Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block into for-3.18

This is to receive 0a30288da1ae ("blk-mq, percpu_ref: implement a
kludge for SCSI blk-mq stall during probe") which implements
__percpu_ref_kill_expedited() to work around SCSI blk-mq stall.  The
commit reverted and patches to implement proper fix will be added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>

1 files changed, 114 insertions, 60 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 93fbcc0f5696..8d217ed04e6e 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -141,6 +141,7 @@ struct kioctx {
 
         struct {
                 unsigned        tail;
+                unsigned        completed_events;
                 spinlock_t      completion_lock;
         } ____cacheline_aligned_in_smp;
 
@@ -192,7 +193,6 @@ static struct file *aio_private_file(struct kioctx *ctx, loff_t nr_pages)
         }
 
         file->f_flags = O_RDWR;
-        file->private_data = ctx;
         return file;
 }
 
@@ -202,7 +202,7 @@ static struct dentry *aio_mount(struct file_system_type *fs_type,
         static const struct dentry_operations ops = {
                 .d_dname        = simple_dname,
         };
-        return mount_pseudo(fs_type, "aio:", NULL, &ops, 0xa10a10a1);
+        return mount_pseudo(fs_type, "aio:", NULL, &ops, AIO_RING_MAGIC);
 }
 
 /* aio_setup
@@ -556,8 +556,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
         struct aio_ring *ring;
 
         spin_lock(&mm->ioctx_lock);
-        rcu_read_lock();
-        table = rcu_dereference(mm->ioctx_table);
+        table = rcu_dereference_raw(mm->ioctx_table);
 
         while (1) {
                 if (table)
@@ -565,7 +564,6 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
                                 if (!table->table[i]) {
                                         ctx->id = i;
                                         table->table[i] = ctx;
-                                        rcu_read_unlock();
                                         spin_unlock(&mm->ioctx_lock);
 
                                         /* While kioctx setup is in progress,
@@ -579,8 +577,6 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
                                 }
 
                 new_nr = (table ? table->nr : 1) * 4;
-
-                rcu_read_unlock();
                 spin_unlock(&mm->ioctx_lock);
 
                 table = kzalloc(sizeof(*table) + sizeof(struct kioctx *) *
@@ -591,8 +587,7 @@ static int ioctx_add_table(struct kioctx *ctx, struct mm_struct *mm)
                 table->nr = new_nr;
 
                 spin_lock(&mm->ioctx_lock);
-                rcu_read_lock();
-                old = rcu_dereference(mm->ioctx_table);
+                old = rcu_dereference_raw(mm->ioctx_table);
 
                 if (!old) {
                         rcu_assign_pointer(mm->ioctx_table, table);
@@ -739,12 +734,9 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx *ctx,
 
 
         spin_lock(&mm->ioctx_lock);
-        rcu_read_lock();
-        table = rcu_dereference(mm->ioctx_table);
-
+        table = rcu_dereference_raw(mm->ioctx_table);
         WARN_ON(ctx != table->table[ctx->id]);
         table->table[ctx->id] = NULL;
-        rcu_read_unlock();
         spin_unlock(&mm->ioctx_lock);
 
         /* percpu_ref_kill() will do the necessary call_rcu() */
@@ -793,40 +785,35 @@ EXPORT_SYMBOL(wait_on_sync_kiocb);
  */
 void exit_aio(struct mm_struct *mm)
 {
-        struct kioctx_table *table;
-        struct kioctx *ctx;
-        unsigned i = 0;
-
-        while (1) {
-                rcu_read_lock();
-                table = rcu_dereference(mm->ioctx_table);
-
-                do {
-                        if (!table || i >= table->nr) {
-                                rcu_read_unlock();
-                                rcu_assign_pointer(mm->ioctx_table, NULL);
-                                if (table)
-                                        kfree(table);
-                                return;
-                        }
+        struct kioctx_table *table = rcu_dereference_raw(mm->ioctx_table);
+        int i;
 
-                        ctx = table->table[i++];
-                } while (!ctx);
+        if (!table)
+                return;
 
-                rcu_read_unlock();
+        for (i = 0; i < table->nr; ++i) {
+                struct kioctx *ctx = table->table[i];
+                struct completion requests_done =
+                        COMPLETION_INITIALIZER_ONSTACK(requests_done);
 
+                if (!ctx)
+                        continue;
                 /*
-                 * We don't need to bother with munmap() here -
-                 * exit_mmap(mm) is coming and it'll unmap everything.
-                 * Since aio_free_ring() uses non-zero ->mmap_size
-                 * as indicator that it needs to unmap the area,
-                 * just set it to 0; aio_free_ring() is the only
-                 * place that uses ->mmap_size, so it's safe.
+                 * We don't need to bother with munmap() here - exit_mmap(mm)
+                 * is coming and it'll unmap everything. And we simply can't,
+                 * this is not necessarily our ->mm.
+                 * Since kill_ioctx() uses non-zero ->mmap_size as indicator
+                 * that it needs to unmap the area, just set it to 0.
                  */
                 ctx->mmap_size = 0;
+                kill_ioctx(mm, ctx, &requests_done);
 
-                kill_ioctx(mm, ctx, NULL);
+                /* Wait until all IO for the context are done. */
+                wait_for_completion(&requests_done);
         }
+
+        RCU_INIT_POINTER(mm->ioctx_table, NULL);
+        kfree(table);
 }
 
 static void put_reqs_available(struct kioctx *ctx, unsigned nr)
@@ -834,10 +821,8 @@ static void put_reqs_available(struct kioctx *ctx, unsigned nr)
         struct kioctx_cpu *kcpu;
         unsigned long flags;
 
-        preempt_disable();
-        kcpu = this_cpu_ptr(ctx->cpu);
-
         local_irq_save(flags);
+        kcpu = this_cpu_ptr(ctx->cpu);
         kcpu->reqs_available += nr;
 
         while (kcpu->reqs_available >= ctx->req_batch * 2) {
@@ -846,7 +831,6 @@ static void put_reqs_available(struct kioctx *ctx, unsigned nr)
         }
 
         local_irq_restore(flags);
-        preempt_enable();
 }
 
 static bool get_reqs_available(struct kioctx *ctx)
@@ -855,10 +839,8 @@ static bool get_reqs_available(struct kioctx *ctx)
         bool ret = false;
         unsigned long flags;
 
-        preempt_disable();
-        kcpu = this_cpu_ptr(ctx->cpu);
-
         local_irq_save(flags);
+        kcpu = this_cpu_ptr(ctx->cpu);
         if (!kcpu->reqs_available) {
                 int old, avail = atomic_read(&ctx->reqs_available);
 
@@ -878,10 +860,71 @@ static bool get_reqs_available(struct kioctx *ctx)
         kcpu->reqs_available--;
 out:
         local_irq_restore(flags);
-        preempt_enable();
         return ret;
 }
 
+/* refill_reqs_available
+ *      Updates the reqs_available reference counts used for tracking the
+ *      number of free slots in the completion ring.  This can be called
+ *      from aio_complete() (to optimistically update reqs_available) or
+ *      from aio_get_req() (the we're out of events case).  It must be
+ *      called holding ctx->completion_lock.
+ */
+static void refill_reqs_available(struct kioctx *ctx, unsigned head,
+                                  unsigned tail)
+{
+        unsigned events_in_ring, completed;
+
+        /* Clamp head since userland can write to it. */
+        head %= ctx->nr_events;
+        if (head <= tail)
+                events_in_ring = tail - head;
+        else
+                events_in_ring = ctx->nr_events - (head - tail);
+
+        completed = ctx->completed_events;
+        if (events_in_ring < completed)
+                completed -= events_in_ring;
+        else
+                completed = 0;
+
+        if (!completed)
+                return;
+
+        ctx->completed_events -= completed;
+        put_reqs_available(ctx, completed);
+}
+
+/* user_refill_reqs_available
+ *      Called to refill reqs_available when aio_get_req() encounters an
+ *      out of space in the completion ring.
+ */
+static void user_refill_reqs_available(struct kioctx *ctx)
+{
+        spin_lock_irq(&ctx->completion_lock);
+        if (ctx->completed_events) {
+                struct aio_ring *ring;
+                unsigned head;
+
+                /* Access of ring->head may race with aio_read_events_ring()
+                 * here, but that's okay since whether we read the old version
+                 * or the new version, and either will be valid.  The important
+                 * part is that head cannot pass tail since we prevent
+                 * aio_complete() from updating tail by holding
+                 * ctx->completion_lock.  Even if head is invalid, the check
+                 * against ctx->completed_events below will make sure we do the
+                 * safe/right thing.
+                 */
+                ring = kmap_atomic(ctx->ring_pages[0]);
+                head = ring->head;
+                kunmap_atomic(ring);
+
+                refill_reqs_available(ctx, head, ctx->tail);
+        }
+
+        spin_unlock_irq(&ctx->completion_lock);
+}
+
 /* aio_get_req
  *      Allocate a slot for an aio request.
  * Returns NULL if no requests are free.
@@ -890,8 +933,11 @@ static inline struct kiocb *aio_get_req(struct kioctx *ctx)
 {
         struct kiocb *req;
 
-        if (!get_reqs_available(ctx))
-                return NULL;
+        if (!get_reqs_available(ctx)) {
+                user_refill_reqs_available(ctx);
+                if (!get_reqs_available(ctx))
+                        return NULL;
+        }
 
         req = kmem_cache_alloc(kiocb_cachep, GFP_KERNEL|__GFP_ZERO);
         if (unlikely(!req))
@@ -950,8 +996,8 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
         struct kioctx   *ctx = iocb->ki_ctx;
         struct aio_ring *ring;
         struct io_event *ev_page, *event;
+        unsigned tail, pos, head;
         unsigned long   flags;
-        unsigned tail, pos;
 
         /*
          * Special case handling for sync iocbs:
@@ -1012,10 +1058,14 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
         ctx->tail = tail;
 
         ring = kmap_atomic(ctx->ring_pages[0]);
+        head = ring->head;
         ring->tail = tail;
         kunmap_atomic(ring);
         flush_dcache_page(ctx->ring_pages[0]);
 
+        ctx->completed_events++;
+        if (ctx->completed_events > 1)
+                refill_reqs_available(ctx, head, tail);
         spin_unlock_irqrestore(&ctx->completion_lock, flags);
 
         pr_debug("added to ring %p at [%u]\n", iocb, tail);
@@ -1030,7 +1080,6 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
 
         /* everything turned out well, dispose of the aiocb. */
         kiocb_free(iocb);
-        put_reqs_available(ctx, 1);
 
         /*
          * We have to order our ring_info tail store above and test
@@ -1047,7 +1096,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
 }
 EXPORT_SYMBOL(aio_complete);
 
-/* aio_read_events
+/* aio_read_events_ring
  *      Pull an event off of the ioctx's event ring.  Returns the number of
  *      events fetched
  */
@@ -1067,6 +1116,12 @@ static long aio_read_events_ring(struct kioctx *ctx,
         tail = ring->tail;
         kunmap_atomic(ring);
 
+        /*
+         * Ensure that once we've read the current tail pointer, that
+         * we also see the events that were stored up to the tail.
+         */
+        smp_rmb();
+
         pr_debug("h%u t%u m%u\n", head, tail, ctx->nr_events);
 
         if (head == tail)
@@ -1270,12 +1325,12 @@ static ssize_t aio_setup_vectored_rw(struct kiocb *kiocb,
         if (compat)
                 ret = compat_rw_copy_check_uvector(rw,
                                 (struct compat_iovec __user *)buf,
-                                *nr_segs, 1, *iovec, iovec);
+                                *nr_segs, UIO_FASTIOV, *iovec, iovec);
         else
 #endif
                 ret = rw_copy_check_uvector(rw,
                                 (struct iovec __user *)buf,
-                                *nr_segs, 1, *iovec, iovec);
+                                *nr_segs, UIO_FASTIOV, *iovec, iovec);
         if (ret < 0)
                 return ret;
 
@@ -1299,9 +1354,8 @@ static ssize_t aio_setup_single_vector(struct kiocb *kiocb,
 }
 
 /*
- * aio_setup_iocb:
- *      Performs the initial checks and aio retry method
- *      setup for the kiocb at the time of io submission.
+ * aio_run_iocb:
+ *      Performs the initial checks and io submission.
  */
 static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
                             char __user *buf, bool compat)
@@ -1313,7 +1367,7 @@ static ssize_t aio_run_iocb(struct kiocb *req, unsigned opcode,
         fmode_t mode;
         aio_rw_op *rw_op;
         rw_iter_op *iter_op;
-        struct iovec inline_vec, *iovec = &inline_vec;
+        struct iovec inline_vecs[UIO_FASTIOV], *iovec = inline_vecs;
         struct iov_iter iter;
 
         switch (opcode) {
@@ -1348,7 +1402,7 @@ rw_common:
                 if (!ret)
                         ret = rw_verify_area(rw, file, &req->ki_pos, req->ki_nbytes);
                 if (ret < 0) {
-                        if (iovec != &inline_vec)
+                        if (iovec != inline_vecs)
                                 kfree(iovec);
                         return ret;
                 }
@@ -1395,7 +1449,7 @@ rw_common:
                 return -EINVAL;
         }
 
-        if (iovec != &inline_vec)
+        if (iovec != inline_vecs)
                 kfree(iovec);
 
         if (ret != -EIOCBQUEUED) {