Merge tag 'asoc-v5.1' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-next

ASoC: Updates for v5.1

Lots and lots of new drivers so far, a highlight being the MediaTek
BTCVSD which is a driver for a Bluetooth radio chip - the first such
driver we've had upstream.  Hopefully we will soon also see a baseband
with an upstream driver!

 - Support for only powering up channels that are actively being used.
 - Quite a few improvements to simplify the generic card drivers,
   especially the merge of the SCU cards into the main generic drivers.
 - Lots of fixes for probing on Intel systems, trying to rationalize
   things to look more standard from a framework point of view.
 - New drivers for Asahi Kasei Microdevices AK4497, Cirrus Logic CS4341,
   Google ChromeOS embedded controllers, Ingenic JZ4725B, MediaTek
   BTCVSD, MT8183 and MT6358, NXP MICFIL, Rockchip RK3328, Spreadtrum
   DMA controllers, Qualcomm WCD9335, Xilinx S/PDIF and PCM formatters.

1 files changed, 38 insertions, 2 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index b40168fcc94a..36855c1f8daf 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -331,11 +331,22 @@ struct inode_switch_wbs_context {
         struct work_struct      work;
 };
 
+static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi)
+{
+        down_write(&bdi->wb_switch_rwsem);
+}
+
+static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi)
+{
+        up_write(&bdi->wb_switch_rwsem);
+}
+
 static void inode_switch_wbs_work_fn(struct work_struct *work)
 {
         struct inode_switch_wbs_context *isw =
                 container_of(work, struct inode_switch_wbs_context, work);
         struct inode *inode = isw->inode;
+        struct backing_dev_info *bdi = inode_to_bdi(inode);
         struct address_space *mapping = inode->i_mapping;
         struct bdi_writeback *old_wb = inode->i_wb;
         struct bdi_writeback *new_wb = isw->new_wb;
@@ -344,6 +355,12 @@ static void inode_switch_wbs_work_fn(struct work_struct *work)
         bool switched = false;
 
         /*
+         * If @inode switches cgwb membership while sync_inodes_sb() is
+         * being issued, sync_inodes_sb() might miss it.  Synchronize.
+         */
+        down_read(&bdi->wb_switch_rwsem);
+
+        /*
          * By the time control reaches here, RCU grace period has passed
          * since I_WB_SWITCH assertion and all wb stat update transactions
          * between unlocked_inode_to_wb_begin/end() are guaranteed to be
@@ -428,6 +445,8 @@ skip_switch:
         spin_unlock(&new_wb->list_lock);
         spin_unlock(&old_wb->list_lock);
 
+        up_read(&bdi->wb_switch_rwsem);
+
         if (switched) {
                 wb_wakeup(new_wb);
                 wb_put(old_wb);
@@ -468,9 +487,18 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
         if (inode->i_state & I_WB_SWITCH)
                 return;
 
+        /*
+         * Avoid starting new switches while sync_inodes_sb() is in
+         * progress.  Otherwise, if the down_write protected issue path
+         * blocks heavily, we might end up starting a large number of
+         * switches which will block on the rwsem.
+         */
+        if (!down_read_trylock(&bdi->wb_switch_rwsem))
+                return;
+
         isw = kzalloc(sizeof(*isw), GFP_ATOMIC);
         if (!isw)
-                return;
+                goto out_unlock;
 
         /* find and pin the new wb */
         rcu_read_lock();
@@ -504,12 +532,14 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
          * Let's continue after I_WB_SWITCH is guaranteed to be visible.
          */
         call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
-        return;
+        goto out_unlock;
 
 out_free:
         if (isw->new_wb)
                 wb_put(isw->new_wb);
         kfree(isw);
+out_unlock:
+        up_read(&bdi->wb_switch_rwsem);
 }
 
 /**
@@ -887,6 +917,9 @@ fs_initcall(cgroup_writeback_init);
 
 #else   /* CONFIG_CGROUP_WRITEBACK */
 
+static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
+static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi) { }
+
 static struct bdi_writeback *
 locked_inode_to_wb_and_lock_list(struct inode *inode)
         __releases(&inode->i_lock)
@@ -2413,8 +2446,11 @@ void sync_inodes_sb(struct super_block *sb)
                 return;
         WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
+        /* protect against inode wb switch, see inode_switch_wbs_work_fn() */
+        bdi_down_write_wb_switch_rwsem(bdi);
         bdi_split_work_to_wbs(bdi, &work, false);
         wb_wait_for_completion(bdi, &done);
+        bdi_up_write_wb_switch_rwsem(bdi);
 
         wait_sb_inodes(sb);
 }