patches/drivers-block-zram-Replace-bit-spinlocks-with-rtmute.patch

From 84f3382e0a349c4ad9f6b277b8bc7f2742d380c2 Mon Sep 17 00:00:00 2001
From: Mike Galbraith <umgwanakikbuti@gmail.com>
Date: Thu, 31 Mar 2016 04:08:28 +0200
Subject: [PATCH] drivers/block/zram: Replace bit spinlocks with rtmutex for
 -rt

They're nondeterministic, and lead to ___might_sleep() splats in -rt.
OTOH, they're a lot less wasteful than an rtmutex per page.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[PG: restructure patch for wrappers added in mainline 86c49814d449]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index debee952dcc1..b758e3db2e30 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -422,6 +422,7 @@ static DEVICE_ATTR_RO(io_stat);
 static DEVICE_ATTR_RO(mm_stat);
 static DEVICE_ATTR_RO(debug_stat);
 
+#ifndef CONFIG_PREEMPT_RT_BASE
 static void zram_slot_lock(struct zram *zram, u32 index)
 {
 	bit_spin_lock(ZRAM_ACCESS, &zram->table[index].value);
@@ -431,6 +432,19 @@ static void zram_slot_unlock(struct zram *zram, u32 index)
 {
 	bit_spin_unlock(ZRAM_ACCESS, &zram->table[index].value);
 }
+#else /* CONFIG_PREEMPT_RT_BASE */
+static void zram_slot_lock(struct zram *zram, u32 index)
+{
+	spin_lock(&zram->table[index].lock);
+	__set_bit(ZRAM_ACCESS, &zram->table[index].value);
+}
+
+static void zram_slot_unlock(struct zram *zram, u32 index)
+{
+	__clear_bit(ZRAM_ACCESS, &zram->table[index].value);
+	spin_unlock(&zram->table[index].lock);
+}
+#endif /* CONFIG_PREEMPT_RT_BASE */
 
 static bool zram_same_page_read(struct zram *zram, u32 index,
 				struct page *page,
@@ -504,6 +518,8 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 		return false;
 	}
 
+	zram_meta_init_table_locks(zram, disksize);
+
 	return true;
 }
 
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index e34e44d02e3e..53c74fed2561 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -76,6 +76,9 @@ struct zram_table_entry {
 		unsigned long element;
 	};
 	unsigned long value;
+#ifdef CONFIG_PREEMPT_RT_BASE
+	spinlock_t lock;
+#endif
 };
 
 struct zram_stats {
@@ -116,4 +119,20 @@ struct zram {
 	 */
 	bool claim; /* Protected by bdev->bd_mutex */
 };
+
+#ifndef CONFIG_PREEMPT_RT_BASE
+static inline void zram_meta_init_table_locks(struct zram *zram, u64 disksize) { }
+#else /* CONFIG_PREEMPT_RT_BASE */
+static inline void zram_meta_init_table_locks(struct zram *zram, u64 disksize)
+{
+        size_t num_pages = disksize >> PAGE_SHIFT;
+        size_t index;
+
+        for (index = 0; index < num_pages; index++) {
+		spinlock_t *lock = &zram->table[index].lock;
+		spin_lock_init(lock);
+        }
+}
+#endif /* CONFIG_PREEMPT_RT_BASE */
+
 #endif
-- 
2.1.4