Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / io_uring / kbuf.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#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>

#include "io_uring.h"
#include "opdef.h"
#include "kbuf.h"
#include "memmap.h"

/* BIDs are addressed by a 16-bit field in a CQE */
#define MAX_BIDS_PER_BGID (1 << 16)

struct kmem_cache *io_buf_cachep;

struct io_provide_buf {
        struct file                     *file;
        __u64                           addr;
        __u32                           len;
        __u32                           bgid;
        __u32                           nbufs;
        __u16                           bid;
};

static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
                                                        unsigned int bgid)
{
        lockdep_assert_held(&ctx->uring_lock);

        return xa_load(&ctx->io_bl_xa, bgid);
}

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 the RCU lookup from mmap does.
         */
        bl->bgid = bgid;
        atomic_set(&bl->refs, 1);
        return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
}

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;

        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);
        req->flags &= ~REQ_F_BUFFER_SELECTED;
        req->buf_index = buf->bgid;

        io_ring_submit_unlock(ctx, issue_flags);
        return true;
}

void __io_put_kbuf(struct io_kiocb *req, int len, unsigned issue_flags)
{
        /*
         * 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 (issue_flags & IO_URING_F_UNLOCKED) {
                struct io_ring_ctx *ctx = req->ctx;

                spin_lock(&ctx->completion_lock);
                __io_put_kbuf_list(req, len, &ctx->io_buffers_comp);
                spin_unlock(&ctx->completion_lock);
        } else {
                lockdep_assert_held(&req->ctx->uring_lock);

                __io_put_kbuf_list(req, len, &req->ctx->io_buffers_cache);
        }
}

static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
                                              struct io_buffer_list *bl)
{
        if (!list_empty(&bl->buf_list)) {
                struct io_buffer *kbuf;

                kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
                list_del(&kbuf->list);
                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;
                return u64_to_user_ptr(kbuf->addr);
        }
        return NULL;
}

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 void __user *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_uring_buf *buf;

        tail = smp_load_acquire(&br->tail);
        if (unlikely(tail == head))
                return NULL;

        if (head + 1 == tail)
                req->flags |= REQ_F_BL_EMPTY;

        buf = io_ring_head_to_buf(br, head, bl->mask);
        if (*len == 0 || *len > buf->len)
                *len = buf->len;
        req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
        req->buf_list = bl;
        req->buf_index = buf->bid;

        if (issue_flags & IO_URING_F_UNLOCKED || !io_file_can_poll(req)) {
                /*
                 * 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).
                 */
                io_kbuf_commit(req, bl, *len, 1);
                req->buf_list = NULL;
        }
        return u64_to_user_ptr(buf->addr);
}

void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
                              unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        void __user *ret = NULL;

        io_ring_submit_lock(req->ctx, issue_flags);

        bl = io_buffer_get_list(ctx, req->buf_index);
        if (likely(bl)) {
                if (bl->flags & IOBL_BUF_RING)
                        ret = io_ring_buffer_select(req, len, bl, issue_flags);
                else
                        ret = io_provided_buffer_select(req, len, bl);
        }
        io_ring_submit_unlock(req->ctx, issue_flags);
        return ret;
}

/* 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);

                if (unlikely(!len))
                        return -ENOBUFS;
                /*
                 * Limit incremental buffers to 1 segment. No point trying
                 * to peek ahead and map more than we need, when the buffers
                 * themselves should be large when setup with
                 * IOU_PBUF_RING_INC.
                 */
                if (bl->flags & IOBL_INC) {
                        nr_avail = 1;
                } else {
                        size_t needed;

                        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;
        }

        /* 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 = buf->bid;
        do {
                u32 len = 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))
                                buf->len = len;
                }

                iov->iov_base = u64_to_user_ptr(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;
        return iov - arg->iovs;
}

int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
                      unsigned int issue_flags)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        int ret = -ENOENT;

        io_ring_submit_lock(ctx, issue_flags);
        bl = io_buffer_get_list(ctx, req->buf_index);
        if (unlikely(!bl))
                goto out_unlock;

        if (bl->flags & IOBL_BUF_RING) {
                ret = io_ring_buffers_peek(req, arg, bl);
                /*
                 * 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.
                 */
                if (ret > 0) {
                        req->flags |= REQ_F_BUFFERS_COMMIT | REQ_F_BL_NO_RECYCLE;
                        io_kbuf_commit(req, bl, arg->out_len, ret);
                }
        } else {
                ret = io_provided_buffers_select(req, &arg->out_len, bl, arg->iovs);
        }
out_unlock:
        io_ring_submit_unlock(ctx, issue_flags);
        return ret;
}

int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg)
{
        struct io_ring_ctx *ctx = req->ctx;
        struct io_buffer_list *bl;
        int ret;

        lockdep_assert_held(&ctx->uring_lock);

        bl = io_buffer_get_list(ctx, req->buf_index);
        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;
                return ret;
        }

        /* don't support multiple buffer selections for legacy */
        return io_provided_buffers_select(req, &arg->max_len, bl, arg->iovs);
}

static int __io_remove_buffers(struct io_ring_ctx *ctx,
                               struct io_buffer_list *bl, unsigned nbufs)
{
        unsigned i = 0;

        /* shouldn't happen */
        if (!nbufs)
                return 0;

        if (bl->flags & IOBL_BUF_RING) {
                i = bl->buf_ring->tail - bl->head;
                if (bl->buf_nr_pages) {
                        int j;

                        if (!(bl->flags & IOBL_MMAP)) {
                                for (j = 0; j < bl->buf_nr_pages; j++)
                                        unpin_user_page(bl->buf_pages[j]);
                        }
                        io_pages_unmap(bl->buf_ring, &bl->buf_pages,
                                        &bl->buf_nr_pages, bl->flags & IOBL_MMAP);
                        bl->flags &= ~IOBL_MMAP;
                }
                /* make sure it's seen as empty */
                INIT_LIST_HEAD(&bl->buf_list);
                bl->flags &= ~IOBL_BUF_RING;
                return i;
        }

        /* protects io_buffers_cache */
        lockdep_assert_held(&ctx->uring_lock);

        while (!list_empty(&bl->buf_list)) {
                struct io_buffer *nxt;

                nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
                list_move(&nxt->list, &ctx->io_buffers_cache);
                if (++i == nbufs)
                        return i;
                cond_resched();
        }

        return i;
}

void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
{
        if (atomic_dec_and_test(&bl->refs)) {
                __io_remove_buffers(ctx, bl, -1U);
                kfree_rcu(bl, rcu);
        }
}

void io_destroy_buffers(struct io_ring_ctx *ctx)
{
        struct io_buffer_list *bl;
        struct list_head *item, *tmp;
        struct io_buffer *buf;
        unsigned long index;

        xa_for_each(&ctx->io_bl_xa, index, bl) {
                xa_erase(&ctx->io_bl_xa, bl->bgid);
                io_put_bl(ctx, bl);
        }

        /*
         * Move deferred locked entries to cache before pruning
         */
        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);

        list_for_each_safe(item, tmp, &ctx->io_buffers_cache) {
                buf = list_entry(item, struct io_buffer, list);
                kmem_cache_free(io_buf_cachep, buf);
        }
}

int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
        struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
        u64 tmp;

        if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
            sqe->splice_fd_in)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        if (!tmp || tmp > MAX_BIDS_PER_BGID)
                return -EINVAL;

        memset(p, 0, sizeof(*p));
        p->nbufs = tmp;
        p->bgid = READ_ONCE(sqe->buf_group);
        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->flags & IOBL_BUF_RING))
                        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;
        struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
        u64 tmp;

        if (sqe->rw_flags || sqe->splice_fd_in)
                return -EINVAL;

        tmp = READ_ONCE(sqe->fd);
        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 (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;

        p->bgid = READ_ONCE(sqe->buf_group);
        tmp = READ_ONCE(sqe->off);
        if (tmp > USHRT_MAX)
                return -E2BIG;
        if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
                return -EINVAL;
        p->bid = tmp;
        return 0;
}

#define IO_BUFFER_ALLOC_BATCH 64

static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
{
        struct io_buffer *bufs[IO_BUFFER_ALLOC_BATCH];
        int allocated;

        /*
         * 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
         * batch of buffer entries and add those to our freelist.
         */

        allocated = kmem_cache_alloc_bulk(io_buf_cachep, GFP_KERNEL_ACCOUNT,
                                          ARRAY_SIZE(bufs), (void **) bufs);
        if (unlikely(!allocated)) {
                /*
                 * Bulk alloc is all-or-nothing. If we fail to get a batch,
                 * retry single alloc to be on the safe side.
                 */
                bufs[0] = kmem_cache_alloc(io_buf_cachep, GFP_KERNEL);
                if (!bufs[0])
                        return -ENOMEM;
                allocated = 1;
        }

        while (allocated)
                list_add_tail(&bufs[--allocated]->list, &ctx->io_buffers_cache);

        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;

        for (i = 0; i < pbuf->nbufs; i++) {
                if (list_empty(&ctx->io_buffers_cache) &&
                    io_refill_buffer_cache(ctx))
                        break;
                buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
                                        list);
                list_move_tail(&buf->list, &bl->buf_list);
                buf->addr = addr;
                buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
                buf->bid = bid;
                buf->bgid = pbuf->bgid;
                addr += pbuf->len;
                bid++;
                cond_resched();
        }

        return i ? 0 : -ENOMEM;
}

int io_provide_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);

        bl = io_buffer_get_list(ctx, p->bgid);
        if (unlikely(!bl)) {
                bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
                if (!bl) {
                        ret = -ENOMEM;
                        goto err;
                }
                INIT_LIST_HEAD(&bl->buf_list);
                ret = io_buffer_add_list(ctx, bl, p->bgid);
                if (ret) {
                        /*
                         * Doesn't need rcu free as it was never visible, but
                         * let's keep it consistent throughout.
                         */
                        kfree_rcu(bl, rcu);
                        goto err;
                }
        }
        /* can't add buffers via this command for a mapped buffer ring */
        if (bl->flags & IOBL_BUF_RING) {
                ret = -EINVAL;
                goto err;
        }

        ret = io_add_buffers(ctx, p, bl);
err:
        io_ring_submit_unlock(ctx, issue_flags);

        if (ret < 0)
                req_set_fail(req);
        io_req_set_res(req, ret, 0);
        return IOU_OK;
}

static int io_pin_pbuf_ring(struct io_uring_buf_reg *reg,
                            struct io_buffer_list *bl)
{
        struct io_uring_buf_ring *br = NULL;
        struct page **pages;
        int nr_pages, ret;

        pages = io_pin_pages(reg->ring_addr,
                             flex_array_size(br, bufs, reg->ring_entries),
                             &nr_pages);
        if (IS_ERR(pages))
                return PTR_ERR(pages);

        br = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
        if (!br) {
                ret = -ENOMEM;
                goto error_unpin;
        }

#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->ring_addr | (unsigned long) br) & (SHM_COLOUR - 1)) {
                ret = -EINVAL;
                goto error_unpin;
        }
#endif
        bl->buf_pages = pages;
        bl->buf_nr_pages = nr_pages;
        bl->buf_ring = br;
        bl->flags |= IOBL_BUF_RING;
        bl->flags &= ~IOBL_MMAP;
        return 0;
error_unpin:
        unpin_user_pages(pages, nr_pages);
        kvfree(pages);
        vunmap(br);
        return ret;
}

static int io_alloc_pbuf_ring(struct io_ring_ctx *ctx,
                              struct io_uring_buf_reg *reg,
                              struct io_buffer_list *bl)
{
        size_t ring_size;

        ring_size = reg->ring_entries * sizeof(struct io_uring_buf_ring);

        bl->buf_ring = io_pages_map(&bl->buf_pages, &bl->buf_nr_pages, ring_size);
        if (IS_ERR(bl->buf_ring)) {
                bl->buf_ring = NULL;
                return -ENOMEM;
        }

        bl->flags |= (IOBL_BUF_RING | IOBL_MMAP);
        return 0;
}

int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
{
        struct io_uring_buf_reg reg;
        struct io_buffer_list *bl, *free_bl = NULL;
        int ret;

        lockdep_assert_held(&ctx->uring_lock);

        if (copy_from_user(&reg, arg, sizeof(reg)))
                return -EFAULT;

        if (reg.resv[0] || reg.resv[1] || reg.resv[2])
                return -EINVAL;
        if (reg.flags & ~(IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC))
                return -EINVAL;
        if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
                if (!reg.ring_addr)
                        return -EFAULT;
                if (reg.ring_addr & ~PAGE_MASK)
                        return -EINVAL;
        } else {
                if (reg.ring_addr)
                        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;

        bl = io_buffer_get_list(ctx, reg.bgid);
        if (bl) {
                /* if mapped buffer ring OR classic exists, don't allow */
                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;
        }

        if (!(reg.flags & IOU_PBUF_RING_MMAP))
                ret = io_pin_pbuf_ring(&reg, bl);
        else
                ret = io_alloc_pbuf_ring(ctx, &reg, bl);

        if (!ret) {
                bl->nr_entries = reg.ring_entries;
                bl->mask = reg.ring_entries - 1;
                if (reg.flags & IOU_PBUF_RING_INC)
                        bl->flags |= IOBL_INC;

                io_buffer_add_list(ctx, bl, reg.bgid);
                return 0;
        }

        kfree_rcu(free_bl, rcu);
        return ret;
}

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.resv[0] || reg.resv[1] || reg.resv[2])
                return -EINVAL;
        if (reg.flags)
                return -EINVAL;

        bl = io_buffer_get_list(ctx, reg.bgid);
        if (!bl)
                return -ENOENT;
        if (!(bl->flags & IOBL_BUF_RING))
                return -EINVAL;

        xa_erase(&ctx->io_bl_xa, bl->bgid);
        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;
        int i;

        if (copy_from_user(&buf_status, arg, sizeof(buf_status)))
                return -EFAULT;

        for (i = 0; i < ARRAY_SIZE(buf_status.resv); i++)
                if (buf_status.resv[i])
                        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_buffer_list *io_pbuf_get_bl(struct io_ring_ctx *ctx,
                                      unsigned long bgid)
{
        struct io_buffer_list *bl;
        bool ret;

        /*
         * We have to be a bit careful here - we're inside mmap and cannot grab
         * the uring_lock. This means the buffer_list could be simultaneously
         * going away, if someone is trying to be sneaky. Look it up under rcu
         * so we know it's not going away, and attempt to grab a reference to
         * it. If the ref is already zero, then fail the mapping. If successful,
         * the caller will call io_put_bl() to drop the the reference at at the
         * end. This may then safely free the buffer_list (and drop the pages)
         * at that point, vm_insert_pages() would've already grabbed the
         * necessary vma references.
         */
        rcu_read_lock();
        bl = xa_load(&ctx->io_bl_xa, bgid);
        /* must be a mmap'able buffer ring and have pages */
        ret = false;
        if (bl && bl->flags & IOBL_MMAP)
                ret = atomic_inc_not_zero(&bl->refs);
        rcu_read_unlock();

        if (ret)
                return bl;

        return ERR_PTR(-EINVAL);
}

int io_pbuf_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct io_ring_ctx *ctx = file->private_data;
        loff_t pgoff = vma->vm_pgoff << PAGE_SHIFT;
        struct io_buffer_list *bl;
        int bgid, ret;

        bgid = (pgoff & ~IORING_OFF_MMAP_MASK) >> IORING_OFF_PBUF_SHIFT;
        bl = io_pbuf_get_bl(ctx, bgid);
        if (IS_ERR(bl))
                return PTR_ERR(bl);

        ret = io_uring_mmap_pages(ctx, vma, bl->buf_pages, bl->buf_nr_pages);
        io_put_bl(ctx, bl);
        return ret;
}