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Commit 0900beae authored by Jerome Marchand's avatar Jerome Marchand Committed by Greg Kroah-Hartman
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staging: zram: fix zram locking 



Currently init_lock only prevents concurrent execution of zram_init_device()
and zram_reset_device() but not zram_make_request() nor sysfs store functions.

This patch changes init_lock into a rw_semaphore. A write lock is taken by
init, reset and store functions, a read lock is taken by zram_make_request().
Also, avoids to release the lock before calling __zram_reset_device() for
cleaning after a failed init, thus preventing any concurrent task to see an
inconsistent state of zram.

Signed-off-by: default avatarJerome Marchand <jmarchan@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent a1c821ae

drivers/staging/zram/zram_drv.c

+29 −17
Original line number Diff line number Diff line
@@ -560,27 +560,34 @@ static int zram_make_request(struct request_queue *queue, struct bio *bio) 
{

	struct zram *zram = queue->queuedata;



	if (unlikely(!zram->init_done) && zram_init_device(zram))

		goto error;



	down_read(&zram->init_lock);

	if (unlikely(!zram->init_done))

		goto error_unlock;



	if (!valid_io_request(zram, bio)) {

		zram_stat64_inc(zram, &zram->stats.invalid_io);

		bio_io_error(bio);

		return 0;

	}



	if (unlikely(!zram->init_done) && zram_init_device(zram)) {

		bio_io_error(bio);

		return 0;

		goto error_unlock;

	}



	__zram_make_request(zram, bio, bio_data_dir(bio));

	up_read(&zram->init_lock);



	return 0;



error_unlock:

	up_read(&zram->init_lock);

error:

	bio_io_error(bio);

	return 0;

}



void zram_reset_device(struct zram *zram)

void __zram_reset_device(struct zram *zram)

{

	size_t index;



	mutex_lock(&zram->init_lock);

	zram->init_done = 0;



	/* Free various per-device buffers */
@@ -617,7 +624,13 @@ void zram_reset_device(struct zram *zram) 
	memset(&zram->stats, 0, sizeof(zram->stats));



	zram->disksize = 0;

	mutex_unlock(&zram->init_lock);

}



void zram_reset_device(struct zram *zram)

{

	down_write(&zram->init_lock);

	__zram_reset_device(zram);

	up_write(&zram->init_lock);

}



int zram_init_device(struct zram *zram)
@@ -625,10 +638,10 @@ int zram_init_device(struct zram *zram) 
	int ret;

	size_t num_pages;



	mutex_lock(&zram->init_lock);

	down_write(&zram->init_lock);



	if (zram->init_done) {

		mutex_unlock(&zram->init_lock);

		up_write(&zram->init_lock);

		return 0;

	}
@@ -671,15 +684,14 @@ int zram_init_device(struct zram *zram) 
	}



	zram->init_done = 1;

	mutex_unlock(&zram->init_lock);

	up_write(&zram->init_lock);



	pr_debug("Initialization done!\n");

	return 0;



fail:

	mutex_unlock(&zram->init_lock);

	zram_reset_device(zram);



	__zram_reset_device(zram);

	up_write(&zram->init_lock);

	pr_err("Initialization failed: err=%d\n", ret);

	return ret;

}
@@ -703,7 +715,7 @@ static int create_device(struct zram *zram, int device_id) 
	int ret = 0;



	init_rwsem(&zram->lock);

	mutex_init(&zram->init_lock);

	init_rwsem(&zram->init_lock);

	spin_lock_init(&zram->stat64_lock);



	zram->queue = blk_alloc_queue(GFP_KERNEL);

drivers/staging/zram/zram_drv.h

+3 −3
Original line number Diff line number Diff line
@@ -112,8 +112,8 @@ struct zram { 
	struct request_queue *queue;

	struct gendisk *disk;

	int init_done;

	/* Prevent concurrent execution of device init and reset */

	struct mutex init_lock;

	/* Prevent concurrent execution of device init, reset and R/W request */

	struct rw_semaphore init_lock;

	/*

	 * This is the limit on amount of *uncompressed* worth of data

	 * we can store in a disk.
@@ -130,6 +130,6 @@ extern struct attribute_group zram_disk_attr_group; 
#endif



extern int zram_init_device(struct zram *zram);

extern void zram_reset_device(struct zram *zram);

extern void __zram_reset_device(struct zram *zram);



#endif

drivers/staging/zram/zram_sysfs.c

+12 −6
Original line number Diff line number Diff line
@@ -55,19 +55,23 @@ static ssize_t disksize_store(struct device *dev, 
		struct device_attribute *attr, const char *buf, size_t len)

{

	int ret;

	u64 disksize;

	struct zram *zram = dev_to_zram(dev);



	ret = strict_strtoull(buf, 10, &disksize);

	if (ret)

		return ret;



	down_write(&zram->init_lock);

	if (zram->init_done) {

		up_write(&zram->init_lock);

		pr_info("Cannot change disksize for initialized device\n");

		return -EBUSY;

	}



	ret = strict_strtoull(buf, 10, &zram->disksize);

	if (ret)

		return ret;



	zram->disksize = PAGE_ALIGN(zram->disksize);

	zram->disksize = PAGE_ALIGN(disksize);

	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);

	up_write(&zram->init_lock);



	return len;

}
@@ -106,8 +110,10 @@ static ssize_t reset_store(struct device *dev, 
	if (bdev)

		fsync_bdev(bdev);



	down_write(&zram->init_lock);

	if (zram->init_done)

		zram_reset_device(zram);

		__zram_reset_device(zram);

	up_write(&zram->init_lock);



	return len;

}