zram: Replace bit spinlocks with a spinlock_t.

The bit spinlock disables preemption. The spinlock_t lock becomes a sleeping
lock on PREEMPT_RT and it can not be acquired in this context. In this locked
section, zs_free() acquires a zs_pool::lock, and there is access to
zram::wb_limit_lock.

Add a spinlock_t for locking. Keep the set/ clear ZRAM_LOCK bit after
the lock has been acquired/ dropped. The size of struct zram_table_entry
increases by 4 bytes due to lock and additional 4 bytes padding with
CONFIG_ZRAM_TRACK_ENTRY_ACTIME enabled.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240906141520.730009-2-bigeasy@linutronix.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index efcb8d9d274c319cb7157e68d6e242b44b8626fc..c1f0f2da1ec32fb5ae12c925df9e306648de3247 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -59,17 +59,24 @@ static int zram_read_page(struct zram *zram, struct page *page, u32 index,
 
 static int zram_slot_trylock(struct zram *zram, u32 index)
 {
-       return bit_spin_trylock(ZRAM_LOCK, &zram->table[index].flags);
+       int ret;
+
+       ret = spin_trylock(&zram->table[index].lock);
+       if (ret)
+               __set_bit(ZRAM_LOCK, &zram->table[index].flags);
+       return ret;
 }
 
 static void zram_slot_lock(struct zram *zram, u32 index)
 {
-       bit_spin_lock(ZRAM_LOCK, &zram->table[index].flags);
+       spin_lock(&zram->table[index].lock);
+       __set_bit(ZRAM_LOCK, &zram->table[index].flags);
 }
 
 static void zram_slot_unlock(struct zram *zram, u32 index)
 {
-       bit_spin_unlock(ZRAM_LOCK, &zram->table[index].flags);
+       __clear_bit(ZRAM_LOCK, &zram->table[index].flags);
+       spin_unlock(&zram->table[index].lock);
 }
 
 static inline bool init_done(struct zram *zram)
@@ -1211,7 +1218,7 @@ static void zram_meta_free(struct zram *zram, u64 disksize)
 
 static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 {
-       size_t num_pages;
+       size_t num_pages, index;
 
        num_pages = disksize >> PAGE_SHIFT;
        zram->table = vzalloc(array_size(num_pages, sizeof(*zram->table)));
@@ -1226,6 +1233,9 @@ static bool zram_meta_alloc(struct zram *zram, u64 disksize)
 
        if (!huge_class_size)
                huge_class_size = zs_huge_class_size(zram->mem_pool);
+
+       for (index = 0; index < num_pages; index++)
+               spin_lock_init(&zram->table[index].lock);
        return true;
 }
 

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 35e322144629224741c922618123ab5847023b79..dcc3c106ce713419fb99940527739fdbef4d2914 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -69,6 +69,7 @@ struct zram_table_entry {
                unsigned long element;
        };
        unsigned long flags;
+       spinlock_t lock;
 #ifdef CONFIG_ZRAM_TRACK_ENTRY_ACTIME
        ktime_t ac_time;
 #endif