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TOMOYO Linux Cross Reference
Linux/fs/aio.c

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  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/signal.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 <linux/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 __rcu     *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 rcu_work         free_rwork;     /* see free_ioctx() */
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         struct dentry *root = mount_pseudo(fs_type, "aio:", NULL, &ops,
243                                            AIO_RING_MAGIC);
244 
245         if (!IS_ERR(root))
246                 root->d_sb->s_iflags |= SB_I_NOEXEC;
247         return root;
248 }
249 
250 /* aio_setup
251  *      Creates the slab caches used by the aio routines, panic on
252  *      failure as this is done early during the boot sequence.
253  */
254 static int __init aio_setup(void)
255 {
256         static struct file_system_type aio_fs = {
257                 .name           = "aio",
258                 .mount          = aio_mount,
259                 .kill_sb        = kill_anon_super,
260         };
261         aio_mnt = kern_mount(&aio_fs);
262         if (IS_ERR(aio_mnt))
263                 panic("Failed to create aio fs mount.");
264 
265         kiocb_cachep = KMEM_CACHE(aio_kiocb, SLAB_HWCACHE_ALIGN|SLAB_PANIC);
266         kioctx_cachep = KMEM_CACHE(kioctx,SLAB_HWCACHE_ALIGN|SLAB_PANIC);
267 
268         pr_debug("sizeof(struct page) = %zu\n", sizeof(struct page));
269 
270         return 0;
271 }
272 __initcall(aio_setup);
273 
274 static void put_aio_ring_file(struct kioctx *ctx)
275 {
276         struct file *aio_ring_file = ctx->aio_ring_file;
277         struct address_space *i_mapping;
278 
279         if (aio_ring_file) {
280                 truncate_setsize(file_inode(aio_ring_file), 0);
281 
282                 /* Prevent further access to the kioctx from migratepages */
283                 i_mapping = aio_ring_file->f_mapping;
284                 spin_lock(&i_mapping->private_lock);
285                 i_mapping->private_data = NULL;
286                 ctx->aio_ring_file = NULL;
287                 spin_unlock(&i_mapping->private_lock);
288 
289                 fput(aio_ring_file);
290         }
291 }
292 
293 static void aio_free_ring(struct kioctx *ctx)
294 {
295         int i;
296 
297         /* Disconnect the kiotx from the ring file.  This prevents future
298          * accesses to the kioctx from page migration.
299          */
300         put_aio_ring_file(ctx);
301 
302         for (i = 0; i < ctx->nr_pages; i++) {
303                 struct page *page;
304                 pr_debug("pid(%d) [%d] page->count=%d\n", current->pid, i,
305                                 page_count(ctx->ring_pages[i]));
306                 page = ctx->ring_pages[i];
307                 if (!page)
308                         continue;
309                 ctx->ring_pages[i] = NULL;
310                 put_page(page);
311         }
312 
313         if (ctx->ring_pages && ctx->ring_pages != ctx->internal_pages) {
314                 kfree(ctx->ring_pages);
315                 ctx->ring_pages = NULL;
316         }
317 }
318 
319 static int aio_ring_mremap(struct vm_area_struct *vma)
320 {
321         struct file *file = vma->vm_file;
322         struct mm_struct *mm = vma->vm_mm;
323         struct kioctx_table *table;
324         int i, res = -EINVAL;
325 
326         spin_lock(&mm->ioctx_lock);
327         rcu_read_lock();
328         table = rcu_dereference(mm->ioctx_table);
329         for (i = 0; i < table->nr; i++) {
330                 struct kioctx *ctx;
331 
332                 ctx = rcu_dereference(table->table[i]);
333                 if (ctx && ctx->aio_ring_file == file) {
334                         if (!atomic_read(&ctx->dead)) {
335                                 ctx->user_id = ctx->mmap_base = vma->vm_start;
336                                 res = 0;
337                         }
338                         break;
339                 }
340         }
341 
342         rcu_read_unlock();
343         spin_unlock(&mm->ioctx_lock);
344         return res;
345 }
346 
347 static const struct vm_operations_struct aio_ring_vm_ops = {
348         .mremap         = aio_ring_mremap,
349 #if IS_ENABLED(CONFIG_MMU)
350         .fault          = filemap_fault,
351         .map_pages      = filemap_map_pages,
352         .page_mkwrite   = filemap_page_mkwrite,
353 #endif
354 };
355 
356 static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
357 {
358         vma->vm_flags |= VM_DONTEXPAND;
359         vma->vm_ops = &aio_ring_vm_ops;
360         return 0;
361 }
362 
363 static const struct file_operations aio_ring_fops = {
364         .mmap = aio_ring_mmap,
365 };
366 
367 #if IS_ENABLED(CONFIG_MIGRATION)
368 static int aio_migratepage(struct address_space *mapping, struct page *new,
369                         struct page *old, enum migrate_mode mode)
370 {
371         struct kioctx *ctx;
372         unsigned long flags;
373         pgoff_t idx;
374         int rc;
375 
376         /*
377          * We cannot support the _NO_COPY case here, because copy needs to
378          * happen under the ctx->completion_lock. That does not work with the
379          * migration workflow of MIGRATE_SYNC_NO_COPY.
380          */
381         if (mode == MIGRATE_SYNC_NO_COPY)
382                 return -EINVAL;
383 
384         rc = 0;
385 
386         /* mapping->private_lock here protects against the kioctx teardown.  */
387         spin_lock(&mapping->private_lock);
388         ctx = mapping->private_data;
389         if (!ctx) {
390                 rc = -EINVAL;
391                 goto out;
392         }
393 
394         /* The ring_lock mutex.  The prevents aio_read_events() from writing
395          * to the ring's head, and prevents page migration from mucking in
396          * a partially initialized kiotx.
397          */
398         if (!mutex_trylock(&ctx->ring_lock)) {
399                 rc = -EAGAIN;
400                 goto out;
401         }
402 
403         idx = old->index;
404         if (idx < (pgoff_t)ctx->nr_pages) {
405                 /* Make sure the old page hasn't already been changed */
406                 if (ctx->ring_pages[idx] != old)
407                         rc = -EAGAIN;
408         } else
409                 rc = -EINVAL;
410 
411         if (rc != 0)
412                 goto out_unlock;
413 
414         /* Writeback must be complete */
415         BUG_ON(PageWriteback(old));
416         get_page(new);
417 
418         rc = migrate_page_move_mapping(mapping, new, old, NULL, mode, 1);
419         if (rc != MIGRATEPAGE_SUCCESS) {
420                 put_page(new);
421                 goto out_unlock;
422         }
423 
424         /* Take completion_lock to prevent other writes to the ring buffer
425          * while the old page is copied to the new.  This prevents new
426          * events from being lost.
427          */
428         spin_lock_irqsave(&ctx->completion_lock, flags);
429         migrate_page_copy(new, old);
430         BUG_ON(ctx->ring_pages[idx] != old);
431         ctx->ring_pages[idx] = new;
432         spin_unlock_irqrestore(&ctx->completion_lock, flags);
433 
434         /* The old page is no longer accessible. */
435         put_page(old);
436 
437 out_unlock:
438         mutex_unlock(&ctx->ring_lock);
439 out:
440         spin_unlock(&mapping->private_lock);
441         return rc;
442 }
443 #endif
444 
445 static const struct address_space_operations aio_ctx_aops = {
446         .set_page_dirty = __set_page_dirty_no_writeback,
447 #if IS_ENABLED(CONFIG_MIGRATION)
448         .migratepage    = aio_migratepage,
449 #endif
450 };
451 
452 static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
453 {
454         struct aio_ring *ring;
455         struct mm_struct *mm = current->mm;
456         unsigned long size, unused;
457         int nr_pages;
458         int i;
459         struct file *file;
460 
461         /* Compensate for the ring buffer's head/tail overlap entry */
462         nr_events += 2; /* 1 is required, 2 for good luck */
463 
464         size = sizeof(struct aio_ring);
465         size += sizeof(struct io_event) * nr_events;
466 
467         nr_pages = PFN_UP(size);
468         if (nr_pages < 0)
469                 return -EINVAL;
470 
471         file = aio_private_file(ctx, nr_pages);
472         if (IS_ERR(file)) {
473                 ctx->aio_ring_file = NULL;
474                 return -ENOMEM;
475         }
476 
477         ctx->aio_ring_file = file;
478         nr_events = (PAGE_SIZE * nr_pages - sizeof(struct aio_ring))
479                         / sizeof(struct io_event);
480 
481         ctx->ring_pages = ctx->internal_pages;
482         if (nr_pages > AIO_RING_PAGES) {
483                 ctx->ring_pages = kcalloc(nr_pages, sizeof(struct page *),
484                                           GFP_KERNEL);
485                 if (!ctx->ring_pages) {
486                         put_aio_ring_file(ctx);
487                         return -ENOMEM;
488                 }
489         }
490 
491         for (i = 0; i < nr_pages; i++) {
492                 struct page *page;
493                 page = find_or_create_page(file->f_mapping,
494                                            i, GFP_HIGHUSER | __GFP_ZERO);
495                 if (!page)
496                         break;
497                 pr_debug("pid(%d) page[%d]->count=%d\n",
498                          current->pid, i, page_count(page));
499                 SetPageUptodate(page);
500                 unlock_page(page);
501 
502                 ctx->ring_pages[i] = page;
503         }
504         ctx->nr_pages = i;
505 
506         if (unlikely(i != nr_pages)) {
507                 aio_free_ring(ctx);
508                 return -ENOMEM;
509         }
510 
511         ctx->mmap_size = nr_pages * PAGE_SIZE;
512         pr_debug("attempting mmap of %lu bytes\n", ctx->mmap_size);
513 
514         if (down_write_killable(&mm->mmap_sem)) {
515                 ctx->mmap_size = 0;
516                 aio_free_ring(ctx);
517                 return -EINTR;
518         }
519 
520         ctx->mmap_base = do_mmap_pgoff(ctx->aio_ring_file, 0, ctx->mmap_size,
521                                        PROT_READ | PROT_WRITE,
522                                        MAP_SHARED, 0, &unused, NULL);
523         up_write(&mm->mmap_sem);
524         if (IS_ERR((void *)ctx->mmap_base)) {
525                 ctx->mmap_size = 0;
526                 aio_free_ring(ctx);
527                 return -ENOMEM;
528         }
529 
530         pr_debug("mmap address: 0x%08lx\n", ctx->mmap_base);
531 
532         ctx->user_id = ctx->mmap_base;
533         ctx->nr_events = nr_events; /* trusted copy */
534 
535         ring = kmap_atomic(ctx->ring_pages[0]);
536         ring->nr = nr_events;   /* user copy */
537         ring->id = ~0U;
538         ring->head = ring->tail = 0;
539         ring->magic = AIO_RING_MAGIC;
540         ring->compat_features = AIO_RING_COMPAT_FEATURES;
541         ring->incompat_features = AIO_RING_INCOMPAT_FEATURES;
542         ring->header_length = sizeof(struct aio_ring);
543         kunmap_atomic(ring);
544         flush_dcache_page(ctx->ring_pages[0]);
545 
546         return 0;
547 }
548 
549 #define AIO_EVENTS_PER_PAGE     (PAGE_SIZE / sizeof(struct io_event))
550 #define AIO_EVENTS_FIRST_PAGE   ((PAGE_SIZE - sizeof(struct aio_ring)) / sizeof(struct io_event))
551 #define AIO_EVENTS_OFFSET       (AIO_EVENTS_PER_PAGE - AIO_EVENTS_FIRST_PAGE)
552 
553 void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel)
554 {
555         struct aio_kiocb *req = container_of(iocb, struct aio_kiocb, common);
556         struct kioctx *ctx = req->ki_ctx;
557         unsigned long flags;
558 
559         spin_lock_irqsave(&ctx->ctx_lock, flags);
560 
561         if (!req->ki_list.next)
562                 list_add(&req->ki_list, &ctx->active_reqs);
563 
564         req->ki_cancel = cancel;
565 
566         spin_unlock_irqrestore(&ctx->ctx_lock, flags);
567 }
568 EXPORT_SYMBOL(kiocb_set_cancel_fn);
569 
570 static int kiocb_cancel(struct aio_kiocb *kiocb)
571 {
572         kiocb_cancel_fn *old, *cancel;
573 
574         /*
575          * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it
576          * actually has a cancel function, hence the cmpxchg()
577          */
578 
579         cancel = READ_ONCE(kiocb->ki_cancel);
580         do {
581                 if (!cancel || cancel == KIOCB_CANCELLED)
582                         return -EINVAL;
583 
584                 old = cancel;
585                 cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED);
586         } while (cancel != old);
587 
588         return cancel(&kiocb->common);
589 }
590 
591 /*
592  * free_ioctx() should be RCU delayed to synchronize against the RCU
593  * protected lookup_ioctx() and also needs process context to call
594  * aio_free_ring().  Use rcu_work.
595  */
596 static void free_ioctx(struct work_struct *work)
597 {
598         struct kioctx *ctx = container_of(to_rcu_work(work), struct kioctx,
599                                           free_rwork);
600         pr_debug("freeing %p\n", ctx);
601 
602         aio_free_ring(ctx);
603         free_percpu(ctx->cpu);
604         percpu_ref_exit(&ctx->reqs);
605         percpu_ref_exit(&ctx->users);
606         kmem_cache_free(kioctx_cachep, ctx);
607 }
608 
609 static void free_ioctx_reqs(struct percpu_ref *ref)
610 {
611         struct kioctx *ctx = container_of(ref, struct kioctx, reqs);
612 
613         /* At this point we know that there are no any in-flight requests */
614         if (ctx->rq_wait && atomic_dec_and_test(&ctx->rq_wait->count))
615                 complete(&ctx->rq_wait->comp);
616 
617         /* Synchronize against RCU protected table->table[] dereferences */
618         INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
619         queue_rcu_work(system_wq, &ctx->free_rwork);
620 }
621 
622 /*
623  * When this function runs, the kioctx has been removed from the "hash table"
624  * and ctx->users has dropped to 0, so we know no more kiocbs can be submitted -
625  * now it's safe to cancel any that need to be.
626  */
627 static void free_ioctx_users(struct percpu_ref *ref)
628 {
629         struct kioctx *ctx = container_of(ref, struct kioctx, users);
630         struct aio_kiocb *req;
631 
632         spin_lock_irq(&ctx->ctx_lock);
633 
634         while (!list_empty(&ctx->active_reqs)) {
635                 req = list_first_entry(&ctx->active_reqs,
636                                        struct aio_kiocb, ki_list);
637                 kiocb_cancel(req);
638                 list_del_init(&req->ki_list);
639         }
640 
641         spin_unlock_irq(&ctx->ctx_lock);
642 
643         percpu_ref_kill(&ctx->reqs);
644         percpu_ref_put(&ctx->reqs);
645 }
646 
647 static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
648 {
649         unsigned i, new_nr;
650         struct kioctx_table *table, *old;
651         struct aio_ring *ring;
652 
653         spin_lock(&mm->ioctx_lock);
654         table = rcu_dereference_raw(mm->ioctx_table);
655 
656         while (1) {
657                 if (table)
658                         for (i = 0; i < table->nr; i++)
659                                 if (!rcu_access_pointer(table->table[i])) {
660                                         ctx->id = i;
661                                         rcu_assign_pointer(table->table[i], ctx);
662                                         spin_unlock(&mm->ioctx_lock);
663 
664                                         /* While kioctx setup is in progress,
665                                          * we are protected from page migration
666                                          * changes ring_pages by ->ring_lock.
667                                          */
668                                         ring = kmap_atomic(ctx->ring_pages[0]);
669                                         ring->id = ctx->id;
670                                         kunmap_atomic(ring);
671                                         return 0;
672                                 }
673 
674                 new_nr = (table ? table->nr : 1) * 4;
675                 spin_unlock(&mm->ioctx_lock);
676 
677                 table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
678                                 new_nr, GFP_KERNEL);
679                 if (!table)
680                         return -ENOMEM;
681 
682                 table->nr = new_nr;
683 
684                 spin_lock(&mm->ioctx_lock);
685                 old = rcu_dereference_raw(mm->ioctx_table);
686 
687                 if (!old) {
688                         rcu_assign_pointer(mm->ioctx_table, table);
689                 } else if (table->nr > old->nr) {
690                         memcpy(table->table, old->table,
691                                old->nr * sizeof(struct kioctx *));
692 
693                         rcu_assign_pointer(mm->ioctx_table, table);
694                         kfree_rcu(old, rcu);
695                 } else {
696                         kfree(table);
697                         table = old;
698                 }
699         }
700 }
701 
702 static void aio_nr_sub(unsigned nr)
703 {
704         spin_lock(&aio_nr_lock);
705         if (WARN_ON(aio_nr - nr > aio_nr))
706                 aio_nr = 0;
707         else
708                 aio_nr -= nr;
709         spin_unlock(&aio_nr_lock);
710 }
711 
712 /* ioctx_alloc
713  *      Allocates and initializes an ioctx.  Returns an ERR_PTR if it failed.
714  */
715 static struct kioctx *ioctx_alloc(unsigned nr_events)
716 {
717         struct mm_struct *mm = current->mm;
718         struct kioctx *ctx;
719         int err = -ENOMEM;
720 
721         /*
722          * Store the original nr_events -- what userspace passed to io_setup(),
723          * for counting against the global limit -- before it changes.
724          */
725         unsigned int max_reqs = nr_events;
726 
727         /*
728          * We keep track of the number of available ringbuffer slots, to prevent
729          * overflow (reqs_available), and we also use percpu counters for this.
730          *
731          * So since up to half the slots might be on other cpu's percpu counters
732          * and unavailable, double nr_events so userspace sees what they
733          * expected: additionally, we move req_batch slots to/from percpu
734          * counters at a time, so make sure that isn't 0:
735          */
736         nr_events = max(nr_events, num_possible_cpus() * 4);
737         nr_events *= 2;
738 
739         /* Prevent overflows */
740         if (nr_events > (0x10000000U / sizeof(struct io_event))) {
741                 pr_debug("ENOMEM: nr_events too high\n");
742                 return ERR_PTR(-EINVAL);
743         }
744 
745         if (!nr_events || (unsigned long)max_reqs > aio_max_nr)
746                 return ERR_PTR(-EAGAIN);
747 
748         ctx = kmem_cache_zalloc(kioctx_cachep, GFP_KERNEL);
749         if (!ctx)
750                 return ERR_PTR(-ENOMEM);
751 
752         ctx->max_reqs = max_reqs;
753 
754         spin_lock_init(&ctx->ctx_lock);
755         spin_lock_init(&ctx->completion_lock);
756         mutex_init(&ctx->ring_lock);
757         /* Protect against page migration throughout kiotx setup by keeping
758          * the ring_lock mutex held until setup is complete. */
759         mutex_lock(&ctx->ring_lock);
760         init_waitqueue_head(&ctx->wait);
761 
762         INIT_LIST_HEAD(&ctx->active_reqs);
763 
764         if (percpu_ref_init(&ctx->users, free_ioctx_users, 0, GFP_KERNEL))
765                 goto err;
766 
767         if (percpu_ref_init(&ctx->reqs, free_ioctx_reqs, 0, GFP_KERNEL))
768                 goto err;
769 
770         ctx->cpu = alloc_percpu(struct kioctx_cpu);
771         if (!ctx->cpu)
772                 goto err;
773 
774         err = aio_setup_ring(ctx, nr_events);
775         if (err < 0)
776                 goto err;
777 
778         atomic_set(&ctx->reqs_available, ctx->nr_events - 1);
779         ctx->req_batch = (ctx->nr_events - 1) / (num_possible_cpus() * 4);
780         if (ctx->req_batch < 1)
781                 ctx->req_batch = 1;
782 
783         /* limit the number of system wide aios */
784         spin_lock(&aio_nr_lock);
785         if (aio_nr + ctx->max_reqs > aio_max_nr ||
786             aio_nr + ctx->max_reqs < aio_nr) {
787                 spin_unlock(&aio_nr_lock);
788                 err = -EAGAIN;
789                 goto err_ctx;
790         }
791         aio_nr += ctx->max_reqs;
792         spin_unlock(&aio_nr_lock);
793 
794         percpu_ref_get(&ctx->users);    /* io_setup() will drop this ref */
795         percpu_ref_get(&ctx->reqs);     /* free_ioctx_users() will drop this */
796 
797         err = ioctx_add_table(ctx, mm);
798         if (err)
799                 goto err_cleanup;
800 
801         /* Release the ring_lock mutex now that all setup is complete. */
802         mutex_unlock(&ctx->ring_lock);
803 
804         pr_debug("allocated ioctx %p[%ld]: mm=%p mask=0x%x\n",
805                  ctx, ctx->user_id, mm, ctx->nr_events);
806         return ctx;
807 
808 err_cleanup:
809         aio_nr_sub(ctx->max_reqs);
810 err_ctx:
811         atomic_set(&ctx->dead, 1);
812         if (ctx->mmap_size)
813                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
814         aio_free_ring(ctx);
815 err:
816         mutex_unlock(&ctx->ring_lock);
817         free_percpu(ctx->cpu);
818         percpu_ref_exit(&ctx->reqs);
819         percpu_ref_exit(&ctx->users);
820         kmem_cache_free(kioctx_cachep, ctx);
821         pr_debug("error allocating ioctx %d\n", err);
822         return ERR_PTR(err);
823 }
824 
825 /* kill_ioctx
826  *      Cancels all outstanding aio requests on an aio context.  Used
827  *      when the processes owning a context have all exited to encourage
828  *      the rapid destruction of the kioctx.
829  */
830 static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
831                       struct ctx_rq_wait *wait)
832 {
833         struct kioctx_table *table;
834 
835         spin_lock(&mm->ioctx_lock);
836         if (atomic_xchg(&ctx->dead, 1)) {
837                 spin_unlock(&mm->ioctx_lock);
838                 return -EINVAL;
839         }
840 
841         table = rcu_dereference_raw(mm->ioctx_table);
842         WARN_ON(ctx != rcu_access_pointer(table->table[ctx->id]));
843         RCU_INIT_POINTER(table->table[ctx->id], NULL);
844         spin_unlock(&mm->ioctx_lock);
845 
846         /* free_ioctx_reqs() will do the necessary RCU synchronization */
847         wake_up_all(&ctx->wait);
848 
849         /*
850          * It'd be more correct to do this in free_ioctx(), after all
851          * the outstanding kiocbs have finished - but by then io_destroy
852          * has already returned, so io_setup() could potentially return
853          * -EAGAIN with no ioctxs actually in use (as far as userspace
854          *  could tell).
855          */
856         aio_nr_sub(ctx->max_reqs);
857 
858         if (ctx->mmap_size)
859                 vm_munmap(ctx->mmap_base, ctx->mmap_size);
860 
861         ctx->rq_wait = wait;
862         percpu_ref_kill(&ctx->users);
863         return 0;
864 }
865 
866 /*
867  * exit_aio: called when the last user of mm goes away.  At this point, there is
868  * no way for any new requests to be submited or any of the io_* syscalls to be
869  * called on the context.
870  *
871  * There may be outstanding kiocbs, but free_ioctx() will explicitly wait on
872  * them.
873  */
874 void exit_aio(struct mm_struct *mm)
875 {
876         struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
877         struct ctx_rq_wait wait;
878         int i, skipped;
879 
880         if (!table)
881                 return;
882 
883         atomic_set(&wait.count, table->nr);
884         init_completion(&wait.comp);
885 
886         skipped = 0;
887         for (i = 0; i < table->nr; ++i) {
888                 struct kioctx *ctx =
889                         rcu_dereference_protected(table->table[i], true);
890 
891                 if (!ctx) {
892                         skipped++;
893                         continue;
894                 }
895 
896                 /*
897                  * We don't need to bother with munmap() here - exit_mmap(mm)
898                  * is coming and it'll unmap everything. And we simply can't,
899                  * this is not necessarily our ->mm.
900                  * Since kill_ioctx() uses non-zero ->mmap_size as indicator
901                  * that it needs to unmap the area, just set it to 0.
902                  */
903                 ctx->mmap_size = 0;
904                 kill_ioctx(mm, ctx, &wait);
905         }
906 
907         if (!atomic_sub_and_test(skipped, &wait.count)) {
908                 /* Wait until all IO for the context are done. */
909                 wait_for_completion(&wait.comp);
910         }
911 
912         RCU_INIT_POINTER(mm->ioctx_table, NULL);
913         kfree(table);
914 }
915 
916 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
917 {
918         struct kioctx_cpu *kcpu;
919         unsigned long flags;
920 
921         local_irq_save(flags);
922         kcpu = this_cpu_ptr(ctx->cpu);
923         kcpu->reqs_available += nr;
924 
925         while (kcpu->reqs_available >= ctx->req_batch * 2) {
926                 kcpu->reqs_available -= ctx->req_batch;
927                 atomic_add(ctx->req_batch, &ctx->reqs_available);
928         }
929 
930         local_irq_restore(flags);
931 }
932 
933 static bool get_reqs_available(struct kioctx *ctx)
934 {
935         struct kioctx_cpu *kcpu;
936         bool ret = false;
937         unsigned long flags;
938 
939         local_irq_save(flags);
940         kcpu = this_cpu_ptr(ctx->cpu);
941         if (!kcpu->reqs_available) {
942                 int old, avail = atomic_read(&ctx->reqs_available);
943 
944                 do {
945                         if (avail < ctx->req_batch)
946                                 goto out;
947 
948                         old = avail;
949                         avail = atomic_cmpxchg(&ctx->reqs_available,
950                                                avail, avail - ctx->req_batch);
951                 } while (avail != old);
952 
953                 kcpu->reqs_available += ctx->req_batch;
954         }
955 
956         ret = true;
957         kcpu->reqs_available--;
958 out:
959         local_irq_restore(flags);
960         return ret;
961 }
962 
963 /* refill_reqs_available
964  *      Updates the reqs_available reference counts used for tracking the
965  *      number of free slots in the completion ring.  This can be called
966  *      from aio_complete() (to optimistically update reqs_available) or
967  *      from aio_get_req() (the we're out of events case).  It must be
968  *      called holding ctx->completion_lock.
969  */
970 static void refill_reqs_available(struct kioctx *ctx, unsigned head,
971                                   unsigned tail)
972 {
973         unsigned events_in_ring, completed;
974 
975         /* Clamp head since userland can write to it. */
976         head %= ctx->nr_events;
977         if (head <= tail)
978                 events_in_ring = tail - head;
979         else
980                 events_in_ring = ctx->nr_events - (head - tail);
981 
982         completed = ctx->completed_events;
983         if (events_in_ring < completed)
984                 completed -= events_in_ring;
985         else
986                 completed = 0;
987 
988         if (!completed)
989                 return;
990 
991         ctx->completed_events -= completed;
992         put_reqs_available(ctx, completed);
993 }
994 
995 /* user_refill_reqs_available
996  *      Called to refill reqs_available when aio_get_req() encounters an
997  *      out of space in the completion ring.
998  */
999 static void user_refill_reqs_available(struct kioctx *ctx)
1000 {
1001         spin_lock_irq(&ctx->completion_lock);
1002         if (ctx->completed_events) {
1003                 struct aio_ring *ring;
1004                 unsigned head;
1005 
1006                 /* Access of ring->head may race with aio_read_events_ring()
1007                  * here, but that's okay since whether we read the old version
1008                  * or the new version, and either will be valid.  The important
1009                  * part is that head cannot pass tail since we prevent
1010                  * aio_complete() from updating tail by holding
1011                  * ctx->completion_lock.  Even if head is invalid, the check
1012                  * against ctx->completed_events below will make sure we do the
1013                  * safe/right thing.
1014                  */
1015                 ring = kmap_atomic(ctx->ring_pages[0]);
1016                 head = ring->head;
1017                 kunmap_atomic(ring);
1018 
1019                 refill_reqs_available(ctx, head, ctx->tail);
1020         }
1021 
1022         spin_unlock_irq(&ctx->completion_lock);
1023 }
1024 
1025 /* aio_get_req
1026  *      Allocate a slot for an aio request.
1027  * Returns NULL if no requests are free.
1028  */
1029 static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
1030 {
1031         struct aio_kiocb *req;
1032 
1033         if (!get_reqs_available(ctx)) {
1034                 user_refill_reqs_available(ctx);
1035                 if (!get_reqs_available(ctx))
1036                         return NULL;
1037         }
1038 
1039         req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
1040         if (unlikely(!req))
1041                 goto out_put;
1042 
1043         percpu_ref_get(&ctx->reqs);
1044 
1045         req->ki_ctx = ctx;
1046         return req;
1047 out_put:
1048         put_reqs_available(ctx, 1);
1049         return NULL;
1050 }
1051 
1052 static void kiocb_free(struct aio_kiocb *req)
1053 {
1054         if (req->common.ki_filp)
1055                 fput(req->common.ki_filp);
1056         if (req->ki_eventfd != NULL)
1057                 eventfd_ctx_put(req->ki_eventfd);
1058         kmem_cache_free(kiocb_cachep, req);
1059 }
1060 
1061 static struct kioctx *lookup_ioctx(unsigned long ctx_id)
1062 {
1063         struct aio_ring __user *ring  = (void __user *)ctx_id;
1064         struct mm_struct *mm = current->mm;
1065         struct kioctx *ctx, *ret = NULL;
1066         struct kioctx_table *table;
1067         unsigned id;
1068 
1069         if (get_user(id, &ring->id))
1070                 return NULL;
1071 
1072         rcu_read_lock();
1073         table = rcu_dereference(mm->ioctx_table);
1074 
1075         if (!table || id >= table->nr)
1076                 goto out;
1077 
1078         ctx = rcu_dereference(table->table[id]);
1079         if (ctx && ctx->user_id == ctx_id) {
1080                 if (percpu_ref_tryget_live(&ctx->users))
1081                         ret = ctx;
1082         }
1083 out:
1084         rcu_read_unlock();
1085         return ret;
1086 }
1087 
1088 /* aio_complete
1089  *      Called when the io request on the given iocb is complete.
1090  */
1091 static void aio_complete(struct kiocb *kiocb, long res, long res2)
1092 {
1093         struct aio_kiocb *iocb = container_of(kiocb, struct aio_kiocb, common);
1094         struct kioctx   *ctx = iocb->ki_ctx;
1095         struct aio_ring *ring;
1096         struct io_event *ev_page, *event;
1097         unsigned tail, pos, head;
1098         unsigned long   flags;
1099 
1100         if (kiocb->ki_flags & IOCB_WRITE) {
1101                 struct file *file = kiocb->ki_filp;
1102 
1103                 /*
1104                  * Tell lockdep we inherited freeze protection from submission
1105                  * thread.
1106                  */
1107                 if (S_ISREG(file_inode(file)->i_mode))
1108                         __sb_writers_acquired(file_inode(file)->i_sb, SB_FREEZE_WRITE);
1109                 file_end_write(file);
1110         }
1111 
1112         /*
1113          * Special case handling for sync iocbs:
1114          *  - events go directly into the iocb for fast handling
1115          *  - the sync task with the iocb in its stack holds the single iocb
1116          *    ref, no other paths have a way to get another ref
1117          *  - the sync task helpfully left a reference to itself in the iocb
1118          */
1119         BUG_ON(is_sync_kiocb(kiocb));
1120 
1121         if (iocb->ki_list.next) {
1122                 unsigned long flags;
1123 
1124                 spin_lock_irqsave(&ctx->ctx_lock, flags);
1125                 list_del(&iocb->ki_list);
1126                 spin_unlock_irqrestore(&ctx->ctx_lock, flags);
1127         }
1128 
1129         /*
1130          * Add a completion event to the ring buffer. Must be done holding
1131          * ctx->completion_lock to prevent other code from messing with the tail
1132          * pointer since we might be called from irq context.
1133          */
1134         spin_lock_irqsave(&ctx->completion_lock, flags);
1135 
1136         tail = ctx->tail;
1137         pos = tail + AIO_EVENTS_OFFSET;
1138 
1139         if (++tail >= ctx->nr_events)
1140                 tail = 0;
1141 
1142         ev_page = kmap_atomic(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1143         event = ev_page + pos % AIO_EVENTS_PER_PAGE;
1144 
1145         event->obj = (u64)(unsigned long)iocb->ki_user_iocb;
1146         event->data = iocb->ki_user_data;
1147         event->res = res;
1148         event->res2 = res2;
1149 
1150         kunmap_atomic(ev_page);
1151         flush_dcache_page(ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE]);
1152 
1153         pr_debug("%p[%u]: %p: %p %Lx %lx %lx\n",
1154                  ctx, tail, iocb, iocb->ki_user_iocb, iocb->ki_user_data,
1155                  res, res2);
1156 
1157         /* after flagging the request as done, we
1158          * must never even look at it again
1159          */
1160         smp_wmb();      /* make event visible before updating tail */
1161 
1162         ctx->tail = tail;
1163 
1164         ring = kmap_atomic(ctx->ring_pages[0]);
1165         head = ring->head;
1166         ring->tail = tail;
1167         kunmap_atomic(ring);
1168         flush_dcache_page(ctx->ring_pages[0]);
1169 
1170         ctx->completed_events++;
1171         if (ctx->completed_events > 1)
1172                 refill_reqs_available(ctx, head, tail);
1173         spin_unlock_irqrestore(&ctx->completion_lock, flags);
1174 
1175         pr_debug("added to ring %p at [%u]\n", iocb, tail);
1176 
1177         /*
1178          * Check if the user asked us to deliver the result through an
1179          * eventfd. The eventfd_signal() function is safe to be called
1180          * from IRQ context.
1181          */
1182         if (iocb->ki_eventfd != NULL)
1183                 eventfd_signal(iocb->ki_eventfd, 1);
1184 
1185         /* everything turned out well, dispose of the aiocb. */
1186         kiocb_free(iocb);
1187 
1188         /*
1189          * We have to order our ring_info tail store above and test
1190          * of the wait list below outside the wait lock.  This is
1191          * like in wake_up_bit() where clearing a bit has to be
1192          * ordered with the unlocked test.
1193          */
1194         smp_mb();
1195 
1196         if (waitqueue_active(&ctx->wait))
1197                 wake_up(&ctx->wait);
1198 
1199         percpu_ref_put(&ctx->reqs);
1200 }
1201 
1202 /* aio_read_events_ring
1203  *      Pull an event off of the ioctx's event ring.  Returns the number of
1204  *      events fetched
1205  */
1206 static long aio_read_events_ring(struct kioctx *ctx,
1207                                  struct io_event __user *event, long nr)
1208 {
1209         struct aio_ring *ring;
1210         unsigned head, tail, pos;
1211         long ret = 0;
1212         int copy_ret;
1213 
1214         /*
1215          * The mutex can block and wake us up and that will cause
1216          * wait_event_interruptible_hrtimeout() to schedule without sleeping
1217          * and repeat. This should be rare enough that it doesn't cause
1218          * peformance issues. See the comment in read_events() for more detail.
1219          */
1220         sched_annotate_sleep();
1221         mutex_lock(&ctx->ring_lock);
1222 
1223         /* Access to ->ring_pages here is protected by ctx->ring_lock. */
1224         ring = kmap_atomic(ctx->ring_pages[0]);
1225         head = ring->head;
1226         tail = ring->tail;
1227         kunmap_atomic(ring);
1228 
1229         /*
1230          * Ensure that once we've read the current tail pointer, that
1231          * we also see the events that were stored up to the tail.
1232          */
1233         smp_rmb();
1234 
1235         pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
1236 
1237         if (head == tail)
1238                 goto out;
1239 
1240         head %= ctx->nr_events;
1241         tail %= ctx->nr_events;
1242 
1243         while (ret < nr) {
1244                 long avail;
1245                 struct io_event *ev;
1246                 struct page *page;
1247 
1248                 avail = (head <= tail ?  tail : ctx->nr_events) - head;
1249                 if (head == tail)
1250                         break;
1251 
1252                 avail = min(avail, nr - ret);
1253                 avail = min_t(long, avail, AIO_EVENTS_PER_PAGE -
1254                             ((head + AIO_EVENTS_OFFSET) % AIO_EVENTS_PER_PAGE));
1255 
1256                 pos = head + AIO_EVENTS_OFFSET;
1257                 page = ctx->ring_pages[pos / AIO_EVENTS_PER_PAGE];
1258                 pos %= AIO_EVENTS_PER_PAGE;
1259 
1260                 ev = kmap(page);
1261                 copy_ret = copy_to_user(event + ret, ev + pos,
1262                                         sizeof(*ev) * avail);
1263                 kunmap(page);
1264 
1265                 if (unlikely(copy_ret)) {
1266                         ret = -EFAULT;
1267                         goto out;
1268                 }
1269 
1270                 ret += avail;
1271                 head += avail;
1272                 head %= ctx->nr_events;
1273         }
1274 
1275         ring = kmap_atomic(ctx->ring_pages[0]);
1276         ring->head = head;
1277         kunmap_atomic(ring);
1278         flush_dcache_page(ctx->ring_pages[0]);
1279 
1280         pr_debug("%li  h%u t%u\n", ret, head, tail);
1281 out:
1282         mutex_unlock(&ctx->ring_lock);
1283 
1284         return ret;
1285 }
1286 
1287 static bool aio_read_events(struct kioctx *ctx, long min_nr, long nr,
1288                             struct io_event __user *event, long *i)
1289 {
1290         long ret = aio_read_events_ring(ctx, event + *i, nr - *i);
1291 
1292         if (ret > 0)
1293                 *i += ret;
1294 
1295         if (unlikely(atomic_read(&ctx->dead)))
1296                 ret = -EINVAL;
1297 
1298         if (!*i)
1299                 *i = ret;
1300 
1301         return ret < 0 || *i >= min_nr;
1302 }
1303 
1304 static long read_events(struct kioctx *ctx, long min_nr, long nr,
1305                         struct io_event __user *event,
1306                         ktime_t until)
1307 {
1308         long ret = 0;
1309 
1310         /*
1311          * Note that aio_read_events() is being called as the conditional - i.e.
1312          * we're calling it after prepare_to_wait() has set task state to
1313          * TASK_INTERRUPTIBLE.
1314          *
1315          * But aio_read_events() can block, and if it blocks it's going to flip
1316          * the task state back to TASK_RUNNING.
1317          *
1318          * This should be ok, provided it doesn't flip the state back to
1319          * TASK_RUNNING and return 0 too much - that causes us to spin. That
1320          * will only happen if the mutex_lock() call blocks, and we then find
1321          * the ringbuffer empty. So in practice we should be ok, but it's
1322          * something to be aware of when touching this code.
1323          */
1324         if (until == 0)
1325                 aio_read_events(ctx, min_nr, nr, event, &ret);
1326         else
1327                 wait_event_interruptible_hrtimeout(ctx->wait,
1328                                 aio_read_events(ctx, min_nr, nr, event, &ret),
1329                                 until);
1330 
1331         if (!ret && signal_pending(current))
1332                 ret = -EINTR;
1333 
1334         return ret;
1335 }
1336 
1337 /* sys_io_setup:
1338  *      Create an aio_context capable of receiving at least nr_events.
1339  *      ctxp must not point to an aio_context that already exists, and
1340  *      must be initialized to 0 prior to the call.  On successful
1341  *      creation of the aio_context, *ctxp is filled in with the resulting 
1342  *      handle.  May fail with -EINVAL if *ctxp is not initialized,
1343  *      if the specified nr_events exceeds internal limits.  May fail 
1344  *      with -EAGAIN if the specified nr_events exceeds the user's limit 
1345  *      of available events.  May fail with -ENOMEM if insufficient kernel
1346  *      resources are available.  May fail with -EFAULT if an invalid
1347  *      pointer is passed for ctxp.  Will fail with -ENOSYS if not
1348  *      implemented.
1349  */
1350 SYSCALL_DEFINE2(io_setup, unsigned, nr_events, aio_context_t __user *, ctxp)
1351 {
1352         struct kioctx *ioctx = NULL;
1353         unsigned long ctx;
1354         long ret;
1355 
1356         ret = get_user(ctx, ctxp);
1357         if (unlikely(ret))
1358                 goto out;
1359 
1360         ret = -EINVAL;
1361         if (unlikely(ctx || nr_events == 0)) {
1362                 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1363                          ctx, nr_events);
1364                 goto out;
1365         }
1366 
1367         ioctx = ioctx_alloc(nr_events);
1368         ret = PTR_ERR(ioctx);
1369         if (!IS_ERR(ioctx)) {
1370                 ret = put_user(ioctx->user_id, ctxp);
1371                 if (ret)
1372                         kill_ioctx(current->mm, ioctx, NULL);
1373                 percpu_ref_put(&ioctx->users);
1374         }
1375 
1376 out:
1377         return ret;
1378 }
1379 
1380 #ifdef CONFIG_COMPAT
1381 COMPAT_SYSCALL_DEFINE2(io_setup, unsigned, nr_events, u32 __user *, ctx32p)
1382 {
1383         struct kioctx *ioctx = NULL;
1384         unsigned long ctx;
1385         long ret;
1386 
1387         ret = get_user(ctx, ctx32p);
1388         if (unlikely(ret))
1389                 goto out;
1390 
1391         ret = -EINVAL;
1392         if (unlikely(ctx || nr_events == 0)) {
1393                 pr_debug("EINVAL: ctx %lu nr_events %u\n",
1394                          ctx, nr_events);
1395                 goto out;
1396         }
1397 
1398         ioctx = ioctx_alloc(nr_events);
1399         ret = PTR_ERR(ioctx);
1400         if (!IS_ERR(ioctx)) {
1401                 /* truncating is ok because it's a user address */
1402                 ret = put_user((u32)ioctx->user_id, ctx32p);
1403                 if (ret)
1404                         kill_ioctx(current->mm, ioctx, NULL);
1405                 percpu_ref_put(&ioctx->users);
1406         }
1407 
1408 out:
1409         return ret;
1410 }
1411 #endif
1412 
1413 /* sys_io_destroy:
1414  *      Destroy the aio_context specified.  May cancel any outstanding 
1415  *      AIOs and block on completion.  Will fail with -ENOSYS if not
1416  *      implemented.  May fail with -EINVAL if the context pointed to
1417  *      is invalid.
1418  */
1419 SYSCALL_DEFINE1(io_destroy, aio_context_t, ctx)
1420 {
1421         struct kioctx *ioctx = lookup_ioctx(ctx);
1422         if (likely(NULL != ioctx)) {
1423                 struct ctx_rq_wait wait;
1424                 int ret;
1425 
1426                 init_completion(&wait.comp);
1427                 atomic_set(&wait.count, 1);
1428 
1429                 /* Pass requests_done to kill_ioctx() where it can be set
1430                  * in a thread-safe way. If we try to set it here then we have
1431                  * a race condition if two io_destroy() called simultaneously.
1432                  */
1433                 ret = kill_ioctx(current->mm, ioctx, &wait);
1434                 percpu_ref_put(&ioctx->users);
1435 
1436                 /* Wait until all IO for the context are done. Otherwise kernel
1437                  * keep using user-space buffers even if user thinks the context
1438                  * is destroyed.
1439                  */
1440                 if (!ret)
1441                         wait_for_completion(&wait.comp);
1442 
1443                 return ret;
1444         }
1445         pr_debug("EINVAL: invalid context id\n");
1446         return -EINVAL;
1447 }
1448 
1449 static int aio_setup_rw(int rw, struct iocb *iocb, struct iovec **iovec,
1450                 bool vectored, bool compat, struct iov_iter *iter)
1451 {
1452         void __user *buf = (void __user *)(uintptr_t)iocb->aio_buf;
1453         size_t len = iocb->aio_nbytes;
1454 
1455         if (!vectored) {
1456                 ssize_t ret = import_single_range(rw, buf, len, *iovec, iter);
1457                 *iovec = NULL;
1458                 return ret;
1459         }
1460 #ifdef CONFIG_COMPAT
1461         if (compat)
1462                 return compat_import_iovec(rw, buf, len, UIO_FASTIOV, iovec,
1463                                 iter);
1464 #endif
1465         return import_iovec(rw, buf, len, UIO_FASTIOV, iovec, iter);
1466 }
1467 
1468 static inline ssize_t aio_ret(struct kiocb *req, ssize_t ret)
1469 {
1470         switch (ret) {
1471         case -EIOCBQUEUED:
1472                 return ret;
1473         case -ERESTARTSYS:
1474         case -ERESTARTNOINTR:
1475         case -ERESTARTNOHAND:
1476         case -ERESTART_RESTARTBLOCK:
1477                 /*
1478                  * There's no easy way to restart the syscall since other AIO's
1479                  * may be already running. Just fail this IO with EINTR.
1480                  */
1481                 ret = -EINTR;
1482                 /*FALLTHRU*/
1483         default:
1484                 aio_complete(req, ret, 0);
1485                 return 0;
1486         }
1487 }
1488 
1489 static ssize_t aio_read(struct kiocb *req, struct iocb *iocb, bool vectored,
1490                 bool compat)
1491 {
1492         struct file *file = req->ki_filp;
1493         struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
1494         struct iov_iter iter;
1495         ssize_t ret;
1496 
1497         if (unlikely(!(file->f_mode & FMODE_READ)))
1498                 return -EBADF;
1499         if (unlikely(!file->f_op->read_iter))
1500                 return -EINVAL;
1501 
1502         ret = aio_setup_rw(READ, iocb, &iovec, vectored, compat, &iter);
1503         if (ret)
1504                 return ret;
1505         ret = rw_verify_area(READ, file, &req->ki_pos, iov_iter_count(&iter));
1506         if (!ret)
1507                 ret = aio_ret(req, call_read_iter(file, req, &iter));
1508         kfree(iovec);
1509         return ret;
1510 }
1511 
1512 static ssize_t aio_write(struct kiocb *req, struct iocb *iocb, bool vectored,
1513                 bool compat)
1514 {
1515         struct file *file = req->ki_filp;
1516         struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
1517         struct iov_iter iter;
1518         ssize_t ret;
1519 
1520         if (unlikely(!(file->f_mode & FMODE_WRITE)))
1521                 return -EBADF;
1522         if (unlikely(!file->f_op->write_iter))
1523                 return -EINVAL;
1524 
1525         ret = aio_setup_rw(WRITE, iocb, &iovec, vectored, compat, &iter);
1526         if (ret)
1527                 return ret;
1528         ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
1529         if (!ret) {
1530                 req->ki_flags |= IOCB_WRITE;
1531                 file_start_write(file);
1532                 ret = aio_ret(req, call_write_iter(file, req, &iter));
1533                 /*
1534                  * We release freeze protection in aio_complete().  Fool lockdep
1535                  * by telling it the lock got released so that it doesn't
1536                  * complain about held lock when we return to userspace.
1537                  */
1538                 if (S_ISREG(file_inode(file)->i_mode))
1539                         __sb_writers_release(file_inode(file)->i_sb, SB_FREEZE_WRITE);
1540         }
1541         kfree(iovec);
1542         return ret;
1543 }
1544 
1545 static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
1546                          struct iocb *iocb, bool compat)
1547 {
1548         struct aio_kiocb *req;
1549         struct file *file;
1550         ssize_t ret;
1551 
1552         /* enforce forwards compatibility on users */
1553         if (unlikely(iocb->aio_reserved2)) {
1554                 pr_debug("EINVAL: reserve field set\n");
1555                 return -EINVAL;
1556         }
1557 
1558         /* prevent overflows */
1559         if (unlikely(
1560             (iocb->aio_buf != (unsigned long)iocb->aio_buf) ||
1561             (iocb->aio_nbytes != (size_t)iocb->aio_nbytes) ||
1562             ((ssize_t)iocb->aio_nbytes < 0)
1563            )) {
1564                 pr_debug("EINVAL: overflow check\n");
1565                 return -EINVAL;
1566         }
1567 
1568         req = aio_get_req(ctx);
1569         if (unlikely(!req))
1570                 return -EAGAIN;
1571 
1572         req->common.ki_filp = file = fget(iocb->aio_fildes);
1573         if (unlikely(!req->common.ki_filp)) {
1574                 ret = -EBADF;
1575                 goto out_put_req;
1576         }
1577         req->common.ki_pos = iocb->aio_offset;
1578         req->common.ki_complete = aio_complete;
1579         req->common.ki_flags = iocb_flags(req->common.ki_filp);
1580         req->common.ki_hint = file_write_hint(file);
1581 
1582         if (iocb->aio_flags & IOCB_FLAG_RESFD) {
1583                 /*
1584                  * If the IOCB_FLAG_RESFD flag of aio_flags is set, get an
1585                  * instance of the file* now. The file descriptor must be
1586                  * an eventfd() fd, and will be signaled for each completed
1587                  * event using the eventfd_signal() function.
1588                  */
1589                 req->ki_eventfd = eventfd_ctx_fdget((int) iocb->aio_resfd);
1590                 if (IS_ERR(req->ki_eventfd)) {
1591                         ret = PTR_ERR(req->ki_eventfd);
1592                         req->ki_eventfd = NULL;
1593                         goto out_put_req;
1594                 }
1595 
1596                 req->common.ki_flags |= IOCB_EVENTFD;
1597         }
1598 
1599         ret = kiocb_set_rw_flags(&req->common, iocb->aio_rw_flags);
1600         if (unlikely(ret)) {
1601                 pr_debug("EINVAL: aio_rw_flags\n");
1602                 goto out_put_req;
1603         }
1604 
1605         ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
1606         if (unlikely(ret)) {
1607                 pr_debug("EFAULT: aio_key\n");
1608                 goto out_put_req;
1609         }
1610 
1611         req->ki_user_iocb = user_iocb;
1612         req->ki_user_data = iocb->aio_data;
1613 
1614         get_file(file);
1615         switch (iocb->aio_lio_opcode) {
1616         case IOCB_CMD_PREAD:
1617                 ret = aio_read(&req->common, iocb, false, compat);
1618                 break;
1619         case IOCB_CMD_PWRITE:
1620                 ret = aio_write(&req->common, iocb, false, compat);
1621                 break;
1622         case IOCB_CMD_PREADV:
1623                 ret = aio_read(&req->common, iocb, true, compat);
1624                 break;
1625         case IOCB_CMD_PWRITEV:
1626                 ret = aio_write(&req->common, iocb, true, compat);
1627                 break;
1628         default:
1629                 pr_debug("invalid aio operation %d\n", iocb->aio_lio_opcode);
1630                 ret = -EINVAL;
1631                 break;
1632         }
1633         fput(file);
1634 
1635         if (ret && ret != -EIOCBQUEUED)
1636                 goto out_put_req;
1637         return 0;
1638 out_put_req:
1639         put_reqs_available(ctx, 1);
1640         percpu_ref_put(&ctx->reqs);
1641         kiocb_free(req);
1642         return ret;
1643 }
1644 
1645 static long do_io_submit(aio_context_t ctx_id, long nr,
1646                           struct iocb __user *__user *iocbpp, bool compat)
1647 {
1648         struct kioctx *ctx;
1649         long ret = 0;
1650         int i = 0;
1651         struct blk_plug plug;
1652 
1653         if (unlikely(nr < 0))
1654                 return -EINVAL;
1655 
1656         if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
1657                 nr = LONG_MAX/sizeof(*iocbpp);
1658 
1659         if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
1660                 return -EFAULT;
1661 
1662         ctx = lookup_ioctx(ctx_id);
1663         if (unlikely(!ctx)) {
1664                 pr_debug("EINVAL: invalid context id\n");
1665                 return -EINVAL;
1666         }
1667 
1668         blk_start_plug(&plug);
1669 
1670         /*
1671          * AKPM: should this return a partial result if some of the IOs were
1672          * successfully submitted?
1673          */
1674         for (i=0; i<nr; i++) {
1675                 struct iocb __user *user_iocb;
1676                 struct iocb tmp;
1677 
1678                 if (unlikely(__get_user(user_iocb, iocbpp + i))) {
1679                         ret = -EFAULT;
1680                         break;
1681                 }
1682 
1683                 if (unlikely(copy_from_user(&tmp, user_iocb, sizeof(tmp)))) {
1684                         ret = -EFAULT;
1685                         break;
1686                 }
1687 
1688                 ret = io_submit_one(ctx, user_iocb, &tmp, compat);
1689                 if (ret)
1690                         break;
1691         }
1692         blk_finish_plug(&plug);
1693 
1694         percpu_ref_put(&ctx->users);
1695         return i ? i : ret;
1696 }
1697 
1698 /* sys_io_submit:
1699  *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
1700  *      the number of iocbs queued.  May return -EINVAL if the aio_context
1701  *      specified by ctx_id is invalid, if nr is < 0, if the iocb at
1702  *      *iocbpp[0] is not properly initialized, if the operation specified
1703  *      is invalid for the file descriptor in the iocb.  May fail with
1704  *      -EFAULT if any of the data structures point to invalid data.  May
1705  *      fail with -EBADF if the file descriptor specified in the first
1706  *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
1707  *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
1708  *      fail with -ENOSYS if not implemented.
1709  */
1710 SYSCALL_DEFINE3(io_submit, aio_context_t, ctx_id, long, nr,
1711                 struct iocb __user * __user *, iocbpp)
1712 {
1713         return do_io_submit(ctx_id, nr, iocbpp, 0);
1714 }
1715 
1716 #ifdef CONFIG_COMPAT
1717 static inline long
1718 copy_iocb(long nr, u32 __user *ptr32, struct iocb __user * __user *ptr64)
1719 {
1720         compat_uptr_t uptr;
1721         int i;
1722 
1723         for (i = 0; i < nr; ++i) {
1724                 if (get_user(uptr, ptr32 + i))
1725                         return -EFAULT;
1726                 if (put_user(compat_ptr(uptr), ptr64 + i))
1727                         return -EFAULT;
1728         }
1729         return 0;
1730 }
1731 
1732 #define MAX_AIO_SUBMITS         (PAGE_SIZE/sizeof(struct iocb *))
1733 
1734 COMPAT_SYSCALL_DEFINE3(io_submit, compat_aio_context_t, ctx_id,
1735                        int, nr, u32 __user *, iocb)
1736 {
1737         struct iocb __user * __user *iocb64;
1738         long ret;
1739 
1740         if (unlikely(nr < 0))
1741                 return -EINVAL;
1742 
1743         if (nr > MAX_AIO_SUBMITS)
1744                 nr = MAX_AIO_SUBMITS;
1745 
1746         iocb64 = compat_alloc_user_space(nr * sizeof(*iocb64));
1747         ret = copy_iocb(nr, iocb, iocb64);
1748         if (!ret)
1749                 ret = do_io_submit(ctx_id, nr, iocb64, 1);
1750         return ret;
1751 }
1752 #endif
1753 
1754 /* lookup_kiocb
1755  *      Finds a given iocb for cancellation.
1756  */
1757 static struct aio_kiocb *
1758 lookup_kiocb(struct kioctx *ctx, struct iocb __user *iocb, u32 key)
1759 {
1760         struct aio_kiocb *kiocb;
1761 
1762         assert_spin_locked(&ctx->ctx_lock);
1763 
1764         if (key != KIOCB_KEY)
1765                 return NULL;
1766 
1767         /* TODO: use a hash or array, this sucks. */
1768         list_for_each_entry(kiocb, &ctx->active_reqs, ki_list) {
1769                 if (kiocb->ki_user_iocb == iocb)
1770                         return kiocb;
1771         }
1772         return NULL;
1773 }
1774 
1775 /* sys_io_cancel:
1776  *      Attempts to cancel an iocb previously passed to io_submit.  If
1777  *      the operation is successfully cancelled, the resulting event is
1778  *      copied into the memory pointed to by result without being placed
1779  *      into the completion queue and 0 is returned.  May fail with
1780  *      -EFAULT if any of the data structures pointed to are invalid.
1781  *      May fail with -EINVAL if aio_context specified by ctx_id is
1782  *      invalid.  May fail with -EAGAIN if the iocb specified was not
1783  *      cancelled.  Will fail with -ENOSYS if not implemented.
1784  */
1785 SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb,
1786                 struct io_event __user *, result)
1787 {
1788         struct kioctx *ctx;
1789         struct aio_kiocb *kiocb;
1790         u32 key;
1791         int ret;
1792 
1793         ret = get_user(key, &iocb->aio_key);
1794         if (unlikely(ret))
1795                 return -EFAULT;
1796 
1797         ctx = lookup_ioctx(ctx_id);
1798         if (unlikely(!ctx))
1799                 return -EINVAL;
1800 
1801         spin_lock_irq(&ctx->ctx_lock);
1802 
1803         kiocb = lookup_kiocb(ctx, iocb, key);
1804         if (kiocb)
1805                 ret = kiocb_cancel(kiocb);
1806         else
1807                 ret = -EINVAL;
1808 
1809         spin_unlock_irq(&ctx->ctx_lock);
1810 
1811         if (!ret) {
1812                 /*
1813                  * The result argument is no longer used - the io_event is
1814                  * always delivered via the ring buffer. -EINPROGRESS indicates
1815                  * cancellation is progress:
1816                  */
1817                 ret = -EINPROGRESS;
1818         }
1819 
1820         percpu_ref_put(&ctx->users);
1821 
1822         return ret;
1823 }
1824 
1825 static long do_io_getevents(aio_context_t ctx_id,
1826                 long min_nr,
1827                 long nr,
1828                 struct io_event __user *events,
1829                 struct timespec64 *ts)
1830 {
1831         ktime_t until = ts ? timespec64_to_ktime(*ts) : KTIME_MAX;
1832         struct kioctx *ioctx = lookup_ioctx(ctx_id);
1833         long ret = -EINVAL;
1834 
1835         if (likely(ioctx)) {
1836                 if (likely(min_nr <= nr && min_nr >= 0))
1837                         ret = read_events(ioctx, min_nr, nr, events, until);
1838                 percpu_ref_put(&ioctx->users);
1839         }
1840 
1841         return ret;
1842 }
1843 
1844 /* io_getevents:
1845  *      Attempts to read at least min_nr events and up to nr events from
1846  *      the completion queue for the aio_context specified by ctx_id. If
1847  *      it succeeds, the number of read events is returned. May fail with
1848  *      -EINVAL if ctx_id is invalid, if min_nr is out of range, if nr is
1849  *      out of range, if timeout is out of range.  May fail with -EFAULT
1850  *      if any of the memory specified is invalid.  May return 0 or
1851  *      < min_nr if the timeout specified by timeout has elapsed
1852  *      before sufficient events are available, where timeout == NULL
1853  *      specifies an infinite timeout. Note that the timeout pointed to by
1854  *      timeout is relative.  Will fail with -ENOSYS if not implemented.
1855  */
1856 SYSCALL_DEFINE5(io_getevents, aio_context_t, ctx_id,
1857                 long, min_nr,
1858                 long, nr,
1859                 struct io_event __user *, events,
1860                 struct timespec __user *, timeout)
1861 {
1862         struct timespec64       ts;
1863 
1864         if (timeout) {
1865                 if (unlikely(get_timespec64(&ts, timeout)))
1866                         return -EFAULT;
1867         }
1868 
1869         return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &ts : NULL);
1870 }
1871 
1872 #ifdef CONFIG_COMPAT
1873 COMPAT_SYSCALL_DEFINE5(io_getevents, compat_aio_context_t, ctx_id,
1874                        compat_long_t, min_nr,
1875                        compat_long_t, nr,
1876                        struct io_event __user *, events,
1877                        struct compat_timespec __user *, timeout)
1878 {
1879         struct timespec64 t;
1880 
1881         if (timeout) {
1882                 if (compat_get_timespec64(&t, timeout))
1883                         return -EFAULT;
1884 
1885         }
1886 
1887         return do_io_getevents(ctx_id, min_nr, nr, events, timeout ? &t : NULL);
1888 }
1889 #endif
1890 

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