Version:  2.0.40 2.2.26 2.4.37 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4

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         down_write(&mm->mmap_sem);
500         ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
501                                        PROT_READ | PROT_WRITE,
502                                        MAP_SHARED, 0, &unused);
503         up_write(&mm->mmap_sem);
504         if (IS_ERR((void *)ctx->mmap_base)) {
505                 ctx->mmap_size = 0;
506                 aio_free_ring(ctx);
507                 return -ENOMEM;
508         }
509 
510         pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
511 
512         ctx->user_id = ctx->mmap_base;
513         ctx->nr_events = nr_events; /* trusted copy */
514 
515         ring = kmap_atomic(ctx->ring_pages[0]);
516         ring->nr = nr_events;   /* user copy */
517         ring->id = ~0U;
518         ring->head = ring->tail = 0;
519         ring->magic = AIO_RING_MAGIC;
520         ring->compat_features = AIO_RING_COMPAT_FEATURES;
521         ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
522         ring->header_length = sizeof(struct aio_ring);
523         kunmap_atomic(ring);
524         flush_dcache_page(ctx->ring_pages[0]);
525 
526         return 0;
527 }
528 
529 #define AIO_EVENTS_PER_PAGE     (PAGE_SIZE / sizeof(struct io_event))
530 #define AIO_EVENTS_FIRST_PAGE   ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
531 #define AIO_EVENTS_OFFSET       (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
532 
533 void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
534 {
535         struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
536         struct kioctx *ctx = req->ki_ctx;
537         unsigned long flags;
538 
539         spin_lock_irqsave(&ctx->ctx_lock, flags);
540 
541         if (!req->ki_list.next)
542                 list_add(&req->ki_list, &ctx->active_reqs);
543 
544         req->ki_cancel = cancel;
545 
546         spin_unlock_irqrestore(&ctx->ctx_lock, flags);
547 }
548 EXPORT_SYMBOL(kiocb_set_cancel_fn);
549 
550 static int kiocb_cancel(struct aio_kiocb *kiocb)
551 {
552         kiocb_cancel_fn *old, *cancel;
553 
554         /*
555          * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
556          * actually has a cancel function, hence the cmpxchg()
557          */
558 
559         cancel = ACCESS_ONCE(kiocb->ki_cancel);
560         do {
561                 if (!cancel || cancel == KIOCB_CANCELLED)
562                         return -EINVAL;
563 
564                 old = cancel;
565                 cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
566         } while (cancel != old);
567 
568         return cancel(&kiocb->common);
569 }
570 
571 static void free_ioctx(struct work_struct *work)
572 {
573         struct kioctx *ctx = container_of(work, struct kioctx, free_work);
574 
575         pr_debug("freeing %p\n", ctx);
576 
577         aio_free_ring(ctx);
578         free_percpu(ctx->cpu);
579         percpu_ref_exit(&ctx->reqs);
580         percpu_ref_exit(&ctx->users);
581         kmem_cache_free(kioctx_cachep, ctx);
582 }
583 
584 static void free_ioctx_reqs(struct percpu_ref *ref)
585 {
586         struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
587 
588         /* At this point we know that there are no any in-flight requests */
589         if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
590                 complete(&ctx->rq_wait->comp);
591 
592         INIT_WORK(&ctx->free_work, free_ioctx);
593         schedule_work(&ctx->free_work);
594 }
595 
596 /*
597  * When this function runs, the kioctx has been removed from the "hash table"
598  * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
599  * now it's safe to cancel any that need to be.
600  */
601 static void free_ioctx_users(struct percpu_ref *ref)
602 {
603         struct kioctx *ctx = container_of(ref, struct kioctx, users);
604         struct aio_kiocb *req;
605 
606         spin_lock_irq(&ctx->ctx_lock);
607 
608         while (!list_empty(&ctx->active_reqs)) {
609                 req = list_first_entry(&ctx->active_reqs,
610                                        struct aio_kiocb, ki_list);
611 
612                 list_del_init(&req->ki_list);
613                 kiocb_cancel(req);
614         }
615 
616         spin_unlock_irq(&ctx->ctx_lock);
617 
618         percpu_ref_kill(&ctx->reqs);
619         percpu_ref_put(&ctx->reqs);
620 }
621 
622 static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
623 {
624         unsigned i, new_nr;
625         struct kioctx_table *table, *old;
626         struct aio_ring *ring;
627 
628         spin_lock(&mm->ioctx_lock);
629         table = rcu_dereference_raw(mm->ioctx_table);
630 
631         while (1) {
632                 if (table)
633                         for (i = 0; i < table->nr; i++)
634                                 if (!table->table[i]) {
635                                         ctx->id = i;
636                                         table->table[i] = ctx;
637                                         spin_unlock(&mm->ioctx_lock);
638 
639                                         /* While kioctx setup is in progress,
640                                          * we are protected from page migration
641                                          * changes ring_pages by ->ring_lock.
642                                          */
643                                         ring = kmap_atomic(ctx->ring_pages[0]);
644                                         ring->id = ctx->id;
645                                         kunmap_atomic(ring);
646                                         return 0;
647                                 }
648 
649                 new_nr = (table ? table->nr : 1) * 4;
650                 spin_unlock(&mm->ioctx_lock);
651 
652                 table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
653                                 new_nr, GFP_KERNEL);
654                 if (!table)
655                         return -ENOMEM;
656 
657                 table->nr = new_nr;
658 
659                 spin_lock(&mm->ioctx_lock);
660                 old = rcu_dereference_raw(mm->ioctx_table);
661 
662                 if (!old) {
663                         rcu_assign_pointer(mm->ioctx_table, table);
664                 } else if (table->nr > old->nr) {
665                         memcpy(table->table, old->table,
666                                old->nr * sizeof(struct kioctx *));
667 
668                         rcu_assign_pointer(mm->ioctx_table, table);
669                         kfree_rcu(old, rcu);
670                 } else {
671                         kfree(table);
672                         table = old;
673                 }
674         }
675 }
676 
677 static void aio_nr_sub(unsigned nr)
678 {
679         spin_lock(&aio_nr_lock);
680         if (WARN_ON(aio_nr - nr > aio_nr))
681                 aio_nr = 0;
682         else
683                 aio_nr -= nr;
684         spin_unlock(&aio_nr_lock);
685 }
686 
687 /* ioctx_alloc
688  *      Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
689  */
690 static struct kioctx *ioctx_alloc(unsigned nr_events)
691 {
692         struct mm_struct *mm = current->mm;
693         struct kioctx *ctx;
694         int err = -ENOMEM;
695 
696         /*
697          * We keep track of the number of available ringbuffer slots, to prevent
698          * overflow (reqs_available), and we also use percpu counters for this.
699          *
700          * So since up to half the slots might be on other cpu's percpu counters
701          * and unavailable, double nr_events so userspace sees what they
702          * expected: additionally, we move req_batch slots to/from percpu
703          * counters at a time, so make sure that isn't 0:
704          */
705         nr_events = max(nr_events, num_possible_cpus() * 4);
706         nr_events *= 2;
707 
708         /* Prevent overflows */
709         if (nr_events > (0x10000000U / sizeof(struct io_event))) {
710                 pr_debug("ENOMEM: nr_events too high\n");
711                 return ERR_PTR(-EINVAL);
712         }
713 
714         if (!nr_events || (unsigned long)nr_events > (aio_max_nr * 2UL))
715                 return ERR_PTR(-EAGAIN);
716 
717         ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
718         if (!ctx)
719                 return ERR_PTR(-ENOMEM);
720 
721         ctx->max_reqs = nr_events;
722 
723         spin_lock_init(&ctx->ctx_lock);
724         spin_lock_init(&ctx->completion_lock);
725         mutex_init(&ctx->ring_lock);
726         /* Protect against page migration throughout kiotx setup by keeping
727          * the ring_lock mutex held until setup is complete. */
728         mutex_lock(&ctx->ring_lock);
729         init_waitqueue_head(&ctx->wait);
730 
731         INIT_LIST_HEAD(&ctx->active_reqs);
732 
733         if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
734                 goto err;
735 
736         if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
737                 goto err;
738 
739         ctx->cpu = alloc_percpu(struct kioctx_cpu);
740         if (!ctx->cpu)
741                 goto err;
742 
743         err = aio_setup_ring(ctx);
744         if (err < 0)
745                 goto err;
746 
747         atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
748         ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
749         if (ctx->req_batch < 1)
750                 ctx->req_batch = 1;
751 
752         /* limit the number of system wide aios */
753         spin_lock(&aio_nr_lock);
754         if (aio_nr + nr_events > (aio_max_nr * 2UL) ||
755             aio_nr + nr_events < aio_nr) {
756                 spin_unlock(&aio_nr_lock);
757                 err = -EAGAIN;
758                 goto err_ctx;
759         }
760         aio_nr += ctx->max_reqs;
761         spin_unlock(&aio_nr_lock);
762 
763         percpu_ref_get(&ctx->users);    /* io_setup() will drop this ref */
764         percpu_ref_get(&ctx->reqs);     /* free_ioctx_users() will drop this */
765 
766         err = ioctx_add_table(ctx, mm);
767         if (err)
768                 goto err_cleanup;
769 
770         /* Release the ring_lock mutex now that all setup is complete. */
771         mutex_unlock(&ctx->ring_lock);
772 
773         pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
774                  ctx, ctx->user_id, mm, ctx->nr_events);
775         return ctx;
776 
777 err_cleanup:
778         aio_nr_sub(ctx->max_reqs);
779 err_ctx:
780         atomic_set(&ctx->dead, 1);
781         if (ctx->mmap_size)
782                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
783         aio_free_ring(ctx);
784 err:
785         mutex_unlock(&ctx->ring_lock);
786         free_percpu(ctx->cpu);
787         percpu_ref_exit(&ctx->reqs);
788         percpu_ref_exit(&ctx->users);
789         kmem_cache_free(kioctx_cachep, ctx);
790         pr_debug("error allocating ioctx %d\n", err);
791         return ERR_PTR(err);
792 }
793 
794 /* kill_ioctx
795  *      Cancels all outstanding aio requests on an aio context.  Used
796  *      when the processes owning a context have all exited to encourage
797  *      the rapid destruction of the kioctx.
798  */
799 static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
800                       struct ctx_rq_wait *wait)
801 {
802         struct kioctx_table *table;
803 
804         spin_lock(&mm->ioctx_lock);
805         if (atomic_xchg(&ctx->dead, 1)) {
806                 spin_unlock(&mm->ioctx_lock);
807                 return -EINVAL;
808         }
809 
810         table = rcu_dereference_raw(mm->ioctx_table);
811         WARN_ON(ctx != table->table[ctx->id]);
812         table->table[ctx->id] = NULL;
813         spin_unlock(&mm->ioctx_lock);
814 
815         /* percpu_ref_kill() will do the necessary call_rcu() */
816         wake_up_all(&ctx->wait);
817 
818         /*
819          * It'd be more correct to do this in free_ioctx(), after all
820          * the outstanding kiocbs have finished - but by then io_destroy
821          * has already returned, so io_setup() could potentially return
822          * -EAGAIN with no ioctxs actually in use (as far as userspace
823          *  could tell).
824          */
825         aio_nr_sub(ctx->max_reqs);
826 
827         if (ctx->mmap_size)
828                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
829 
830         ctx->rq_wait = wait;
831         percpu_ref_kill(&ctx->users);
832         return 0;
833 }
834 
835 /*
836  * exit_aio: called when the last user of mm goes away.  At this point, there is
837  * no way for any new requests to be submited or any of the io_* syscalls to be
838  * called on the context.
839  *
840  * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
841  * them.
842  */
843 void exit_aio(struct mm_struct *mm)
844 {
845         struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
846         struct ctx_rq_wait wait;
847         int i, skipped;
848 
849         if (!table)
850                 return;
851 
852         atomic_set(&wait.count, table->nr);
853         init_completion(&wait.comp);
854 
855         skipped = 0;
856         for (i = 0; i < table->nr; ++i) {
857                 struct kioctx *ctx = table->table[i];
858 
859                 if (!ctx) {
860                         skipped++;
861                         continue;
862                 }
863 
864                 /*
865                  * We don't need to bother with munmap() here - exit_mmap(mm)
866                  * is coming and it'll unmap everything. And we simply can't,
867                  * this is not necessarily our ->mm.
868                  * Since kill_ioctx() uses non-zero ->mmap_size as indicator
869                  * that it needs to unmap the area, just set it to 0.
870                  */
871                 ctx->mmap_size = 0;
872                 kill_ioctx(mm, ctx, &wait);
873         }
874 
875         if (!atomic_sub_and_test(skipped, &wait.count)) {
876                 /* Wait until all IO for the context are done. */
877                 wait_for_completion(&wait.comp);
878         }
879 
880         RCU_INIT_POINTER(mm->ioctx_table, NULL);
881         kfree(table);
882 }
883 
884 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
885 {
886         struct kioctx_cpu *kcpu;
887         unsigned long flags;
888 
889         local_irq_save(flags);
890         kcpu = this_cpu_ptr(ctx->cpu);
891         kcpu->reqs_available += nr;
892 
893         while (kcpu->reqs_available >= ctx->req_batch * 2) {
894                 kcpu->reqs_available -= ctx->req_batch;
895                 atomic_add(ctx->req_batch, &ctx->reqs_available);
896         }
897 
898         local_irq_restore(flags);
899 }
900 
901 static bool get_reqs_available(struct kioctx *ctx)
902 {
903         struct kioctx_cpu *kcpu;
904         bool ret = false;
905         unsigned long flags;
906 
907         local_irq_save(flags);
908         kcpu = this_cpu_ptr(ctx->cpu);
909         if (!kcpu->reqs_available) {
910                 int old, avail = atomic_read(&ctx->reqs_available);
911 
912                 do {
913                         if (avail < ctx->req_batch)
914                                 goto out;
915 
916                         old = avail;
917                         avail = atomic_cmpxchg(&ctx->reqs_available,
918                                                avail, avail - ctx->req_batch);
919                 } while (avail != old);
920 
921                 kcpu->reqs_available += ctx->req_batch;
922         }
923 
924         ret = true;
925         kcpu->reqs_available--;
926 out:
927         local_irq_restore(flags);
928         return ret;
929 }
930 
931 /* refill_reqs_available
932  *      Updates the reqs_available reference counts used for tracking the
933  *      number of free slots in the completion ring.  This can be called
934  *      from aio_complete() (to optimistically update reqs_available) or
935  *      from aio_get_req() (the we're out of events case).  It must be
936  *      called holding ctx->completion_lock.
937  */
938 static void refill_reqs_available(struct kioctx *ctx, unsigned head,
939                                   unsigned tail)
940 {
941         unsigned events_in_ring, completed;
942 
943         /* Clamp head since userland can write to it. */
944         head %= ctx->nr_events;
945         if (head <= tail)
946                 events_in_ring = tail - head;
947         else
948                 events_in_ring = ctx->nr_events - (head - tail);
949 
950         completed = ctx->completed_events;
951         if (events_in_ring < completed)
952                 completed -= events_in_ring;
953         else
954                 completed = 0;
955 
956         if (!completed)
957                 return;
958 
959         ctx->completed_events -= completed;
960         put_reqs_available(ctx, completed);
961 }
962 
963 /* user_refill_reqs_available
964  *      Called to refill reqs_available when aio_get_req() encounters an
965  *      out of space in the completion ring.
966  */
967 static void user_refill_reqs_available(struct kioctx *ctx)
968 {
969         spin_lock_irq(&ctx->completion_lock);
970         if (ctx->completed_events) {
971                 struct aio_ring *ring;
972                 unsigned head;
973 
974                 /* Access of ring->head may race with aio_read_events_ring()
975                  * here, but that's okay since whether we read the old version
976                  * or the new version, and either will be valid.  The important
977                  * part is that head cannot pass tail since we prevent
978                  * aio_complete() from updating tail by holding
979                  * ctx->completion_lock.  Even if head is invalid, the check
980                  * against ctx->completed_events below will make sure we do the
981                  * safe/right thing.
982                  */
983                 ring = kmap_atomic(ctx->ring_pages[0]);
984                 head = ring->head;
985                 kunmap_atomic(ring);
986 
987                 refill_reqs_available(ctx, head, ctx->tail);
988         }
989 
990         spin_unlock_irq(&ctx->completion_lock);
991 }
992 
993 /* aio_get_req
994  *      Allocate a slot for an aio request.
995  * Returns NULL if no requests are free.
996  */
997 static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
998 {
999         struct aio_kiocb *req;
1000 
1001         if (!get_reqs_available(ctx)) {
1002                 user_refill_reqs_available(ctx);
1003                 if (!get_reqs_available(ctx))
1004                         return NULL;
1005         }
1006 
1007         req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
1008         if (unlikely(!req))
1009                 goto out_put;
1010 
1011         percpu_ref_get(&ctx->reqs);
1012 
1013         req->ki_ctx = ctx;
1014         return req;
1015 out_put:
1016         put_reqs_available(ctx, 1);
1017         return NULL;
1018 }
1019 
1020 static void kiocb_free(struct aio_kiocb *req)
1021 {
1022         if (req->common.ki_filp)
1023                 fput(req->common.ki_filp);
1024         if (req->ki_eventfd != NULL)
1025                 eventfd_ctx_put(req->ki_eventfd);
1026         kmem_cache_free(kiocb_cachep, req);
1027 }
1028 
1029 static struct kioctx *lookup_ioctx(unsigned long ctx_id)
1030 {
1031         struct aio_ring __user *ring  = (void __user *)ctx_id;
1032         struct mm_struct *mm = current->mm;
1033         struct kioctx *ctx, *ret = NULL;
1034         struct kioctx_table *table;
1035         unsigned id;
1036 
1037         if (get_user(id, &ring->id))
1038                 return NULL;
1039 
1040         rcu_read_lock();
1041         table = rcu_dereference(mm->ioctx_table);
1042 
1043         if (!table || id >= table->nr)
1044                 goto out;
1045 
1046         ctx = table->table[id];
1047         if (ctx && ctx->user_id == ctx_id) {
1048                 percpu_ref_get(&ctx->users);
1049                 ret = ctx;
1050         }
1051 out:
1052         rcu_read_unlock();
1053         return ret;
1054 }
1055 
1056 /* aio_complete
1057  *      Called when the io request on the given iocb is complete.
1058  */
1059 static void aio_complete(struct kiocb *kiocb, long res, long res2)
1060 {
1061         struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, common);
1062         struct kioctx   *ctx = iocb->ki_ctx;
1063         struct aio_ring *ring;
1064         struct io_event *ev_page, *event;
1065         unsigned tail, pos, head;
1066         unsigned long   flags;
1067 
1068         /*
1069          * Special case handling for sync iocbs:
1070          *  - events go directly into the iocb for fast handling
1071          *  - the sync task with the iocb in its stack holds the single iocb
1072          *    ref, no other paths have a way to get another ref
1073          *  - the sync task helpfully left a reference to itself in the iocb
1074          */
1075         BUG_ON(is_sync_kiocb(kiocb));
1076 
1077         if (iocb->ki_list.next) {
1078                 unsigned long flags;
1079 
1080                 spin_lock_irqsave(&ctx->ctx_lock, flags);
1081                 list_del(&iocb->ki_list);
1082                 spin_unlock_irqrestore(&ctx->ctx_lock, flags);
1083         }
1084 
1085         /*
1086          * Add a completion event to the ring buffer. Must be done holding
1087          * ctx->completion_lock to prevent other code from messing with the tail
1088          * pointer since we might be called from irq context.
1089          */
1090         spin_lock_irqsave(&ctx->completion_lock, flags);
1091 
1092         tail = ctx->tail;
1093         pos = tail + AIO_EVENTS_OFFSET;
1094 
1095         if (++tail >= ctx->nr_events)
1096                 tail = 0;
1097 
1098         ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1099         event = ev_page + pos % AIO_EVENTS_PER_PAGE;
1100 
1101         event->obj = (u64)(unsigned long)iocb->ki_user_iocb;
1102         event->data = iocb->ki_user_data;
1103         event->res = res;
1104         event->res2 = res2;
1105 
1106         kunmap_atomic(ev_page);
1107         flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1108 
1109         pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
1110                  ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
1111                  res, res2);
1112 
1113         /* after flagging the request as done, we
1114          * must never even look at it again
1115          */
1116         smp_wmb();      /* make event visible before updating tail */
1117 
1118         ctx->tail = tail;
1119 
1120         ring = kmap_atomic(ctx->ring_pages[0]);
1121         head = ring->head;
1122         ring->tail = tail;
1123         kunmap_atomic(ring);
1124         flush_dcache_page(ctx->ring_pages[0]);
1125 
1126         ctx->completed_events++;
1127         if (ctx->completed_events > 1)
1128                 refill_reqs_available(ctx, head, tail);
1129         spin_unlock_irqrestore(&ctx->completion_lock, flags);
1130 
1131         pr_debug("added to ring %p at [%u]\n", iocb, tail);
1132 
1133         /*
1134          * Check if the user asked us to deliver the result through an
1135          * eventfd. The eventfd_signal() function is safe to be called
1136          * from IRQ context.
1137          */
1138         if (iocb->ki_eventfd != NULL)
1139                 eventfd_signal(iocb->ki_eventfd, 1);
1140 
1141         /* everything turned out well, dispose of the aiocb. */
1142         kiocb_free(iocb);
1143 
1144         /*
1145          * We have to order our ring_info tail store above and test
1146          * of the wait list below outside the wait lock.  This is
1147          * like in wake_up_bit() where clearing a bit has to be
1148          * ordered with the unlocked test.
1149          */
1150         smp_mb();
1151 
1152         if (waitqueue_active(&ctx->wait))
1153                 wake_up(&ctx->wait);
1154 
1155         percpu_ref_put(&ctx->reqs);
1156 }
1157 
1158 /* aio_read_events_ring
1159  *      Pull an event off of the ioctx's event ring.  Returns the number of
1160  *      events fetched
1161  */
1162 static long aio_read_events_ring(struct kioctx *ctx,
1163                                  struct io_event __user *event, long nr)
1164 {
1165         struct aio_ring *ring;
1166         unsigned head, tail, pos;
1167         long ret = 0;
1168         int copy_ret;
1169 
1170         /*
1171          * The mutex can block and wake us up and that will cause
1172          * wait_event_interruptible_hrtimeout() to schedule without sleeping
1173          * and repeat. This should be rare enough that it doesn't cause
1174          * peformance issues. See the comment in read_events() for more detail.
1175          */
1176         sched_annotate_sleep();
1177         mutex_lock(&ctx->ring_lock);
1178 
1179         /* Access to ->ring_pages here is protected by ctx->ring_lock. */
1180         ring = kmap_atomic(ctx->ring_pages[0]);
1181         head = ring->head;
1182         tail = ring->tail;
1183         kunmap_atomic(ring);
1184 
1185         /*
1186          * Ensure that once we've read the current tail pointer, that
1187          * we also see the events that were stored up to the tail.
1188          */
1189         smp_rmb();
1190 
1191         pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
1192 
1193         if (head == tail)
1194                 goto out;
1195 
1196         head %= ctx->nr_events;
1197         tail %= ctx->nr_events;
1198 
1199         while (ret < nr) {
1200                 long avail;
1201                 struct io_event *ev;
1202                 struct page *page;
1203 
1204                 avail = (head <= tail ?  tail : ctx->nr_events) - head;
1205                 if (head == tail)
1206                         break;
1207 
1208                 avail = min(avail, nr - ret);
1209                 avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
1210                             ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
1211 
1212                 pos = head + AIO_EVENTS_OFFSET;
1213                 page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
1214                 pos %= AIO_EVENTS_PER_PAGE;
1215 
1216                 ev = kmap(page);
1217                 copy_ret = copy_to_user(event + ret, ev + pos,
1218                                         sizeof(*ev) * avail);
1219                 kunmap(page);
1220 
1221                 if (unlikely(copy_ret)) {
1222                         ret = -EFAULT;
1223                         goto out;
1224                 }
1225 
1226                 ret += avail;
1227                 head += avail;
1228                 head %= ctx->nr_events;
1229         }
1230 
1231         ring = kmap_atomic(ctx->ring_pages[0]);
1232         ring->head = head;
1233         kunmap_atomic(ring);
1234         flush_dcache_page(ctx->ring_pages[0]);
1235 
1236         pr_debug("%li  h%u t%u\n", ret, head, tail);
1237 out:
1238         mutex_unlock(&ctx->ring_lock);
1239 
1240         return ret;
1241 }
1242 
1243 static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
1244                             struct io_event __user *event, long *i)
1245 {
1246         long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
1247 
1248         if (ret > 0)
1249                 *i += ret;
1250 
1251         if (unlikely(atomic_read(&ctx->dead)))
1252                 ret = -EINVAL;
1253 
1254         if (!*i)
1255                 *i = ret;
1256 
1257         return ret < 0 || *i >= min_nr;
1258 }
1259 
1260 static long read_events(struct kioctx *ctx, long min_nr, long nr,
1261                         struct io_event __user *event,
1262                         struct timespec __user *timeout)
1263 {
1264         ktime_t until = { .tv64 = KTIME_MAX };
1265         long ret = 0;
1266 
1267         if (timeout) {
1268                 struct timespec ts;
1269 
1270                 if (unlikely(copy_from_user(&ts, timeout, sizeof(ts))))
1271                         return -EFAULT;
1272 
1273                 until = timespec_to_ktime(ts);
1274         }
1275 
1276         /*
1277          * Note that aio_read_events() is being called as the conditional - i.e.
1278          * we're calling it after prepare_to_wait() has set task state to
1279          * TASK_INTERRUPTIBLE.
1280          *
1281          * But aio_read_events() can block, and if it blocks it's going to flip
1282          * the task state back to TASK_RUNNING.
1283          *
1284          * This should be ok, provided it doesn't flip the state back to
1285          * TASK_RUNNING and return 0 too much - that causes us to spin. That
1286          * will only happen if the mutex_lock() call blocks, and we then find
1287          * the ringbuffer empty. So in practice we should be ok, but it's
1288          * something to be aware of when touching this code.
1289          */
1290         if (until.tv64 == 0)
1291                 aio_read_events(ctx, min_nr, nr, event, &ret);
1292         else
1293                 wait_event_interruptible_hrtimeout(ctx->wait,
1294                                 aio_read_events(ctx, min_nr, nr, event, &ret),
1295                                 until);
1296 
1297         if (!ret && signal_pending(current))
1298                 ret = -EINTR;
1299 
1300         return ret;
1301 }
1302 
1303 /* sys_io_setup:
1304  *      Create an aio_context capable of receiving at least nr_events.
1305  *      ctxp must not point to an aio_context that already exists, and
1306  *      must be initialized to 0 prior to the call.  On successful
1307  *      creation of the aio_context, *ctxp is filled in with the resulting 
1308  *      handle.  May fail with -EINVAL if *ctxp is not initialized,
1309  *      if the specified nr_events exceeds internal limits.  May fail 
1310  *      with -EAGAIN if the specified nr_events exceeds the user's limit 
1311  *      of available events.  May fail with -ENOMEM if insufficient kernel
1312  *      resources are available.  May fail with -EFAULT if an invalid
1313  *      pointer is passed for ctxp.  Will fail with -ENOSYS if not
1314  *      implemented.
1315  */
1316 SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
1317 {
1318         struct kioctx *ioctx = NULL;
1319         unsigned long ctx;
1320         long ret;
1321 
1322         ret = get_user(ctx, ctxp);
1323         if (unlikely(ret))
1324                 goto out;
1325 
1326         ret = -EINVAL;
1327         if (unlikely(ctx || nr_events == 0)) {
1328                 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1329                          ctx, nr_events);
1330                 goto out;
1331         }
1332 
1333         ioctx = ioctx_alloc(nr_events);
1334         ret = PTR_ERR(ioctx);
1335         if (!IS_ERR(ioctx)) {
1336                 ret = put_user(ioctx->user_id, ctxp);
1337                 if (ret)
1338                         kill_ioctx(current->mm, ioctx, NULL);
1339                 percpu_ref_put(&ioctx->users);
1340         }
1341 
1342 out:
1343         return ret;
1344 }
1345 
1346 /* sys_io_destroy:
1347  *      Destroy the aio_context specified.  May cancel any outstanding 
1348  *      AIOs and block on completion.  Will fail with -ENOSYS if not
1349  *      implemented.  May fail with -EINVAL if the context pointed to
1350  *      is invalid.
1351  */
1352 SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
1353 {
1354         struct kioctx *ioctx = lookup_ioctx(ctx);
1355         if (likely(NULL != ioctx)) {
1356                 struct ctx_rq_wait wait;
1357                 int ret;
1358 
1359                 init_completion(&wait.comp);
1360                 atomic_set(&wait.count, 1);
1361 
1362                 /* Pass requests_done to kill_ioctx() where it can be set
1363                  * in a thread-safe way. If we try to set it here then we have
1364                  * a race condition if two io_destroy() called simultaneously.
1365                  */
1366                 ret = kill_ioctx(current->mm, ioctx, &wait);
1367                 percpu_ref_put(&ioctx->users);
1368 
1369                 /* Wait until all IO for the context are done. Otherwise kernel
1370                  * keep using user-space buffers even if user thinks the context
1371                  * is destroyed.
1372                  */
1373                 if (!ret)
1374                         wait_for_completion(&wait.comp);
1375 
1376                 return ret;
1377         }
1378         pr_debug("EINVAL: invalid context id\n");
1379         return -EINVAL;
1380 }
1381 
1382 typedef ssize_t (rw_iter_op)(struct kiocb *, struct iov_iter *);
1383 
1384 static int aio_setup_vectored_rw(int rw, char __user *buf, size_t len,
1385                                  struct iovec **iovec,
1386                                  bool compat,
1387                                  struct iov_iter *iter)
1388 {
1389 #ifdef CONFIG_COMPAT
1390         if (compat)
1391                 return compat_import_iovec(rw,
1392                                 (struct compat_iovec __user *)buf,
1393                                 len, UIO_FASTIOV, iovec, iter);
1394 #endif
1395         return import_iovec(rw, (struct iovec __user *)buf,
1396                                 len, UIO_FASTIOV, iovec, iter);
1397 }
1398 
1399 /*
1400  * aio_run_iocb:
1401  *      Performs the initial checks and io submission.
1402  */
1403 static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
1404                             char __user *buf, size_t len, bool compat)
1405 {
1406         struct file *file = req->ki_filp;
1407         ssize_t ret;
1408         int rw;
1409         fmode_t mode;
1410         rw_iter_op *iter_op;
1411         struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
1412         struct iov_iter iter;
1413 
1414         switch (opcode) {
1415         case IOCB_CMD_PREAD:
1416         case IOCB_CMD_PREADV:
1417                 mode    = FMODE_READ;
1418                 rw      = READ;
1419                 iter_op = file->f_op->read_iter;
1420                 goto rw_common;
1421 
1422         case IOCB_CMD_PWRITE:
1423         case IOCB_CMD_PWRITEV:
1424                 mode    = FMODE_WRITE;
1425                 rw      = WRITE;
1426                 iter_op = file->f_op->write_iter;
1427                 goto rw_common;
1428 rw_common:
1429                 if (unlikely(!(file->f_mode & mode)))
1430                         return -EBADF;
1431 
1432                 if (!iter_op)
1433                         return -EINVAL;
1434 
1435                 if (opcode == IOCB_CMD_PREADV || opcode == IOCB_CMD_PWRITEV)
1436                         ret = aio_setup_vectored_rw(rw, buf, len,
1437                                                 &iovec, compat, &iter);
1438                 else {
1439                         ret = import_single_range(rw, buf, len, iovec, &iter);
1440                         iovec = NULL;
1441                 }
1442                 if (!ret)
1443                         ret = rw_verify_area(rw, file, &req->ki_pos,
1444                                              iov_iter_count(&iter));
1445                 if (ret < 0) {
1446                         kfree(iovec);
1447                         return ret;
1448                 }
1449 
1450                 len = ret;
1451 
1452                 if (rw == WRITE)
1453                         file_start_write(file);
1454 
1455                 ret = iter_op(req, &iter);
1456 
1457                 if (rw == WRITE)
1458                         file_end_write(file);
1459                 kfree(iovec);
1460                 break;
1461 
1462         case IOCB_CMD_FDSYNC:
1463                 if (!file->f_op->aio_fsync)
1464                         return -EINVAL;
1465 
1466                 ret = file->f_op->aio_fsync(req, 1);
1467                 break;
1468 
1469         case IOCB_CMD_FSYNC:
1470                 if (!file->f_op->aio_fsync)
1471                         return -EINVAL;
1472 
1473                 ret = file->f_op->aio_fsync(req, 0);
1474                 break;
1475 
1476         default:
1477                 pr_debug("EINVAL: no operation provided\n");
1478                 return -EINVAL;
1479         }
1480 
1481         if (ret != -EIOCBQUEUED) {
1482                 /*
1483                  * There's no easy way to restart the syscall since other AIO's
1484                  * may be already running. Just fail this IO with EINTR.
1485                  */
1486                 if (unlikely(ret == -ERESTARTSYS || ret == -ERESTARTNOINTR ||
1487                              ret == -ERESTARTNOHAND ||
1488                              ret == -ERESTART_RESTARTBLOCK))
1489                         ret = -EINTR;
1490                 aio_complete(req, ret, 0);
1491         }
1492 
1493         return 0;
1494 }
1495 
1496 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1497                          struct iocb *iocb, bool compat)
1498 {
1499         struct aio_kiocb *req;
1500         ssize_t ret;
1501 
1502         /* enforce forwards compatibility on users */
1503         if (unlikely(iocb->aio_reserved1 || iocb->aio_reserved2)) {
1504                 pr_debug("EINVAL: reserve field set\n");
1505                 return -EINVAL;
1506         }
1507 
1508         /* prevent overflows */
1509         if (unlikely(
1510             (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1511             (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1512             ((ssize_t)iocb->aio_nbytes < 0)
1513            )) {
1514                 pr_debug("EINVAL: overflow check\n");
1515                 return -EINVAL;
1516         }
1517 
1518         req = aio_get_req(ctx);
1519         if (unlikely(!req))
1520                 return -EAGAIN;
1521 
1522         req->common.ki_filp = fget(iocb->aio_fildes);
1523         if (unlikely(!req->common.ki_filp)) {
1524                 ret = -EBADF;
1525                 goto out_put_req;
1526         }
1527         req->common.ki_pos = iocb->aio_offset;
1528         req->common.ki_complete = aio_complete;
1529         req->common.ki_flags = iocb_flags(req->common.ki_filp);
1530 
1531         if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1532                 /*
1533                  * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1534                  * instance of the file* now. The file descriptor must be
1535                  * an eventfd() fd, and will be signaled for each completed
1536                  * event using the eventfd_signal() function.
1537                  */
1538                 req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1539                 if (IS_ERR(req->ki_eventfd)) {
1540                         ret = PTR_ERR(req->ki_eventfd);
1541                         req->ki_eventfd = NULL;
1542                         goto out_put_req;
1543                 }
1544 
1545                 req->common.ki_flags |= IOCB_EVENTFD;
1546         }
1547 
1548         ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1549         if (unlikely(ret)) {
1550                 pr_debug("EFAULT: aio_key\n");
1551                 goto out_put_req;
1552         }
1553 
1554         req->ki_user_iocb = user_iocb;
1555         req->ki_user_data = iocb->aio_data;
1556 
1557         ret = aio_run_iocb(&req->common, iocb->aio_lio_opcode,
1558                            (char __user *)(unsigned long)iocb->aio_buf,
1559                            iocb->aio_nbytes,
1560                            compat);
1561         if (ret)
1562                 goto out_put_req;
1563 
1564         return 0;
1565 out_put_req:
1566         put_reqs_available(ctx, 1);
1567         percpu_ref_put(&ctx->reqs);
1568         kiocb_free(req);
1569         return ret;
1570 }
1571 
1572 long do_io_submit(aio_context_t ctx_id, long nr,
1573                   struct iocb __user *__user *iocbpp, bool compat)
1574 {
1575         struct kioctx *ctx;
1576         long ret = 0;
1577         int i = 0;
1578         struct blk_plug plug;
1579 
1580         if (unlikely(nr < 0))
1581                 return -EINVAL;
1582 
1583         if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1584                 nr = LONG_MAX/sizeof(*iocbpp);
1585 
1586         if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1587                 return -EFAULT;
1588 
1589         ctx = lookup_ioctx(ctx_id);
1590         if (unlikely(!ctx)) {
1591                 pr_debug("EINVAL: invalid context id\n");
1592                 return -EINVAL;
1593         }
1594 
1595         blk_start_plug(&plug);
1596 
1597         /*
1598          * AKPM: should this return a partial result if some of the IOs were
1599          * successfully submitted?
1600          */
1601         for (i=0; i<nr; i++) {
1602                 struct iocb __user *user_iocb;
1603                 struct iocb tmp;
1604 
1605                 if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1606                         ret = -EFAULT;
1607                         break;
1608                 }
1609 
1610                 if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1611                         ret = -EFAULT;
1612                         break;
1613                 }
1614 
1615                 ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1616                 if (ret)
1617                         break;
1618         }
1619         blk_finish_plug(&plug);
1620 
1621         percpu_ref_put(&ctx->users);
1622         return i ? i : ret;
1623 }
1624 
1625 /* sys_io_submit:
1626  *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
1627  *      the number of iocbs queued.  May return -EINVAL if the aio_context
1628  *      specified by ctx_id is invalid, if nr is < 0, if the iocb at
1629  *      *iocbpp[0] is not properly initialized, if the operation specified
1630  *      is invalid for the file descriptor in the iocb.  May fail with
1631  *      -EFAULT if any of the data structures point to invalid data.  May
1632  *      fail with -EBADF if the file descriptor specified in the first
1633  *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
1634  *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
1635  *      fail with -ENOSYS if not implemented.
1636  */
1637 SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1638                 struct iocb __user * __user *, iocbpp)
1639 {
1640         return do_io_submit(ctx_id, nr, iocbpp, 0);
1641 }
1642 
1643 /* lookup_kiocb
1644  *      Finds a given iocb for cancellation.
1645  */
1646 static struct aio_kiocb *
1647 lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb, u32 key)
1648 {
1649         struct aio_kiocb *kiocb;
1650 
1651         assert_spin_locked(&ctx->ctx_lock);
1652 
1653         if (key != KIOCB_KEY)
1654                 return NULL;
1655 
1656         /* TODO: use a hash or array, this sucks. */
1657         list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
1658                 if (kiocb->ki_user_iocb == iocb)
1659                         return kiocb;
1660         }
1661         return NULL;
1662 }
1663 
1664 /* sys_io_cancel:
1665  *      Attempts to cancel an iocb previously passed to io_submit.  If
1666  *      the operation is successfully cancelled, the resulting event is
1667  *      copied into the memory pointed to by result without being placed
1668  *      into the completion queue and 0 is returned.  May fail with
1669  *      -EFAULT if any of the data structures pointed to are invalid.
1670  *      May fail with -EINVAL if aio_context specified by ctx_id is
1671  *      invalid.  May fail with -EAGAIN if the iocb specified was not
1672  *      cancelled.  Will fail with -ENOSYS if not implemented.
1673  */
1674 SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1675                 struct io_event __user *, result)
1676 {
1677         struct kioctx *ctx;
1678         struct aio_kiocb *kiocb;
1679         u32 key;
1680         int ret;
1681 
1682         ret = get_user(key, &iocb->aio_key);
1683         if (unlikely(ret))
1684                 return -EFAULT;
1685 
1686         ctx = lookup_ioctx(ctx_id);
1687         if (unlikely(!ctx))
1688                 return -EINVAL;
1689 
1690         spin_lock_irq(&ctx->ctx_lock);
1691 
1692         kiocb = lookup_kiocb(ctx, iocb, key);
1693         if (kiocb)
1694                 ret = kiocb_cancel(kiocb);
1695         else
1696                 ret = -EINVAL;
1697 
1698         spin_unlock_irq(&ctx->ctx_lock);
1699 
1700         if (!ret) {
1701                 /*
1702                  * The result argument is no longer used - the io_event is
1703                  * always delivered via the ring buffer. -EINPROGRESS indicates
1704                  * cancellation is progress:
1705                  */
1706                 ret = -EINPROGRESS;
1707         }
1708 
1709         percpu_ref_put(&ctx->users);
1710 
1711         return ret;
1712 }
1713 
1714 /* io_getevents:
1715  *      Attempts to read at least min_nr events and up to nr events from
1716  *      the completion queue for the aio_context specified by ctx_id. If
1717  *      it succeeds, the number of read events is returned. May fail with
1718  *      -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1719  *      out of range, if timeout is out of range.  May fail with -EFAULT
1720  *      if any of the memory specified is invalid.  May return 0 or
1721  *      < min_nr if the timeout specified by timeout has elapsed
1722  *      before sufficient events are available, where timeout == NULL
1723  *      specifies an infinite timeout. Note that the timeout pointed to by
1724  *      timeout is relative.  Will fail with -ENOSYS if not implemented.
1725  */
1726 SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1727                 long, min_nr,
1728                 long, nr,
1729                 struct io_event __user *, events,
1730                 struct timespec __user *, timeout)
1731 {
1732         struct kioctx *ioctx = lookup_ioctx(ctx_id);
1733         long ret = -EINVAL;
1734 
1735         if (likely(ioctx)) {
1736                 if (likely(min_nr <= nr && min_nr >= 0))
1737                         ret = read_events(ioctx, min_nr, nr, events, timeout);
1738                 percpu_ref_put(&ioctx->users);
1739         }
1740         return ret;
1741 }
1742 

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