// 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)

/* 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;
        __u32                           nbufs;
        __u16                           bid;
};

static bool io_kbuf_inc_commit(struct io_buffer_list *bl, int len)
{
        /* No data consumed, return false early to avoid consuming the buffer */
        if (!len)
                return false;

        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)
{
        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 lookups from mmap do.
         */
        bl->bgid = bgid;
        guard(mutex)(&ctx->mmap_lock);
        return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
}

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;

        io_ring_submit_lock(ctx, issue_flags);

        buf = req->kbuf;
        bl = io_buffer_get_list(ctx, buf->bgid);
        /*
         * If the buffer list was upgraded to a ring-based one, or removed,
         * while the request was in-flight in io-wq, drop it.
         */
        if (bl && !(bl->flags & IOBL_BUF_RING)) {
                list_add(&buf->list, &bl->buf_list);
                bl->nbufs++;
        } else {
                kfree(buf);
        }
        req->flags &= ~REQ_F_BUFFER_SELECTED;
        req->kbuf = NULL;

        io_ring_submit_unlock(ctx, issue_flags);
        return true;
}

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);
                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;
                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 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) && !io_is_uring_cmd(req))
                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;
        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)) {
                if (!io_kbuf_commit(req, sel.buf_list, *len, 1))
                        req->flags |= REQ_F_BUF_MORE;
                sel.buf_list = NULL;
        }
        return sel;
}

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;

        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_objs(struct iovec, nr_avail);
                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 = 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;
        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 (sel->buf_list->flags & IOBL_BUF_RING) {
                ret = io_ring_buffers_peek(req, arg, sel->buf_list);
                /*
                 * 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;
                        if (!io_kbuf_commit(req, sel->buf_list, arg->out_len, ret))
                                req->flags |= REQ_F_BUF_MORE;
                }
        } 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 ret;
}

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;
        int ret;

        lockdep_assert_held(&ctx->uring_lock);

        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;
        }

        /* 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);
        if (ret && (req->flags & REQ_F_BUF_MORE))
                ret = false;

        req->flags &= ~(REQ_F_BUFFER_RING | REQ_F_BUF_MORE);
        return ret;
}

unsigned int __io_put_kbufs(struct io_kiocb *req, struct io_buffer_list *bl,
                            int len, int nbufs)
{
        unsigned int ret;

        ret = IORING_CQE_F_BUFFER | (req->buf_index << IORING_CQE_BUFFER_SHIFT);

        if (unlikely(!(req->flags & REQ_F_BUFFER_RING))) {
                io_kbuf_drop_legacy(req);
                return ret;
        }

        if (!__io_put_kbuf_ring(req, bl, len, nbufs))
                ret |= IORING_CQE_F_BUF_MORE;
        return ret;
}

static int io_remove_buffers_legacy(struct io_ring_ctx *ctx,
                                    struct io_buffer_list *bl,
                                    unsigned long nbufs)
{
        unsigned long i = 0;
        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);
                bl->nbufs--;
                kfree(nxt);
                cond_resched();
        }
        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;

        while (1) {
                unsigned long index = 0;

                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);
        }
}

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)
{
        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_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 (!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;
        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;
}

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 ret = -ENOMEM, i, bid = pbuf->bid;

        for (i = 0; i < pbuf->nbufs; i++) {
                /*
                 * 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 = kmalloc_obj(*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;
                buf->bgid = pbuf->bgid;
                addr += pbuf->len;
                bid++;
                cond_resched();
        }

        return i ? 0 : ret;
}

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);
        int ret;

        if (!bl) {
                if (req->opcode != IORING_OP_PROVIDE_BUFFERS)
                        return -ENOENT;
                bl = kzalloc_obj(*bl, GFP_KERNEL_ACCOUNT);
                if (!bl)
                        return -ENOMEM;

                INIT_LIST_HEAD(&bl->buf_list);
                ret = io_buffer_add_list(req->ctx, bl, p->bgid);
                if (ret) {
                        kfree(bl);
                        return ret;
                }
        }
        /* 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;

        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_COMPLETE;
}

int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
{
        struct io_uring_buf_reg reg;
        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 (!mem_is_zero(reg.resv, sizeof(reg.resv)))
                return -EINVAL;
        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;

        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;
                io_destroy_bl(ctx, bl);
        }

        bl = kzalloc_obj(*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);

#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

        bl->nr_entries = reg.ring_entries;
        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;
        ret = io_buffer_add_list(ctx, bl, reg.bgid);
        if (!ret)
                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)
{
        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 (!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->flags & IOBL_BUF_RING))
                return -EINVAL;

        scoped_guard(mutex, &ctx->mmap_lock)
                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;

        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;
}