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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/errno.h>
4#include <linux/fs.h>
5#include <linux/file.h>
6#include <linux/mm.h>
7#include <linux/slab.h>
8#include <linux/namei.h>
9#include <linux/poll.h>
10#include <linux/io_uring.h>
11
12#include <uapi/linux/io_uring.h>
13
14#include "io_uring.h"
15#include "opdef.h"
16#include "kbuf.h"
17
18#define IO_BUFFER_LIST_BUF_PER_PAGE (PAGE_SIZE / sizeof(struct io_uring_buf))
19
20#define BGID_ARRAY 64
21
22struct io_provide_buf {
23 struct file *file;
24 __u64 addr;
25 __u32 len;
26 __u32 bgid;
27 __u16 nbufs;
28 __u16 bid;
29};
30
31static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
32 unsigned int bgid)
33{
34 if (ctx->io_bl && bgid < BGID_ARRAY)
35 return &ctx->io_bl[bgid];
36
37 return xa_load(&ctx->io_bl_xa, bgid);
38}
39
40static int io_buffer_add_list(struct io_ring_ctx *ctx,
41 struct io_buffer_list *bl, unsigned int bgid)
42{
43 bl->bgid = bgid;
44 if (bgid < BGID_ARRAY)
45 return 0;
46
47 return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
48}
49
50void io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
51{
52 struct io_ring_ctx *ctx = req->ctx;
53 struct io_buffer_list *bl;
54 struct io_buffer *buf;
55
56 /*
57 * For legacy provided buffer mode, don't recycle if we already did
58 * IO to this buffer. For ring-mapped provided buffer mode, we should
59 * increment ring->head to explicitly monopolize the buffer to avoid
60 * multiple use.
61 */
62 if (req->flags & REQ_F_PARTIAL_IO)
63 return;
64
65 io_ring_submit_lock(ctx, issue_flags);
66
67 buf = req->kbuf;
68 bl = io_buffer_get_list(ctx, buf->bgid);
69 list_add(&buf->list, &bl->buf_list);
70 req->flags &= ~REQ_F_BUFFER_SELECTED;
71 req->buf_index = buf->bgid;
72
73 io_ring_submit_unlock(ctx, issue_flags);
74 return;
75}
76
77unsigned int __io_put_kbuf(struct io_kiocb *req, unsigned issue_flags)
78{
79 unsigned int cflags;
80
81 /*
82 * We can add this buffer back to two lists:
83 *
84 * 1) The io_buffers_cache list. This one is protected by the
85 * ctx->uring_lock. If we already hold this lock, add back to this
86 * list as we can grab it from issue as well.
87 * 2) The io_buffers_comp list. This one is protected by the
88 * ctx->completion_lock.
89 *
90 * We migrate buffers from the comp_list to the issue cache list
91 * when we need one.
92 */
93 if (req->flags & REQ_F_BUFFER_RING) {
94 /* no buffers to recycle for this case */
95 cflags = __io_put_kbuf_list(req, NULL);
96 } else if (issue_flags & IO_URING_F_UNLOCKED) {
97 struct io_ring_ctx *ctx = req->ctx;
98
99 spin_lock(&ctx->completion_lock);
100 cflags = __io_put_kbuf_list(req, &ctx->io_buffers_comp);
101 spin_unlock(&ctx->completion_lock);
102 } else {
103 lockdep_assert_held(&req->ctx->uring_lock);
104
105 cflags = __io_put_kbuf_list(req, &req->ctx->io_buffers_cache);
106 }
107 return cflags;
108}
109
110static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
111 struct io_buffer_list *bl)
112{
113 if (!list_empty(&bl->buf_list)) {
114 struct io_buffer *kbuf;
115
116 kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
117 list_del(&kbuf->list);
118 if (*len == 0 || *len > kbuf->len)
119 *len = kbuf->len;
120 req->flags |= REQ_F_BUFFER_SELECTED;
121 req->kbuf = kbuf;
122 req->buf_index = kbuf->bid;
123 return u64_to_user_ptr(kbuf->addr);
124 }
125 return NULL;
126}
127
128static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
129 struct io_buffer_list *bl,
130 unsigned int issue_flags)
131{
132 struct io_uring_buf_ring *br = bl->buf_ring;
133 struct io_uring_buf *buf;
134 __u16 head = bl->head;
135
136 if (unlikely(smp_load_acquire(&br->tail) == head))
137 return NULL;
138
139 head &= bl->mask;
140 if (head < IO_BUFFER_LIST_BUF_PER_PAGE) {
141 buf = &br->bufs[head];
142 } else {
143 int off = head & (IO_BUFFER_LIST_BUF_PER_PAGE - 1);
144 int index = head / IO_BUFFER_LIST_BUF_PER_PAGE;
145 buf = page_address(bl->buf_pages[index]);
146 buf += off;
147 }
148 if (*len == 0 || *len > buf->len)
149 *len = buf->len;
150 req->flags |= REQ_F_BUFFER_RING;
151 req->buf_list = bl;
152 req->buf_index = buf->bid;
153
154 if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) {
155 /*
156 * If we came in unlocked, we have no choice but to consume the
157 * buffer here, otherwise nothing ensures that the buffer won't
158 * get used by others. This does mean it'll be pinned until the
159 * IO completes, coming in unlocked means we're being called from
160 * io-wq context and there may be further retries in async hybrid
161 * mode. For the locked case, the caller must call commit when
162 * the transfer completes (or if we get -EAGAIN and must poll of
163 * retry).
164 */
165 req->buf_list = NULL;
166 bl->head++;
167 }
168 return u64_to_user_ptr(buf->addr);
169}
170
171void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
172 unsigned int issue_flags)
173{
174 struct io_ring_ctx *ctx = req->ctx;
175 struct io_buffer_list *bl;
176 void __user *ret = NULL;
177
178 io_ring_submit_lock(req->ctx, issue_flags);
179
180 bl = io_buffer_get_list(ctx, req->buf_index);
181 if (likely(bl)) {
182 if (bl->buf_nr_pages)
183 ret = io_ring_buffer_select(req, len, bl, issue_flags);
184 else
185 ret = io_provided_buffer_select(req, len, bl);
186 }
187 io_ring_submit_unlock(req->ctx, issue_flags);
188 return ret;
189}
190
191static __cold int io_init_bl_list(struct io_ring_ctx *ctx)
192{
193 int i;
194
195 ctx->io_bl = kcalloc(BGID_ARRAY, sizeof(struct io_buffer_list),
196 GFP_KERNEL);
197 if (!ctx->io_bl)
198 return -ENOMEM;
199
200 for (i = 0; i < BGID_ARRAY; i++) {
201 INIT_LIST_HEAD(&ctx->io_bl[i].buf_list);
202 ctx->io_bl[i].bgid = i;
203 }
204
205 return 0;
206}
207
208static int __io_remove_buffers(struct io_ring_ctx *ctx,
209 struct io_buffer_list *bl, unsigned nbufs)
210{
211 unsigned i = 0;
212
213 /* shouldn't happen */
214 if (!nbufs)
215 return 0;
216
217 if (bl->buf_nr_pages) {
218 int j;
219
220 i = bl->buf_ring->tail - bl->head;
221 for (j = 0; j < bl->buf_nr_pages; j++)
222 unpin_user_page(bl->buf_pages[j]);
223 kvfree(bl->buf_pages);
224 bl->buf_pages = NULL;
225 bl->buf_nr_pages = 0;
226 /* make sure it's seen as empty */
227 INIT_LIST_HEAD(&bl->buf_list);
228 return i;
229 }
230
231 /* the head kbuf is the list itself */
232 while (!list_empty(&bl->buf_list)) {
233 struct io_buffer *nxt;
234
235 nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
236 list_del(&nxt->list);
237 if (++i == nbufs)
238 return i;
239 cond_resched();
240 }
241 i++;
242
243 return i;
244}
245
246void io_destroy_buffers(struct io_ring_ctx *ctx)
247{
248 struct io_buffer_list *bl;
249 unsigned long index;
250 int i;
251
252 for (i = 0; i < BGID_ARRAY; i++) {
253 if (!ctx->io_bl)
254 break;
255 __io_remove_buffers(ctx, &ctx->io_bl[i], -1U);
256 }
257
258 xa_for_each(&ctx->io_bl_xa, index, bl) {
259 xa_erase(&ctx->io_bl_xa, bl->bgid);
260 __io_remove_buffers(ctx, bl, -1U);
261 kfree(bl);
262 }
263
264 while (!list_empty(&ctx->io_buffers_pages)) {
265 struct page *page;
266
267 page = list_first_entry(&ctx->io_buffers_pages, struct page, lru);
268 list_del_init(&page->lru);
269 __free_page(page);
270 }
271}
272
273int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
274{
275 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
276 u64 tmp;
277
278 if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
279 sqe->splice_fd_in)
280 return -EINVAL;
281
282 tmp = READ_ONCE(sqe->fd);
283 if (!tmp || tmp > USHRT_MAX)
284 return -EINVAL;
285
286 memset(p, 0, sizeof(*p));
287 p->nbufs = tmp;
288 p->bgid = READ_ONCE(sqe->buf_group);
289 return 0;
290}
291
292int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
293{
294 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
295 struct io_ring_ctx *ctx = req->ctx;
296 struct io_buffer_list *bl;
297 int ret = 0;
298
299 io_ring_submit_lock(ctx, issue_flags);
300
301 ret = -ENOENT;
302 bl = io_buffer_get_list(ctx, p->bgid);
303 if (bl) {
304 ret = -EINVAL;
305 /* can't use provide/remove buffers command on mapped buffers */
306 if (!bl->buf_nr_pages)
307 ret = __io_remove_buffers(ctx, bl, p->nbufs);
308 }
309 io_ring_submit_unlock(ctx, issue_flags);
310 if (ret < 0)
311 req_set_fail(req);
312 io_req_set_res(req, ret, 0);
313 return IOU_OK;
314}
315
316int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
317{
318 unsigned long size, tmp_check;
319 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
320 u64 tmp;
321
322 if (sqe->rw_flags || sqe->splice_fd_in)
323 return -EINVAL;
324
325 tmp = READ_ONCE(sqe->fd);
326 if (!tmp || tmp > USHRT_MAX)
327 return -E2BIG;
328 p->nbufs = tmp;
329 p->addr = READ_ONCE(sqe->addr);
330 p->len = READ_ONCE(sqe->len);
331
332 if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
333 &size))
334 return -EOVERFLOW;
335 if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
336 return -EOVERFLOW;
337
338 size = (unsigned long)p->len * p->nbufs;
339 if (!access_ok(u64_to_user_ptr(p->addr), size))
340 return -EFAULT;
341
342 p->bgid = READ_ONCE(sqe->buf_group);
343 tmp = READ_ONCE(sqe->off);
344 if (tmp > USHRT_MAX)
345 return -E2BIG;
346 if (tmp + p->nbufs >= USHRT_MAX)
347 return -EINVAL;
348 p->bid = tmp;
349 return 0;
350}
351
352static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
353{
354 struct io_buffer *buf;
355 struct page *page;
356 int bufs_in_page;
357
358 /*
359 * Completions that don't happen inline (eg not under uring_lock) will
360 * add to ->io_buffers_comp. If we don't have any free buffers, check
361 * the completion list and splice those entries first.
362 */
363 if (!list_empty_careful(&ctx->io_buffers_comp)) {
364 spin_lock(&ctx->completion_lock);
365 if (!list_empty(&ctx->io_buffers_comp)) {
366 list_splice_init(&ctx->io_buffers_comp,
367 &ctx->io_buffers_cache);
368 spin_unlock(&ctx->completion_lock);
369 return 0;
370 }
371 spin_unlock(&ctx->completion_lock);
372 }
373
374 /*
375 * No free buffers and no completion entries either. Allocate a new
376 * page worth of buffer entries and add those to our freelist.
377 */
378 page = alloc_page(GFP_KERNEL_ACCOUNT);
379 if (!page)
380 return -ENOMEM;
381
382 list_add(&page->lru, &ctx->io_buffers_pages);
383
384 buf = page_address(page);
385 bufs_in_page = PAGE_SIZE / sizeof(*buf);
386 while (bufs_in_page) {
387 list_add_tail(&buf->list, &ctx->io_buffers_cache);
388 buf++;
389 bufs_in_page--;
390 }
391
392 return 0;
393}
394
395static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
396 struct io_buffer_list *bl)
397{
398 struct io_buffer *buf;
399 u64 addr = pbuf->addr;
400 int i, bid = pbuf->bid;
401
402 for (i = 0; i < pbuf->nbufs; i++) {
403 if (list_empty(&ctx->io_buffers_cache) &&
404 io_refill_buffer_cache(ctx))
405 break;
406 buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
407 list);
408 list_move_tail(&buf->list, &bl->buf_list);
409 buf->addr = addr;
410 buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
411 buf->bid = bid;
412 buf->bgid = pbuf->bgid;
413 addr += pbuf->len;
414 bid++;
415 cond_resched();
416 }
417
418 return i ? 0 : -ENOMEM;
419}
420
421int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
422{
423 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
424 struct io_ring_ctx *ctx = req->ctx;
425 struct io_buffer_list *bl;
426 int ret = 0;
427
428 io_ring_submit_lock(ctx, issue_flags);
429
430 if (unlikely(p->bgid < BGID_ARRAY && !ctx->io_bl)) {
431 ret = io_init_bl_list(ctx);
432 if (ret)
433 goto err;
434 }
435
436 bl = io_buffer_get_list(ctx, p->bgid);
437 if (unlikely(!bl)) {
438 bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
439 if (!bl) {
440 ret = -ENOMEM;
441 goto err;
442 }
443 INIT_LIST_HEAD(&bl->buf_list);
444 ret = io_buffer_add_list(ctx, bl, p->bgid);
445 if (ret) {
446 kfree(bl);
447 goto err;
448 }
449 }
450 /* can't add buffers via this command for a mapped buffer ring */
451 if (bl->buf_nr_pages) {
452 ret = -EINVAL;
453 goto err;
454 }
455
456 ret = io_add_buffers(ctx, p, bl);
457err:
458 io_ring_submit_unlock(ctx, issue_flags);
459
460 if (ret < 0)
461 req_set_fail(req);
462 io_req_set_res(req, ret, 0);
463 return IOU_OK;
464}
465
466int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
467{
468 struct io_uring_buf_ring *br;
469 struct io_uring_buf_reg reg;
470 struct io_buffer_list *bl, *free_bl = NULL;
471 struct page **pages;
472 int nr_pages;
473
474 if (copy_from_user(®, arg, sizeof(reg)))
475 return -EFAULT;
476
477 if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
478 return -EINVAL;
479 if (!reg.ring_addr)
480 return -EFAULT;
481 if (reg.ring_addr & ~PAGE_MASK)
482 return -EINVAL;
483 if (!is_power_of_2(reg.ring_entries))
484 return -EINVAL;
485
486 /* cannot disambiguate full vs empty due to head/tail size */
487 if (reg.ring_entries >= 65536)
488 return -EINVAL;
489
490 if (unlikely(reg.bgid < BGID_ARRAY && !ctx->io_bl)) {
491 int ret = io_init_bl_list(ctx);
492 if (ret)
493 return ret;
494 }
495
496 bl = io_buffer_get_list(ctx, reg.bgid);
497 if (bl) {
498 /* if mapped buffer ring OR classic exists, don't allow */
499 if (bl->buf_nr_pages || !list_empty(&bl->buf_list))
500 return -EEXIST;
501 } else {
502 free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
503 if (!bl)
504 return -ENOMEM;
505 }
506
507 pages = io_pin_pages(reg.ring_addr,
508 struct_size(br, bufs, reg.ring_entries),
509 &nr_pages);
510 if (IS_ERR(pages)) {
511 kfree(free_bl);
512 return PTR_ERR(pages);
513 }
514
515 br = page_address(pages[0]);
516 bl->buf_pages = pages;
517 bl->buf_nr_pages = nr_pages;
518 bl->nr_entries = reg.ring_entries;
519 bl->buf_ring = br;
520 bl->mask = reg.ring_entries - 1;
521 io_buffer_add_list(ctx, bl, reg.bgid);
522 return 0;
523}
524
525int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
526{
527 struct io_uring_buf_reg reg;
528 struct io_buffer_list *bl;
529
530 if (copy_from_user(®, arg, sizeof(reg)))
531 return -EFAULT;
532 if (reg.pad || reg.resv[0] || reg.resv[1] || reg.resv[2])
533 return -EINVAL;
534
535 bl = io_buffer_get_list(ctx, reg.bgid);
536 if (!bl)
537 return -ENOENT;
538 if (!bl->buf_nr_pages)
539 return -EINVAL;
540
541 __io_remove_buffers(ctx, bl, -1U);
542 if (bl->bgid >= BGID_ARRAY) {
543 xa_erase(&ctx->io_bl_xa, bl->bgid);
544 kfree(bl);
545 }
546 return 0;
547}
1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/errno.h>
4#include <linux/fs.h>
5#include <linux/file.h>
6#include <linux/mm.h>
7#include <linux/slab.h>
8#include <linux/namei.h>
9#include <linux/poll.h>
10#include <linux/vmalloc.h>
11#include <linux/io_uring.h>
12
13#include <uapi/linux/io_uring.h>
14
15#include "io_uring.h"
16#include "opdef.h"
17#include "kbuf.h"
18#include "memmap.h"
19
20/* BIDs are addressed by a 16-bit field in a CQE */
21#define MAX_BIDS_PER_BGID (1 << 16)
22
23struct kmem_cache *io_buf_cachep;
24
25struct io_provide_buf {
26 struct file *file;
27 __u64 addr;
28 __u32 len;
29 __u32 bgid;
30 __u32 nbufs;
31 __u16 bid;
32};
33
34static inline struct io_buffer_list *io_buffer_get_list(struct io_ring_ctx *ctx,
35 unsigned int bgid)
36{
37 lockdep_assert_held(&ctx->uring_lock);
38
39 return xa_load(&ctx->io_bl_xa, bgid);
40}
41
42static int io_buffer_add_list(struct io_ring_ctx *ctx,
43 struct io_buffer_list *bl, unsigned int bgid)
44{
45 /*
46 * Store buffer group ID and finally mark the list as visible.
47 * The normal lookup doesn't care about the visibility as we're
48 * always under the ->uring_lock, but the RCU lookup from mmap does.
49 */
50 bl->bgid = bgid;
51 atomic_set(&bl->refs, 1);
52 return xa_err(xa_store(&ctx->io_bl_xa, bgid, bl, GFP_KERNEL));
53}
54
55bool io_kbuf_recycle_legacy(struct io_kiocb *req, unsigned issue_flags)
56{
57 struct io_ring_ctx *ctx = req->ctx;
58 struct io_buffer_list *bl;
59 struct io_buffer *buf;
60
61 io_ring_submit_lock(ctx, issue_flags);
62
63 buf = req->kbuf;
64 bl = io_buffer_get_list(ctx, buf->bgid);
65 list_add(&buf->list, &bl->buf_list);
66 req->flags &= ~REQ_F_BUFFER_SELECTED;
67 req->buf_index = buf->bgid;
68
69 io_ring_submit_unlock(ctx, issue_flags);
70 return true;
71}
72
73void __io_put_kbuf(struct io_kiocb *req, int len, unsigned issue_flags)
74{
75 /*
76 * We can add this buffer back to two lists:
77 *
78 * 1) The io_buffers_cache list. This one is protected by the
79 * ctx->uring_lock. If we already hold this lock, add back to this
80 * list as we can grab it from issue as well.
81 * 2) The io_buffers_comp list. This one is protected by the
82 * ctx->completion_lock.
83 *
84 * We migrate buffers from the comp_list to the issue cache list
85 * when we need one.
86 */
87 if (issue_flags & IO_URING_F_UNLOCKED) {
88 struct io_ring_ctx *ctx = req->ctx;
89
90 spin_lock(&ctx->completion_lock);
91 __io_put_kbuf_list(req, len, &ctx->io_buffers_comp);
92 spin_unlock(&ctx->completion_lock);
93 } else {
94 lockdep_assert_held(&req->ctx->uring_lock);
95
96 __io_put_kbuf_list(req, len, &req->ctx->io_buffers_cache);
97 }
98}
99
100static void __user *io_provided_buffer_select(struct io_kiocb *req, size_t *len,
101 struct io_buffer_list *bl)
102{
103 if (!list_empty(&bl->buf_list)) {
104 struct io_buffer *kbuf;
105
106 kbuf = list_first_entry(&bl->buf_list, struct io_buffer, list);
107 list_del(&kbuf->list);
108 if (*len == 0 || *len > kbuf->len)
109 *len = kbuf->len;
110 if (list_empty(&bl->buf_list))
111 req->flags |= REQ_F_BL_EMPTY;
112 req->flags |= REQ_F_BUFFER_SELECTED;
113 req->kbuf = kbuf;
114 req->buf_index = kbuf->bid;
115 return u64_to_user_ptr(kbuf->addr);
116 }
117 return NULL;
118}
119
120static int io_provided_buffers_select(struct io_kiocb *req, size_t *len,
121 struct io_buffer_list *bl,
122 struct iovec *iov)
123{
124 void __user *buf;
125
126 buf = io_provided_buffer_select(req, len, bl);
127 if (unlikely(!buf))
128 return -ENOBUFS;
129
130 iov[0].iov_base = buf;
131 iov[0].iov_len = *len;
132 return 1;
133}
134
135static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len,
136 struct io_buffer_list *bl,
137 unsigned int issue_flags)
138{
139 struct io_uring_buf_ring *br = bl->buf_ring;
140 __u16 tail, head = bl->head;
141 struct io_uring_buf *buf;
142 void __user *ret;
143
144 tail = smp_load_acquire(&br->tail);
145 if (unlikely(tail == head))
146 return NULL;
147
148 if (head + 1 == tail)
149 req->flags |= REQ_F_BL_EMPTY;
150
151 buf = io_ring_head_to_buf(br, head, bl->mask);
152 if (*len == 0 || *len > buf->len)
153 *len = buf->len;
154 req->flags |= REQ_F_BUFFER_RING | REQ_F_BUFFERS_COMMIT;
155 req->buf_list = bl;
156 req->buf_index = buf->bid;
157 ret = u64_to_user_ptr(buf->addr);
158
159 if (issue_flags & IO_URING_F_UNLOCKED || !io_file_can_poll(req)) {
160 /*
161 * If we came in unlocked, we have no choice but to consume the
162 * buffer here, otherwise nothing ensures that the buffer won't
163 * get used by others. This does mean it'll be pinned until the
164 * IO completes, coming in unlocked means we're being called from
165 * io-wq context and there may be further retries in async hybrid
166 * mode. For the locked case, the caller must call commit when
167 * the transfer completes (or if we get -EAGAIN and must poll of
168 * retry).
169 */
170 io_kbuf_commit(req, bl, *len, 1);
171 req->buf_list = NULL;
172 }
173 return ret;
174}
175
176void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
177 unsigned int issue_flags)
178{
179 struct io_ring_ctx *ctx = req->ctx;
180 struct io_buffer_list *bl;
181 void __user *ret = NULL;
182
183 io_ring_submit_lock(req->ctx, issue_flags);
184
185 bl = io_buffer_get_list(ctx, req->buf_index);
186 if (likely(bl)) {
187 if (bl->flags & IOBL_BUF_RING)
188 ret = io_ring_buffer_select(req, len, bl, issue_flags);
189 else
190 ret = io_provided_buffer_select(req, len, bl);
191 }
192 io_ring_submit_unlock(req->ctx, issue_flags);
193 return ret;
194}
195
196/* cap it at a reasonable 256, will be one page even for 4K */
197#define PEEK_MAX_IMPORT 256
198
199static int io_ring_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg,
200 struct io_buffer_list *bl)
201{
202 struct io_uring_buf_ring *br = bl->buf_ring;
203 struct iovec *iov = arg->iovs;
204 int nr_iovs = arg->nr_iovs;
205 __u16 nr_avail, tail, head;
206 struct io_uring_buf *buf;
207
208 tail = smp_load_acquire(&br->tail);
209 head = bl->head;
210 nr_avail = min_t(__u16, tail - head, UIO_MAXIOV);
211 if (unlikely(!nr_avail))
212 return -ENOBUFS;
213
214 buf = io_ring_head_to_buf(br, head, bl->mask);
215 if (arg->max_len) {
216 u32 len = READ_ONCE(buf->len);
217
218 if (unlikely(!len))
219 return -ENOBUFS;
220 /*
221 * Limit incremental buffers to 1 segment. No point trying
222 * to peek ahead and map more than we need, when the buffers
223 * themselves should be large when setup with
224 * IOU_PBUF_RING_INC.
225 */
226 if (bl->flags & IOBL_INC) {
227 nr_avail = 1;
228 } else {
229 size_t needed;
230
231 needed = (arg->max_len + len - 1) / len;
232 needed = min_not_zero(needed, (size_t) PEEK_MAX_IMPORT);
233 if (nr_avail > needed)
234 nr_avail = needed;
235 }
236 }
237
238 /*
239 * only alloc a bigger array if we know we have data to map, eg not
240 * a speculative peek operation.
241 */
242 if (arg->mode & KBUF_MODE_EXPAND && nr_avail > nr_iovs && arg->max_len) {
243 iov = kmalloc_array(nr_avail, sizeof(struct iovec), GFP_KERNEL);
244 if (unlikely(!iov))
245 return -ENOMEM;
246 if (arg->mode & KBUF_MODE_FREE)
247 kfree(arg->iovs);
248 arg->iovs = iov;
249 nr_iovs = nr_avail;
250 } else if (nr_avail < nr_iovs) {
251 nr_iovs = nr_avail;
252 }
253
254 /* set it to max, if not set, so we can use it unconditionally */
255 if (!arg->max_len)
256 arg->max_len = INT_MAX;
257
258 req->buf_index = buf->bid;
259 do {
260 u32 len = buf->len;
261
262 /* truncate end piece, if needed, for non partial buffers */
263 if (len > arg->max_len) {
264 len = arg->max_len;
265 if (!(bl->flags & IOBL_INC))
266 buf->len = len;
267 }
268
269 iov->iov_base = u64_to_user_ptr(buf->addr);
270 iov->iov_len = len;
271 iov++;
272
273 arg->out_len += len;
274 arg->max_len -= len;
275 if (!arg->max_len)
276 break;
277
278 buf = io_ring_head_to_buf(br, ++head, bl->mask);
279 } while (--nr_iovs);
280
281 if (head == tail)
282 req->flags |= REQ_F_BL_EMPTY;
283
284 req->flags |= REQ_F_BUFFER_RING;
285 req->buf_list = bl;
286 return iov - arg->iovs;
287}
288
289int io_buffers_select(struct io_kiocb *req, struct buf_sel_arg *arg,
290 unsigned int issue_flags)
291{
292 struct io_ring_ctx *ctx = req->ctx;
293 struct io_buffer_list *bl;
294 int ret = -ENOENT;
295
296 io_ring_submit_lock(ctx, issue_flags);
297 bl = io_buffer_get_list(ctx, req->buf_index);
298 if (unlikely(!bl))
299 goto out_unlock;
300
301 if (bl->flags & IOBL_BUF_RING) {
302 ret = io_ring_buffers_peek(req, arg, bl);
303 /*
304 * Don't recycle these buffers if we need to go through poll.
305 * Nobody else can use them anyway, and holding on to provided
306 * buffers for a send/write operation would happen on the app
307 * side anyway with normal buffers. Besides, we already
308 * committed them, they cannot be put back in the queue.
309 */
310 if (ret > 0) {
311 req->flags |= REQ_F_BUFFERS_COMMIT | REQ_F_BL_NO_RECYCLE;
312 io_kbuf_commit(req, bl, arg->out_len, ret);
313 }
314 } else {
315 ret = io_provided_buffers_select(req, &arg->out_len, bl, arg->iovs);
316 }
317out_unlock:
318 io_ring_submit_unlock(ctx, issue_flags);
319 return ret;
320}
321
322int io_buffers_peek(struct io_kiocb *req, struct buf_sel_arg *arg)
323{
324 struct io_ring_ctx *ctx = req->ctx;
325 struct io_buffer_list *bl;
326 int ret;
327
328 lockdep_assert_held(&ctx->uring_lock);
329
330 bl = io_buffer_get_list(ctx, req->buf_index);
331 if (unlikely(!bl))
332 return -ENOENT;
333
334 if (bl->flags & IOBL_BUF_RING) {
335 ret = io_ring_buffers_peek(req, arg, bl);
336 if (ret > 0)
337 req->flags |= REQ_F_BUFFERS_COMMIT;
338 return ret;
339 }
340
341 /* don't support multiple buffer selections for legacy */
342 return io_provided_buffers_select(req, &arg->max_len, bl, arg->iovs);
343}
344
345static int __io_remove_buffers(struct io_ring_ctx *ctx,
346 struct io_buffer_list *bl, unsigned nbufs)
347{
348 unsigned i = 0;
349
350 /* shouldn't happen */
351 if (!nbufs)
352 return 0;
353
354 if (bl->flags & IOBL_BUF_RING) {
355 i = bl->buf_ring->tail - bl->head;
356 if (bl->buf_nr_pages) {
357 int j;
358
359 if (!(bl->flags & IOBL_MMAP)) {
360 for (j = 0; j < bl->buf_nr_pages; j++)
361 unpin_user_page(bl->buf_pages[j]);
362 }
363 io_pages_unmap(bl->buf_ring, &bl->buf_pages,
364 &bl->buf_nr_pages, bl->flags & IOBL_MMAP);
365 bl->flags &= ~IOBL_MMAP;
366 }
367 /* make sure it's seen as empty */
368 INIT_LIST_HEAD(&bl->buf_list);
369 bl->flags &= ~IOBL_BUF_RING;
370 return i;
371 }
372
373 /* protects io_buffers_cache */
374 lockdep_assert_held(&ctx->uring_lock);
375
376 while (!list_empty(&bl->buf_list)) {
377 struct io_buffer *nxt;
378
379 nxt = list_first_entry(&bl->buf_list, struct io_buffer, list);
380 list_move(&nxt->list, &ctx->io_buffers_cache);
381 if (++i == nbufs)
382 return i;
383 cond_resched();
384 }
385
386 return i;
387}
388
389void io_put_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
390{
391 if (atomic_dec_and_test(&bl->refs)) {
392 __io_remove_buffers(ctx, bl, -1U);
393 kfree_rcu(bl, rcu);
394 }
395}
396
397void io_destroy_buffers(struct io_ring_ctx *ctx)
398{
399 struct io_buffer_list *bl;
400 struct list_head *item, *tmp;
401 struct io_buffer *buf;
402 unsigned long index;
403
404 xa_for_each(&ctx->io_bl_xa, index, bl) {
405 xa_erase(&ctx->io_bl_xa, bl->bgid);
406 io_put_bl(ctx, bl);
407 }
408
409 /*
410 * Move deferred locked entries to cache before pruning
411 */
412 spin_lock(&ctx->completion_lock);
413 if (!list_empty(&ctx->io_buffers_comp))
414 list_splice_init(&ctx->io_buffers_comp, &ctx->io_buffers_cache);
415 spin_unlock(&ctx->completion_lock);
416
417 list_for_each_safe(item, tmp, &ctx->io_buffers_cache) {
418 buf = list_entry(item, struct io_buffer, list);
419 kmem_cache_free(io_buf_cachep, buf);
420 }
421}
422
423static void io_destroy_bl(struct io_ring_ctx *ctx, struct io_buffer_list *bl)
424{
425 xa_erase(&ctx->io_bl_xa, bl->bgid);
426 io_put_bl(ctx, bl);
427}
428
429int io_remove_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
430{
431 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
432 u64 tmp;
433
434 if (sqe->rw_flags || sqe->addr || sqe->len || sqe->off ||
435 sqe->splice_fd_in)
436 return -EINVAL;
437
438 tmp = READ_ONCE(sqe->fd);
439 if (!tmp || tmp > MAX_BIDS_PER_BGID)
440 return -EINVAL;
441
442 memset(p, 0, sizeof(*p));
443 p->nbufs = tmp;
444 p->bgid = READ_ONCE(sqe->buf_group);
445 return 0;
446}
447
448int io_remove_buffers(struct io_kiocb *req, unsigned int issue_flags)
449{
450 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
451 struct io_ring_ctx *ctx = req->ctx;
452 struct io_buffer_list *bl;
453 int ret = 0;
454
455 io_ring_submit_lock(ctx, issue_flags);
456
457 ret = -ENOENT;
458 bl = io_buffer_get_list(ctx, p->bgid);
459 if (bl) {
460 ret = -EINVAL;
461 /* can't use provide/remove buffers command on mapped buffers */
462 if (!(bl->flags & IOBL_BUF_RING))
463 ret = __io_remove_buffers(ctx, bl, p->nbufs);
464 }
465 io_ring_submit_unlock(ctx, issue_flags);
466 if (ret < 0)
467 req_set_fail(req);
468 io_req_set_res(req, ret, 0);
469 return IOU_OK;
470}
471
472int io_provide_buffers_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
473{
474 unsigned long size, tmp_check;
475 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
476 u64 tmp;
477
478 if (sqe->rw_flags || sqe->splice_fd_in)
479 return -EINVAL;
480
481 tmp = READ_ONCE(sqe->fd);
482 if (!tmp || tmp > MAX_BIDS_PER_BGID)
483 return -E2BIG;
484 p->nbufs = tmp;
485 p->addr = READ_ONCE(sqe->addr);
486 p->len = READ_ONCE(sqe->len);
487
488 if (check_mul_overflow((unsigned long)p->len, (unsigned long)p->nbufs,
489 &size))
490 return -EOVERFLOW;
491 if (check_add_overflow((unsigned long)p->addr, size, &tmp_check))
492 return -EOVERFLOW;
493
494 size = (unsigned long)p->len * p->nbufs;
495 if (!access_ok(u64_to_user_ptr(p->addr), size))
496 return -EFAULT;
497
498 p->bgid = READ_ONCE(sqe->buf_group);
499 tmp = READ_ONCE(sqe->off);
500 if (tmp > USHRT_MAX)
501 return -E2BIG;
502 if (tmp + p->nbufs > MAX_BIDS_PER_BGID)
503 return -EINVAL;
504 p->bid = tmp;
505 return 0;
506}
507
508#define IO_BUFFER_ALLOC_BATCH 64
509
510static int io_refill_buffer_cache(struct io_ring_ctx *ctx)
511{
512 struct io_buffer *bufs[IO_BUFFER_ALLOC_BATCH];
513 int allocated;
514
515 /*
516 * Completions that don't happen inline (eg not under uring_lock) will
517 * add to ->io_buffers_comp. If we don't have any free buffers, check
518 * the completion list and splice those entries first.
519 */
520 if (!list_empty_careful(&ctx->io_buffers_comp)) {
521 spin_lock(&ctx->completion_lock);
522 if (!list_empty(&ctx->io_buffers_comp)) {
523 list_splice_init(&ctx->io_buffers_comp,
524 &ctx->io_buffers_cache);
525 spin_unlock(&ctx->completion_lock);
526 return 0;
527 }
528 spin_unlock(&ctx->completion_lock);
529 }
530
531 /*
532 * No free buffers and no completion entries either. Allocate a new
533 * batch of buffer entries and add those to our freelist.
534 */
535
536 allocated = kmem_cache_alloc_bulk(io_buf_cachep, GFP_KERNEL_ACCOUNT,
537 ARRAY_SIZE(bufs), (void **) bufs);
538 if (unlikely(!allocated)) {
539 /*
540 * Bulk alloc is all-or-nothing. If we fail to get a batch,
541 * retry single alloc to be on the safe side.
542 */
543 bufs[0] = kmem_cache_alloc(io_buf_cachep, GFP_KERNEL);
544 if (!bufs[0])
545 return -ENOMEM;
546 allocated = 1;
547 }
548
549 while (allocated)
550 list_add_tail(&bufs[--allocated]->list, &ctx->io_buffers_cache);
551
552 return 0;
553}
554
555static int io_add_buffers(struct io_ring_ctx *ctx, struct io_provide_buf *pbuf,
556 struct io_buffer_list *bl)
557{
558 struct io_buffer *buf;
559 u64 addr = pbuf->addr;
560 int i, bid = pbuf->bid;
561
562 for (i = 0; i < pbuf->nbufs; i++) {
563 if (list_empty(&ctx->io_buffers_cache) &&
564 io_refill_buffer_cache(ctx))
565 break;
566 buf = list_first_entry(&ctx->io_buffers_cache, struct io_buffer,
567 list);
568 list_move_tail(&buf->list, &bl->buf_list);
569 buf->addr = addr;
570 buf->len = min_t(__u32, pbuf->len, MAX_RW_COUNT);
571 buf->bid = bid;
572 buf->bgid = pbuf->bgid;
573 addr += pbuf->len;
574 bid++;
575 cond_resched();
576 }
577
578 return i ? 0 : -ENOMEM;
579}
580
581int io_provide_buffers(struct io_kiocb *req, unsigned int issue_flags)
582{
583 struct io_provide_buf *p = io_kiocb_to_cmd(req, struct io_provide_buf);
584 struct io_ring_ctx *ctx = req->ctx;
585 struct io_buffer_list *bl;
586 int ret = 0;
587
588 io_ring_submit_lock(ctx, issue_flags);
589
590 bl = io_buffer_get_list(ctx, p->bgid);
591 if (unlikely(!bl)) {
592 bl = kzalloc(sizeof(*bl), GFP_KERNEL_ACCOUNT);
593 if (!bl) {
594 ret = -ENOMEM;
595 goto err;
596 }
597 INIT_LIST_HEAD(&bl->buf_list);
598 ret = io_buffer_add_list(ctx, bl, p->bgid);
599 if (ret) {
600 /*
601 * Doesn't need rcu free as it was never visible, but
602 * let's keep it consistent throughout.
603 */
604 kfree_rcu(bl, rcu);
605 goto err;
606 }
607 }
608 /* can't add buffers via this command for a mapped buffer ring */
609 if (bl->flags & IOBL_BUF_RING) {
610 ret = -EINVAL;
611 goto err;
612 }
613
614 ret = io_add_buffers(ctx, p, bl);
615err:
616 io_ring_submit_unlock(ctx, issue_flags);
617
618 if (ret < 0)
619 req_set_fail(req);
620 io_req_set_res(req, ret, 0);
621 return IOU_OK;
622}
623
624static int io_pin_pbuf_ring(struct io_uring_buf_reg *reg,
625 struct io_buffer_list *bl)
626{
627 struct io_uring_buf_ring *br = NULL;
628 struct page **pages;
629 int nr_pages, ret;
630
631 pages = io_pin_pages(reg->ring_addr,
632 flex_array_size(br, bufs, reg->ring_entries),
633 &nr_pages);
634 if (IS_ERR(pages))
635 return PTR_ERR(pages);
636
637 br = vmap(pages, nr_pages, VM_MAP, PAGE_KERNEL);
638 if (!br) {
639 ret = -ENOMEM;
640 goto error_unpin;
641 }
642
643#ifdef SHM_COLOUR
644 /*
645 * On platforms that have specific aliasing requirements, SHM_COLOUR
646 * is set and we must guarantee that the kernel and user side align
647 * nicely. We cannot do that if IOU_PBUF_RING_MMAP isn't set and
648 * the application mmap's the provided ring buffer. Fail the request
649 * if we, by chance, don't end up with aligned addresses. The app
650 * should use IOU_PBUF_RING_MMAP instead, and liburing will handle
651 * this transparently.
652 */
653 if ((reg->ring_addr | (unsigned long) br) & (SHM_COLOUR - 1)) {
654 ret = -EINVAL;
655 goto error_unpin;
656 }
657#endif
658 bl->buf_pages = pages;
659 bl->buf_nr_pages = nr_pages;
660 bl->buf_ring = br;
661 bl->flags |= IOBL_BUF_RING;
662 bl->flags &= ~IOBL_MMAP;
663 return 0;
664error_unpin:
665 unpin_user_pages(pages, nr_pages);
666 kvfree(pages);
667 vunmap(br);
668 return ret;
669}
670
671static int io_alloc_pbuf_ring(struct io_ring_ctx *ctx,
672 struct io_uring_buf_reg *reg,
673 struct io_buffer_list *bl)
674{
675 size_t ring_size;
676
677 ring_size = reg->ring_entries * sizeof(struct io_uring_buf_ring);
678
679 bl->buf_ring = io_pages_map(&bl->buf_pages, &bl->buf_nr_pages, ring_size);
680 if (IS_ERR(bl->buf_ring)) {
681 bl->buf_ring = NULL;
682 return -ENOMEM;
683 }
684
685 bl->flags |= (IOBL_BUF_RING | IOBL_MMAP);
686 return 0;
687}
688
689int io_register_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
690{
691 struct io_uring_buf_reg reg;
692 struct io_buffer_list *bl, *free_bl = NULL;
693 int ret;
694
695 lockdep_assert_held(&ctx->uring_lock);
696
697 if (copy_from_user(®, arg, sizeof(reg)))
698 return -EFAULT;
699
700 if (reg.resv[0] || reg.resv[1] || reg.resv[2])
701 return -EINVAL;
702 if (reg.flags & ~(IOU_PBUF_RING_MMAP | IOU_PBUF_RING_INC))
703 return -EINVAL;
704 if (!(reg.flags & IOU_PBUF_RING_MMAP)) {
705 if (!reg.ring_addr)
706 return -EFAULT;
707 if (reg.ring_addr & ~PAGE_MASK)
708 return -EINVAL;
709 } else {
710 if (reg.ring_addr)
711 return -EINVAL;
712 }
713
714 if (!is_power_of_2(reg.ring_entries))
715 return -EINVAL;
716
717 /* cannot disambiguate full vs empty due to head/tail size */
718 if (reg.ring_entries >= 65536)
719 return -EINVAL;
720
721 bl = io_buffer_get_list(ctx, reg.bgid);
722 if (bl) {
723 /* if mapped buffer ring OR classic exists, don't allow */
724 if (bl->flags & IOBL_BUF_RING || !list_empty(&bl->buf_list))
725 return -EEXIST;
726 io_destroy_bl(ctx, bl);
727 }
728
729 free_bl = bl = kzalloc(sizeof(*bl), GFP_KERNEL);
730 if (!bl)
731 return -ENOMEM;
732
733 if (!(reg.flags & IOU_PBUF_RING_MMAP))
734 ret = io_pin_pbuf_ring(®, bl);
735 else
736 ret = io_alloc_pbuf_ring(ctx, ®, bl);
737
738 if (!ret) {
739 bl->nr_entries = reg.ring_entries;
740 bl->mask = reg.ring_entries - 1;
741 if (reg.flags & IOU_PBUF_RING_INC)
742 bl->flags |= IOBL_INC;
743
744 io_buffer_add_list(ctx, bl, reg.bgid);
745 return 0;
746 }
747
748 kfree_rcu(free_bl, rcu);
749 return ret;
750}
751
752int io_unregister_pbuf_ring(struct io_ring_ctx *ctx, void __user *arg)
753{
754 struct io_uring_buf_reg reg;
755 struct io_buffer_list *bl;
756
757 lockdep_assert_held(&ctx->uring_lock);
758
759 if (copy_from_user(®, arg, sizeof(reg)))
760 return -EFAULT;
761 if (reg.resv[0] || reg.resv[1] || reg.resv[2])
762 return -EINVAL;
763 if (reg.flags)
764 return -EINVAL;
765
766 bl = io_buffer_get_list(ctx, reg.bgid);
767 if (!bl)
768 return -ENOENT;
769 if (!(bl->flags & IOBL_BUF_RING))
770 return -EINVAL;
771
772 xa_erase(&ctx->io_bl_xa, bl->bgid);
773 io_put_bl(ctx, bl);
774 return 0;
775}
776
777int io_register_pbuf_status(struct io_ring_ctx *ctx, void __user *arg)
778{
779 struct io_uring_buf_status buf_status;
780 struct io_buffer_list *bl;
781 int i;
782
783 if (copy_from_user(&buf_status, arg, sizeof(buf_status)))
784 return -EFAULT;
785
786 for (i = 0; i < ARRAY_SIZE(buf_status.resv); i++)
787 if (buf_status.resv[i])
788 return -EINVAL;
789
790 bl = io_buffer_get_list(ctx, buf_status.buf_group);
791 if (!bl)
792 return -ENOENT;
793 if (!(bl->flags & IOBL_BUF_RING))
794 return -EINVAL;
795
796 buf_status.head = bl->head;
797 if (copy_to_user(arg, &buf_status, sizeof(buf_status)))
798 return -EFAULT;
799
800 return 0;
801}
802
803struct io_buffer_list *io_pbuf_get_bl(struct io_ring_ctx *ctx,
804 unsigned long bgid)
805{
806 struct io_buffer_list *bl;
807 bool ret;
808
809 /*
810 * We have to be a bit careful here - we're inside mmap and cannot grab
811 * the uring_lock. This means the buffer_list could be simultaneously
812 * going away, if someone is trying to be sneaky. Look it up under rcu
813 * so we know it's not going away, and attempt to grab a reference to
814 * it. If the ref is already zero, then fail the mapping. If successful,
815 * the caller will call io_put_bl() to drop the the reference at at the
816 * end. This may then safely free the buffer_list (and drop the pages)
817 * at that point, vm_insert_pages() would've already grabbed the
818 * necessary vma references.
819 */
820 rcu_read_lock();
821 bl = xa_load(&ctx->io_bl_xa, bgid);
822 /* must be a mmap'able buffer ring and have pages */
823 ret = false;
824 if (bl && bl->flags & IOBL_MMAP)
825 ret = atomic_inc_not_zero(&bl->refs);
826 rcu_read_unlock();
827
828 if (ret)
829 return bl;
830
831 return ERR_PTR(-EINVAL);
832}
833
834int io_pbuf_mmap(struct file *file, struct vm_area_struct *vma)
835{
836 struct io_ring_ctx *ctx = file->private_data;
837 loff_t pgoff = vma->vm_pgoff << PAGE_SHIFT;
838 struct io_buffer_list *bl;
839 int bgid, ret;
840
841 bgid = (pgoff & ~IORING_OFF_MMAP_MASK) >> IORING_OFF_PBUF_SHIFT;
842 bl = io_pbuf_get_bl(ctx, bgid);
843 if (IS_ERR(bl))
844 return PTR_ERR(bl);
845
846 ret = io_uring_mmap_pages(ctx, vma, bl->buf_pages, bl->buf_nr_pages);
847 io_put_bl(ctx, bl);
848 return ret;
849}