1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/errno.h>
5 #include <linux/file.h>
7 #include <linux/slab.h>
8 #include <linux/namei.h>
9 #include <linux/poll.h>
10 #include <linux/io_uring.h>
12 #include <uapi/linux/io_uring.h>
18 #define IO_BUFFER_LIST_BUF_PER_PAGE (PAGE_SIZE / sizeof(struct io_uring_buf))
22 /* BIDs are addressed by a 16-bit field in a CQE */
23 #define MAX_BIDS_PER_BGID (1 << 16)
25 struct kmem_cache *io_buf_cachep;
27 struct io_provide_buf {
37 struct hlist_node list;
43 static struct io_buffer_list *__io_buffer_get_list(struct io_ring_ctx *ctx,
44 struct io_buffer_list *bl,
47 if (bl && bgid < BGID_ARRAY)
50 return xa_load(&ctx->io_bl_xa, bgid);
53 static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
56 lockdep_assert_held(&ctx->uring_lock);
58 return __io_buffer_get_list(ctx, ctx->io_bl, bgid);
61 static int io_buffer_add_list(struct io_ring_ctx *ctx,
62 struct io_buffer_list *bl, unsigned int bgid)
65 * Store buffer group ID and finally mark the list as visible.
66 * The normal lookup doesn't care about the visibility as we're
67 * always under the ->uring_lock, but the RCU lookup from mmap does.
70 smp_store_release(&bl->is_ready, 1);
72 if (bgid < BGID_ARRAY)
75 return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
78 bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
80 struct io_ring_ctx *ctx = req->ctx;
81 struct io_buffer_list *bl;
82 struct io_buffer *buf;
85 * For legacy provided buffer mode, don't recycle if we already did
86 * IO to this buffer. For ring-mapped provided buffer mode, we should
87 * increment ring->head to explicitly monopolize the buffer to avoid
90 if (req->flags & REQ_F_PARTIAL_IO)
93 io_ring_submit_lock(ctx, issue_flags);
96 bl = io_buffer_get_list(ctx, buf->bgid);
97 list_add(&buf->list, &bl->buf_list);
98 req->flags &= ~REQ_F_BUFFER_SELECTED;
99 req->buf_index = buf->bgid;
101 io_ring_submit_unlock(ctx, issue_flags);
105 unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
110 * We can add this buffer back to two lists:
112 * 1) The io_buffers_cache list. This one is protected by the
113 * ctx->uring_lock. If we already hold this lock, add back to this
114 * list as we can grab it from issue as well.
115 * 2) The io_buffers_comp list. This one is protected by the
116 * ctx->completion_lock.
118 * We migrate buffers from the comp_list to the issue cache list
121 if (req->flags & REQ_F_BUFFER_RING) {
122 /* no buffers to recycle for this case */
123 cflags = __io_put_kbuf_list(req, NULL);
124 } else if (issue_flags & IO_URING_F_UNLOCKED) {
125 struct io_ring_ctx *ctx = req->ctx;
127 spin_lock(&ctx->completion_lock);
128 cflags = __io_put_kbuf_list(req, &ctx->io_buffers_comp);
129 spin_unlock(&ctx->completion_lock);
131 lockdep_assert_held(&req->ctx->uring_lock);
133 cflags = __io_put_kbuf_list(req, &req->ctx->io_buffers_cache);
138 static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
139 struct io_buffer_list *bl)
141 if (!list_empty(&bl->buf_list)) {
142 struct io_buffer *kbuf;
144 kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
145 list_del(&kbuf->list);
146 if (*len == 0 || *len > kbuf->len)
148 req->flags |= REQ_F_BUFFER_SELECTED;
150 req->buf_index = kbuf->bid;
151 return u64_to_user_ptr(kbuf->addr);
156 static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
157 struct io_buffer_list *bl,
158 unsigned int issue_flags)
160 struct io_uring_buf_ring *br = bl->buf_ring;
161 struct io_uring_buf *buf;
162 __u16 head = bl->head;
164 if (unlikely(smp_load_acquire(&br->tail) == head))
168 /* mmaped buffers are always contig */
169 if (bl->is_mmap || head < IO_BUFFER_LIST_BUF_PER_PAGE) {
170 buf = &br->bufs[head];
172 int off = head & (IO_BUFFER_LIST_BUF_PER_PAGE - 1);
173 int index = head / IO_BUFFER_LIST_BUF_PER_PAGE;
174 buf = page_address(bl->buf_pages[index]);
177 if (*len == 0 || *len > buf->len)
179 req->flags |= REQ_F_BUFFER_RING;
181 req->buf_index = buf->bid;
183 if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) {
185 * If we came in unlocked, we have no choice but to consume the
186 * buffer here, otherwise nothing ensures that the buffer won't
187 * get used by others. This does mean it'll be pinned until the
188 * IO completes, coming in unlocked means we're being called from
189 * io-wq context and there may be further retries in async hybrid
190 * mode. For the locked case, the caller must call commit when
191 * the transfer completes (or if we get -EAGAIN and must poll of
194 req->buf_list = NULL;
197 return u64_to_user_ptr(buf->addr);
200 void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
201 unsigned int issue_flags)
203 struct io_ring_ctx *ctx = req->ctx;
204 struct io_buffer_list *bl;
205 void __user *ret = NULL;
207 io_ring_submit_lock(req->ctx, issue_flags);
209 bl = io_buffer_get_list(ctx, req->buf_index);
212 ret = io_ring_buffer_select(req, len, bl, issue_flags);
214 ret = io_provided_buffer_select(req, len, bl);
216 io_ring_submit_unlock(req->ctx, issue_flags);
220 static __cold int io_init_bl_list(struct io_ring_ctx *ctx)
222 struct io_buffer_list *bl;
225 bl = kcalloc(BGID_ARRAY, sizeof(struct io_buffer_list), GFP_KERNEL);
229 for (i = 0; i < BGID_ARRAY; i++) {
230 INIT_LIST_HEAD(&bl[i].buf_list);
234 smp_store_release(&ctx->io_bl, bl);
239 * Mark the given mapped range as free for reuse
241 static void io_kbuf_mark_free(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
243 struct io_buf_free *ibf;
245 hlist_for_each_entry(ibf, &ctx->io_buf_list, list) {
246 if (bl->buf_ring == ibf->mem) {
252 /* can't happen... */
256 static int __io_remove_buffers(struct io_ring_ctx *ctx,
257 struct io_buffer_list *bl, unsigned nbufs)
261 /* shouldn't happen */
266 i = bl->buf_ring->tail - bl->head;
269 * io_kbuf_list_free() will free the page(s) at
272 io_kbuf_mark_free(ctx, bl);
275 } else if (bl->buf_nr_pages) {
278 for (j = 0; j < bl->buf_nr_pages; j++)
279 unpin_user_page(bl->buf_pages[j]);
280 kvfree(bl->buf_pages);
281 bl->buf_pages = NULL;
282 bl->buf_nr_pages = 0;
284 /* make sure it's seen as empty */
285 INIT_LIST_HEAD(&bl->buf_list);
290 /* protects io_buffers_cache */
291 lockdep_assert_held(&ctx->uring_lock);
293 while (!list_empty(&bl->buf_list)) {
294 struct io_buffer *nxt;
296 nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
297 list_move(&nxt->list, &ctx->io_buffers_cache);
306 void io_destroy_buffers(struct io_ring_ctx *ctx)
308 struct io_buffer_list *bl;
309 struct list_head *item, *tmp;
310 struct io_buffer *buf;
314 for (i = 0; i < BGID_ARRAY; i++) {
317 __io_remove_buffers(ctx, &ctx->io_bl[i], -1U);
320 xa_for_each(&ctx->io_bl_xa, index, bl) {
321 xa_erase(&ctx->io_bl_xa, bl->bgid);
322 __io_remove_buffers(ctx, bl, -1U);
327 * Move deferred locked entries to cache before pruning
329 spin_lock(&ctx->completion_lock);
330 if (!list_empty(&ctx->io_buffers_comp))
331 list_splice_init(&ctx->io_buffers_comp, &ctx->io_buffers_cache);
332 spin_unlock(&ctx->completion_lock);
334 list_for_each_safe(item, tmp, &ctx->io_buffers_cache) {
335 buf = list_entry(item, struct io_buffer, list);
336 kmem_cache_free(io_buf_cachep, buf);
340 int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
342 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
345 if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
349 tmp = READ_ONCE(sqe->fd);
350 if (!tmp || tmp > MAX_BIDS_PER_BGID)
353 memset(p, 0, sizeof(*p));
355 p->bgid = READ_ONCE(sqe->buf_group);
359 int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
361 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
362 struct io_ring_ctx *ctx = req->ctx;
363 struct io_buffer_list *bl;
366 io_ring_submit_lock(ctx, issue_flags);
369 bl = io_buffer_get_list(ctx, p->bgid);
372 /* can't use provide/remove buffers command on mapped buffers */
374 ret = __io_remove_buffers(ctx, bl, p->nbufs);
376 io_ring_submit_unlock(ctx, issue_flags);
379 io_req_set_res(req, ret, 0);
383 int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
385 unsigned long size, tmp_check;
386 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
389 if (sqe->rw_flags || sqe->splice_fd_in)
392 tmp = READ_ONCE(sqe->fd);
393 if (!tmp || tmp > MAX_BIDS_PER_BGID)
396 p->addr = READ_ONCE(sqe->addr);
397 p->len = READ_ONCE(sqe->len);
399 if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
402 if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
405 size = (unsigned long)p->len * p->nbufs;
406 if (!access_ok(u64_to_user_ptr(p->addr), size))
409 p->bgid = READ_ONCE(sqe->buf_group);
410 tmp = READ_ONCE(sqe->off);
413 if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
419 #define IO_BUFFER_ALLOC_BATCH 64
421 static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
423 struct io_buffer *bufs[IO_BUFFER_ALLOC_BATCH];
427 * Completions that don't happen inline (eg not under uring_lock) will
428 * add to ->io_buffers_comp. If we don't have any free buffers, check
429 * the completion list and splice those entries first.
431 if (!list_empty_careful(&ctx->io_buffers_comp)) {
432 spin_lock(&ctx->completion_lock);
433 if (!list_empty(&ctx->io_buffers_comp)) {
434 list_splice_init(&ctx->io_buffers_comp,
435 &ctx->io_buffers_cache);
436 spin_unlock(&ctx->completion_lock);
439 spin_unlock(&ctx->completion_lock);
443 * No free buffers and no completion entries either. Allocate a new
444 * batch of buffer entries and add those to our freelist.
447 allocated = kmem_cache_alloc_bulk(io_buf_cachep, GFP_KERNEL_ACCOUNT,
448 ARRAY_SIZE(bufs), (void **) bufs);
449 if (unlikely(!allocated)) {
451 * Bulk alloc is all-or-nothing. If we fail to get a batch,
452 * retry single alloc to be on the safe side.
454 bufs[0] = kmem_cache_alloc(io_buf_cachep, GFP_KERNEL);
461 list_add_tail(&bufs[--allocated]->list, &ctx->io_buffers_cache);
466 static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
467 struct io_buffer_list *bl)
469 struct io_buffer *buf;
470 u64 addr = pbuf->addr;
471 int i, bid = pbuf->bid;
473 for (i = 0; i < pbuf->nbufs; i++) {
474 if (list_empty(&ctx->io_buffers_cache) &&
475 io_refill_buffer_cache(ctx))
477 buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
479 list_move_tail(&buf->list, &bl->buf_list);
481 buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
483 buf->bgid = pbuf->bgid;
489 return i ? 0 : -ENOMEM;
492 int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
494 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
495 struct io_ring_ctx *ctx = req->ctx;
496 struct io_buffer_list *bl;
499 io_ring_submit_lock(ctx, issue_flags);
501 if (unlikely(p->bgid < BGID_ARRAY && !ctx->io_bl)) {
502 ret = io_init_bl_list(ctx);
507 bl = io_buffer_get_list(ctx, p->bgid);
509 bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
514 INIT_LIST_HEAD(&bl->buf_list);
515 ret = io_buffer_add_list(ctx, bl, p->bgid);
518 * Doesn't need rcu free as it was never visible, but
519 * let's keep it consistent throughout. Also can't
520 * be a lower indexed array group, as adding one
521 * where lookup failed cannot happen.
523 if (p->bgid >= BGID_ARRAY)
530 /* can't add buffers via this command for a mapped buffer ring */
536 ret = io_add_buffers(ctx, p, bl);
538 io_ring_submit_unlock(ctx, issue_flags);
542 io_req_set_res(req, ret, 0);
546 static int io_pin_pbuf_ring(struct io_uring_buf_reg *reg,
547 struct io_buffer_list *bl)
549 struct io_uring_buf_ring *br;
553 pages = io_pin_pages(reg->ring_addr,
554 flex_array_size(br, bufs, reg->ring_entries),
557 return PTR_ERR(pages);
560 * Apparently some 32-bit boxes (ARM) will return highmem pages,
561 * which then need to be mapped. We could support that, but it'd
562 * complicate the code and slowdown the common cases quite a bit.
563 * So just error out, returning -EINVAL just like we did on kernels
564 * that didn't support mapped buffer rings.
566 for (i = 0; i < nr_pages; i++)
567 if (PageHighMem(pages[i]))
570 br = page_address(pages[0]);
573 * On platforms that have specific aliasing requirements, SHM_COLOUR
574 * is set and we must guarantee that the kernel and user side align
575 * nicely. We cannot do that if IOU_PBUF_RING_MMAP isn't set and
576 * the application mmap's the provided ring buffer. Fail the request
577 * if we, by chance, don't end up with aligned addresses. The app
578 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
579 * this transparently.
581 if ((reg->ring_addr | (unsigned long) br) & (SHM_COLOUR - 1))
584 bl->buf_pages = pages;
585 bl->buf_nr_pages = nr_pages;
591 for (i = 0; i < nr_pages; i++)
592 unpin_user_page(pages[i]);
598 * See if we have a suitable region that we can reuse, rather than allocate
599 * both a new io_buf_free and mem region again. We leave it on the list as
600 * even a reused entry will need freeing at ring release.
602 static struct io_buf_free *io_lookup_buf_free_entry(struct io_ring_ctx *ctx,
605 struct io_buf_free *ibf, *best = NULL;
608 hlist_for_each_entry(ibf, &ctx->io_buf_list, list) {
611 if (ibf->inuse || ibf->size < ring_size)
613 dist = ibf->size - ring_size;
614 if (!best || dist < best_dist) {
625 static int io_alloc_pbuf_ring(struct io_ring_ctx *ctx,
626 struct io_uring_buf_reg *reg,
627 struct io_buffer_list *bl)
629 struct io_buf_free *ibf;
633 ring_size = reg->ring_entries * sizeof(struct io_uring_buf_ring);
635 /* Reuse existing entry, if we can */
636 ibf = io_lookup_buf_free_entry(ctx, ring_size);
638 ptr = io_mem_alloc(ring_size);
642 /* Allocate and store deferred free entry */
643 ibf = kmalloc(sizeof(*ibf), GFP_KERNEL_ACCOUNT);
649 ibf->size = ring_size;
650 hlist_add_head(&ibf->list, &ctx->io_buf_list);
653 bl->buf_ring = ibf->mem;
659 int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
661 struct io_uring_buf_reg reg;
662 struct io_buffer_list *bl, *free_bl = NULL;
665 lockdep_assert_held(&ctx->uring_lock);
667 if (copy_from_user(®, arg, sizeof(reg)))
670 if (reg.resv[0] || reg.resv[1] || reg.resv[2])
672 if (reg.flags & ~IOU_PBUF_RING_MMAP)
674 if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
677 if (reg.ring_addr & ~PAGE_MASK)
684 if (!is_power_of_2(reg.ring_entries))
687 /* cannot disambiguate full vs empty due to head/tail size */
688 if (reg.ring_entries >= 65536)
691 if (unlikely(reg.bgid < BGID_ARRAY && !ctx->io_bl)) {
692 int ret = io_init_bl_list(ctx);
697 bl = io_buffer_get_list(ctx, reg.bgid);
699 /* if mapped buffer ring OR classic exists, don't allow */
700 if (bl->is_mapped || !list_empty(&bl->buf_list))
703 free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
708 if (!(reg.flags & IOU_PBUF_RING_MMAP))
709 ret = io_pin_pbuf_ring(®, bl);
711 ret = io_alloc_pbuf_ring(ctx, ®, bl);
714 bl->nr_entries = reg.ring_entries;
715 bl->mask = reg.ring_entries - 1;
717 io_buffer_add_list(ctx, bl, reg.bgid);
721 kfree_rcu(free_bl, rcu);
725 int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
727 struct io_uring_buf_reg reg;
728 struct io_buffer_list *bl;
730 lockdep_assert_held(&ctx->uring_lock);
732 if (copy_from_user(®, arg, sizeof(reg)))
734 if (reg.resv[0] || reg.resv[1] || reg.resv[2])
739 bl = io_buffer_get_list(ctx, reg.bgid);
745 __io_remove_buffers(ctx, bl, -1U);
746 if (bl->bgid >= BGID_ARRAY) {
747 xa_erase(&ctx->io_bl_xa, bl->bgid);
753 void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid)
755 struct io_buffer_list *bl;
757 bl = __io_buffer_get_list(ctx, smp_load_acquire(&ctx->io_bl), bgid);
760 * Ensure the list is fully setup. Only strictly needed for RCU lookup
761 * via mmap, and in that case only for the array indexed groups. For
762 * the xarray lookups, it's either visible and ready, or not at all.
764 if (!smp_load_acquire(&bl->is_ready))
766 if (!bl || !bl->is_mmap)
773 * Called at or after ->release(), free the mmap'ed buffers that we used
774 * for memory mapped provided buffer rings.
776 void io_kbuf_mmap_list_free(struct io_ring_ctx *ctx)
778 struct io_buf_free *ibf;
779 struct hlist_node *tmp;
781 hlist_for_each_entry_safe(ibf, tmp, &ctx->io_buf_list, list) {
782 hlist_del(&ibf->list);
783 io_mem_free(ibf->mem);