_list *bl)
+{
+	struct io_uring_buf_ring *br = bl->buf_ring;
+	struct iovec *iov = arg->iovs;
+	int nr_iovs = arg->nr_iovs;
+	__u16 nr_avail, tail, head;
+	struct io_uring_buf *buf;
+
+	tail = smp_load_acquire(&br->tail);
+	head = bl->head;
+	nr_avail = min_t(__u16, tail - head, UIO_MAXIOV);
+	if (unlikely(!nr_avail))
+		return -ENOBUFS;
+
+	buf = io_ring_head_to_buf(br, head, bl->mask);
+	if (arg->max_len) {
+		u32 len = READ_ONCE(buf->len);
+		size_t needed;
+
+		if (unlikely(!len))
+			return -ENOBUFS;
+		needed = (arg->max_len + len - 1) / len;
+		needed = min_not_zero(needed, (size_t) PEEK_MAX_IMPORT);
+		if (nr_avail > needed)
+			nr_avail = needed;
+	}
+
+	/*
+	 * only alloc a bigger array if we know we have data to map, eg not
+	 * a speculative peek operation.
+	 */
+	if (arg->mode & KBUF_MODE_EXPAND && nr_avail > nr_iovs && arg->max_len) {
+		iov = kmalloc_array(nr_avail, sizeof(struct iovec), GFP_KERNEL);
+		if (unlikely(!iov))
+			return -ENOMEM;
+		if (arg->mode & KBUF_MODE_FREE)
+			kfree(arg->iovs);
+		arg->iovs = iov;
+		nr_iovs = nr_avail;
+	} else if (nr_avail < nr_iovs) {
+		nr_iovs = nr_avail;
 	}
-	if (*len == 0 || *len > buf->len)
-		*len = buf->len;
+
+	/* set it to max, if not set, so we can use it unconditionally */
+	if (!arg->max_len)
+		arg->max_len = INT_MAX;
+
+	req->buf_index = READ_ONCE(buf->bid);
+	do {
+		u32 len = READ_ONCE(buf->len);
+
+		/* truncate end piece, if needed, for non partial buffers */
+		if (len > arg->max_len) {
+			len = arg->max_len;
+			if (!(bl->flags & IOBL_INC)) {
+				arg->partial_map = 1;
+				if (iov != arg->iovs)
+					break;
+				WRITE_ONCE(buf->len, len);
+			}
+		}
+
+		iov->iov_base = u64_to_user_ptr(READ_ONCE(buf->addr));
+		iov->iov_len = len;
+		iov++;
+
+		arg->out_len += len;
+		arg->max_len -= len;
+		if (!arg->max_len)
+			break;
+
+		buf = io_ring_head_to_buf(br, ++head, bl->mask);
+	} while (--nr_iovs);
+
+	if (head == tail)
+		req->flags |= REQ_F_BL_EMPTY;
+
 	req->flags |= REQ_F_BUFFER_RING;
-	req->buf_list = bl;
-	req->buf_index = buf->bid;
+	return iov - arg->iovs;
+}
+
+int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
+		      struct io_br_sel *sel, unsigned int issue_flags)
+{
+	struct io_ring_ctx *ctx = req->ctx;
+	int ret = -ENOENT;
+
+	io_ring_submit_lock(ctx, issue_flags);
+	sel->buf_list = io_buffer_get_list(ctx, arg->buf_group);
+	if (unlikely(!sel->buf_list))
+		goto out_unlock;
 
-	if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) {
+	if (sel->buf_list->flags & IOBL_BUF_RING) {
+		ret = io_ring_buffers_peek(req, arg, sel->buf_list);
 		/*
-		 * If we came in unlocked, we have no choice but to consume the
-		 * buffer here, otherwise nothing ensures that the buffer won't
-		 * get used by others. This does mean it'll be pinned until the
-		 * IO completes, coming in unlocked means we're being called from
-		 * io-wq context and there may be further retries in async hybrid
-		 * mode. For the locked case, the caller must call commit when
-		 * the transfer completes (or if we get -EAGAIN and must poll of
-		 * retry).
+		 * Don't recycle these buffers if we need to go through poll.
+		 * Nobody else can use them anyway, and holding on to provided
+		 * buffers for a send/write operation would happen on the app
+		 * side anyway with normal buffers. Besides, we already
+		 * committed them, they cannot be put back in the queue.
 		 */
-		req->buf_list = NULL;
-		bl->head++;
+		if (ret > 0) {
+			req->flags |= REQ_F_BUFFERS_COMMIT | REQ_F_BL_NO_RECYCLE;
+			io_kbuf_commit(req, sel->buf_list, arg->out_len, ret);
+		}
+	} else {
+		ret = io_provided_buffers_select(req, &arg->out_len, sel->buf_list, arg->iovs);
+	}
+out_unlock:
+	if (issue_flags & IO_URING_F_UNLOCKED) {
+		sel->buf_list = NULL;
+		mutex_unlock(&ctx->uring_lock);
 	}
-	return u64_to_user_ptr(buf->addr);
+	return ret;
 }
 
-void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
-			      unsigned int issue_flags)
+int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
+		    struct io_br_sel *sel)
 {
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
-	void __user *ret = NULL;
+	int ret;
 
-	io_ring_submit_lock(req->ctx, issue_flags);
+	lockdep_assert_held(&ctx->uring_lock);
 
-	bl = io_buffer_get_list(ctx, req->buf_index);
-	if (likely(bl)) {
-		if (bl->buf_nr_pages)
-			ret = io_ring_buffer_select(req, len, bl, issue_flags);
-		else
-			ret = io_provided_buffer_select(req, len, bl);
+	bl = io_buffer_get_list(ctx, arg->buf_group);
+	if (unlikely(!bl))
+		return -ENOENT;
+
+	if (bl->flags & IOBL_BUF_RING) {
+		ret = io_ring_buffers_peek(req, arg, bl);
+		if (ret > 0)
+			req->flags |= REQ_F_BUFFERS_COMMIT;
+		sel->buf_list = bl;
+		return ret;
 	}
-	io_ring_submit_unlock(req->ctx, issue_flags);
+
+	/* don't support multiple buffer selections for legacy */
+	sel->buf_list = NULL;
+	return io_provided_buffers_select(req, &arg->max_len, bl, arg->iovs);
+}
+
+static inline bool __io_put_kbuf_ring(struct io_kiocb *req,
+				      struct io_buffer_list *bl, int len, int nr)
+{
+	bool ret = true;
+
+	if (bl)
+		ret = io_kbuf_commit(req, bl, len, nr);
+
+	req->flags &= ~REQ_F_BUFFER_RING;
 	return ret;
 }
 
-static __cold int io_init_bl_list(struct io_ring_ctx *ctx)
+unsigned int __io_put_kbufs(struct io_kiocb *req, struct io_buffer_list *bl,
+			    int len, int nbufs)
 {
-	int i;
+	unsigned int ret;
 
-	ctx->io_bl = kcalloc(BGID_ARRAY, sizeof(struct io_buffer_list),
-				GFP_KERNEL);
-	if (!ctx->io_bl)
-		return -ENOMEM;
+	ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);
 
-	for (i = 0; i < BGID_ARRAY; i++) {
-		INIT_LIST_HEAD(&ctx->io_bl[i].buf_list);
-		ctx->io_bl[i].bgid = i;
+	if (unlikely(!(req->flags & REQ_F_BUFFER_RING))) {
+		io_kbuf_drop_legacy(req);
+		return ret;
 	}
 
-	return 0;
+	if (!__io_put_kbuf_ring(req, bl, len, nbufs))
+		ret |= IORING_CQE_F_BUF_MORE;
+	return ret;
 }
 
-static int __io_remove_buffers(struct io_ring_ctx *ctx,
-			       struct io_buffer_list *bl, unsigned nbufs)
+static int io_remove_buffers_legacy(struct io_ring_ctx *ctx,
+				    struct io_buffer_list *bl,
+				    unsigned long nbufs)
 {
-	unsigned i = 0;
-
-	/* shouldn't happen */
-	if (!nbufs)
-		return 0;
-
-	if (bl->buf_nr_pages) {
-		int j;
-
-		i = bl->buf_ring->tail - bl->head;
-		for (j = 0; j < bl->buf_nr_pages; j++)
-			unpin_user_page(bl->buf_pages[j]);
-		kvfree(bl->buf_pages);
-		bl->buf_pages = NULL;
-		bl->buf_nr_pages = 0;
-		/* make sure it's seen as empty */
-		INIT_LIST_HEAD(&bl->buf_list);
-		return i;
-	}
+	unsigned long i = 0;
+	struct io_buffer *nxt;
 
-	/* the head kbuf is the list itself */
-	while (!list_empty(&bl->buf_list)) {
-		struct io_buffer *nxt;
+	/* protects io_buffers_cache */
+	lockdep_assert_held(&ctx->uring_lock);
+	WARN_ON_ONCE(bl->flags & IOBL_BUF_RING);
 
+	for (i = 0; i < nbufs && !list_empty(&bl->buf_list); i++) {
 		nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
 		list_del(&nxt->list);
-		if (++i == nbufs)
-			return i;
+		bl->nbufs--;
+		kfree(nxt);
 		cond_resched();
 	}
-	i++;
-
 	return i;
 }
 
+static void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+	if (bl->flags & IOBL_BUF_RING)
+		io_free_region(ctx->user, &bl->region);
+	else
+		io_remove_buffers_legacy(ctx, bl, -1U);
+
+	kfree(bl);
+}
+
 void io_destroy_buffers(struct io_ring_ctx *ctx)
 {
 	struct io_buffer_list *bl;
-	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);
-	}
+	while (1) {
+		unsigned long index = 0;
 
-	xa_for_each(&ctx->io_bl_xa, index, bl) {
-		xa_erase(&ctx->io_bl_xa, bl->bgid);
-		__io_remove_buffers(ctx, bl, -1U);
-		kfree(bl);
+		scoped_guard(mutex, &ctx->mmap_lock) {
+			bl = xa_find(&ctx->io_bl_xa, &index, ULONG_MAX, XA_PRESENT);
+			if (bl)
+				xa_erase(&ctx->io_bl_xa, bl->bgid);
+		}
+		if (!bl)
+			break;
+		io_put_bl(ctx, bl);
 	}
+}
 
-	while (!list_empty(&ctx->io_buffers_pages)) {
-		struct page *page;
-
-		page = list_first_entry(&ctx->io_buffers_pages, struct page, lru);
-		list_del_init(&page->lru);
-		__free_page(page);
-	}
+static void io_destroy_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
+{
+	scoped_guard(mutex, &ctx->mmap_lock)
+		WARN_ON_ONCE(xa_erase(&ctx->io_bl_xa, bl->bgid) != bl);
+	io_put_bl(ctx, bl);
 }
 
 int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
@@ -280,7 +470,7 @@ int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		return -EINVAL;
 
 	tmp = READ_ONCE(sqe->fd);
-	if (!tmp || tmp > USHRT_MAX)
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
 		return -EINVAL;
 
 	memset(p, 0, sizeof(*p));
@@ -289,30 +479,6 @@ int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	return 0;
 }
 
-int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
-{
-	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
-	struct io_ring_ctx *ctx = req->ctx;
-	struct io_buffer_list *bl;
-	int ret = 0;
-
-	io_ring_submit_lock(ctx, issue_flags);
-
-	ret = -ENOENT;
-	bl = io_buffer_get_list(ctx, p->bgid);
-	if (bl) {
-		ret = -EINVAL;
-		/* can't use provide/remove buffers command on mapped buffers */
-		if (!bl->buf_nr_pages)
-			ret = __io_remove_buffers(ctx, bl, p->nbufs);
-	}
-	io_ring_submit_unlock(ctx, issue_flags);
-	if (ret < 0)
-		req_set_fail(req);
-	io_req_set_res(req, ret, 0);
-	return IOU_OK;
-}
-
 int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	unsigned long size, tmp_check;
@@ -323,19 +489,19 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 		return -EINVAL;
 
 	tmp = READ_ONCE(sqe->fd);
-	if (!tmp || tmp > USHRT_MAX)
+	if (!tmp || tmp > MAX_BIDS_PER_BGID)
 		return -E2BIG;
 	p->nbufs = tmp;
 	p->addr = READ_ONCE(sqe->addr);
 	p->len = READ_ONCE(sqe->len);
+	if (!p->len)
+		return -EINVAL;
 
 	if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
 				&size))
 		return -EOVERFLOW;
 	if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
 		return -EOVERFLOW;
-
-	size = (unsigned long)p->len * p->nbufs;
 	if (!access_ok(u64_to_user_ptr(p->addr), size))
 		return -EFAULT;
 
@@ -343,69 +509,35 @@ int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 	tmp = READ_ONCE(sqe->off);
 	if (tmp > USHRT_MAX)
 		return -E2BIG;
-	if (tmp + p->nbufs >= USHRT_MAX)
+	if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
 		return -EINVAL;
 	p->bid = tmp;
 	return 0;
 }
 
-static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
-{
-	struct io_buffer *buf;
-	struct page *page;
-	int bufs_in_page;
-
-	/*
-	 * Completions that don't happen inline (eg not under uring_lock) will
-	 * add to ->io_buffers_comp. If we don't have any free buffers, check
-	 * the completion list and splice those entries first.
-	 */
-	if (!list_empty_careful(&ctx->io_buffers_comp)) {
-		spin_lock(&ctx->completion_lock);
-		if (!list_empty(&ctx->io_buffers_comp)) {
-			list_splice_init(&ctx->io_buffers_comp,
-						&ctx->io_buffers_cache);
-			spin_unlock(&ctx->completion_lock);
-			return 0;
-		}
-		spin_unlock(&ctx->completion_lock);
-	}
-
-	/*
-	 * No free buffers and no completion entries either. Allocate a new
-	 * page worth of buffer entries and add those to our freelist.
-	 */
-	page = alloc_page(GFP_KERNEL_ACCOUNT);
-	if (!page)
-		return -ENOMEM;
-
-	list_add(&page->lru, &ctx->io_buffers_pages);
-
-	buf = page_address(page);
-	bufs_in_page = PAGE_SIZE / sizeof(*buf);
-	while (bufs_in_page) {
-		list_add_tail(&buf->list, &ctx->io_buffers_cache);
-		buf++;
-		bufs_in_page--;
-	}
-
-	return 0;
-}
-
 static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
 			  struct io_buffer_list *bl)
 {
 	struct io_buffer *buf;
 	u64 addr = pbuf->addr;
-	int i, bid = pbuf->bid;
+	int ret = -ENOMEM, i, bid = pbuf->bid;
 
 	for (i = 0; i < pbuf->nbufs; i++) {
-		if (list_empty(&ctx->io_buffers_cache) &&
-		    io_refill_buffer_cache(ctx))
+		/*
+		 * Nonsensical to have more than sizeof(bid) buffers in a
+		 * buffer list, as the application then has no way of knowing
+		 * which duplicate bid refers to what buffer.
+		 */
+		if (bl->nbufs == USHRT_MAX) {
+			ret = -EOVERFLOW;
 			break;
-		buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
-					list);
-		list_move_tail(&buf->list, &bl->buf_list);
+		}
+		buf = kmalloc(sizeof(*buf), GFP_KERNEL_ACCOUNT);
+		if (!buf)
+			break;
+
+		list_add_tail(&buf->list, &bl->buf_list);
+		bl->nbufs++;
 		buf->addr = addr;
 		buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
 		buf->bid = bid;
@@ -415,111 +547,134 @@ static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
 		cond_resched();
 	}
 
-	return i ? 0 : -ENOMEM;
+	return i ? 0 : ret;
 }
 
-int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
+static int __io_manage_buffers_legacy(struct io_kiocb *req,
+					struct io_buffer_list *bl)
 {
 	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
-	struct io_ring_ctx *ctx = req->ctx;
-	struct io_buffer_list *bl;
-	int ret = 0;
-
-	io_ring_submit_lock(ctx, issue_flags);
+	int ret;
 
-	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)) {
+	if (!bl) {
+		if (req->opcode != IORING_OP_PROVIDE_BUFFERS)
+			return -ENOENT;
 		bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
-		if (!bl) {
-			ret = -ENOMEM;
-			goto err;
-		}
+		if (!bl)
+			return -ENOMEM;
+
 		INIT_LIST_HEAD(&bl->buf_list);
-		ret = io_buffer_add_list(ctx, bl, p->bgid);
+		ret = io_buffer_add_list(req->ctx, bl, p->bgid);
 		if (ret) {
 			kfree(bl);
-			goto err;
+			return ret;
 		}
 	}
-	/* can't add buffers via this command for a mapped buffer ring */
-	if (bl->buf_nr_pages) {
-		ret = -EINVAL;
-		goto err;
-	}
+	/* can't use provide/remove buffers command on mapped buffers */
+	if (bl->flags & IOBL_BUF_RING)
+		return -EINVAL;
+	if (req->opcode == IORING_OP_PROVIDE_BUFFERS)
+		return io_add_buffers(req->ctx, p, bl);
+	return io_remove_buffers_legacy(req->ctx, bl, p->nbufs);
+}
+
+int io_manage_buffers_legacy(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_buffer_list *bl;
+	int ret;
 
-	ret = io_add_buffers(ctx, p, bl);
-err:
+	io_ring_submit_lock(ctx, issue_flags);
+	bl = io_buffer_get_list(ctx, p->bgid);
+	ret = __io_manage_buffers_legacy(req, bl);
 	io_ring_submit_unlock(ctx, issue_flags);
 
 	if (ret < 0)
 		req_set_fail(req);
 	io_req_set_res(req, ret, 0);
-	return IOU_OK;
+	return IOU_COMPLETE;
 }
 
 int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 {
-	struct io_uring_buf_ring *br;
 	struct io_uring_buf_reg reg;
-	struct io_buffer_list *bl, *free_bl = NULL;
-	struct page **pages;
-	int nr_pages;
+	struct io_buffer_list *bl;
+	struct io_uring_region_desc rd;
+	struct io_uring_buf_ring *br;
+	unsigned long mmap_offset;
+	unsigned long ring_size;
+	int ret;
+
+	lockdep_assert_held(&ctx->uring_lock);
 
 	if (copy_from_user(&reg, arg, sizeof(reg)))
 		return -EFAULT;
-
-	if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
+	if (!mem_is_zero(reg.resv, sizeof(reg.resv)))
 		return -EINVAL;
-	if (!reg.ring_addr)
-		return -EFAULT;
-	if (reg.ring_addr & ~PAGE_MASK)
+	if (reg.flags & ~(IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC))
 		return -EINVAL;
 	if (!is_power_of_2(reg.ring_entries))
 		return -EINVAL;
-
 	/* cannot disambiguate full vs empty due to head/tail size */
 	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 */
-		if (bl->buf_nr_pages || !list_empty(&bl->buf_list))
+		if (bl->flags & IOBL_BUF_RING || !list_empty(&bl->buf_list))
 			return -EEXIST;
-	} else {
-		free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
-		if (!bl)
-			return -ENOMEM;
+		io_destroy_bl(ctx, bl);
+	}
+
+	bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
+	if (!bl)
+		return -ENOMEM;
+
+	mmap_offset = (unsigned long)reg.bgid << IORING_OFF_PBUF_SHIFT;
+	ring_size = flex_array_size(br, bufs, reg.ring_entries);
+
+	memset(&rd, 0, sizeof(rd));
+	rd.size = PAGE_ALIGN(ring_size);
+	if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
+		rd.user_addr = reg.ring_addr;
+		rd.flags |= IORING_MEM_REGION_TYPE_USER;
 	}
+	ret = io_create_region(ctx, &bl->region, &rd, mmap_offset);
+	if (ret)
+		goto fail;
+	br = io_region_get_ptr(&bl->region);
 
-	pages = io_pin_pages(reg.ring_addr,
-			     struct_size(br, bufs, reg.ring_entries),
-			     &nr_pages);
-	if (IS_ERR(pages)) {
-		kfree(free_bl);
-		return PTR_ERR(pages);
+#ifdef SHM_COLOUR
+	/*
+	 * On platforms that have specific aliasing requirements, SHM_COLOUR
+	 * is set and we must guarantee that the kernel and user side align
+	 * nicely. We cannot do that if IOU_PBUF_RING_MMAP isn't set and
+	 * the application mmap's the provided ring buffer. Fail the request
+	 * if we, by chance, don't end up with aligned addresses. The app
+	 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
+	 * this transparently.
+	 */
+	if (!(reg.flags & IOU_PBUF_RING_MMAP) &&
+	    ((reg.ring_addr | (unsigned long)br) & (SHM_COLOUR - 1))) {
+		ret = -EINVAL;
+		goto fail;
 	}
+#endif
 
-	br = page_address(pages[0]);
-	bl->buf_pages = pages;
-	bl->buf_nr_pages = nr_pages;
 	bl->nr_entries = reg.ring_entries;
-	bl->buf_ring = br;
 	bl->mask = reg.ring_entries - 1;
+	bl->flags |= IOBL_BUF_RING;
+	bl->buf_ring = br;
+	if (reg.flags & IOU_PBUF_RING_INC)
+		bl->flags |= IOBL_INC;
 	io_buffer_add_list(ctx, bl, reg.bgid);
 	return 0;
+fail:
+	io_free_region(ctx->user, &bl->region);
+	kfree(bl);
+	return ret;
 }
 
 int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
@@ -527,21 +682,58 @@ int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
 	struct io_uring_buf_reg reg;
 	struct io_buffer_list *bl;
 
+	lockdep_assert_held(&ctx->uring_lock);
+
 	if (copy_from_user(&reg, arg, sizeof(reg)))
 		return -EFAULT;
-	if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
+	if (!mem_is_zero(reg.resv, sizeof(reg.resv)) || reg.flags)
 		return -EINVAL;
 
 	bl = io_buffer_get_list(ctx, reg.bgid);
 	if (!bl)
 		return -ENOENT;
-	if (!bl->buf_nr_pages)
+	if (!(bl->flags & IOBL_BUF_RING))
 		return -EINVAL;
 
-	__io_remove_buffers(ctx, bl, -1U);
-	if (bl->bgid >= BGID_ARRAY) {
+	scoped_guard(mutex, &ctx->mmap_lock)
 		xa_erase(&ctx->io_bl_xa, bl->bgid);
-		kfree(bl);
-	}
+
+	io_put_bl(ctx, bl);
 	return 0;
 }
+
+int io_register_pbuf_status(struct io_ring_ctx *ctx, void __user *arg)
+{
+	struct io_uring_buf_status buf_status;
+	struct io_buffer_list *bl;
+
+	if (copy_from_user(&buf_status, arg, sizeof(buf_status)))
+		return -EFAULT;
+	if (!mem_is_zero(buf_status.resv, sizeof(buf_status.resv)))
+		return -EINVAL;
+
+	bl = io_buffer_get_list(ctx, buf_status.buf_group);
+	if (!bl)
+		return -ENOENT;
+	if (!(bl->flags & IOBL_BUF_RING))
+		return -EINVAL;
+
+	buf_status.head = bl->head;
+	if (copy_to_user(arg, &buf_status, sizeof(buf_status)))
+		return -EFAULT;
+
+	return 0;
+}
+
+struct io_mapped_region *io_pbuf_get_region(struct io_ring_ctx *ctx,
+					    unsigned int bgid)
+{
+	struct io_buffer_list *bl;
+
+	lockdep_assert_held(&ctx->mmap_lock);
+
+	bl = xa_load(&ctx->io_bl_xa, bgid);
+	if (!bl || !(bl->flags & IOBL_BUF_RING))
+		return NULL;
+	return &bl->region;
+}