freezer: unexport refrigerator() and update try_to_freeze() slightly

There is no reason to export two functions for entering the
refrigerator.  Calling refrigerator() instead of try_to_freeze()
doesn't save anything noticeable or removes any race condition.

* Rename refrigerator() to __refrigerator() and make it return bool
  indicating whether it scheduled out for freezing.

* Update try_to_freeze() to return bool and relay the return value of
  __refrigerator() if freezing().

* Convert all refrigerator() users to try_to_freeze().

* Update documentation accordingly.

* While at it, add might_sleep() to try_to_freeze().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Samuel Ortiz <samuel@sortiz.org>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: KONISHI Ryusuke <konishi.ryusuke@lab.ntt.co.jp>
Cc: Christoph Hellwig <hch@infradead.org>

1 files changed, 2 insertions, 6 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 62afe5c5694e..622654fe051f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1579,9 +1579,7 @@ static int cleaner_kthread(void *arg)
                         btrfs_run_defrag_inodes(root->fs_info);
                 }
 
-                if (freezing(current)) {
-                        refrigerator();
-                } else {
+                if (!try_to_freeze()) {
                         set_current_state(TASK_INTERRUPTIBLE);
                         if (!kthread_should_stop())
                                 schedule();
@@ -1635,9 +1633,7 @@ sleep:
                 wake_up_process(root->fs_info->cleaner_kthread);
                 mutex_unlock(&root->fs_info->transaction_kthread_mutex);
 
-                if (freezing(current)) {
-                        refrigerator();
-                } else {
+                if (!try_to_freeze()) {
                         set_current_state(TASK_INTERRUPTIBLE);
                         if (!kthread_should_stop() &&
                             !btrfs_transaction_blocked(root->fs_info))