Commit 9518e5bf authored by Mike Galbraith's avatar Mike Galbraith Committed by Jens Axboe
Browse files

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: default avatarMike Galbraith <umgwanakikbuti@gmail.com>
Reviewed-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20240906141520.730009-2-bigeasy@linutronix.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 296dbc72

drivers/block/zram/zram_drv.c

+14 −4
Original line number Diff line number Diff line
@@ -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;

}

drivers/block/zram/zram_drv.h

+1 −0
Original line number Diff line number Diff line
@@ -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