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Linux/fs/aio.c

  1 /*
  2  *      An async IO implementation for Linux
  3  *      Written by Benjamin LaHaise <bcrl@kvack.org>
  4  *
  5  *      Implements an efficient asynchronous io interface.
  6  *
  7  *      Copyright 2000, 2001, 2002 Red Hat, Inc.  All Rights Reserved.
  8  *
  9  *      See ../COPYING for licensing terms.
 10  */
 11 #define pr_fmt(fmt) "%s: " fmt, __func__
 12 
 13 #include <linux/kernel.h>
 14 #include <linux/init.h>
 15 #include <linux/errno.h>
 16 #include <linux/time.h>
 17 #include <linux/aio_abi.h>
 18 #include <linux/export.h>
 19 #include <linux/syscalls.h>
 20 #include <linux/backing-dev.h>
 21 #include <linux/uio.h>
 22 
 23 #include <linux/sched.h>
 24 #include <linux/fs.h>
 25 #include <linux/file.h>
 26 #include <linux/mm.h>
 27 #include <linux/mman.h>
 28 #include <linux/mmu_context.h>
 29 #include <linux/percpu.h>
 30 #include <linux/slab.h>
 31 #include <linux/timer.h>
 32 #include <linux/aio.h>
 33 #include <linux/highmem.h>
 34 #include <linux/workqueue.h>
 35 #include <linux/security.h>
 36 #include <linux/eventfd.h>
 37 #include <linux/blkdev.h>
 38 #include <linux/compat.h>
 39 #include <linux/migrate.h>
 40 #include <linux/ramfs.h>
 41 #include <linux/percpu-refcount.h>
 42 #include <linux/mount.h>
 43 
 44 #include <asm/kmap_types.h>
 45 #include <asm/uaccess.h>
 46 
 47 #include "internal.h"
 48 
 49 #define AIO_RING_MAGIC                  0xa10a10a1
 50 #define AIO_RING_COMPAT_FEATURES        1
 51 #define AIO_RING_INCOMPAT_FEATURES      0
 52 struct aio_ring {
 53         unsigned        id;     /* kernel internal index number */
 54         unsigned        nr;     /* number of io_events */
 55         unsigned        head;   /* Written to by userland or under ring_lock
 56                                  * mutex by aio_read_events_ring(). */
 57         unsigned        tail;
 58 
 59         unsigned        magic;
 60         unsigned        compat_features;
 61         unsigned        incompat_features;
 62         unsigned        header_length;  /* size of aio_ring */
 63 
 64 
 65         struct io_event         io_events[0];
 66 }; /* 128 bytes + ring size */
 67 
 68 #define AIO_RING_PAGES  8
 69 
 70 struct kioctx_table {
 71         struct rcu_head rcu;
 72         unsigned        nr;
 73         struct kioctx   *table[];
 74 };
 75 
 76 struct kioctx_cpu {
 77         unsigned                reqs_available;
 78 };
 79 
 80 struct ctx_rq_wait {
 81         struct completion comp;
 82         atomic_t count;
 83 };
 84 
 85 struct kioctx {
 86         struct percpu_ref       users;
 87         atomic_t                dead;
 88 
 89         struct percpu_ref       reqs;
 90 
 91         unsigned long           user_id;
 92 
 93         struct __percpu kioctx_cpu *cpu;
 94 
 95         /*
 96          * For percpu reqs_available, number of slots we move to/from global
 97          * counter at a time:
 98          */
 99         unsigned                req_batch;
100         /*
101          * This is what userspace passed to io_setup(), it's not used for
102          * anything but counting against the global max_reqs quota.
103          *
104          * The real limit is nr_events - 1, which will be larger (see
105          * aio_setup_ring())
106          */
107         unsigned                max_reqs;
108 
109         /* Size of ringbuffer, in units of struct io_event */
110         unsigned                nr_events;
111 
112         unsigned long           mmap_base;
113         unsigned long           mmap_size;
114 
115         struct page             **ring_pages;
116         long                    nr_pages;
117 
118         struct work_struct      free_work;
119 
120         /*
121          * signals when all in-flight requests are done
122          */
123         struct ctx_rq_wait      *rq_wait;
124 
125         struct {
126                 /*
127                  * This counts the number of available slots in the ringbuffer,
128                  * so we avoid overflowing it: it's decremented (if positive)
129                  * when allocating a kiocb and incremented when the resulting
130                  * io_event is pulled off the ringbuffer.
131                  *
132                  * We batch accesses to it with a percpu version.
133                  */
134                 atomic_t        reqs_available;
135         } ____cacheline_aligned_in_smp;
136 
137         struct {
138                 spinlock_t      ctx_lock;
139                 struct list_head active_reqs;   /* used for cancellation */
140         } ____cacheline_aligned_in_smp;
141 
142         struct {
143                 struct mutex    ring_lock;
144                 wait_queue_head_t wait;
145         } ____cacheline_aligned_in_smp;
146 
147         struct {
148                 unsigned        tail;
149                 unsigned        completed_events;
150                 spinlock_t      completion_lock;
151         } ____cacheline_aligned_in_smp;
152 
153         struct page             *internal_pages[AIO_RING_PAGES];
154         struct file             *aio_ring_file;
155 
156         unsigned                id;
157 };
158 
159 /*
160  * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
161  * cancelled or completed (this makes a certain amount of sense because
162  * successful cancellation - io_cancel() - does deliver the completion to
163  * userspace).
164  *
165  * And since most things don't implement kiocb cancellation and we'd really like
166  * kiocb completion to be lockless when possible, we use ki_cancel to
167  * synchronize cancellation and completion - we only set it to KIOCB_CANCELLED
168  * with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel().
169  */
170 #define KIOCB_CANCELLED         ((void *) (~0ULL))
171 
172 struct aio_kiocb {
173         struct kiocb            common;
174 
175         struct kioctx           *ki_ctx;
176         kiocb_cancel_fn         *ki_cancel;
177 
178         struct iocb __user      *ki_user_iocb;  /* user's aiocb */
179         __u64                   ki_user_data;   /* user's data for completion */
180 
181         struct list_head        ki_list;        /* the aio core uses this
182                                                  * for cancellation */
183 
184         /*
185          * If the aio_resfd field of the userspace iocb is not zero,
186          * this is the underlying eventfd context to deliver events to.
187          */
188         struct eventfd_ctx      *ki_eventfd;
189 };
190 
191 /*------ sysctl variables----*/
192 static DEFINE_SPINLOCK(aio_nr_lock);
193 unsigned long aio_nr;           /* current system wide number of aio requests */
194 unsigned long aio_max_nr = 0x10000; /* system wide maximum number of aio requests */
195 /*----end sysctl variables---*/
196 
197 static struct kmem_cache        *kiocb_cachep;
198 static struct kmem_cache        *kioctx_cachep;
199 
200 static struct vfsmount *aio_mnt;
201 
202 static const struct file_operations aio_ring_fops;
203 static const struct address_space_operations aio_ctx_aops;
204 
205 static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
206 {
207         struct qstr this = QSTR_INIT("[aio]", 5);
208         struct file *file;
209         struct path path;
210         struct inode *inode = alloc_anon_inode(aio_mnt->mnt_sb);
211         if (IS_ERR(inode))
212                 return ERR_CAST(inode);
213 
214         inode->i_mapping->a_ops = &aio_ctx_aops;
215         inode->i_mapping->private_data = ctx;
216         inode->i_size = PAGE_SIZE * nr_pages;
217 
218         path.dentry = d_alloc_pseudo(aio_mnt->mnt_sb, &this);
219         if (!path.dentry) {
220                 iput(inode);
221                 return ERR_PTR(-ENOMEM);
222         }
223         path.mnt = mntget(aio_mnt);
224 
225         d_instantiate(path.dentry, inode);
226         file = alloc_file(&path, FMODE_READ | FMODE_WRITE, &aio_ring_fops);
227         if (IS_ERR(file)) {
228                 path_put(&path);
229                 return file;
230         }
231 
232         file->f_flags = O_RDWR;
233         return file;
234 }
235 
236 static struct dentry *aio_mount(struct file_system_type *fs_type,
237                                 int flags, const char *dev_name, void *data)
238 {
239         static const struct dentry_operations ops = {
240                 .d_dname        = simple_dname,
241         };
242         return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
243 }
244 
245 /* aio_setup
246  *      Creates the slab caches used by the aio routines, panic on
247  *      failure as this is done early during the boot sequence.
248  */
249 static int __init aio_setup(void)
250 {
251         static struct file_system_type aio_fs = {
252                 .name           = "aio",
253                 .mount          = aio_mount,
254                 .kill_sb        = kill_anon_super,
255         };
256         aio_mnt = kern_mount(&aio_fs);
257         if (IS_ERR(aio_mnt))
258                 panic("Failed to create aio fs mount.");
259 
260         kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
261         kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
262 
263         pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
264 
265         return 0;
266 }
267 __initcall(aio_setup);
268 
269 static void put_aio_ring_file(struct kioctx *ctx)
270 {
271         struct file *aio_ring_file = ctx->aio_ring_file;
272         if (aio_ring_file) {
273                 truncate_setsize(aio_ring_file->f_inode, 0);
274 
275                 /* Prevent further access to the kioctx from migratepages */
276                 spin_lock(&aio_ring_file->f_inode->i_mapping->private_lock);
277                 aio_ring_file->f_inode->i_mapping->private_data = NULL;
278                 ctx->aio_ring_file = NULL;
279                 spin_unlock(&aio_ring_file->f_inode->i_mapping->private_lock);
280 
281                 fput(aio_ring_file);
282         }
283 }
284 
285 static void aio_free_ring(struct kioctx *ctx)
286 {
287         int i;
288 
289         /* Disconnect the kiotx from the ring file.  This prevents future
290          * accesses to the kioctx from page migration.
291          */
292         put_aio_ring_file(ctx);
293 
294         for (i = 0; i < ctx->nr_pages; i++) {
295                 struct page *page;
296                 pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
297                                 page_count(ctx->ring_pages[i]));
298                 page = ctx->ring_pages[i];
299                 if (!page)
300                         continue;
301                 ctx->ring_pages[i] = NULL;
302                 put_page(page);
303         }
304 
305         if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
306                 kfree(ctx->ring_pages);
307                 ctx->ring_pages = NULL;
308         }
309 }
310 
311 static int aio_ring_mremap(struct vm_area_struct *vma)
312 {
313         struct file *file = vma->vm_file;
314         struct mm_struct *mm = vma->vm_mm;
315         struct kioctx_table *table;
316         int i, res = -EINVAL;
317 
318         spin_lock(&mm->ioctx_lock);
319         rcu_read_lock();
320         table = rcu_dereference(mm->ioctx_table);
321         for (i = 0; i < table->nr; i++) {
322                 struct kioctx *ctx;
323 
324                 ctx = table->table[i];
325                 if (ctx && ctx->aio_ring_file == file) {
326                         if (!atomic_read(&ctx->dead)) {
327                                 ctx->user_id = ctx->mmap_base = vma->vm_start;
328                                 res = 0;
329                         }
330                         break;
331                 }
332         }
333 
334         rcu_read_unlock();
335         spin_unlock(&mm->ioctx_lock);
336         return res;
337 }
338 
339 static const struct vm_operations_struct aio_ring_vm_ops = {
340         .mremap         = aio_ring_mremap,
341 #if IS_ENABLED(CONFIG_MMU)
342         .fault          = filemap_fault,
343         .map_pages      = filemap_map_pages,
344         .page_mkwrite   = filemap_page_mkwrite,
345 #endif
346 };
347 
348 static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
349 {
350         vma->vm_flags |= VM_DONTEXPAND;
351         vma->vm_ops = &aio_ring_vm_ops;
352         return 0;
353 }
354 
355 static const struct file_operations aio_ring_fops = {
356         .mmap = aio_ring_mmap,
357 };
358 
359 #if IS_ENABLED(CONFIG_MIGRATION)
360 static int aio_migratepage(struct address_space *mapping, struct page *new,
361                         struct page *old, enum migrate_mode mode)
362 {
363         struct kioctx *ctx;
364         unsigned long flags;
365         pgoff_t idx;
366         int rc;
367 
368         rc = 0;
369 
370         /* mapping->private_lock here protects against the kioctx teardown.  */
371         spin_lock(&mapping->private_lock);
372         ctx = mapping->private_data;
373         if (!ctx) {
374                 rc = -EINVAL;
375                 goto out;
376         }
377 
378         /* The ring_lock mutex.  The prevents aio_read_events() from writing
379          * to the ring's head, and prevents page migration from mucking in
380          * a partially initialized kiotx.
381          */
382         if (!mutex_trylock(&ctx->ring_lock)) {
383                 rc = -EAGAIN;
384                 goto out;
385         }
386 
387         idx = old->index;
388         if (idx < (pgoff_t)ctx->nr_pages) {
389                 /* Make sure the old page hasn't already been changed */
390                 if (ctx->ring_pages[idx] != old)
391                         rc = -EAGAIN;
392         } else
393                 rc = -EINVAL;
394 
395         if (rc != 0)
396                 goto out_unlock;
397 
398         /* Writeback must be complete */
399         BUG_ON(PageWriteback(old));
400         get_page(new);
401 
402         rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
403         if (rc != MIGRATEPAGE_SUCCESS) {
404                 put_page(new);
405                 goto out_unlock;
406         }
407 
408         /* Take completion_lock to prevent other writes to the ring buffer
409          * while the old page is copied to the new.  This prevents new
410          * events from being lost.
411          */
412         spin_lock_irqsave(&ctx->completion_lock, flags);
413         migrate_page_copy(new, old);
414         BUG_ON(ctx->ring_pages[idx] != old);
415         ctx->ring_pages[idx] = new;
416         spin_unlock_irqrestore(&ctx->completion_lock, flags);
417 
418         /* The old page is no longer accessible. */
419         put_page(old);
420 
421 out_unlock:
422         mutex_unlock(&ctx->ring_lock);
423 out:
424         spin_unlock(&mapping->private_lock);
425         return rc;
426 }
427 #endif
428 
429 static const struct address_space_operations aio_ctx_aops = {
430         .set_page_dirty = __set_page_dirty_no_writeback,
431 #if IS_ENABLED(CONFIG_MIGRATION)
432         .migratepage    = aio_migratepage,
433 #endif
434 };
435 
436 static int aio_setup_ring(struct kioctx *ctx)
437 {
438         struct aio_ring *ring;
439         unsigned nr_events = ctx->max_reqs;
440         struct mm_struct *mm = current->mm;
441         unsigned long size, unused;
442         int nr_pages;
443         int i;
444         struct file *file;
445 
446         /* Compensate for the ring buffer's head/tail overlap entry */
447         nr_events += 2; /* 1 is required, 2 for good luck */
448 
449         size = sizeof(struct aio_ring);
450         size += sizeof(struct io_event) * nr_events;
451 
452         nr_pages = PFN_UP(size);
453         if (nr_pages < 0)
454                 return -EINVAL;
455 
456         file = aio_private_file(ctx, nr_pages);
457         if (IS_ERR(file)) {
458                 ctx->aio_ring_file = NULL;
459                 return -ENOMEM;
460         }
461 
462         ctx->aio_ring_file = file;
463         nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
464                         / sizeof(struct io_event);
465 
466         ctx->ring_pages = ctx->internal_pages;
467         if (nr_pages > AIO_RING_PAGES) {
468                 ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
469                                           GFP_KERNEL);
470                 if (!ctx->ring_pages) {
471                         put_aio_ring_file(ctx);
472                         return -ENOMEM;
473                 }
474         }
475 
476         for (i = 0; i < nr_pages; i++) {
477                 struct page *page;
478                 page = find_or_create_page(file->f_inode->i_mapping,
479                                            i, GFP_HIGHUSER | __GFP_ZERO);
480                 if (!page)
481                         break;
482                 pr_debug("pid(%d) page[%d]->count=%d\n",
483                          current->pid, i, page_count(page));
484                 SetPageUptodate(page);
485                 unlock_page(page);
486 
487                 ctx->ring_pages[i] = page;
488         }
489         ctx->nr_pages = i;
490 
491         if (unlikely(i != nr_pages)) {
492                 aio_free_ring(ctx);
493                 return -ENOMEM;
494         }
495 
496         ctx->mmap_size = nr_pages * PAGE_SIZE;
497         pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
498 
499         if (down_write_killable(&mm->mmap_sem)) {
500                 ctx->mmap_size = 0;
501                 aio_free_ring(ctx);
502                 return -EINTR;
503         }
504 
505         ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
506                                        PROT_READ | PROT_WRITE,
507                                        MAP_SHARED, 0, &unused);
508         up_write(&mm->mmap_sem);
509         if (IS_ERR((void *)ctx->mmap_base)) {
510                 ctx->mmap_size = 0;
511                 aio_free_ring(ctx);
512                 return -ENOMEM;
513         }
514 
515         pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
516 
517         ctx->user_id = ctx->mmap_base;
518         ctx->nr_events = nr_events; /* trusted copy */
519 
520         ring = kmap_atomic(ctx->ring_pages[0]);
521         ring->nr = nr_events;   /* user copy */
522         ring->id = ~0U;
523         ring->head = ring->tail = 0;
524         ring->magic = AIO_RING_MAGIC;
525         ring->compat_features = AIO_RING_COMPAT_FEATURES;
526         ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
527         ring->header_length = sizeof(struct aio_ring);
528         kunmap_atomic(ring);
529         flush_dcache_page(ctx->ring_pages[0]);
530 
531         return 0;
532 }
533 
534 #define AIO_EVENTS_PER_PAGE     (PAGE_SIZE / sizeof(struct io_event))
535 #define AIO_EVENTS_FIRST_PAGE   ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
536 #define AIO_EVENTS_OFFSET       (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
537 
538 void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
539 {
540         struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
541         struct kioctx *ctx = req->ki_ctx;
542         unsigned long flags;
543 
544         spin_lock_irqsave(&ctx->ctx_lock, flags);
545 
546         if (!req->ki_list.next)
547                 list_add(&req->ki_list, &ctx->active_reqs);
548 
549         req->ki_cancel = cancel;
550 
551         spin_unlock_irqrestore(&ctx->ctx_lock, flags);
552 }
553 EXPORT_SYMBOL(kiocb_set_cancel_fn);
554 
555 static int kiocb_cancel(struct aio_kiocb *kiocb)
556 {
557         kiocb_cancel_fn *old, *cancel;
558 
559         /*
560          * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
561          * actually has a cancel function, hence the cmpxchg()
562          */
563 
564         cancel = ACCESS_ONCE(kiocb->ki_cancel);
565         do {
566                 if (!cancel || cancel == KIOCB_CANCELLED)
567                         return -EINVAL;
568 
569                 old = cancel;
570                 cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
571         } while (cancel != old);
572 
573         return cancel(&kiocb->common);
574 }
575 
576 static void free_ioctx(struct work_struct *work)
577 {
578         struct kioctx *ctx = container_of(work, struct kioctx, free_work);
579 
580         pr_debug("freeing %p\n", ctx);
581 
582         aio_free_ring(ctx);
583         free_percpu(ctx->cpu);
584         percpu_ref_exit(&ctx->reqs);
585         percpu_ref_exit(&ctx->users);
586         kmem_cache_free(kioctx_cachep, ctx);
587 }
588 
589 static void free_ioctx_reqs(struct percpu_ref *ref)
590 {
591         struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
592 
593         /* At this point we know that there are no any in-flight requests */
594         if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
595                 complete(&ctx->rq_wait->comp);
596 
597         INIT_WORK(&ctx->free_work, free_ioctx);
598         schedule_work(&ctx->free_work);
599 }
600 
601 /*
602  * When this function runs, the kioctx has been removed from the "hash table"
603  * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
604  * now it's safe to cancel any that need to be.
605  */
606 static void free_ioctx_users(struct percpu_ref *ref)
607 {
608         struct kioctx *ctx = container_of(ref, struct kioctx, users);
609         struct aio_kiocb *req;
610 
611         spin_lock_irq(&ctx->ctx_lock);
612 
613         while (!list_empty(&ctx->active_reqs)) {
614                 req = list_first_entry(&ctx->active_reqs,
615                                        struct aio_kiocb, ki_list);
616 
617                 list_del_init(&req->ki_list);
618                 kiocb_cancel(req);
619         }
620 
621         spin_unlock_irq(&ctx->ctx_lock);
622 
623         percpu_ref_kill(&ctx->reqs);
624         percpu_ref_put(&ctx->reqs);
625 }
626 
627 static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
628 {
629         unsigned i, new_nr;
630         struct kioctx_table *table, *old;
631         struct aio_ring *ring;
632 
633         spin_lock(&mm->ioctx_lock);
634         table = rcu_dereference_raw(mm->ioctx_table);
635 
636         while (1) {
637                 if (table)
638                         for (i = 0; i < table->nr; i++)
639                                 if (!table->table[i]) {
640                                         ctx->id = i;
641                                         table->table[i] = ctx;
642                                         spin_unlock(&mm->ioctx_lock);
643 
644                                         /* While kioctx setup is in progress,
645                                          * we are protected from page migration
646                                          * changes ring_pages by ->ring_lock.
647                                          */
648                                         ring = kmap_atomic(ctx->ring_pages[0]);
649                                         ring->id = ctx->id;
650                                         kunmap_atomic(ring);
651                                         return 0;
652                                 }
653 
654                 new_nr = (table ? table->nr : 1) * 4;
655                 spin_unlock(&mm->ioctx_lock);
656 
657                 table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
658                                 new_nr, GFP_KERNEL);
659                 if (!table)
660                         return -ENOMEM;
661 
662                 table->nr = new_nr;
663 
664                 spin_lock(&mm->ioctx_lock);
665                 old = rcu_dereference_raw(mm->ioctx_table);
666 
667                 if (!old) {
668                         rcu_assign_pointer(mm->ioctx_table, table);
669                 } else if (table->nr > old->nr) {
670                         memcpy(table->table, old->table,
671                                old->nr * sizeof(struct kioctx *));
672 
673                         rcu_assign_pointer(mm->ioctx_table, table);
674                         kfree_rcu(old, rcu);
675                 } else {
676                         kfree(table);
677                         table = old;
678                 }
679         }
680 }
681 
682 static void aio_nr_sub(unsigned nr)
683 {
684         spin_lock(&aio_nr_lock);
685         if (WARN_ON(aio_nr - nr > aio_nr))
686                 aio_nr = 0;
687         else
688                 aio_nr -= nr;
689         spin_unlock(&aio_nr_lock);
690 }
691 
692 /* ioctx_alloc
693  *      Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
694  */
695 static struct kioctx *ioctx_alloc(unsigned nr_events)
696 {
697         struct mm_struct *mm = current->mm;
698         struct kioctx *ctx;
699         int err = -ENOMEM;
700 
701         /*
702          * We keep track of the number of available ringbuffer slots, to prevent
703          * overflow (reqs_available), and we also use percpu counters for this.
704          *
705          * So since up to half the slots might be on other cpu's percpu counters
706          * and unavailable, double nr_events so userspace sees what they
707          * expected: additionally, we move req_batch slots to/from percpu
708          * counters at a time, so make sure that isn't 0:
709          */
710         nr_events = max(nr_events, num_possible_cpus() * 4);
711         nr_events *= 2;
712 
713         /* Prevent overflows */
714         if (nr_events > (0x10000000U / sizeof(struct io_event))) {
715                 pr_debug("ENOMEM: nr_events too high\n");
716                 return ERR_PTR(-EINVAL);
717         }
718 
719         if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
720                 return ERR_PTR(-EAGAIN);
721 
722         ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
723         if (!ctx)
724                 return ERR_PTR(-ENOMEM);
725 
726         ctx->max_reqs = nr_events;
727 
728         spin_lock_init(&ctx->ctx_lock);
729         spin_lock_init(&ctx->completion_lock);
730         mutex_init(&ctx->ring_lock);
731         /* Protect against page migration throughout kiotx setup by keeping
732          * the ring_lock mutex held until setup is complete. */
733         mutex_lock(&ctx->ring_lock);
734         init_waitqueue_head(&ctx->wait);
735 
736         INIT_LIST_HEAD(&ctx->active_reqs);
737 
738         if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
739                 goto err;
740 
741         if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
742                 goto err;
743 
744         ctx->cpu = alloc_percpu(struct kioctx_cpu);
745         if (!ctx->cpu)
746                 goto err;
747 
748         err = aio_setup_ring(ctx);
749         if (err < 0)
750                 goto err;
751 
752         atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
753         ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
754         if (ctx->req_batch < 1)
755                 ctx->req_batch = 1;
756 
757         /* limit the number of system wide aios */
758         spin_lock(&aio_nr_lock);
759         if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
760             aio_nr + nr_events < aio_nr) {
761                 spin_unlock(&aio_nr_lock);
762                 err = -EAGAIN;
763                 goto err_ctx;
764         }
765         aio_nr += ctx->max_reqs;
766         spin_unlock(&aio_nr_lock);
767 
768         percpu_ref_get(&ctx->users);    /* io_setup() will drop this ref */
769         percpu_ref_get(&ctx->reqs);     /* free_ioctx_users() will drop this */
770 
771         err = ioctx_add_table(ctx, mm);
772         if (err)
773                 goto err_cleanup;
774 
775         /* Release the ring_lock mutex now that all setup is complete. */
776         mutex_unlock(&ctx->ring_lock);
777 
778         pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
779                  ctx, ctx->user_id, mm, ctx->nr_events);
780         return ctx;
781 
782 err_cleanup:
783         aio_nr_sub(ctx->max_reqs);
784 err_ctx:
785         atomic_set(&ctx->dead, 1);
786         if (ctx->mmap_size)
787                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
788         aio_free_ring(ctx);
789 err:
790         mutex_unlock(&ctx->ring_lock);
791         free_percpu(ctx->cpu);
792         percpu_ref_exit(&ctx->reqs);
793         percpu_ref_exit(&ctx->users);
794         kmem_cache_free(kioctx_cachep, ctx);
795         pr_debug("error allocating ioctx %d\n", err);
796         return ERR_PTR(err);
797 }
798 
799 /* kill_ioctx
800  *      Cancels all outstanding aio requests on an aio context.  Used
801  *      when the processes owning a context have all exited to encourage
802  *      the rapid destruction of the kioctx.
803  */
804 static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
805                       struct ctx_rq_wait *wait)
806 {
807         struct kioctx_table *table;
808 
809         spin_lock(&mm->ioctx_lock);
810         if (atomic_xchg(&ctx->dead, 1)) {
811                 spin_unlock(&mm->ioctx_lock);
812                 return -EINVAL;
813         }
814 
815         table = rcu_dereference_raw(mm->ioctx_table);
816         WARN_ON(ctx != table->table[ctx->id]);
817         table->table[ctx->id] = NULL;
818         spin_unlock(&mm->ioctx_lock);
819 
820         /* percpu_ref_kill() will do the necessary call_rcu() */
821         wake_up_all(&ctx->wait);
822 
823         /*
824          * It'd be more correct to do this in free_ioctx(), after all
825          * the outstanding kiocbs have finished - but by then io_destroy
826          * has already returned, so io_setup() could potentially return
827          * -EAGAIN with no ioctxs actually in use (as far as userspace
828          *  could tell).
829          */
830         aio_nr_sub(ctx->max_reqs);
831 
832         if (ctx->mmap_size)
833                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
834 
835         ctx->rq_wait = wait;
836         percpu_ref_kill(&ctx->users);
837         return 0;
838 }
839 
840 /*
841  * exit_aio: called when the last user of mm goes away.  At this point, there is
842  * no way for any new requests to be submited or any of the io_* syscalls to be
843  * called on the context.
844  *
845  * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
846  * them.
847  */
848 void exit_aio(struct mm_struct *mm)
849 {
850         struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
851         struct ctx_rq_wait wait;
852         int i, skipped;
853 
854         if (!table)
855                 return;
856 
857         atomic_set(&wait.count, table->nr);
858         init_completion(&wait.comp);
859 
860         skipped = 0;
861         for (i = 0; i < table->nr; ++i) {
862                 struct kioctx *ctx = table->table[i];
863 
864                 if (!ctx) {
865                         skipped++;
866                         continue;
867                 }
868 
869                 /*
870                  * We don't need to bother with munmap() here - exit_mmap(mm)
871                  * is coming and it'll unmap everything. And we simply can't,
872                  * this is not necessarily our ->mm.
873                  * Since kill_ioctx() uses non-zero ->mmap_size as indicator
874                  * that it needs to unmap the area, just set it to 0.
875                  */
876                 ctx->mmap_size = 0;
877                 kill_ioctx(mm, ctx, &wait);
878         }
879 
880         if (!atomic_sub_and_test(skipped, &wait.count)) {
881                 /* Wait until all IO for the context are done. */
882                 wait_for_completion(&wait.comp);
883         }
884 
885         RCU_INIT_POINTER(mm->ioctx_table, NULL);
886         kfree(table);
887 }
888 
889 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
890 {
891         struct kioctx_cpu *kcpu;
892         unsigned long flags;
893 
894         local_irq_save(flags);
895         kcpu = this_cpu_ptr(ctx->cpu);
896         kcpu->reqs_available += nr;
897 
898         while (kcpu->reqs_available >= ctx->req_batch * 2) {
899                 kcpu->reqs_available -= ctx->req_batch;
900                 atomic_add(ctx->req_batch, &ctx->reqs_available);
901         }
902 
903         local_irq_restore(flags);
904 }
905 
906 static bool get_reqs_available(struct kioctx *ctx)
907 {
908         struct kioctx_cpu *kcpu;
909         bool ret = false;
910         unsigned long flags;
911 
912         local_irq_save(flags);
913         kcpu = this_cpu_ptr(ctx->cpu);
914         if (!kcpu->reqs_available) {
915                 int old, avail = atomic_read(&ctx->reqs_available);
916 
917                 do {
918                         if (avail < ctx->req_batch)
919                                 goto out;
920 
921                         old = avail;
922                         avail = atomic_cmpxchg(&ctx->reqs_available,
923                                                avail, avail - ctx->req_batch);
924                 } while (avail != old);
925 
926                 kcpu->reqs_available += ctx->req_batch;
927         }
928 
929         ret = true;
930         kcpu->reqs_available--;
931 out:
932         local_irq_restore(flags);
933         return ret;
934 }
935 
936 /* refill_reqs_available
937  *      Updates the reqs_available reference counts used for tracking the
938  *      number of free slots in the completion ring.  This can be called
939  *      from aio_complete() (to optimistically update reqs_available) or
940  *      from aio_get_req() (the we're out of events case).  It must be
941  *      called holding ctx->completion_lock.
942  */
943 static void refill_reqs_available(struct kioctx *ctx, unsigned head,
944                                   unsigned tail)
945 {
946         unsigned events_in_ring, completed;
947 
948         /* Clamp head since userland can write to it. */
949         head %= ctx->nr_events;
950         if (head <= tail)
951                 events_in_ring = tail - head;
952         else
953                 events_in_ring = ctx->nr_events - (head - tail);
954 
955         completed = ctx->completed_events;
956         if (events_in_ring < completed)
957                 completed -= events_in_ring;
958         else
959                 completed = 0;
960 
961         if (!completed)
962                 return;
963 
964         ctx->completed_events -= completed;
965         put_reqs_available(ctx, completed);
966 }
967 
968 /* user_refill_reqs_available
969  *      Called to refill reqs_available when aio_get_req() encounters an
970  *      out of space in the completion ring.
971  */
972 static void user_refill_reqs_available(struct kioctx *ctx)
973 {
974         spin_lock_irq(&ctx->completion_lock);
975         if (ctx->completed_events) {
976                 struct aio_ring *ring;
977                 unsigned head;
978 
979                 /* Access of ring->head may race with aio_read_events_ring()
980                  * here, but that's okay since whether we read the old version
981                  * or the new version, and either will be valid.  The important
982                  * part is that head cannot pass tail since we prevent
983                  * aio_complete() from updating tail by holding
984                  * ctx->completion_lock.  Even if head is invalid, the check
985                  * against ctx->completed_events below will make sure we do the
986                  * safe/right thing.
987                  */
988                 ring = kmap_atomic(ctx->ring_pages[0]);
989                 head = ring->head;
990                 kunmap_atomic(ring);
991 
992                 refill_reqs_available(ctx, head, ctx->tail);
993         }
994 
995         spin_unlock_irq(&ctx->completion_lock);
996 }
997 
998 /* aio_get_req
999  *      Allocate a slot for an aio request.
1000  * Returns NULL if no requests are free.
1001  */
1002 static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
1003 {
1004         struct aio_kiocb *req;
1005 
1006         if (!get_reqs_available(ctx)) {
1007                 user_refill_reqs_available(ctx);
1008                 if (!get_reqs_available(ctx))
1009                         return NULL;
1010         }
1011 
1012         req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
1013         if (unlikely(!req))
1014                 goto out_put;
1015 
1016         percpu_ref_get(&ctx->reqs);
1017 
1018         req->ki_ctx = ctx;
1019         return req;
1020 out_put:
1021         put_reqs_available(ctx, 1);
1022         return NULL;
1023 }
1024 
1025 static void kiocb_free(struct aio_kiocb *req)
1026 {
1027         if (req->common.ki_filp)
1028                 fput(req->common.ki_filp);
1029         if (req->ki_eventfd != NULL)
1030                 eventfd_ctx_put(req->ki_eventfd);
1031         kmem_cache_free(kiocb_cachep, req);
1032 }
1033 
1034 static struct kioctx *lookup_ioctx(unsigned long ctx_id)
1035 {
1036         struct aio_ring __user *ring  = (void __user *)ctx_id;
1037         struct mm_struct *mm = current->mm;
1038         struct kioctx *ctx, *ret = NULL;
1039         struct kioctx_table *table;
1040         unsigned id;
1041 
1042         if (get_user(id, &ring->id))
1043                 return NULL;
1044 
1045         rcu_read_lock();
1046         table = rcu_dereference(mm->ioctx_table);
1047 
1048         if (!table || id >= table->nr)
1049                 goto out;
1050 
1051         ctx = table->table[id];
1052         if (ctx && ctx->user_id == ctx_id) {
1053                 percpu_ref_get(&ctx->users);
1054                 ret = ctx;
1055         }
1056 out:
1057         rcu_read_unlock();
1058         return ret;
1059 }
1060 
1061 /* aio_complete
1062  *      Called when the io request on the given iocb is complete.
1063  */
1064 static void aio_complete(struct kiocb *kiocb, long res, long res2)
1065 {
1066         struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, common);
1067         struct kioctx   *ctx = iocb->ki_ctx;
1068         struct aio_ring *ring;
1069         struct io_event *ev_page, *event;
1070         unsigned tail, pos, head;
1071         unsigned long   flags;
1072 
1073         /*
1074          * Special case handling for sync iocbs:
1075          *  - events go directly into the iocb for fast handling
1076          *  - the sync task with the iocb in its stack holds the single iocb
1077          *    ref, no other paths have a way to get another ref
1078          *  - the sync task helpfully left a reference to itself in the iocb
1079          */
1080         BUG_ON(is_sync_kiocb(kiocb));
1081 
1082         if (iocb->ki_list.next) {
1083                 unsigned long flags;
1084 
1085                 spin_lock_irqsave(&ctx->ctx_lock, flags);
1086                 list_del(&iocb->ki_list);
1087                 spin_unlock_irqrestore(&ctx->ctx_lock, flags);
1088         }
1089 
1090         /*
1091          * Add a completion event to the ring buffer. Must be done holding
1092          * ctx->completion_lock to prevent other code from messing with the tail
1093          * pointer since we might be called from irq context.
1094          */
1095         spin_lock_irqsave(&ctx->completion_lock, flags);
1096 
1097         tail = ctx->tail;
1098         pos = tail + AIO_EVENTS_OFFSET;
1099 
1100         if (++tail >= ctx->nr_events)
1101                 tail = 0;
1102 
1103         ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1104         event = ev_page + pos % AIO_EVENTS_PER_PAGE;
1105 
1106         event->obj = (u64)(unsigned long)iocb->ki_user_iocb;
1107         event->data = iocb->ki_user_data;
1108         event->res = res;
1109         event->res2 = res2;
1110 
1111         kunmap_atomic(ev_page);
1112         flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1113 
1114         pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
1115                  ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
1116                  res, res2);
1117 
1118         /* after flagging the request as done, we
1119          * must never even look at it again
1120          */
1121         smp_wmb();      /* make event visible before updating tail */
1122 
1123         ctx->tail = tail;
1124 
1125         ring = kmap_atomic(ctx->ring_pages[0]);
1126         head = ring->head;
1127         ring->tail = tail;
1128         kunmap_atomic(ring);
1129         flush_dcache_page(ctx->ring_pages[0]);
1130 
1131         ctx->completed_events++;
1132         if (ctx->completed_events > 1)
1133                 refill_reqs_available(ctx, head, tail);
1134         spin_unlock_irqrestore(&ctx->completion_lock, flags);
1135 
1136         pr_debug("added to ring %p at [%u]\n", iocb, tail);
1137 
1138         /*
1139          * Check if the user asked us to deliver the result through an
1140          * eventfd. The eventfd_signal() function is safe to be called
1141          * from IRQ context.
1142          */
1143         if (iocb->ki_eventfd != NULL)
1144                 eventfd_signal(iocb->ki_eventfd, 1);
1145 
1146         /* everything turned out well, dispose of the aiocb. */
1147         kiocb_free(iocb);
1148 
1149         /*
1150          * We have to order our ring_info tail store above and test
1151          * of the wait list below outside the wait lock.  This is
1152          * like in wake_up_bit() where clearing a bit has to be
1153          * ordered with the unlocked test.
1154          */
1155         smp_mb();
1156 
1157         if (waitqueue_active(&ctx->wait))
1158                 wake_up(&ctx->wait);
1159 
1160         percpu_ref_put(&ctx->reqs);
1161 }
1162 
1163 /* aio_read_events_ring
1164  *      Pull an event off of the ioctx's event ring.  Returns the number of
1165  *      events fetched
1166  */
1167 static long aio_read_events_ring(struct kioctx *ctx,
1168                                  struct io_event __user *event, long nr)
1169 {
1170         struct aio_ring *ring;
1171         unsigned head, tail, pos;
1172         long ret = 0;
1173         int copy_ret;
1174 
1175         /*
1176          * The mutex can block and wake us up and that will cause
1177          * wait_event_interruptible_hrtimeout() to schedule without sleeping
1178          * and repeat. This should be rare enough that it doesn't cause
1179          * peformance issues. See the comment in read_events() for more detail.
1180          */
1181         sched_annotate_sleep();
1182         mutex_lock(&ctx->ring_lock);
1183 
1184         /* Access to ->ring_pages here is protected by ctx->ring_lock. */
1185         ring = kmap_atomic(ctx->ring_pages[0]);
1186         head = ring->head;
1187         tail = ring->tail;
1188         kunmap_atomic(ring);
1189 
1190         /*
1191          * Ensure that once we've read the current tail pointer, that
1192          * we also see the events that were stored up to the tail.
1193          */
1194         smp_rmb();
1195 
1196         pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
1197 
1198         if (head == tail)
1199                 goto out;
1200 
1201         head %= ctx->nr_events;
1202         tail %= ctx->nr_events;
1203 
1204         while (ret < nr) {
1205                 long avail;
1206                 struct io_event *ev;
1207                 struct page *page;
1208 
1209                 avail = (head <= tail ?  tail : ctx->nr_events) - head;
1210                 if (head == tail)
1211                         break;
1212 
1213                 avail = min(avail, nr - ret);
1214                 avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
1215                             ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
1216 
1217                 pos = head + AIO_EVENTS_OFFSET;
1218                 page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
1219                 pos %= AIO_EVENTS_PER_PAGE;
1220 
1221                 ev = kmap(page);
1222                 copy_ret = copy_to_user(event + ret, ev + pos,
1223                                         sizeof(*ev) * avail);
1224                 kunmap(page);
1225 
1226                 if (unlikely(copy_ret)) {
1227                         ret = -EFAULT;
1228                         goto out;
1229                 }
1230 
1231                 ret += avail;
1232                 head += avail;
1233                 head %= ctx->nr_events;
1234         }
1235 
1236         ring = kmap_atomic(ctx->ring_pages[0]);
1237         ring->head = head;
1238         kunmap_atomic(ring);
1239         flush_dcache_page(ctx->ring_pages[0]);
1240 
1241         pr_debug("%li  h%u t%u\n", ret, head, tail);
1242 out:
1243         mutex_unlock(&ctx->ring_lock);
1244 
1245         return ret;
1246 }
1247 
1248 static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
1249                             struct io_event __user *event, long *i)
1250 {
1251         long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
1252 
1253         if (ret > 0)
1254                 *i += ret;
1255 
1256         if (unlikely(atomic_read(&ctx->dead)))
1257                 ret = -EINVAL;
1258 
1259         if (!*i)
1260                 *i = ret;
1261 
1262         return ret < 0 || *i >= min_nr;
1263 }
1264 
1265 static long read_events(struct kioctx *ctx, long min_nr, long nr,
1266                         struct io_event __user *event,
1267                         struct timespec __user *timeout)
1268 {
1269         ktime_t until = { .tv64 = KTIME_MAX };
1270         long ret = 0;
1271 
1272         if (timeout) {
1273                 struct timespec ts;
1274 
1275                 if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
1276                         return -EFAULT;
1277 
1278                 until = timespec_to_ktime(ts);
1279         }
1280 
1281         /*
1282          * Note that aio_read_events() is being called as the conditional - i.e.
1283          * we're calling it after prepare_to_wait() has set task state to
1284          * TASK_INTERRUPTIBLE.
1285          *
1286          * But aio_read_events() can block, and if it blocks it's going to flip
1287          * the task state back to TASK_RUNNING.
1288          *
1289          * This should be ok, provided it doesn't flip the state back to
1290          * TASK_RUNNING and return 0 too much - that causes us to spin. That
1291          * will only happen if the mutex_lock() call blocks, and we then find
1292          * the ringbuffer empty. So in practice we should be ok, but it's
1293          * something to be aware of when touching this code.
1294          */
1295         if (until.tv64 == 0)
1296                 aio_read_events(ctx, min_nr, nr, event, &ret);
1297         else
1298                 wait_event_interruptible_hrtimeout(ctx->wait,
1299                                 aio_read_events(ctx, min_nr, nr, event, &ret),
1300                                 until);
1301 
1302         if (!ret && signal_pending(current))
1303                 ret = -EINTR;
1304 
1305         return ret;
1306 }
1307 
1308 /* sys_io_setup:
1309  *      Create an aio_context capable of receiving at least nr_events.
1310  *      ctxp must not point to an aio_context that already exists, and
1311  *      must be initialized to 0 prior to the call.  On successful
1312  *      creation of the aio_context, *ctxp is filled in with the resulting 
1313  *      handle.  May fail with -EINVAL if *ctxp is not initialized,
1314  *      if the specified nr_events exceeds internal limits.  May fail 
1315  *      with -EAGAIN if the specified nr_events exceeds the user's limit 
1316  *      of available events.  May fail with -ENOMEM if insufficient kernel
1317  *      resources are available.  May fail with -EFAULT if an invalid
1318  *      pointer is passed for ctxp.  Will fail with -ENOSYS if not
1319  *      implemented.
1320  */
1321 SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
1322 {
1323         struct kioctx *ioctx = NULL;
1324         unsigned long ctx;
1325         long ret;
1326 
1327         ret = get_user(ctx, ctxp);
1328         if (unlikely(ret))
1329                 goto out;
1330 
1331         ret = -EINVAL;
1332         if (unlikely(ctx || nr_events == 0)) {
1333                 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1334                          ctx, nr_events);
1335                 goto out;
1336         }
1337 
1338         ioctx = ioctx_alloc(nr_events);
1339         ret = PTR_ERR(ioctx);
1340         if (!IS_ERR(ioctx)) {
1341                 ret = put_user(ioctx->user_id, ctxp);
1342                 if (ret)
1343                         kill_ioctx(current->mm, ioctx, NULL);
1344                 percpu_ref_put(&ioctx->users);
1345         }
1346 
1347 out:
1348         return ret;
1349 }
1350 
1351 /* sys_io_destroy:
1352  *      Destroy the aio_context specified.  May cancel any outstanding 
1353  *      AIOs and block on completion.  Will fail with -ENOSYS if not
1354  *      implemented.  May fail with -EINVAL if the context pointed to
1355  *      is invalid.
1356  */
1357 SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
1358 {
1359         struct kioctx *ioctx = lookup_ioctx(ctx);
1360         if (likely(NULL != ioctx)) {
1361                 struct ctx_rq_wait wait;
1362                 int ret;
1363 
1364                 init_completion(&wait.comp);
1365                 atomic_set(&wait.count, 1);
1366 
1367                 /* Pass requests_done to kill_ioctx() where it can be set
1368                  * in a thread-safe way. If we try to set it here then we have
1369                  * a race condition if two io_destroy() called simultaneously.
1370                  */
1371                 ret = kill_ioctx(current->mm, ioctx, &wait);
1372                 percpu_ref_put(&ioctx->users);
1373 
1374                 /* Wait until all IO for the context are done. Otherwise kernel
1375                  * keep using user-space buffers even if user thinks the context
1376                  * is destroyed.
1377                  */
1378                 if (!ret)
1379                         wait_for_completion(&wait.comp);
1380 
1381                 return ret;
1382         }
1383         pr_debug("EINVAL: invalid context id\n");
1384         return -EINVAL;
1385 }
1386 
1387 typedef ssize_t (rw_iter_op)(struct kiocb *, struct iov_iter *);
1388 
1389 static int aio_setup_vectored_rw(int rw, char __user *buf, size_t len,
1390                                  struct iovec **iovec,
1391                                  bool compat,
1392                                  struct iov_iter *iter)
1393 {
1394 #ifdef CONFIG_COMPAT
1395         if (compat)
1396                 return compat_import_iovec(rw,
1397                                 (struct compat_iovec __user *)buf,
1398                                 len, UIO_FASTIOV, iovec, iter);
1399 #endif
1400         return import_iovec(rw, (struct iovec __user *)buf,
1401                                 len, UIO_FASTIOV, iovec, iter);
1402 }
1403 
1404 /*
1405  * aio_run_iocb:
1406  *      Performs the initial checks and io submission.
1407  */
1408 static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
1409                             char __user *buf, size_t len, bool compat)
1410 {
1411         struct file *file = req->ki_filp;
1412         ssize_t ret;
1413         int rw;
1414         fmode_t mode;
1415         rw_iter_op *iter_op;
1416         struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
1417         struct iov_iter iter;
1418 
1419         switch (opcode) {
1420         case IOCB_CMD_PREAD:
1421         case IOCB_CMD_PREADV:
1422                 mode    = FMODE_READ;
1423                 rw      = READ;
1424                 iter_op = file->f_op->read_iter;
1425                 goto rw_common;
1426 
1427         case IOCB_CMD_PWRITE:
1428         case IOCB_CMD_PWRITEV:
1429                 mode    = FMODE_WRITE;
1430                 rw      = WRITE;
1431                 iter_op = file->f_op->write_iter;
1432                 goto rw_common;
1433 rw_common:
1434                 if (unlikely(!(file->f_mode & mode)))
1435                         return -EBADF;
1436 
1437                 if (!iter_op)
1438                         return -EINVAL;
1439 
1440                 if (opcode == IOCB_CMD_PREADV || opcode == IOCB_CMD_PWRITEV)
1441                         ret = aio_setup_vectored_rw(rw, buf, len,
1442                                                 &iovec, compat, &iter);
1443                 else {
1444                         ret = import_single_range(rw, buf, len, iovec, &iter);
1445                         iovec = NULL;
1446                 }
1447                 if (!ret)
1448                         ret = rw_verify_area(rw, file, &req->ki_pos,
1449                                              iov_iter_count(&iter));
1450                 if (ret < 0) {
1451                         kfree(iovec);
1452                         return ret;
1453                 }
1454 
1455                 if (rw == WRITE)
1456                         file_start_write(file);
1457 
1458                 ret = iter_op(req, &iter);
1459 
1460                 if (rw == WRITE)
1461                         file_end_write(file);
1462                 kfree(iovec);
1463                 break;
1464 
1465         case IOCB_CMD_FDSYNC:
1466                 if (!file->f_op->aio_fsync)
1467                         return -EINVAL;
1468 
1469                 ret = file->f_op->aio_fsync(req, 1);
1470                 break;
1471 
1472         case IOCB_CMD_FSYNC:
1473                 if (!file->f_op->aio_fsync)
1474                         return -EINVAL;
1475 
1476                 ret = file->f_op->aio_fsync(req, 0);
1477                 break;
1478 
1479         default:
1480                 pr_debug("EINVAL: no operation provided\n");
1481                 return -EINVAL;
1482         }
1483 
1484         if (ret != -EIOCBQUEUED) {
1485                 /*
1486                  * There's no easy way to restart the syscall since other AIO's
1487                  * may be already running. Just fail this IO with EINTR.
1488                  */
1489                 if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
1490                              ret == -ERESTARTNOHAND ||
1491                              ret == -ERESTART_RESTARTBLOCK))
1492                         ret = -EINTR;
1493                 aio_complete(req, ret, 0);
1494         }
1495 
1496         return 0;
1497 }
1498 
1499 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1500                          struct iocb *iocb, bool compat)
1501 {
1502         struct aio_kiocb *req;
1503         ssize_t ret;
1504 
1505         /* enforce forwards compatibility on users */
1506         if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1507                 pr_debug("EINVAL: reserve field set\n");
1508                 return -EINVAL;
1509         }
1510 
1511         /* prevent overflows */
1512         if (unlikely(
1513             (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1514             (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1515             ((ssize_t)iocb->aio_nbytes < 0)
1516            )) {
1517                 pr_debug("EINVAL: overflow check\n");
1518                 return -EINVAL;
1519         }
1520 
1521         req = aio_get_req(ctx);
1522         if (unlikely(!req))
1523                 return -EAGAIN;
1524 
1525         req->common.ki_filp = fget(iocb->aio_fildes);
1526         if (unlikely(!req->common.ki_filp)) {
1527                 ret = -EBADF;
1528                 goto out_put_req;
1529         }
1530         req->common.ki_pos = iocb->aio_offset;
1531         req->common.ki_complete = aio_complete;
1532         req->common.ki_flags = iocb_flags(req->common.ki_filp);
1533 
1534         if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1535                 /*
1536                  * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1537                  * instance of the file* now. The file descriptor must be
1538                  * an eventfd() fd, and will be signaled for each completed
1539                  * event using the eventfd_signal() function.
1540                  */
1541                 req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1542                 if (IS_ERR(req->ki_eventfd)) {
1543                         ret = PTR_ERR(req->ki_eventfd);
1544                         req->ki_eventfd = NULL;
1545                         goto out_put_req;
1546                 }
1547 
1548                 req->common.ki_flags |= IOCB_EVENTFD;
1549         }
1550 
1551         ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1552         if (unlikely(ret)) {
1553                 pr_debug("EFAULT: aio_key\n");
1554                 goto out_put_req;
1555         }
1556 
1557         req->ki_user_iocb = user_iocb;
1558         req->ki_user_data = iocb->aio_data;
1559 
1560         ret = aio_run_iocb(&req->common, iocb->aio_lio_opcode,
1561                            (char __user *)(unsigned long)iocb->aio_buf,
1562                            iocb->aio_nbytes,
1563                            compat);
1564         if (ret)
1565                 goto out_put_req;
1566 
1567         return 0;
1568 out_put_req:
1569         put_reqs_available(ctx, 1);
1570         percpu_ref_put(&ctx->reqs);
1571         kiocb_free(req);
1572         return ret;
1573 }
1574 
1575 long do_io_submit(aio_context_t ctx_id, long nr,
1576                   struct iocb __user *__user *iocbpp, bool compat)
1577 {
1578         struct kioctx *ctx;
1579         long ret = 0;
1580         int i = 0;
1581         struct blk_plug plug;
1582 
1583         if (unlikely(nr < 0))
1584                 return -EINVAL;
1585 
1586         if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1587                 nr = LONG_MAX/sizeof(*iocbpp);
1588 
1589         if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1590                 return -EFAULT;
1591 
1592         ctx = lookup_ioctx(ctx_id);
1593         if (unlikely(!ctx)) {
1594                 pr_debug("EINVAL: invalid context id\n");
1595                 return -EINVAL;
1596         }
1597 
1598         blk_start_plug(&plug);
1599 
1600         /*
1601          * AKPM: should this return a partial result if some of the IOs were
1602          * successfully submitted?
1603          */
1604         for (i=0; i<nr; i++) {
1605                 struct iocb __user *user_iocb;
1606                 struct iocb tmp;
1607 
1608                 if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1609                         ret = -EFAULT;
1610                         break;
1611                 }
1612 
1613                 if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1614                         ret = -EFAULT;
1615                         break;
1616                 }
1617 
1618                 ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1619                 if (ret)
1620                         break;
1621         }
1622         blk_finish_plug(&plug);
1623 
1624         percpu_ref_put(&ctx->users);
1625         return i ? i : ret;
1626 }
1627 
1628 /* sys_io_submit:
1629  *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
1630  *      the number of iocbs queued.  May return -EINVAL if the aio_context
1631  *      specified by ctx_id is invalid, if nr is < 0, if the iocb at
1632  *      *iocbpp[0] is not properly initialized, if the operation specified
1633  *      is invalid for the file descriptor in the iocb.  May fail with
1634  *      -EFAULT if any of the data structures point to invalid data.  May
1635  *      fail with -EBADF if the file descriptor specified in the first
1636  *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
1637  *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
1638  *      fail with -ENOSYS if not implemented.
1639  */
1640 SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1641                 struct iocb __user * __user *, iocbpp)
1642 {
1643         return do_io_submit(ctx_id, nr, iocbpp, 0);
1644 }
1645 
1646 /* lookup_kiocb
1647  *      Finds a given iocb for cancellation.
1648  */
1649 static struct aio_kiocb *
1650 lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb, u32 key)
1651 {
1652         struct aio_kiocb *kiocb;
1653 
1654         assert_spin_locked(&ctx->ctx_lock);
1655 
1656         if (key != KIOCB_KEY)
1657                 return NULL;
1658 
1659         /* TODO: use a hash or array, this sucks. */
1660         list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
1661                 if (kiocb->ki_user_iocb == iocb)
1662                         return kiocb;
1663         }
1664         return NULL;
1665 }
1666 
1667 /* sys_io_cancel:
1668  *      Attempts to cancel an iocb previously passed to io_submit.  If
1669  *      the operation is successfully cancelled, the resulting event is
1670  *      copied into the memory pointed to by result without being placed
1671  *      into the completion queue and 0 is returned.  May fail with
1672  *      -EFAULT if any of the data structures pointed to are invalid.
1673  *      May fail with -EINVAL if aio_context specified by ctx_id is
1674  *      invalid.  May fail with -EAGAIN if the iocb specified was not
1675  *      cancelled.  Will fail with -ENOSYS if not implemented.
1676  */
1677 SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1678                 struct io_event __user *, result)
1679 {
1680         struct kioctx *ctx;
1681         struct aio_kiocb *kiocb;
1682         u32 key;
1683         int ret;
1684 
1685         ret = get_user(key, &iocb->aio_key);
1686         if (unlikely(ret))
1687                 return -EFAULT;
1688 
1689         ctx = lookup_ioctx(ctx_id);
1690         if (unlikely(!ctx))
1691                 return -EINVAL;
1692 
1693         spin_lock_irq(&ctx->ctx_lock);
1694 
1695         kiocb = lookup_kiocb(ctx, iocb, key);
1696         if (kiocb)
1697                 ret = kiocb_cancel(kiocb);
1698         else
1699                 ret = -EINVAL;
1700 
1701         spin_unlock_irq(&ctx->ctx_lock);
1702 
1703         if (!ret) {
1704                 /*
1705                  * The result argument is no longer used - the io_event is
1706                  * always delivered via the ring buffer. -EINPROGRESS indicates
1707                  * cancellation is progress:
1708                  */
1709                 ret = -EINPROGRESS;
1710         }
1711 
1712         percpu_ref_put(&ctx->users);
1713 
1714         return ret;
1715 }
1716 
1717 /* io_getevents:
1718  *      Attempts to read at least min_nr events and up to nr events from
1719  *      the completion queue for the aio_context specified by ctx_id. If
1720  *      it succeeds, the number of read events is returned. May fail with
1721  *      -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1722  *      out of range, if timeout is out of range.  May fail with -EFAULT
1723  *      if any of the memory specified is invalid.  May return 0 or
1724  *      < min_nr if the timeout specified by timeout has elapsed
1725  *      before sufficient events are available, where timeout == NULL
1726  *      specifies an infinite timeout. Note that the timeout pointed to by
1727  *      timeout is relative.  Will fail with -ENOSYS if not implemented.
1728  */
1729 SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1730                 long, min_nr,
1731                 long, nr,
1732                 struct io_event __user *, events,
1733                 struct timespec __user *, timeout)
1734 {
1735         struct kioctx *ioctx = lookup_ioctx(ctx_id);
1736         long ret = -EINVAL;
1737 
1738         if (likely(ioctx)) {
1739                 if (likely(min_nr <= nr && min_nr >= 0))
1740                         ret = read_events(ioctx, min_nr, nr, events, timeout);
1741                 percpu_ref_put(&ioctx->users);
1742         }
1743         return ret;
1744 }
1745 

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