[PATCH 1/5] aio: Move aio_nr increment to separate function

[Kirill Tkhai]

There is no functional changes, only a preparation
for next patches.

Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
---
 fs/aio.c |   44 ++++++++++++++++++++++++++++++++------------
 1 file changed, 32 insertions(+), 12 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index e6de7715228c..04209c0561b2 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -694,13 +694,39 @@ static int ioctx_add_table(struct kioctx *ctx, struct 
mm_struct *mm)
        }
 }
 
-static void aio_nr_sub(unsigned nr)
+static bool __try_to_charge_aio_nr(unsigned nr)
+{
+       if (aio_nr + nr > aio_max_nr ||
+           aio_nr + nr < aio_nr)
+               return false;
+
+       aio_nr += nr;
+       return true;
+}
+
+static void __uncharge_aio_nr(unsigned nr)
 {
-       spin_lock(&aio_nr_lock);
        if (WARN_ON(aio_nr - nr > aio_nr))
                aio_nr = 0;
        else
                aio_nr -= nr;
+}
+
+static bool try_to_charge_aio_nr(unsigned nr)
+{
+       bool ret;
+
+       spin_lock(&aio_nr_lock);
+       ret = __try_to_charge_aio_nr(nr);
+       spin_unlock(&aio_nr_lock);
+
+       return ret;
+}
+
+static void uncharge_aio_nr(unsigned nr)
+{
+       spin_lock(&aio_nr_lock);
+       __uncharge_aio_nr(nr);
        spin_unlock(&aio_nr_lock);
 }
 
@@ -776,15 +802,9 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
                ctx->req_batch = 1;
 
        /* limit the number of system wide aios */
-       spin_lock(&aio_nr_lock);
-       if (aio_nr + ctx->max_reqs > aio_max_nr ||
-           aio_nr + ctx->max_reqs < aio_nr) {
-               spin_unlock(&aio_nr_lock);
-               err = -EAGAIN;
+       err = -EAGAIN;
+       if (!try_to_charge_aio_nr(ctx->max_reqs))
                goto err_ctx;
-       }
-       aio_nr += ctx->max_reqs;
-       spin_unlock(&aio_nr_lock);
 
        percpu_ref_get(&ctx->users);    /* io_setup() will drop this ref */
        percpu_ref_get(&ctx->reqs);     /* free_ioctx_users() will drop this */
@@ -801,7 +821,7 @@ static struct kioctx *ioctx_alloc(unsigned nr_events)
        return ctx;
 
 err_cleanup:
-       aio_nr_sub(ctx->max_reqs);
+       uncharge_aio_nr(ctx->max_reqs);
 err_ctx:
        atomic_set(&ctx->dead, 1);
        if (ctx->mmap_size)
@@ -848,7 +868,7 @@ static int kill_ioctx(struct mm_struct *mm, struct kioctx 
*ctx,
         * -EAGAIN with no ioctxs actually in use (as far as userspace
         *  could tell).
         */
-       aio_nr_sub(ctx->max_reqs);
+       uncharge_aio_nr(ctx->max_reqs);
 
        if (ctx->mmap_size)
                vm_munmap(ctx->mmap_base, ctx->mmap_size);