io_uring/rsrc.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/nospec.h>
#include <linux/hugetlb.h>
#include <linux/compat.h>
#include <linux/io_uring.h>
#include <linux/io_uring/cmd.h>

#include <uapi/linux/io_uring.h>

#include "filetable.h"
#include "io_uring.h"
#include "openclose.h"
#include "rsrc.h"
#include "memmap.h"
#include "register.h"

struct io_rsrc_update {
	struct file			*file;
	u64				arg;
	u32				nr_args;
	u32				offset;
};

static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
						   struct iovec *iov);

static int hpage_acct_ref(struct io_ring_ctx *ctx, struct page *hpage,
			  bool *acct_new)
{
	unsigned long key = (unsigned long) hpage;
	unsigned long count;
	void *entry;
	int ret;

	lockdep_assert_held(&ctx->uring_lock);

	entry = xa_load(&ctx->hpage_acct, key);
	if (entry) {
		*acct_new = false;
		count = xa_to_value(entry) + 1;
	} else {
		ret = xa_reserve(&ctx->hpage_acct, key, GFP_KERNEL_ACCOUNT);
		if (ret)
			return ret;
		*acct_new = true;
		count = 1;
	}
	xa_store(&ctx->hpage_acct, key, xa_mk_value(count), GFP_KERNEL_ACCOUNT);
	return 0;
}

static bool hpage_acct_unref(struct io_ring_ctx *ctx, struct page *hpage)
{
	unsigned long key = (unsigned long) hpage;
	unsigned long count;
	void *entry;

	lockdep_assert_held(&ctx->uring_lock);

	entry = xa_load(&ctx->hpage_acct, key);
	if (WARN_ON_ONCE(!entry))
		return false;
	count = xa_to_value(entry);
	if (count == 1) {
		xa_erase(&ctx->hpage_acct, key);
		return true;
	}
	xa_store(&ctx->hpage_acct, key, xa_mk_value(count - 1), GFP_KERNEL_ACCOUNT);
	return false;
}

/* only define max */
#define IORING_MAX_FIXED_FILES	(1U << 20)
#define IORING_MAX_REG_BUFFERS	(1U << 14)

#define IO_CACHED_BVECS_SEGS	32

int __io_account_mem(struct user_struct *user, unsigned long nr_pages)
{
	unsigned long page_limit, cur_pages, new_pages;

	if (!nr_pages)
		return 0;

	/* Don't allow more pages than we can safely lock */
	page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

	cur_pages = atomic_long_read(&user->locked_vm);
	do {
		new_pages = cur_pages + nr_pages;
		if (new_pages > page_limit)
			return -ENOMEM;
	} while (!atomic_long_try_cmpxchg(&user->locked_vm,
					  &cur_pages, new_pages));
	return 0;
}

void io_unaccount_mem(struct user_struct *user, struct mm_struct *mm_account,
		      unsigned long nr_pages)
{
	if (user)
		__io_unaccount_mem(user, nr_pages);

	if (mm_account)
		atomic64_sub(nr_pages, &mm_account->pinned_vm);
}

int io_account_mem(struct user_struct *user, struct mm_struct *mm_account,
		   unsigned long nr_pages)
{
	int ret;

	if (user) {
		ret = __io_account_mem(user, nr_pages);
		if (ret)
			return ret;
	}

	if (mm_account)
		atomic64_add(nr_pages, &mm_account->pinned_vm);

	return 0;
}

int io_validate_user_buf_range(u64 uaddr, u64 ulen)
{
	unsigned long tmp, base = (unsigned long)uaddr;
	unsigned long acct_len = (unsigned long)PAGE_ALIGN(ulen);

	if (!ulen)
		return -EFAULT;
	/* 32-bit sanity checking */
	if (ulen > ULONG_MAX || uaddr > ULONG_MAX)
		return -EFAULT;
	/* cap to 1TB for 64-bit */
	if (ulen > SZ_1T)
		return -EINVAL;
	if (check_add_overflow(base, acct_len, &tmp))
		return -EOVERFLOW;
	return 0;
}

static void io_release_ubuf(void *priv)
{
	struct io_mapped_ubuf *imu = priv;
	unsigned int i;

	for (i = 0; i < imu->nr_bvecs; i++) {
		struct folio *folio = bvec_folio(&imu->bvec[i]);

		unpin_user_folio(folio, 1);
	}
}

static struct io_mapped_ubuf *io_alloc_imu(struct io_ring_ctx *ctx,
					   int nr_bvecs)
{
	if (nr_bvecs <= IO_CACHED_BVECS_SEGS)
		return io_cache_alloc(&ctx->imu_cache, GFP_KERNEL);
	return kvmalloc_flex(struct io_mapped_ubuf, bvec, nr_bvecs);
}

static void io_free_imu(struct io_ring_ctx *ctx, struct io_mapped_ubuf *imu)
{
	if (imu->nr_bvecs <= IO_CACHED_BVECS_SEGS)
		io_cache_free(&ctx->imu_cache, imu);
	else
		kvfree(imu);
}

static unsigned long io_buffer_unaccount_pages(struct io_ring_ctx *ctx,
					       struct io_mapped_ubuf *imu)
{
	struct page *seen = NULL;
	unsigned long acct = 0;
	int i;

	if (imu->flags & IO_REGBUF_F_KBUF || !ctx->user)
		return 0;

	for (i = 0; i < imu->nr_bvecs; i++) {
		struct page *page = imu->bvec[i].bv_page;
		struct page *hpage;

		if (!PageCompound(page)) {
			acct++;
			continue;
		}

		hpage = compound_head(page);
		if (hpage == seen)
			continue;
		seen = hpage;

		/* Unaccount on last reference */
		if (hpage_acct_unref(ctx, hpage))
			acct += page_size(hpage) >> PAGE_SHIFT;
		cond_resched();
	}

	return acct;
}

static void io_buffer_unmap(struct io_ring_ctx *ctx, struct io_mapped_ubuf *imu)
{
	unsigned long acct_pages = 0;

	/* Always decrement, so it works for cloned buffers too */
	acct_pages = io_buffer_unaccount_pages(ctx, imu);

	if (unlikely(refcount_read(&imu->refs) > 1)) {
		if (!refcount_dec_and_test(&imu->refs))
			return;
	}

	if (acct_pages)
		io_unaccount_mem(ctx->user, ctx->mm_account, acct_pages);
	imu->release(imu->priv);
	io_free_imu(ctx, imu);
}

struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx, int type)
{
	struct io_rsrc_node *node;

	node = io_cache_alloc(&ctx->node_cache, GFP_KERNEL);
	if (node) {
		node->type = type;
		node->refs = 1;
		node->tag = 0;
		node->file_ptr = 0;
	}
	return node;
}

bool io_rsrc_cache_init(struct io_ring_ctx *ctx)
{
	const int imu_cache_size = struct_size_t(struct io_mapped_ubuf, bvec,
						 IO_CACHED_BVECS_SEGS);
	const int node_size = sizeof(struct io_rsrc_node);
	bool ret;

	ret = io_alloc_cache_init(&ctx->node_cache, IO_ALLOC_CACHE_MAX,
				  node_size, 0);
	ret |= io_alloc_cache_init(&ctx->imu_cache, IO_ALLOC_CACHE_MAX,
				   imu_cache_size, 0);
	return ret;
}

void io_rsrc_cache_free(struct io_ring_ctx *ctx)
{
	io_alloc_cache_free(&ctx->node_cache, kfree);
	io_alloc_cache_free(&ctx->imu_cache, kvfree);
}

static void io_clear_table_tags(struct io_rsrc_data *data)
{
	int i;

	for (i = 0; i < data->nr; i++) {
		struct io_rsrc_node *node = data->nodes[i];

		if (node)
			node->tag = 0;
	}
}

__cold void io_rsrc_data_free(struct io_ring_ctx *ctx,
			      struct io_rsrc_data *data)
{
	if (!data->nr)
		return;
	while (data->nr--) {
		if (data->nodes[data->nr])
			io_put_rsrc_node(ctx, data->nodes[data->nr]);
	}
	kvfree(data->nodes);
	data->nodes = NULL;
	data->nr = 0;
}

__cold int io_rsrc_data_alloc(struct io_rsrc_data *data, unsigned nr)
{
	data->nodes = kvmalloc_objs(struct io_rsrc_node *, nr,
				    GFP_KERNEL_ACCOUNT | __GFP_ZERO);
	if (data->nodes) {
		data->nr = nr;
		return 0;
	}
	return -ENOMEM;
}

static int __io_sqe_files_update(struct io_ring_ctx *ctx,
				 struct io_uring_rsrc_update2 *up,
				 unsigned nr_args)
{
	u64 __user *tags = u64_to_user_ptr(up->tags);
	__s32 __user *fds = u64_to_user_ptr(up->data);
	int fd, i, err = 0;
	unsigned int done;

	if (!ctx->file_table.data.nr)
		return -ENXIO;
	if (up->offset + nr_args > ctx->file_table.data.nr)
		return -EINVAL;

	for (done = 0; done < nr_args; done++) {
		u64 tag = 0;

		if ((tags && copy_from_user(&tag, &tags[done], sizeof(tag))) ||
		    copy_from_user(&fd, &fds[done], sizeof(fd))) {
			err = -EFAULT;
			break;
		}
		if ((fd == IORING_REGISTER_FILES_SKIP || fd == -1) && tag) {
			err = -EINVAL;
			break;
		}
		if (fd == IORING_REGISTER_FILES_SKIP)
			continue;

		i = up->offset + done;
		if (i >= ctx->file_table.data.nr)
			break;
		i = array_index_nospec(i, ctx->file_table.data.nr);
		if (io_reset_rsrc_node(ctx, &ctx->file_table.data, i))
			io_file_bitmap_clear(&ctx->file_table, i);

		if (fd != -1) {
			struct file *file = fget(fd);
			struct io_rsrc_node *node;

			if (!file) {
				err = -EBADF;
				break;
			}
			/*
			 * Don't allow io_uring instances to be registered.
			 */
			if (io_is_uring_fops(file)) {
				fput(file);
				err = -EBADF;
				break;
			}
			node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
			if (!node) {
				err = -ENOMEM;
				fput(file);
				break;
			}
			ctx->file_table.data.nodes[i] = node;
			if (tag)
				node->tag = tag;
			io_fixed_file_set(node, file);
			io_file_bitmap_set(&ctx->file_table, i);
		}
	}
	return done ? done : err;
}

static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
				   struct io_uring_rsrc_update2 *up,
				   unsigned int nr_args)
{
	u64 __user *tags = u64_to_user_ptr(up->tags);
	struct iovec fast_iov, *iov;
	struct iovec __user *uvec;
	u64 user_data = up->data;
	__u32 done;
	int i, err;

	if (!ctx->buf_table.nr)
		return -ENXIO;
	if (up->offset + nr_args > ctx->buf_table.nr)
		return -EINVAL;

	for (done = 0; done < nr_args; done++) {
		struct io_rsrc_node *node;
		u64 tag = 0;

		uvec = u64_to_user_ptr(user_data);
		iov = iovec_from_user(uvec, 1, 1, &fast_iov, io_is_compat(ctx));
		if (IS_ERR(iov)) {
			err = PTR_ERR(iov);
			break;
		}
		if (tags && copy_from_user(&tag, &tags[done], sizeof(tag))) {
			err = -EFAULT;
			break;
		}
		node = io_sqe_buffer_register(ctx, iov);
		if (IS_ERR(node)) {
			err = PTR_ERR(node);
			break;
		}
		if (tag) {
			if (!node) {
				err = -EINVAL;
				break;
			}
			node->tag = tag;
		}
		i = array_index_nospec(up->offset + done, ctx->buf_table.nr);
		io_reset_rsrc_node(ctx, &ctx->buf_table, i);
		ctx->buf_table.nodes[i] = node;
		if (io_is_compat(ctx))
			user_data += sizeof(struct compat_iovec);
		else
			user_data += sizeof(struct iovec);
	}
	return done ? done : err;
}

static int __io_register_rsrc_update(struct io_ring_ctx *ctx, unsigned type,
				     struct io_uring_rsrc_update2 *up,
				     unsigned nr_args)
{
	__u32 tmp;

	lockdep_assert_held(&ctx->uring_lock);

	if (check_add_overflow(up->offset, nr_args, &tmp))
		return -EOVERFLOW;

	switch (type) {
	case IORING_RSRC_FILE:
		return __io_sqe_files_update(ctx, up, nr_args);
	case IORING_RSRC_BUFFER:
		return __io_sqe_buffers_update(ctx, up, nr_args);
	}
	return -EINVAL;
}

int io_register_files_update(struct io_ring_ctx *ctx, void __user *arg,
			     unsigned nr_args)
{
	struct io_uring_rsrc_update2 up;

	if (!nr_args)
		return -EINVAL;
	memset(&up, 0, sizeof(up));
	if (copy_from_user(&up, arg, sizeof(struct io_uring_rsrc_update)))
		return -EFAULT;
	if (up.resv || up.resv2)
		return -EINVAL;
	return __io_register_rsrc_update(ctx, IORING_RSRC_FILE, &up, nr_args);
}

int io_register_rsrc_update(struct io_ring_ctx *ctx, void __user *arg,
			    unsigned size, unsigned type)
{
	struct io_uring_rsrc_update2 up;

	if (size != sizeof(up))
		return -EINVAL;
	if (copy_from_user(&up, arg, sizeof(up)))
		return -EFAULT;
	if (!up.nr || up.resv || up.resv2)
		return -EINVAL;
	return __io_register_rsrc_update(ctx, type, &up, up.nr);
}

__cold int io_register_rsrc(struct io_ring_ctx *ctx, void __user *arg,
			    unsigned int size, unsigned int type)
{
	struct io_uring_rsrc_register rr;

	/* keep it extendible */
	if (size != sizeof(rr))
		return -EINVAL;

	memset(&rr, 0, sizeof(rr));
	if (copy_from_user(&rr, arg, size))
		return -EFAULT;
	if (!rr.nr || rr.resv2)
		return -EINVAL;
	if (rr.flags & ~IORING_RSRC_REGISTER_SPARSE)
		return -EINVAL;

	switch (type) {
	case IORING_RSRC_FILE:
		if (rr.flags & IORING_RSRC_REGISTER_SPARSE && rr.data)
			break;
		return io_sqe_files_register(ctx, u64_to_user_ptr(rr.data),
					     rr.nr, u64_to_user_ptr(rr.tags));
	case IORING_RSRC_BUFFER:
		if (rr.flags & IORING_RSRC_REGISTER_SPARSE && rr.data)
			break;
		return io_sqe_buffers_register(ctx, u64_to_user_ptr(rr.data),
					       rr.nr, u64_to_user_ptr(rr.tags));
	}
	return -EINVAL;
}

int io_files_update_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
	struct io_rsrc_update *up = io_kiocb_to_cmd(req, struct io_rsrc_update);

	if (unlikely(req->flags & (REQ_F_FIXED_FILE | REQ_F_BUFFER_SELECT)))
		return -EINVAL;
	if (sqe->rw_flags || sqe->splice_fd_in)
		return -EINVAL;

	up->offset = READ_ONCE(sqe->off);
	up->nr_args = READ_ONCE(sqe->len);
	if (!up->nr_args)
		return -EINVAL;
	up->arg = READ_ONCE(sqe->addr);
	return 0;
}

static int io_files_update_with_index_alloc(struct io_kiocb *req,
					    unsigned int issue_flags)
{
	struct io_rsrc_update *up = io_kiocb_to_cmd(req, struct io_rsrc_update);
	__s32 __user *fds = u64_to_user_ptr(up->arg);
	unsigned int done;
	struct file *file;
	int ret, fd;

	if (!req->ctx->file_table.data.nr)
		return -ENXIO;

	for (done = 0; done < up->nr_args; done++) {
		if (get_user(fd, &fds[done])) {
			ret = -EFAULT;
			break;
		}

		file = fget(fd);
		if (!file) {
			ret = -EBADF;
			break;
		}
		ret = io_fixed_fd_install(req, issue_flags, file,
					  IORING_FILE_INDEX_ALLOC);
		if (ret < 0)
			break;
		if (put_user(ret, &fds[done])) {
			__io_close_fixed(req->ctx, issue_flags, ret);
			ret = -EFAULT;
			break;
		}
	}

	if (done)
		return done;
	return ret;
}

int io_files_update(struct io_kiocb *req, unsigned int issue_flags)
{
	struct io_rsrc_update *up = io_kiocb_to_cmd(req, struct io_rsrc_update);
	struct io_ring_ctx *ctx = req->ctx;
	struct io_uring_rsrc_update2 up2;
	int ret;

	up2.offset = up->offset;
	up2.data = up->arg;
	up2.nr = 0;
	up2.tags = 0;
	up2.resv = 0;
	up2.resv2 = 0;

	if (up->offset == IORING_FILE_INDEX_ALLOC) {
		ret = io_files_update_with_index_alloc(req, issue_flags);
	} else {
		io_ring_submit_lock(ctx, issue_flags);
		ret = __io_register_rsrc_update(ctx, IORING_RSRC_FILE,
						&up2, up->nr_args);
		io_ring_submit_unlock(ctx, issue_flags);
	}

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

void io_free_rsrc_node(struct io_ring_ctx *ctx, struct io_rsrc_node *node)
{
	if (node->tag)
		io_post_aux_cqe(ctx, node->tag, 0, 0);

	switch (node->type) {
	case IORING_RSRC_FILE:
		fput(io_slot_file(node));
		break;
	case IORING_RSRC_BUFFER:
		io_buffer_unmap(ctx, node->buf);
		break;
	default:
		WARN_ON_ONCE(1);
		break;
	}

	io_cache_free(&ctx->node_cache, node);
}

int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
	if (!ctx->file_table.data.nr)
		return -ENXIO;

	io_free_file_tables(ctx, &ctx->file_table);
	io_file_table_set_alloc_range(ctx, 0, 0);
	return 0;
}

int io_sqe_files_register(struct io_ring_ctx *ctx, void __user *arg,
			  unsigned nr_args, u64 __user *tags)
{
	__s32 __user *fds = (__s32 __user *) arg;
	struct file *file;
	int fd, ret;
	unsigned i;

	if (ctx->file_table.data.nr)
		return -EBUSY;
	if (!nr_args)
		return -EINVAL;
	if (nr_args > IORING_MAX_FIXED_FILES)
		return -EMFILE;
	if (nr_args > rlimit(RLIMIT_NOFILE))
		return -EMFILE;
	if (!io_alloc_file_tables(ctx, &ctx->file_table, nr_args))
		return -ENOMEM;

	for (i = 0; i < nr_args; i++) {
		struct io_rsrc_node *node;
		u64 tag = 0;

		ret = -EFAULT;
		if (tags && copy_from_user(&tag, &tags[i], sizeof(tag)))
			goto fail;
		if (fds && copy_from_user(&fd, &fds[i], sizeof(fd)))
			goto fail;
		/* allow sparse sets */
		if (!fds || fd == -1) {
			ret = -EINVAL;
			if (tag)
				goto fail;
			continue;
		}

		file = fget(fd);
		ret = -EBADF;
		if (unlikely(!file))
			goto fail;

		/*
		 * Don't allow io_uring instances to be registered.
		 */
		if (io_is_uring_fops(file)) {
			fput(file);
			goto fail;
		}
		ret = -ENOMEM;
		node = io_rsrc_node_alloc(ctx, IORING_RSRC_FILE);
		if (!node) {
			fput(file);
			goto fail;
		}
		if (tag)
			node->tag = tag;
		ctx->file_table.data.nodes[i] = node;
		io_fixed_file_set(node, file);
		io_file_bitmap_set(&ctx->file_table, i);
	}

	/* default it to the whole table */
	io_file_table_set_alloc_range(ctx, 0, ctx->file_table.data.nr);
	return 0;
fail:
	io_clear_table_tags(&ctx->file_table.data);
	io_sqe_files_unregister(ctx);
	return ret;
}

int io_sqe_buffers_unregister(struct io_ring_ctx *ctx)
{
	if (!ctx->buf_table.nr)
		return -ENXIO;
	io_rsrc_data_free(ctx, &ctx->buf_table);
	return 0;
}

/*
 * Undo hpage_acct_ref() calls made during io_buffer_account_pin() on failure.
 * This operates on the pages array since imu->bvec isn't populated yet.
 */
static void io_buffer_unaccount_hpages(struct io_ring_ctx *ctx,
				       struct page **pages, int nr_pages)
{
	struct page *seen = NULL;
	int i;

	if (!ctx->user)
		return;

	for (i = 0; i < nr_pages; i++) {
		struct page *hpage;

		if (!PageCompound(pages[i]))
			continue;

		hpage = compound_head(pages[i]);
		if (hpage == seen)
			continue;
		seen = hpage;

		hpage_acct_unref(ctx, hpage);
		cond_resched();
	}
}

static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
				 int nr_pages)
{
	unsigned long acct_pages = 0;
	struct page *seen = NULL;
	int i, ret;

	if (!ctx->user)
		return 0;

	for (i = 0; i < nr_pages; i++) {
		struct page *hpage;
		bool acct_new;

		if (!PageCompound(pages[i])) {
			acct_pages++;
			continue;
		}

		hpage = compound_head(pages[i]);
		if (hpage == seen)
			continue;
		seen = hpage;

		ret = hpage_acct_ref(ctx, hpage, &acct_new);
		if (ret) {
			io_buffer_unaccount_hpages(ctx, pages, i);
			return ret;
		}
		if (acct_new)
			acct_pages += page_size(hpage) >> PAGE_SHIFT;
		cond_resched();
	}

	/* Try to account the memory */
	if (acct_pages) {
		ret = io_account_mem(ctx->user, ctx->mm_account, acct_pages);
		if (ret) {
			/* Undo the refs we just added */
			io_buffer_unaccount_hpages(ctx, pages, nr_pages);
			return ret;
		}
	}

	return 0;
}

static bool io_coalesce_buffer(struct page ***pages, int *nr_pages,
				struct io_imu_folio_data *data)
{
	struct page **page_array = *pages, **new_array = NULL;
	unsigned nr_pages_left = *nr_pages;
	unsigned nr_folios = data->nr_folios;
	unsigned i, j;

	/* Store head pages only*/
	new_array = kvmalloc_objs(struct page *, nr_folios);
	if (!new_array)
		return false;

	for (i = 0, j = 0; i < nr_folios; i++) {
		struct page *p = compound_head(page_array[j]);
		struct folio *folio = page_folio(p);
		unsigned int nr;

		WARN_ON_ONCE(i > 0 && p != page_array[j]);

		nr = i ? data->nr_pages_mid : data->nr_pages_head;
		nr = min(nr, nr_pages_left);
		/* Drop all but one ref, the entire folio will remain pinned. */
		if (nr > 1)
			unpin_user_folio(folio, nr - 1);
		j += nr;
		nr_pages_left -= nr;
		new_array[i] = p;
	}

	WARN_ON_ONCE(j != *nr_pages);

	kvfree(page_array);
	*pages = new_array;
	*nr_pages = nr_folios;
	return true;
}

bool io_check_coalesce_buffer(struct page **page_array, int nr_pages,
			      struct io_imu_folio_data *data)
{
	struct folio *folio = page_folio(page_array[0]);
	unsigned int count = 1, nr_folios = 1;
	int i;

	data->nr_pages_mid = folio_nr_pages(folio);
	data->folio_shift = folio_shift(folio);
	data->first_folio_page_idx = folio_page_idx(folio, page_array[0]);

	/*
	 * Check if pages are contiguous inside a folio, and all folios have
	 * the same page count except for the head and tail.
	 */
	for (i = 1; i < nr_pages; i++) {
		if (page_folio(page_array[i]) == folio &&
			page_array[i] == page_array[i-1] + 1) {
			count++;
			continue;
		}

		if (nr_folios == 1) {
			if (folio_page_idx(folio, page_array[i-1]) !=
				data->nr_pages_mid - 1)
				return false;

			data->nr_pages_head = count;
		} else if (count != data->nr_pages_mid) {
			return false;
		}

		folio = page_folio(page_array[i]);
		if (folio_size(folio) != (1UL << data->folio_shift) ||
			folio_page_idx(folio, page_array[i]) != 0)
			return false;

		count = 1;
		nr_folios++;
	}
	if (nr_folios == 1)
		data->nr_pages_head = count;

	data->nr_folios = nr_folios;
	return true;
}

static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
						   struct iovec *iov)
{
	struct io_mapped_ubuf *imu = NULL;
	struct page **pages = NULL;
	struct io_rsrc_node *node;
	unsigned long off;
	size_t size;
	int ret, nr_pages, i;
	struct io_imu_folio_data data;
	bool coalesced = false;

	if (!iov->iov_base) {
		if (iov->iov_len)
			return ERR_PTR(-EFAULT);
		/* remove the buffer without installing a new one */
		return NULL;
	}

	ret = io_validate_user_buf_range((unsigned long)iov->iov_base,
					 iov->iov_len);
	if (ret)
		return ERR_PTR(ret);

	node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
	if (!node)
		return ERR_PTR(-ENOMEM);

	ret = -ENOMEM;
	pages = io_pin_pages((unsigned long) iov->iov_base, iov->iov_len,
				&nr_pages);
	if (IS_ERR(pages)) {
		ret = PTR_ERR(pages);
		pages = NULL;
		goto done;
	}

	/* If it's huge page(s), try to coalesce them into fewer bvec entries */
	if (nr_pages > 1 && io_check_coalesce_buffer(pages, nr_pages, &data)) {
		if (data.nr_pages_mid != 1)
			coalesced = io_coalesce_buffer(&pages, &nr_pages, &data);
	}

	imu = io_alloc_imu(ctx, nr_pages);
	if (!imu)
		goto done;

	imu->nr_bvecs = nr_pages;
	ret = io_buffer_account_pin(ctx, pages, nr_pages);
	if (ret)
		goto done;

	size = iov->iov_len;
	/* store original address for later verification */
	imu->ubuf = (unsigned long) iov->iov_base;
	imu->len = iov->iov_len;
	imu->folio_shift = PAGE_SHIFT;
	imu->release = io_release_ubuf;
	imu->priv = imu;
	imu->flags = 0;
	imu->dir = IO_BUF_DEST | IO_BUF_SOURCE;
	if (coalesced)
		imu->folio_shift = data.folio_shift;
	refcount_set(&imu->refs, 1);

	off = (unsigned long)iov->iov_base & ~PAGE_MASK;
	if (coalesced)
		off += data.first_folio_page_idx << PAGE_SHIFT;

	node->buf = imu;
	ret = 0;

	for (i = 0; i < nr_pages; i++) {
		size_t vec_len;

		vec_len = min_t(size_t, size, (1UL << imu->folio_shift) - off);
		bvec_set_page(&imu->bvec[i], pages[i], vec_len, off);
		off = 0;
		size -= vec_len;
	}
done:
	if (ret) {
		if (imu)
			io_free_imu(ctx, imu);
		if (pages) {
			for (i = 0; i < nr_pages; i++)
				unpin_user_folio(page_folio(pages[i]), 1);
		}
		io_cache_free(&ctx->node_cache, node);
		node = ERR_PTR(ret);
	}
	kvfree(pages);
	return node;
}

int io_sqe_buffers_register(struct io_ring_ctx *ctx, void __user *arg,
			    unsigned int nr_args, u64 __user *tags)
{
	struct io_rsrc_data data;
	struct iovec fast_iov, *iov = &fast_iov;
	const struct iovec __user *uvec;
	int i, ret;

	BUILD_BUG_ON(IORING_MAX_REG_BUFFERS >= (1u << 16));

	if (ctx->buf_table.nr)
		return -EBUSY;
	if (!nr_args || nr_args > IORING_MAX_REG_BUFFERS)
		return -EINVAL;
	ret = io_rsrc_data_alloc(&data, nr_args);
	if (ret)
		return ret;

	if (!arg)
		memset(iov, 0, sizeof(*iov));

	for (i = 0; i < nr_args; i++) {
		struct io_rsrc_node *node;
		u64 tag = 0;

		if (arg) {
			uvec = (struct iovec __user *) arg;
			iov = iovec_from_user(uvec, 1, 1, &fast_iov, io_is_compat(ctx));
			if (IS_ERR(iov)) {
				ret = PTR_ERR(iov);
				break;
			}
			if (io_is_compat(ctx))
				arg += sizeof(struct compat_iovec);
			else
				arg += sizeof(struct iovec);
		}

		if (tags) {
			if (copy_from_user(&tag, &tags[i], sizeof(tag))) {
				ret = -EFAULT;
				break;
			}
		}

		node = io_sqe_buffer_register(ctx, iov);
		if (IS_ERR(node)) {
			ret = PTR_ERR(node);
			break;
		}
		if (tag) {
			if (!node) {
				ret = -EINVAL;
				break;
			}
			node->tag = tag;
		}
		data.nodes[i] = node;
	}

	ctx->buf_table = data;
	if (ret) {
		io_clear_table_tags(&ctx->buf_table);
		io_sqe_buffers_unregister(ctx);
	}
	return ret;
}

static struct io_mapped_ubuf *io_kernel_buffer_init(struct io_ring_ctx *ctx,
						    unsigned int nr_bvecs,
						    unsigned int total_bytes,
						    u8 dir,
						    void (*release)(void *),
						    void *priv,
						    unsigned int index)
{
	struct io_rsrc_data *data = &ctx->buf_table;
	struct io_mapped_ubuf *imu;
	struct io_rsrc_node *node;

	if (index >= data->nr)
		return ERR_PTR(-EINVAL);
	index = array_index_nospec(index, data->nr);

	if (data->nodes[index])
		return ERR_PTR(-EBUSY);

	node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
	if (!node)
		return ERR_PTR(-ENOMEM);

	imu = io_alloc_imu(ctx, nr_bvecs);
	if (!imu) {
		io_cache_free(&ctx->node_cache, node);
		return ERR_PTR(-ENOMEM);
	}

	imu->ubuf = 0;
	imu->len = total_bytes;
	imu->folio_shift = PAGE_SHIFT;
	imu->nr_bvecs = nr_bvecs;
	refcount_set(&imu->refs, 1);
	imu->release = release;
	imu->priv = priv;
	imu->dir = dir;
	imu->flags = IO_REGBUF_F_KBUF;

	node->buf = imu;
	data->nodes[index] = node;

	return imu;
}

int io_buffer_register_request(struct io_uring_cmd *cmd, struct request *rq,
			       void (*release)(void *), unsigned int index,
			       unsigned int issue_flags)
{
	struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
	struct req_iterator rq_iter;
	struct io_mapped_ubuf *imu;
	struct bio_vec bv;
	/*
	 * blk_rq_nr_phys_segments() may overestimate the number of bvecs
	 * but avoids needing to iterate over the bvecs
	 */
	unsigned int nr_bvecs = blk_rq_nr_phys_segments(rq);
	unsigned int total_bytes = blk_rq_bytes(rq);
	int ret = 0;

	io_ring_submit_lock(ctx, issue_flags);

	imu = io_kernel_buffer_init(ctx, nr_bvecs, total_bytes,
				    1 << rq_data_dir(rq), release, rq, index);
	if (IS_ERR(imu)) {
		ret = PTR_ERR(imu);
		goto unlock;
	}

	nr_bvecs = 0;
	rq_for_each_bvec(bv, rq, rq_iter)
		imu->bvec[nr_bvecs++] = bv;
	imu->nr_bvecs = nr_bvecs;

unlock:
	io_ring_submit_unlock(ctx, issue_flags);
	return ret;
}
EXPORT_SYMBOL_GPL(io_buffer_register_request);

/*
 * bvs is copied internally. caller may free it on return.
 */
int io_buffer_register_bvec(struct io_uring_cmd *cmd, const struct bio_vec *bvs,
			    unsigned int nr_bvecs, void (*release)(void *),
			    void *priv, u8 dir, unsigned int index,
			    unsigned int issue_flags)
{
	struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
	struct io_mapped_ubuf *imu;
	struct bio_vec *bvec;
	unsigned int i, total_bytes = 0;
	int ret = 0;

	for (i = 0; i < nr_bvecs; i++)
		total_bytes += bvs[i].bv_len;

	io_ring_submit_lock(ctx, issue_flags);
	imu = io_kernel_buffer_init(ctx, nr_bvecs, total_bytes, dir, release,
				    priv, index);
	if (IS_ERR(imu)) {
		ret = PTR_ERR(imu);
		goto unlock;
	}

	bvec = imu->bvec;
	for (i = 0; i < nr_bvecs; i++)
		bvec[i] = bvs[i];

unlock:
	io_ring_submit_unlock(ctx, issue_flags);
	return ret;
}
EXPORT_SYMBOL_GPL(io_buffer_register_bvec);

int io_buffer_unregister(struct io_uring_cmd *cmd, unsigned int index,
			 unsigned int issue_flags)
{
	struct io_ring_ctx *ctx = cmd_to_io_kiocb(cmd)->ctx;
	struct io_rsrc_data *data = &ctx->buf_table;
	struct io_rsrc_node *node;
	int ret = 0;

	io_ring_submit_lock(ctx, issue_flags);
	if (index >= data->nr) {
		ret = -EINVAL;
		goto unlock;
	}
	index = array_index_nospec(index, data->nr);

	node = data->nodes[index];
	if (!node) {
		ret = -EINVAL;
		goto unlock;
	}
	if (!(node->buf->flags & IO_REGBUF_F_KBUF)) {
		ret = -EBUSY;
		goto unlock;
	}

	io_put_rsrc_node(ctx, node);
	data->nodes[index] = NULL;
unlock:
	io_ring_submit_unlock(ctx, issue_flags);
	return ret;
}
EXPORT_SYMBOL_GPL(io_buffer_unregister);

static int validate_fixed_range(u64 buf_addr, size_t len,
				const struct io_mapped_ubuf *imu)
{
	u64 buf_end;

	if (unlikely(check_add_overflow(buf_addr, (u64)len, &buf_end)))
		return -EFAULT;
	/* not inside the mapped region */
	if (unlikely(buf_addr < imu->ubuf || buf_end > (imu->ubuf + imu->len)))
		return -EFAULT;
	if (unlikely(len > MAX_RW_COUNT))
		return -EFAULT;
	return 0;
}

static int io_import_kbuf(int ddir, struct iov_iter *iter,
			  struct io_mapped_ubuf *imu, size_t len, size_t offset)
{
	size_t count = len + offset;

	iov_iter_bvec(iter, ddir, imu->bvec, imu->nr_bvecs, count);
	iov_iter_advance(iter, offset);
	return 0;
}

static int io_import_fixed(int ddir, struct iov_iter *iter,
			   struct io_mapped_ubuf *imu,
			   u64 buf_addr, size_t len)
{
	const struct bio_vec *bvec;
	size_t folio_mask;
	unsigned nr_segs;
	size_t offset;
	int ret;

	ret = validate_fixed_range(buf_addr, len, imu);
	if (unlikely(ret))
		return ret;
	if (!(imu->dir & (1 << ddir)))
		return -EFAULT;
	if (unlikely(!len)) {
		iov_iter_bvec(iter, ddir, NULL, 0, 0);
		return 0;
	}

	offset = buf_addr - imu->ubuf;

	if (imu->flags & IO_REGBUF_F_KBUF)
		return io_import_kbuf(ddir, iter, imu, len, offset);

	/*
	 * Don't use iov_iter_advance() here, as it's really slow for
	 * using the latter parts of a big fixed buffer - it iterates
	 * over each segment manually. We can cheat a bit here for user
	 * registered nodes, because we know that:
	 *
	 * 1) it's a BVEC iter, we set it up
	 * 2) all bvecs are the same in size, except potentially the
	 *    first and last bvec
	 */
	folio_mask = (1UL << imu->folio_shift) - 1;
	bvec = imu->bvec;
	if (offset >= bvec->bv_len) {
		unsigned long seg_skip;

		/* skip first vec */
		offset -= bvec->bv_len;
		seg_skip = 1 + (offset >> imu->folio_shift);
		bvec += seg_skip;
		offset &= folio_mask;
	}
	nr_segs = (offset + len + bvec->bv_offset + folio_mask) >> imu->folio_shift;
	iov_iter_bvec(iter, ddir, bvec, nr_segs, len);
	iter->iov_offset = offset;
	return 0;
}

inline struct io_rsrc_node *io_find_buf_node(struct io_kiocb *req,
					     unsigned issue_flags)
{
	struct io_ring_ctx *ctx = req->ctx;
	struct io_rsrc_node *node;

	if (req->flags & REQ_F_BUF_NODE)
		return req->buf_node;
	req->flags |= REQ_F_BUF_NODE;

	io_ring_submit_lock(ctx, issue_flags);
	node = io_rsrc_node_lookup(&ctx->buf_table, req->buf_index);
	if (node) {
		node->refs++;
		req->buf_node = node;
		io_ring_submit_unlock(ctx, issue_flags);
		return node;
	}
	req->flags &= ~REQ_F_BUF_NODE;
	io_ring_submit_unlock(ctx, issue_flags);
	return NULL;
}

int io_import_reg_buf(struct io_kiocb *req, struct iov_iter *iter,
			u64 buf_addr, size_t len, int ddir,
			unsigned issue_flags)
{
	struct io_rsrc_node *node;

	node = io_find_buf_node(req, issue_flags);
	if (!node)
		return -EFAULT;
	return io_import_fixed(ddir, iter, node->buf, buf_addr, len);
}

static int io_buffer_acct_cloned_hpages(struct io_ring_ctx *ctx,
					struct io_mapped_ubuf *imu)
{
	struct page *seen = NULL;
	int i, ret = 0;

	if (imu->flags & IO_REGBUF_F_KBUF || !ctx->user)
		return 0;

	for (i = 0; i < imu->nr_bvecs; i++) {
		struct page *page = imu->bvec[i].bv_page;
		struct page *hpage;
		bool acct_new;

		if (!PageCompound(page))
			continue;

		hpage = compound_head(page);
		if (hpage == seen)
			continue;
		seen = hpage;

		/* Atomically add reference for cloned buffer */
		ret = hpage_acct_ref(ctx, hpage, &acct_new);
		if (ret)
			break;

		cond_resched();
	}

	if (!ret)
		return 0;

	/* Undo refs we added for bvecs [0..i) */
	seen = NULL;
	for (int j = 0; j < i; j++) {
		struct page *p = imu->bvec[j].bv_page;
		struct page *hp;

		if (!PageCompound(p))
			continue;
		hp = compound_head(p);
		if (hp == seen)
			continue;
		seen = hp;
		hpage_acct_unref(ctx, hp);
	}
	return ret;
}

/* Lock two rings at once. The rings must be different! */
static void lock_two_rings(struct io_ring_ctx *ctx1, struct io_ring_ctx *ctx2)
{
	if (ctx1 > ctx2)
		swap(ctx1, ctx2);
	mutex_lock(&ctx1->uring_lock);
	mutex_lock_nested(&ctx2->uring_lock, SINGLE_DEPTH_NESTING);
}

/* Both rings are locked by the caller. */
static int io_clone_buffers(struct io_ring_ctx *ctx, struct io_ring_ctx *src_ctx,
			    struct io_uring_clone_buffers *arg)
{
	struct io_rsrc_data data;
	int i, ret, off, nr;
	unsigned int nbufs;

	lockdep_assert_held(&ctx->uring_lock);
	lockdep_assert_held(&src_ctx->uring_lock);

	/*
	 * Accounting state is shared between the two rings; that only works if
	 * both rings are accounted towards the same counters.
	 */
	if (ctx->user != src_ctx->user || ctx->mm_account != src_ctx->mm_account)
		return -EINVAL;

	/* if offsets are given, must have nr specified too */
	if (!arg->nr && (arg->dst_off || arg->src_off))
		return -EINVAL;
	/* not allowed unless REPLACE is set */
	if (ctx->buf_table.nr && !(arg->flags & IORING_REGISTER_DST_REPLACE))
		return -EBUSY;

	nbufs = src_ctx->buf_table.nr;
	if (!nbufs)
		return -ENXIO;
	if (!arg->nr)
		arg->nr = nbufs;
	else if (arg->nr > nbufs)
		return -EINVAL;
	else if (arg->nr > IORING_MAX_REG_BUFFERS)
		return -EINVAL;
	if (check_add_overflow(arg->nr, arg->src_off, &off) || off > nbufs)
		return -EOVERFLOW;
	if (check_add_overflow(arg->nr, arg->dst_off, &nbufs))
		return -EOVERFLOW;
	if (nbufs > IORING_MAX_REG_BUFFERS)
		return -EINVAL;

	ret = io_rsrc_data_alloc(&data, max(nbufs, ctx->buf_table.nr));
	if (ret)
		return ret;

	/* Copy original dst nodes from before the cloned range */
	for (i = 0; i < min(arg->dst_off, ctx->buf_table.nr); i++) {
		struct io_rsrc_node *node = ctx->buf_table.nodes[i];

		if (node) {
			data.nodes[i] = node;
			node->refs++;
		}
	}

	off = arg->dst_off;
	i = arg->src_off;
	nr = arg->nr;
	while (nr--) {
		struct io_rsrc_node *dst_node, *src_node;

		src_node = io_rsrc_node_lookup(&src_ctx->buf_table, i);
		if (!src_node) {
			dst_node = NULL;
		} else {
			dst_node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
			if (!dst_node) {
				io_rsrc_data_free(ctx, &data);
				return -ENOMEM;
			}

			refcount_inc(&src_node->buf->refs);
			dst_node->buf = src_node->buf;
			/* track compound references to clones */
			ret = io_buffer_acct_cloned_hpages(ctx, src_node->buf);
			if (ret) {
				refcount_dec(&src_node->buf->refs);
				io_cache_free(&ctx->node_cache, dst_node);
				io_rsrc_data_free(ctx, &data);
				return ret;
			}
		}
		data.nodes[off++] = dst_node;
		i++;
	}

	/* Copy original dst nodes from after the cloned range */
	for (i = nbufs; i < ctx->buf_table.nr; i++) {
		struct io_rsrc_node *node = ctx->buf_table.nodes[i];

		if (node) {
			data.nodes[i] = node;
			node->refs++;
		}
	}

	/*
	 * If asked for replace, put the old table. data->nodes[] holds both
	 * old and new nodes at this point.
	 */
	if (arg->flags & IORING_REGISTER_DST_REPLACE)
		io_rsrc_data_free(ctx, &ctx->buf_table);

	/*
	 * ctx->buf_table must be empty now - either the contents are being
	 * replaced and we just freed the table, or the contents are being
	 * copied to a ring that does not have buffers yet (checked at function
	 * entry).
	 */
	WARN_ON_ONCE(ctx->buf_table.nr);
	ctx->buf_table = data;
	return 0;
}

/*
 * Copy the registered buffers from the source ring whose file descriptor
 * is given in the src_fd to the current ring. This is identical to registering
 * the buffers with ctx, except faster as mappings already exist.
 *
 * Since the memory is already accounted once, don't account it again.
 */
int io_register_clone_buffers(struct io_ring_ctx *ctx, void __user *arg)
{
	struct io_uring_clone_buffers buf;
	struct io_ring_ctx *src_ctx;
	bool registered_src;
	struct file *file;
	int ret;

	if (copy_from_user(&buf, arg, sizeof(buf)))
		return -EFAULT;
	if (buf.flags & ~(IORING_REGISTER_SRC_REGISTERED|IORING_REGISTER_DST_REPLACE))
		return -EINVAL;
	if (!(buf.flags & IORING_REGISTER_DST_REPLACE) && ctx->buf_table.nr)
		return -EBUSY;
	if (memchr_inv(buf.pad, 0, sizeof(buf.pad)))
		return -EINVAL;

	registered_src = (buf.flags & IORING_REGISTER_SRC_REGISTERED) != 0;
	file = io_uring_ctx_get_file(buf.src_fd, registered_src);
	if (IS_ERR(file))
		return PTR_ERR(file);

	src_ctx = file->private_data;
	if (src_ctx != ctx) {
		mutex_unlock(&ctx->uring_lock);
		lock_two_rings(ctx, src_ctx);

		if (src_ctx->submitter_task &&
		    src_ctx->submitter_task != current) {
			ret = -EEXIST;
			goto out;
		}
	}

	ret = io_clone_buffers(ctx, src_ctx, &buf);

out:
	if (src_ctx != ctx)
		mutex_unlock(&src_ctx->uring_lock);

	if (!registered_src)
		fput(file);
	return ret;
}

void io_vec_free(struct iou_vec *iv)
{
	if (!iv->iovec)
		return;
	kfree(iv->iovec);
	iv->iovec = NULL;
	iv->nr = 0;
}

int io_vec_realloc(struct iou_vec *iv, unsigned nr_entries)
{
	gfp_t gfp = GFP_KERNEL_ACCOUNT | __GFP_NOWARN;
	struct iovec *iov;

	iov = kmalloc_objs(iov[0], nr_entries, gfp);
	if (!iov)
		return -ENOMEM;

	io_vec_free(iv);
	iv->iovec = iov;
	iv->nr = nr_entries;
	return 0;
}

static int io_vec_fill_bvec(int ddir, struct iov_iter *iter,
				struct io_mapped_ubuf *imu,
				struct iovec *iovec, unsigned nr_iovs,
				struct iou_vec *vec)
{
	unsigned long folio_size = 1UL << imu->folio_shift;
	unsigned long folio_mask = folio_size - 1;
	struct bio_vec *res_bvec = vec->bvec;
	size_t total_len = 0;
	unsigned bvec_idx = 0;
	unsigned iov_idx;

	for (iov_idx = 0; iov_idx < nr_iovs; iov_idx++) {
		size_t iov_len = iovec[iov_idx].iov_len;
		u64 buf_addr = (u64)(uintptr_t)iovec[iov_idx].iov_base;
		struct bio_vec *src_bvec;
		size_t offset;
		int ret;

		ret = validate_fixed_range(buf_addr, iov_len, imu);
		if (unlikely(ret))
			return ret;

		if (unlikely(!iov_len))
			return -EFAULT;
		if (unlikely(check_add_overflow(total_len, iov_len, &total_len)))
			return -EOVERFLOW;

		offset = buf_addr - imu->ubuf;
		/*
		 * Only the first bvec can have non zero bv_offset, account it
		 * here and work with full folios below.
		 */
		offset += imu->bvec[0].bv_offset;

		src_bvec = imu->bvec + (offset >> imu->folio_shift);
		offset &= folio_mask;

		for (; iov_len; offset = 0, bvec_idx++, src_bvec++) {
			size_t seg_size = min_t(size_t, iov_len,
						folio_size - offset);

			bvec_set_page(&res_bvec[bvec_idx],
				      src_bvec->bv_page, seg_size, offset);
			iov_len -= seg_size;
		}
	}
	if (total_len > MAX_RW_COUNT)
		return -EINVAL;

	iov_iter_bvec(iter, ddir, res_bvec, bvec_idx, total_len);
	return 0;
}

static int io_estimate_bvec_size(struct iovec *iov, unsigned nr_iovs,
				 struct io_mapped_ubuf *imu)
{
	unsigned shift = imu->folio_shift;
	size_t max_segs = 0;
	unsigned i;

	for (i = 0; i < nr_iovs; i++) {
		max_segs += (iov[i].iov_len >> shift) + 2;
		if (max_segs > INT_MAX)
			return -EOVERFLOW;
	}
	return max_segs;
}

static int io_vec_fill_kern_bvec(int ddir, struct iov_iter *iter,
				 struct io_mapped_ubuf *imu,
				 struct iovec *iovec, unsigned nr_iovs,
				 struct iou_vec *vec)
{
	const struct bio_vec *src_bvec = imu->bvec;
	struct bio_vec *res_bvec = vec->bvec;
	unsigned res_idx = 0;
	size_t total_len = 0;
	unsigned iov_idx;

	for (iov_idx = 0; iov_idx < nr_iovs; iov_idx++) {
		size_t offset = (size_t)(uintptr_t)iovec[iov_idx].iov_base;
		size_t iov_len = iovec[iov_idx].iov_len;
		struct bvec_iter bi = {
			.bi_size        = offset + iov_len,
		};
		struct bio_vec bv;

		bvec_iter_advance(src_bvec, &bi, offset);
		for_each_mp_bvec(bv, src_bvec, bi, bi)
			res_bvec[res_idx++] = bv;
		total_len += iov_len;
	}
	iov_iter_bvec(iter, ddir, res_bvec, res_idx, total_len);
	return 0;
}

static int iov_kern_bvec_size(const struct iovec *iov,
			      const struct io_mapped_ubuf *imu,
			      unsigned int *nr_seg)
{
	size_t offset = (size_t)(uintptr_t)iov->iov_base;
	const struct bio_vec *bvec = imu->bvec;
	int start = 0, i = 0;
	size_t off = 0;
	int ret;

	ret = validate_fixed_range(offset, iov->iov_len, imu);
	if (unlikely(ret))
		return ret;

	for (i = 0; off < offset + iov->iov_len && i < imu->nr_bvecs;
			off += bvec[i].bv_len, i++) {
		if (offset >= off && offset < off + bvec[i].bv_len)
			start = i;
	}
	*nr_seg = i - start;
	return 0;
}

static int io_kern_bvec_size(struct iovec *iov, unsigned nr_iovs,
			     struct io_mapped_ubuf *imu, unsigned *nr_segs)
{
	unsigned max_segs = 0;
	size_t total_len = 0;
	unsigned i;
	int ret;

	*nr_segs = 0;
	for (i = 0; i < nr_iovs; i++) {
		if (unlikely(!iov[i].iov_len))
			return -EFAULT;
		if (unlikely(check_add_overflow(total_len, iov[i].iov_len,
						&total_len)))
			return -EOVERFLOW;
		ret = iov_kern_bvec_size(&iov[i], imu, &max_segs);
		if (unlikely(ret))
			return ret;
		*nr_segs += max_segs;
	}
	if (total_len > MAX_RW_COUNT)
		return -EINVAL;
	return 0;
}

int io_import_reg_vec(int ddir, struct iov_iter *iter,
			struct io_kiocb *req, struct iou_vec *vec,
			unsigned nr_iovs, unsigned issue_flags)
{
	struct io_rsrc_node *node;
	struct io_mapped_ubuf *imu;
	unsigned iovec_off;
	struct iovec *iov;
	unsigned nr_segs;

	node = io_find_buf_node(req, issue_flags);
	if (!node)
		return -EFAULT;
	imu = node->buf;
	if (!(imu->dir & (1 << ddir)))
		return -EFAULT;

	iovec_off = vec->nr - nr_iovs;
	iov = vec->iovec + iovec_off;

	if (imu->flags & IO_REGBUF_F_KBUF) {
		int ret = io_kern_bvec_size(iov, nr_iovs, imu, &nr_segs);

		if (unlikely(ret))
			return ret;
	} else {
		int ret = io_estimate_bvec_size(iov, nr_iovs, imu);

		if (ret < 0)
			return ret;
		nr_segs = ret;
	}

	if (sizeof(struct bio_vec) > sizeof(struct iovec)) {
		size_t bvec_bytes;

		if (check_mul_overflow((size_t)nr_segs, sizeof(struct bio_vec),
				       &bvec_bytes) ||
		    check_add_overflow(bvec_bytes, sizeof(*iov) - 1,
				       &bvec_bytes))
			return -EOVERFLOW;
		nr_segs = bvec_bytes / sizeof(*iov);
		nr_segs += nr_iovs;
	}

	if (nr_segs > vec->nr) {
		struct iou_vec tmp_vec = {};
		int ret;

		ret = io_vec_realloc(&tmp_vec, nr_segs);
		if (ret)
			return ret;

		iovec_off = tmp_vec.nr - nr_iovs;
		memcpy(tmp_vec.iovec + iovec_off, iov, sizeof(*iov) * nr_iovs);
		io_vec_free(vec);

		*vec = tmp_vec;
		iov = vec->iovec + iovec_off;
		req->flags |= REQ_F_NEED_CLEANUP;
	}

	if (imu->flags & IO_REGBUF_F_KBUF)
		return io_vec_fill_kern_bvec(ddir, iter, imu, iov, nr_iovs, vec);

	return io_vec_fill_bvec(ddir, iter, imu, iov, nr_iovs, vec);
}

int io_prep_reg_iovec(struct io_kiocb *req, struct iou_vec *iv,
		      const struct iovec __user *uvec, size_t uvec_segs)
{
	struct iovec *iov;
	int iovec_off, ret;
	void *res;

	if (uvec_segs > iv->nr) {
		ret = io_vec_realloc(iv, uvec_segs);
		if (ret)
			return ret;
		req->flags |= REQ_F_NEED_CLEANUP;
	}

	/* pad iovec to the right */
	iovec_off = iv->nr - uvec_segs;
	iov = iv->iovec + iovec_off;
	res = iovec_from_user(uvec, uvec_segs, uvec_segs, iov,
			      io_is_compat(req->ctx));
	if (IS_ERR(res))
		return PTR_ERR(res);

	req->flags |= REQ_F_IMPORT_BUFFER;
	return 0;
}