Version:  2.0.40 2.2.26 2.4.37 3.5 3.6 3.7 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

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

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