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))
20 /* BIDs are addressed by a 16-bit field in a CQE */
21 #define MAX_BIDS_PER_BGID (1 << 16)
23 struct kmem_cache
*io_buf_cachep
;
25 struct io_provide_buf
{
35 struct hlist_node list
;
41 static inline struct io_buffer_list
*__io_buffer_get_list(struct io_ring_ctx
*ctx
,
44 return xa_load(&ctx
->io_bl_xa
, bgid
);
47 static inline struct io_buffer_list
*io_buffer_get_list(struct io_ring_ctx
*ctx
,
50 lockdep_assert_held(&ctx
->uring_lock
);
52 return __io_buffer_get_list(ctx
, bgid
);
55 static int io_buffer_add_list(struct io_ring_ctx
*ctx
,
56 struct io_buffer_list
*bl
, unsigned int bgid
)
59 * Store buffer group ID and finally mark the list as visible.
60 * The normal lookup doesn't care about the visibility as we're
61 * always under the ->uring_lock, but the RCU lookup from mmap does.
64 atomic_set(&bl
->refs
, 1);
65 return xa_err(xa_store(&ctx
->io_bl_xa
, bgid
, bl
, GFP_KERNEL
));
68 bool io_kbuf_recycle_legacy(struct io_kiocb
*req
, unsigned issue_flags
)
70 struct io_ring_ctx
*ctx
= req
->ctx
;
71 struct io_buffer_list
*bl
;
72 struct io_buffer
*buf
;
74 io_ring_submit_lock(ctx
, issue_flags
);
77 bl
= io_buffer_get_list(ctx
, buf
->bgid
);
78 list_add(&buf
->list
, &bl
->buf_list
);
79 req
->flags
&= ~REQ_F_BUFFER_SELECTED
;
80 req
->buf_index
= buf
->bgid
;
82 io_ring_submit_unlock(ctx
, issue_flags
);
86 void __io_put_kbuf(struct io_kiocb
*req
, unsigned issue_flags
)
89 * We can add this buffer back to two lists:
91 * 1) The io_buffers_cache list. This one is protected by the
92 * ctx->uring_lock. If we already hold this lock, add back to this
93 * list as we can grab it from issue as well.
94 * 2) The io_buffers_comp list. This one is protected by the
95 * ctx->completion_lock.
97 * We migrate buffers from the comp_list to the issue cache list
100 if (issue_flags
& IO_URING_F_UNLOCKED
) {
101 struct io_ring_ctx
*ctx
= req
->ctx
;
103 spin_lock(&ctx
->completion_lock
);
104 __io_put_kbuf_list(req
, &ctx
->io_buffers_comp
);
105 spin_unlock(&ctx
->completion_lock
);
107 lockdep_assert_held(&req
->ctx
->uring_lock
);
109 __io_put_kbuf_list(req
, &req
->ctx
->io_buffers_cache
);
113 static void __user
*io_provided_buffer_select(struct io_kiocb
*req
, size_t *len
,
114 struct io_buffer_list
*bl
)
116 if (!list_empty(&bl
->buf_list
)) {
117 struct io_buffer
*kbuf
;
119 kbuf
= list_first_entry(&bl
->buf_list
, struct io_buffer
, list
);
120 list_del(&kbuf
->list
);
121 if (*len
== 0 || *len
> kbuf
->len
)
123 if (list_empty(&bl
->buf_list
))
124 req
->flags
|= REQ_F_BL_EMPTY
;
125 req
->flags
|= REQ_F_BUFFER_SELECTED
;
127 req
->buf_index
= kbuf
->bid
;
128 return u64_to_user_ptr(kbuf
->addr
);
133 static void __user
*io_ring_buffer_select(struct io_kiocb
*req
, size_t *len
,
134 struct io_buffer_list
*bl
,
135 unsigned int issue_flags
)
137 struct io_uring_buf_ring
*br
= bl
->buf_ring
;
138 __u16 tail
, head
= bl
->head
;
139 struct io_uring_buf
*buf
;
141 tail
= smp_load_acquire(&br
->tail
);
142 if (unlikely(tail
== head
))
145 if (head
+ 1 == tail
)
146 req
->flags
|= REQ_F_BL_EMPTY
;
149 /* mmaped buffers are always contig */
150 if (bl
->is_mmap
|| head
< IO_BUFFER_LIST_BUF_PER_PAGE
) {
151 buf
= &br
->bufs
[head
];
153 int off
= head
& (IO_BUFFER_LIST_BUF_PER_PAGE
- 1);
154 int index
= head
/ IO_BUFFER_LIST_BUF_PER_PAGE
;
155 buf
= page_address(bl
->buf_pages
[index
]);
158 if (*len
== 0 || *len
> buf
->len
)
160 req
->flags
|= REQ_F_BUFFER_RING
;
162 req
->buf_index
= buf
->bid
;
164 if (issue_flags
& IO_URING_F_UNLOCKED
|| !io_file_can_poll(req
)) {
166 * If we came in unlocked, we have no choice but to consume the
167 * buffer here, otherwise nothing ensures that the buffer won't
168 * get used by others. This does mean it'll be pinned until the
169 * IO completes, coming in unlocked means we're being called from
170 * io-wq context and there may be further retries in async hybrid
171 * mode. For the locked case, the caller must call commit when
172 * the transfer completes (or if we get -EAGAIN and must poll of
175 req
->buf_list
= NULL
;
178 return u64_to_user_ptr(buf
->addr
);
181 void __user
*io_buffer_select(struct io_kiocb
*req
, size_t *len
,
182 unsigned int issue_flags
)
184 struct io_ring_ctx
*ctx
= req
->ctx
;
185 struct io_buffer_list
*bl
;
186 void __user
*ret
= NULL
;
188 io_ring_submit_lock(req
->ctx
, issue_flags
);
190 bl
= io_buffer_get_list(ctx
, req
->buf_index
);
193 ret
= io_ring_buffer_select(req
, len
, bl
, issue_flags
);
195 ret
= io_provided_buffer_select(req
, len
, bl
);
197 io_ring_submit_unlock(req
->ctx
, issue_flags
);
202 * Mark the given mapped range as free for reuse
204 static void io_kbuf_mark_free(struct io_ring_ctx
*ctx
, struct io_buffer_list
*bl
)
206 struct io_buf_free
*ibf
;
208 hlist_for_each_entry(ibf
, &ctx
->io_buf_list
, list
) {
209 if (bl
->buf_ring
== ibf
->mem
) {
215 /* can't happen... */
219 static int __io_remove_buffers(struct io_ring_ctx
*ctx
,
220 struct io_buffer_list
*bl
, unsigned nbufs
)
224 /* shouldn't happen */
228 if (bl
->is_buf_ring
) {
229 i
= bl
->buf_ring
->tail
- bl
->head
;
232 * io_kbuf_list_free() will free the page(s) at
235 io_kbuf_mark_free(ctx
, bl
);
238 } else if (bl
->buf_nr_pages
) {
241 for (j
= 0; j
< bl
->buf_nr_pages
; j
++)
242 unpin_user_page(bl
->buf_pages
[j
]);
243 kvfree(bl
->buf_pages
);
244 bl
->buf_pages
= NULL
;
245 bl
->buf_nr_pages
= 0;
247 /* make sure it's seen as empty */
248 INIT_LIST_HEAD(&bl
->buf_list
);
253 /* protects io_buffers_cache */
254 lockdep_assert_held(&ctx
->uring_lock
);
256 while (!list_empty(&bl
->buf_list
)) {
257 struct io_buffer
*nxt
;
259 nxt
= list_first_entry(&bl
->buf_list
, struct io_buffer
, list
);
260 list_move(&nxt
->list
, &ctx
->io_buffers_cache
);
269 void io_put_bl(struct io_ring_ctx
*ctx
, struct io_buffer_list
*bl
)
271 if (atomic_dec_and_test(&bl
->refs
)) {
272 __io_remove_buffers(ctx
, bl
, -1U);
277 void io_destroy_buffers(struct io_ring_ctx
*ctx
)
279 struct io_buffer_list
*bl
;
280 struct list_head
*item
, *tmp
;
281 struct io_buffer
*buf
;
284 xa_for_each(&ctx
->io_bl_xa
, index
, bl
) {
285 xa_erase(&ctx
->io_bl_xa
, bl
->bgid
);
290 * Move deferred locked entries to cache before pruning
292 spin_lock(&ctx
->completion_lock
);
293 if (!list_empty(&ctx
->io_buffers_comp
))
294 list_splice_init(&ctx
->io_buffers_comp
, &ctx
->io_buffers_cache
);
295 spin_unlock(&ctx
->completion_lock
);
297 list_for_each_safe(item
, tmp
, &ctx
->io_buffers_cache
) {
298 buf
= list_entry(item
, struct io_buffer
, list
);
299 kmem_cache_free(io_buf_cachep
, buf
);
303 int io_remove_buffers_prep(struct io_kiocb
*req
, const struct io_uring_sqe
*sqe
)
305 struct io_provide_buf
*p
= io_kiocb_to_cmd(req
, struct io_provide_buf
);
308 if (sqe
->rw_flags
|| sqe
->addr
|| sqe
->len
|| sqe
->off
||
312 tmp
= READ_ONCE(sqe
->fd
);
313 if (!tmp
|| tmp
> MAX_BIDS_PER_BGID
)
316 memset(p
, 0, sizeof(*p
));
318 p
->bgid
= READ_ONCE(sqe
->buf_group
);
322 int io_remove_buffers(struct io_kiocb
*req
, unsigned int issue_flags
)
324 struct io_provide_buf
*p
= io_kiocb_to_cmd(req
, struct io_provide_buf
);
325 struct io_ring_ctx
*ctx
= req
->ctx
;
326 struct io_buffer_list
*bl
;
329 io_ring_submit_lock(ctx
, issue_flags
);
332 bl
= io_buffer_get_list(ctx
, p
->bgid
);
335 /* can't use provide/remove buffers command on mapped buffers */
336 if (!bl
->is_buf_ring
)
337 ret
= __io_remove_buffers(ctx
, bl
, p
->nbufs
);
339 io_ring_submit_unlock(ctx
, issue_flags
);
342 io_req_set_res(req
, ret
, 0);
346 int io_provide_buffers_prep(struct io_kiocb
*req
, const struct io_uring_sqe
*sqe
)
348 unsigned long size
, tmp_check
;
349 struct io_provide_buf
*p
= io_kiocb_to_cmd(req
, struct io_provide_buf
);
352 if (sqe
->rw_flags
|| sqe
->splice_fd_in
)
355 tmp
= READ_ONCE(sqe
->fd
);
356 if (!tmp
|| tmp
> MAX_BIDS_PER_BGID
)
359 p
->addr
= READ_ONCE(sqe
->addr
);
360 p
->len
= READ_ONCE(sqe
->len
);
362 if (check_mul_overflow((unsigned long)p
->len
, (unsigned long)p
->nbufs
,
365 if (check_add_overflow((unsigned long)p
->addr
, size
, &tmp_check
))
368 size
= (unsigned long)p
->len
* p
->nbufs
;
369 if (!access_ok(u64_to_user_ptr(p
->addr
), size
))
372 p
->bgid
= READ_ONCE(sqe
->buf_group
);
373 tmp
= READ_ONCE(sqe
->off
);
376 if (tmp
+ p
->nbufs
> MAX_BIDS_PER_BGID
)
382 #define IO_BUFFER_ALLOC_BATCH 64
384 static int io_refill_buffer_cache(struct io_ring_ctx
*ctx
)
386 struct io_buffer
*bufs
[IO_BUFFER_ALLOC_BATCH
];
390 * Completions that don't happen inline (eg not under uring_lock) will
391 * add to ->io_buffers_comp. If we don't have any free buffers, check
392 * the completion list and splice those entries first.
394 if (!list_empty_careful(&ctx
->io_buffers_comp
)) {
395 spin_lock(&ctx
->completion_lock
);
396 if (!list_empty(&ctx
->io_buffers_comp
)) {
397 list_splice_init(&ctx
->io_buffers_comp
,
398 &ctx
->io_buffers_cache
);
399 spin_unlock(&ctx
->completion_lock
);
402 spin_unlock(&ctx
->completion_lock
);
406 * No free buffers and no completion entries either. Allocate a new
407 * batch of buffer entries and add those to our freelist.
410 allocated
= kmem_cache_alloc_bulk(io_buf_cachep
, GFP_KERNEL_ACCOUNT
,
411 ARRAY_SIZE(bufs
), (void **) bufs
);
412 if (unlikely(!allocated
)) {
414 * Bulk alloc is all-or-nothing. If we fail to get a batch,
415 * retry single alloc to be on the safe side.
417 bufs
[0] = kmem_cache_alloc(io_buf_cachep
, GFP_KERNEL
);
424 list_add_tail(&bufs
[--allocated
]->list
, &ctx
->io_buffers_cache
);
429 static int io_add_buffers(struct io_ring_ctx
*ctx
, struct io_provide_buf
*pbuf
,
430 struct io_buffer_list
*bl
)
432 struct io_buffer
*buf
;
433 u64 addr
= pbuf
->addr
;
434 int i
, bid
= pbuf
->bid
;
436 for (i
= 0; i
< pbuf
->nbufs
; i
++) {
437 if (list_empty(&ctx
->io_buffers_cache
) &&
438 io_refill_buffer_cache(ctx
))
440 buf
= list_first_entry(&ctx
->io_buffers_cache
, struct io_buffer
,
442 list_move_tail(&buf
->list
, &bl
->buf_list
);
444 buf
->len
= min_t(__u32
, pbuf
->len
, MAX_RW_COUNT
);
446 buf
->bgid
= pbuf
->bgid
;
452 return i
? 0 : -ENOMEM
;
455 int io_provide_buffers(struct io_kiocb
*req
, unsigned int issue_flags
)
457 struct io_provide_buf
*p
= io_kiocb_to_cmd(req
, struct io_provide_buf
);
458 struct io_ring_ctx
*ctx
= req
->ctx
;
459 struct io_buffer_list
*bl
;
462 io_ring_submit_lock(ctx
, issue_flags
);
464 bl
= io_buffer_get_list(ctx
, p
->bgid
);
466 bl
= kzalloc(sizeof(*bl
), GFP_KERNEL_ACCOUNT
);
471 INIT_LIST_HEAD(&bl
->buf_list
);
472 ret
= io_buffer_add_list(ctx
, bl
, p
->bgid
);
475 * Doesn't need rcu free as it was never visible, but
476 * let's keep it consistent throughout.
482 /* can't add buffers via this command for a mapped buffer ring */
483 if (bl
->is_buf_ring
) {
488 ret
= io_add_buffers(ctx
, p
, bl
);
490 io_ring_submit_unlock(ctx
, issue_flags
);
494 io_req_set_res(req
, ret
, 0);
498 static int io_pin_pbuf_ring(struct io_uring_buf_reg
*reg
,
499 struct io_buffer_list
*bl
)
501 struct io_uring_buf_ring
*br
;
505 pages
= io_pin_pages(reg
->ring_addr
,
506 flex_array_size(br
, bufs
, reg
->ring_entries
),
509 return PTR_ERR(pages
);
512 * Apparently some 32-bit boxes (ARM) will return highmem pages,
513 * which then need to be mapped. We could support that, but it'd
514 * complicate the code and slowdown the common cases quite a bit.
515 * So just error out, returning -EINVAL just like we did on kernels
516 * that didn't support mapped buffer rings.
518 for (i
= 0; i
< nr_pages
; i
++)
519 if (PageHighMem(pages
[i
]))
522 br
= page_address(pages
[0]);
525 * On platforms that have specific aliasing requirements, SHM_COLOUR
526 * is set and we must guarantee that the kernel and user side align
527 * nicely. We cannot do that if IOU_PBUF_RING_MMAP isn't set and
528 * the application mmap's the provided ring buffer. Fail the request
529 * if we, by chance, don't end up with aligned addresses. The app
530 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
531 * this transparently.
533 if ((reg
->ring_addr
| (unsigned long) br
) & (SHM_COLOUR
- 1))
536 bl
->buf_pages
= pages
;
537 bl
->buf_nr_pages
= nr_pages
;
543 for (i
= 0; i
< nr_pages
; i
++)
544 unpin_user_page(pages
[i
]);
550 * See if we have a suitable region that we can reuse, rather than allocate
551 * both a new io_buf_free and mem region again. We leave it on the list as
552 * even a reused entry will need freeing at ring release.
554 static struct io_buf_free
*io_lookup_buf_free_entry(struct io_ring_ctx
*ctx
,
557 struct io_buf_free
*ibf
, *best
= NULL
;
560 hlist_for_each_entry(ibf
, &ctx
->io_buf_list
, list
) {
563 if (ibf
->inuse
|| ibf
->size
< ring_size
)
565 dist
= ibf
->size
- ring_size
;
566 if (!best
|| dist
< best_dist
) {
577 static int io_alloc_pbuf_ring(struct io_ring_ctx
*ctx
,
578 struct io_uring_buf_reg
*reg
,
579 struct io_buffer_list
*bl
)
581 struct io_buf_free
*ibf
;
585 ring_size
= reg
->ring_entries
* sizeof(struct io_uring_buf_ring
);
587 /* Reuse existing entry, if we can */
588 ibf
= io_lookup_buf_free_entry(ctx
, ring_size
);
590 ptr
= io_mem_alloc(ring_size
);
594 /* Allocate and store deferred free entry */
595 ibf
= kmalloc(sizeof(*ibf
), GFP_KERNEL_ACCOUNT
);
601 ibf
->size
= ring_size
;
602 hlist_add_head(&ibf
->list
, &ctx
->io_buf_list
);
605 bl
->buf_ring
= ibf
->mem
;
611 int io_register_pbuf_ring(struct io_ring_ctx
*ctx
, void __user
*arg
)
613 struct io_uring_buf_reg reg
;
614 struct io_buffer_list
*bl
, *free_bl
= NULL
;
617 lockdep_assert_held(&ctx
->uring_lock
);
619 if (copy_from_user(®
, arg
, sizeof(reg
)))
622 if (reg
.resv
[0] || reg
.resv
[1] || reg
.resv
[2])
624 if (reg
.flags
& ~IOU_PBUF_RING_MMAP
)
626 if (!(reg
.flags
& IOU_PBUF_RING_MMAP
)) {
629 if (reg
.ring_addr
& ~PAGE_MASK
)
636 if (!is_power_of_2(reg
.ring_entries
))
639 /* cannot disambiguate full vs empty due to head/tail size */
640 if (reg
.ring_entries
>= 65536)
643 bl
= io_buffer_get_list(ctx
, reg
.bgid
);
645 /* if mapped buffer ring OR classic exists, don't allow */
646 if (bl
->is_buf_ring
|| !list_empty(&bl
->buf_list
))
649 free_bl
= bl
= kzalloc(sizeof(*bl
), GFP_KERNEL
);
654 if (!(reg
.flags
& IOU_PBUF_RING_MMAP
))
655 ret
= io_pin_pbuf_ring(®
, bl
);
657 ret
= io_alloc_pbuf_ring(ctx
, ®
, bl
);
660 bl
->nr_entries
= reg
.ring_entries
;
661 bl
->mask
= reg
.ring_entries
- 1;
663 io_buffer_add_list(ctx
, bl
, reg
.bgid
);
667 kfree_rcu(free_bl
, rcu
);
671 int io_unregister_pbuf_ring(struct io_ring_ctx
*ctx
, void __user
*arg
)
673 struct io_uring_buf_reg reg
;
674 struct io_buffer_list
*bl
;
676 lockdep_assert_held(&ctx
->uring_lock
);
678 if (copy_from_user(®
, arg
, sizeof(reg
)))
680 if (reg
.resv
[0] || reg
.resv
[1] || reg
.resv
[2])
685 bl
= io_buffer_get_list(ctx
, reg
.bgid
);
688 if (!bl
->is_buf_ring
)
691 xa_erase(&ctx
->io_bl_xa
, bl
->bgid
);
696 int io_register_pbuf_status(struct io_ring_ctx
*ctx
, void __user
*arg
)
698 struct io_uring_buf_status buf_status
;
699 struct io_buffer_list
*bl
;
702 if (copy_from_user(&buf_status
, arg
, sizeof(buf_status
)))
705 for (i
= 0; i
< ARRAY_SIZE(buf_status
.resv
); i
++)
706 if (buf_status
.resv
[i
])
709 bl
= io_buffer_get_list(ctx
, buf_status
.buf_group
);
712 if (!bl
->is_buf_ring
)
715 buf_status
.head
= bl
->head
;
716 if (copy_to_user(arg
, &buf_status
, sizeof(buf_status
)))
722 struct io_buffer_list
*io_pbuf_get_bl(struct io_ring_ctx
*ctx
,
725 struct io_buffer_list
*bl
;
729 * We have to be a bit careful here - we're inside mmap and cannot grab
730 * the uring_lock. This means the buffer_list could be simultaneously
731 * going away, if someone is trying to be sneaky. Look it up under rcu
732 * so we know it's not going away, and attempt to grab a reference to
733 * it. If the ref is already zero, then fail the mapping. If successful,
734 * the caller will call io_put_bl() to drop the the reference at at the
735 * end. This may then safely free the buffer_list (and drop the pages)
736 * at that point, vm_insert_pages() would've already grabbed the
737 * necessary vma references.
740 bl
= xa_load(&ctx
->io_bl_xa
, bgid
);
741 /* must be a mmap'able buffer ring and have pages */
743 if (bl
&& bl
->is_mmap
)
744 ret
= atomic_inc_not_zero(&bl
->refs
);
750 return ERR_PTR(-EINVAL
);
754 * Called at or after ->release(), free the mmap'ed buffers that we used
755 * for memory mapped provided buffer rings.
757 void io_kbuf_mmap_list_free(struct io_ring_ctx
*ctx
)
759 struct io_buf_free
*ibf
;
760 struct hlist_node
*tmp
;
762 hlist_for_each_entry_safe(ibf
, tmp
, &ctx
->io_buf_list
, list
) {
763 hlist_del(&ibf
->list
);
764 io_mem_free(ibf
->mem
);