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Subject[PATCH 05/17] blktrans: add proper locking
Date
First, use lockless versions of get/put_mtd_device
We don't care what happened to mtd table, because we have a pointer
to mtd device. It guaranteed to exist till we do final put_mtd_device

Also add locking to prevent all kinds or races

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
---
drivers/mtd/mtd_blkdevs.c | 84 ++++++++++++++++++++++++++++----------------
1 files changed, 53 insertions(+), 31 deletions(-)
diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 1b89e59..082969c 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -123,33 +123,33 @@ static int blktrans_open(struct block_device *bdev, fmode_t mode)
{
struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
struct mtd_blktrans_ops *tr = dev->tr;
- int ret = -ENODEV;
-
- if (!get_mtd_device(NULL, dev->mtd->index))
- goto out;
+ int ret = 0;

+ mutex_lock(&dev->lock);
if (dev->open++)
goto out;

if (dev->deleted)
goto out;

+ ret = -ENODEV;
if (!try_module_get(tr->owner))
- goto out_tr;
+ goto out;

- /* FIXME: Locking. A hot pluggable device can go away
- (del_mtd_device can be called for it) without its module
- being unloaded. */
- dev->mtd->usecount++;
+ if (__get_mtd_device(dev->mtd)) {
+ module_put(tr->owner);
+ goto out;
+ }

ret = 0;
if (tr->open && (ret = tr->open(dev))) {
- dev->mtd->usecount--;
- put_mtd_device(dev->mtd);
- out_tr:
module_put(tr->owner);
+ __put_mtd_device(dev->mtd);
+ goto out;
+
}
out:
+ mutex_unlock(&dev->lock);
return ret;
}

@@ -159,17 +159,10 @@ static int blktrans_release(struct gendisk *disk, fmode_t mode)
struct mtd_blktrans_ops *tr = dev->tr;
int ret = 0;

+ mutex_lock(&dev->lock);
if (--dev->open)
- return 0;
-
- if (tr->release)
- ret = tr->release(dev);
+ goto out;

- if (!ret) {
- dev->mtd->usecount--;
- put_mtd_device(dev->mtd);
- module_put(tr->owner);
- }

/* Free the private data */
if (dev->deleted) {
@@ -179,33 +172,59 @@ static int blktrans_release(struct gendisk *disk, fmode_t mode)
return 0;
}

+ ret = tr->release ? tr->release(dev) : 0;
+ module_put(tr->owner);
+
+ if (dev->mtd)
+ __put_mtd_device(dev->mtd);
+out:
+ mutex_unlock(&dev->lock);
return ret;
}

static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
+ int error;
+
+ mutex_lock(&dev->lock);

+ error = -ENODEV;
+ if (dev->deleted)
+ goto out;
+
+ error = -ENOTTY;
if (dev->tr->getgeo)
- return dev->tr->getgeo(dev, geo);
- return -ENOTTY;
+ error = dev->tr->getgeo(dev, geo);
+out:
+ mutex_unlock(&dev->lock);
+ return error;
}

static int blktrans_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long arg)
{
struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
- struct mtd_blktrans_ops *tr = dev->tr;
+ int error = -ENODEV;
+
+ mutex_lock(&dev->lock);
+
+ if (dev->deleted)
+ goto out;
+
+ error = -ENOTTY;

switch (cmd) {
case BLKFLSBUF:
- if (tr->flush)
- return tr->flush(dev);
- /* The core code did the work, we had nothing to do. */
- return 0;
+ if (dev->tr->flush)
+ error = dev->tr->flush(dev);
+ break;
default:
- return -ENOTTY;
+ break;
}
+out:
+ mutex_unlock(&dev->lock);
+ return error;
}

static const struct block_device_operations mtd_blktrans_ops = {
@@ -353,16 +372,19 @@ int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
/* Stop the thread */
kthread_stop(old->thread);

+ /* Tell trans driver to release the device */
+ mutex_lock(&old->lock);
+
if (old->open) {
if (old->tr->release)
old->tr->release(old);
- put_mtd_device(old->mtd);
+ __put_mtd_device(old->mtd);
}

/* From now on, no calls into trans can be made */
/* Mtd device will be gone real soon now */
old->mtd = NULL;
-
+ mutex_unlock(&old->lock);
blk_cleanup_queue(old->rq);
return 0;
}
--
1.6.3.3


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