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Date: Tue, 6 Sep 2011 15:02:11 +0200
From: Jerome Marchand <jmarchan@...hat.com>
To: Greg Kroah-Hartman <gregkh@...e.de>
Cc: Linux Kernel List <linux-kernel@...r.kernel.org>,
Nitin Gupta <ngupta@...are.org>, Jeff Moyer <jmoyer@...hat.com>
Subject: [PATCH 1/2] 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: Jerome Marchand <jmarchan@...hat.com>
---
drivers/staging/zram/zram_drv.c | 46 +++++++++++++++++++++++-------------
drivers/staging/zram/zram_drv.h | 6 ++--
drivers/staging/zram/zram_sysfs.c | 18 +++++++++-----
3 files changed, 44 insertions(+), 26 deletions(-)
diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
index d70ec1a..2d1c8bd 100644
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -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);
diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
index abe5221..3bf134d 100644
--- a/drivers/staging/zram/zram_drv.h
+++ b/drivers/staging/zram/zram_drv.h
@@ -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
diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c
index a70cc01..43670a9 100644
--- a/drivers/staging/zram/zram_sysfs.c
+++ b/drivers/staging/zram/zram_sysfs.c
@@ -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;
}
--
1.7.6
--
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