[PATCH 03/15] blktrans: Hotplug fixes

From: Maxim Levitsky
Date: Mon Feb 22 2010 - 13:43:41 EST

* Add locking where it was missing.
* Don't do a get_mtd_device in blktrans_open because it would lead to a deadlock
instead do that in add_mtd_blktrans_dev.

* Only free the mtd_blktrans_dev structure when the last user exits.

* Flush request queue on device removal.

* Track users, and call tr->release in del_mtd_blktrans_dev
Due to that ->open and release aren't called more that once.

Now it is safe to call del_mtd_blktrans_dev while the device is still in use.

Signed-off-by: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
---
drivers/mtd/ftl.c | 1 -
drivers/mtd/inftlcore.c | 1 -
drivers/mtd/mtd_blkdevs.c | 202 ++++++++++++++++++++++++++++++-----------
drivers/mtd/mtdblock.c | 2 -
drivers/mtd/mtdblock_ro.c | 1 -
drivers/mtd/nftlcore.c | 1 -
drivers/mtd/rfd_ftl.c | 1 -
drivers/mtd/ssfdc.c | 1 -
include/linux/mtd/blktrans.h | 3 +
9 files changed, 151 insertions(+), 62 deletions(-)

diff --git a/drivers/mtd/ftl.c b/drivers/mtd/ftl.c
index e56d6b4..62da9eb 100644
--- a/drivers/mtd/ftl.c
+++ b/drivers/mtd/ftl.c
@@ -1082,7 +1082,6 @@ static void ftl_remove_dev(struct mtd_blktrans_dev *dev)
{
del_mtd_blktrans_dev(dev);
ftl_freepart((partition_t *)dev);
- kfree(dev);
}

static struct mtd_blktrans_ops ftl_tr = {
diff --git a/drivers/mtd/inftlcore.c b/drivers/mtd/inftlcore.c
index 8aca552..015a7fe 100755
--- a/drivers/mtd/inftlcore.c
+++ b/drivers/mtd/inftlcore.c
@@ -139,7 +139,6 @@ static void inftl_remove_dev(struct mtd_blktrans_dev *dev)

kfree(inftl->PUtable);
kfree(inftl->VUtable);
- kfree(inftl);
}

/*
diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index 6a57262..646cc84 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -24,6 +24,40 @@
#include "mtdcore.h"

static LIST_HEAD(blktrans_majors);
+static DEFINE_MUTEX(blktrans_ref_mutex);
+
+void blktrans_dev_release(struct kref *kref)
+{
+ struct mtd_blktrans_dev *dev =
+ container_of(kref, struct mtd_blktrans_dev, ref);
+
+ dev->disk->private_data = NULL;
+ put_disk(dev->disk);
+ list_del(&dev->list);
+ kfree(dev);
+}
+
+static struct mtd_blktrans_dev *blktrans_dev_get(struct gendisk *disk)
+{
+ struct mtd_blktrans_dev *dev;
+
+ mutex_lock(&blktrans_ref_mutex);
+ dev = disk->private_data;
+
+ if (!dev)
+ goto unlock;
+ kref_get(&dev->ref);
+unlock:
+ mutex_unlock(&blktrans_ref_mutex);
+ return dev;
+}
+
+void blktrans_dev_put(struct mtd_blktrans_dev *dev)
+{
+ mutex_lock(&blktrans_ref_mutex);
+ kref_put(&dev->ref, blktrans_dev_release);
+ mutex_unlock(&blktrans_ref_mutex);
+}


static int do_blktrans_request(struct mtd_blktrans_ops *tr,
@@ -111,81 +145,112 @@ static int mtd_blktrans_thread(void *arg)

static void mtd_blktrans_request(struct request_queue *rq)
{
- struct mtd_blktrans_dev *dev = rq->queuedata;
- wake_up_process(dev->thread);
-}
+ struct mtd_blktrans_dev *dev;
+ struct request *req = NULL;
+
+ dev = rq->queuedata;

+ if (!dev)
+ while ((req = blk_fetch_request(rq)) != NULL)
+ __blk_end_request_all(req, -ENODEV);
+ else
+ wake_up_process(dev->thread);
+}

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;
-
- if (!try_module_get(tr->owner))
- goto out_tr;
-
- /* 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++;
-
- ret = 0;
- if (tr->open && (ret = tr->open(dev))) {
- dev->mtd->usecount--;
- put_mtd_device(dev->mtd);
- out_tr:
- module_put(tr->owner);
+ struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
+ int ret;
+
+ if (!dev)
+ return -ERESTARTSYS;
+
+ mutex_lock(&dev->lock);
+
+ if (!dev->mtd) {
+ ret = -ENXIO;
+ goto unlock;
}
- out:
+
+ ret = !dev->open++ && dev->tr->open ? dev->tr->open(dev) : 0;
+
+ /* Take another reference on the device so it won't go away till
+ last release */
+ if (!ret)
+ kref_get(&dev->ref);
+unlock:
+ mutex_unlock(&dev->lock);
+ blktrans_dev_put(dev);
return ret;
}

static int blktrans_release(struct gendisk *disk, fmode_t mode)
{
- struct mtd_blktrans_dev *dev = disk->private_data;
- struct mtd_blktrans_ops *tr = dev->tr;
- int ret = 0;
+ struct mtd_blktrans_dev *dev = blktrans_dev_get(disk);
+ int ret = -ENXIO;

- if (tr->release)
- ret = tr->release(dev);
+ if (!dev)
+ return ret;

- if (!ret) {
- dev->mtd->usecount--;
- put_mtd_device(dev->mtd);
- module_put(tr->owner);
- }
+ mutex_lock(&dev->lock);
+
+ /* Release one reference, we sure its not the last one here*/
+ kref_put(&dev->ref, blktrans_dev_release);

+ if (!dev->mtd)
+ goto unlock;
+
+ ret = !--dev->open && dev->tr->release ? dev->tr->release(dev) : 0;
+unlock:
+ mutex_unlock(&dev->lock);
+ blktrans_dev_put(dev);
return ret;
}

static int blktrans_getgeo(struct block_device *bdev, struct hd_geometry *geo)
{
- struct mtd_blktrans_dev *dev = bdev->bd_disk->private_data;
+ struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
+ int ret = -ENXIO;
+
+ if (!dev)
+ return ret;
+
+ mutex_lock(&dev->lock);

- if (dev->tr->getgeo)
- return dev->tr->getgeo(dev, geo);
- return -ENOTTY;
+ if (!dev->mtd)
+ goto unlock;
+
+ ret = dev->tr->getgeo ? dev->tr->getgeo(dev, geo) : 0;
+unlock:
+ mutex_unlock(&dev->lock);
+ blktrans_dev_put(dev);
+ return ret;
}

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;
+ struct mtd_blktrans_dev *dev = blktrans_dev_get(bdev->bd_disk);
+ int ret = -ENXIO;
+
+ if (!dev)
+ return ret;
+
+ mutex_lock(&dev->lock);
+
+ if (!dev->mtd)
+ goto unlock;

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

static const struct block_device_operations mtd_blktrans_ops = {
@@ -209,6 +274,7 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
BUG();
}

+ mutex_lock(&blktrans_ref_mutex);
list_for_each_entry(d, &tr->devs, list) {
if (new->devnum == -1) {
/* Use first free number */
@@ -220,6 +286,7 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
}
} else if (d->devnum == new->devnum) {
/* Required number taken */
+ mutex_unlock(&blktrans_ref_mutex);
return -EBUSY;
} else if (d->devnum > new->devnum) {
/* Required number was free */
@@ -237,16 +304,20 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
* minor numbers and that the disk naming code below can cope
* with this number. */
if (new->devnum > (MINORMASK >> tr->part_bits) ||
- (tr->part_bits && new->devnum >= 27 * 26))
+ (tr->part_bits && new->devnum >= 27 * 26)) {
+ mutex_unlock(&blktrans_ref_mutex);
goto error1;
+ }

list_add_tail(&new->list, &tr->devs);
added:
+ mutex_unlock(&blktrans_ref_mutex);
+
mutex_init(&new->lock);
+ kref_init(&new->ref);
if (!tr->writesect)
new->readonly = 1;

-
/* Create gendisk */
ret = -ENOMEM;
gd = alloc_disk(1 << tr->part_bits);
@@ -275,7 +346,6 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)

set_capacity(gd, (new->size * tr->blksize) >> 9);

-
/* Create the request queue */
spin_lock_init(&new->queue_lock);
new->rq = blk_init_queue(mtd_blktrans_request, &new->queue_lock);
@@ -292,6 +362,9 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)

gd->queue = new->rq;

+ __get_mtd_device(new->mtd);
+ __module_get(tr->owner);
+
/* Create processing thread */
/* TODO: workqueue ? */
new->thread = kthread_run(mtd_blktrans_thread, new,
@@ -308,6 +381,8 @@ int add_mtd_blktrans_dev(struct mtd_blktrans_dev *new)
add_disk(gd);
return 0;
error4:
+ module_put(tr->owner);
+ __put_mtd_device(new->mtd);
blk_cleanup_queue(new->rq);
error3:
put_disk(new->disk);
@@ -320,20 +395,41 @@ error1:

int del_mtd_blktrans_dev(struct mtd_blktrans_dev *old)
{
+ unsigned long flags;
+
if (mutex_trylock(&mtd_table_mutex)) {
mutex_unlock(&mtd_table_mutex);
BUG();
}

- list_del(&old->list);
-
- /* stop new requests to arrive */
+ /* Stop new requests to arrive */
del_gendisk(old->disk);

/* Stop the thread */
kthread_stop(old->thread);

+ /* Kill current requests */
+ spin_lock_irqsave(&old->queue_lock, flags);
+ old->rq->queuedata = NULL;
+ blk_start_queue(old->rq);
+ spin_unlock_irqrestore(&old->queue_lock, flags);
blk_cleanup_queue(old->rq);
+
+ /* Ask trans driver for release to the mtd device */
+ mutex_lock(&old->lock);
+ if (old->open && old->tr->release) {
+ old->tr->release(old);
+ old->open = 0;
+ }
+
+ __put_mtd_device(old->mtd);
+ module_put(old->tr->owner);
+
+ /* At that point, we don't touch the mtd anymore */
+ old->mtd = NULL;
+
+ mutex_unlock(&old->lock);
+ blktrans_dev_put(old);
return 0;
}

@@ -396,7 +492,6 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
tr->add_mtd(tr, mtd);

mutex_unlock(&mtd_table_mutex);
-
return 0;
}

@@ -406,7 +501,6 @@ int deregister_mtd_blktrans(struct mtd_blktrans_ops *tr)

mutex_lock(&mtd_table_mutex);

-
/* Remove it from the list of active majors */
list_del(&tr->list);

diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
index 69f6bf2..8e5da1e 100644
--- a/drivers/mtd/mtdblock.c
+++ b/drivers/mtd/mtdblock.c
@@ -354,9 +354,7 @@ static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
-
del_mtd_blktrans_dev(dev);
- kfree(mtdblk);
}

static struct mtd_blktrans_ops mtdblock_tr = {
diff --git a/drivers/mtd/mtdblock_ro.c b/drivers/mtd/mtdblock_ro.c
index 852165f..54ff288 100644
--- a/drivers/mtd/mtdblock_ro.c
+++ b/drivers/mtd/mtdblock_ro.c
@@ -49,7 +49,6 @@ static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
{
del_mtd_blktrans_dev(dev);
- kfree(dev);
}

static struct mtd_blktrans_ops mtdblock_tr = {
diff --git a/drivers/mtd/nftlcore.c b/drivers/mtd/nftlcore.c
index 1002e18..a4578bf 100644
--- a/drivers/mtd/nftlcore.c
+++ b/drivers/mtd/nftlcore.c
@@ -126,7 +126,6 @@ static void nftl_remove_dev(struct mtd_blktrans_dev *dev)
del_mtd_blktrans_dev(dev);
kfree(nftl->ReplUnitTable);
kfree(nftl->EUNtable);
- kfree(nftl);
}

/*
diff --git a/drivers/mtd/rfd_ftl.c b/drivers/mtd/rfd_ftl.c
index d2aa9c4..63b83c0 100644
--- a/drivers/mtd/rfd_ftl.c
+++ b/drivers/mtd/rfd_ftl.c
@@ -817,7 +817,6 @@ static void rfd_ftl_remove_dev(struct mtd_blktrans_dev *dev)
vfree(part->sector_map);
kfree(part->header_cache);
kfree(part->blocks);
- kfree(part);
}

static struct mtd_blktrans_ops rfd_ftl_tr = {
diff --git a/drivers/mtd/ssfdc.c b/drivers/mtd/ssfdc.c
index 3f67e00..81c4ecd 100644
--- a/drivers/mtd/ssfdc.c
+++ b/drivers/mtd/ssfdc.c
@@ -375,7 +375,6 @@ static void ssfdcr_remove_dev(struct mtd_blktrans_dev *dev)

del_mtd_blktrans_dev(dev);
kfree(ssfdc->logic_block_map);
- kfree(ssfdc);
}

static int ssfdcr_readsect(struct mtd_blktrans_dev *dev,
diff --git a/include/linux/mtd/blktrans.h b/include/linux/mtd/blktrans.h
index a4b3928..d89b8fb 100644
--- a/include/linux/mtd/blktrans.h
+++ b/include/linux/mtd/blktrans.h
@@ -9,6 +9,7 @@
#define __MTD_TRANS_H__

#include <linux/mutex.h>
+#include <linux/kref.h>

struct hd_geometry;
struct mtd_info;
@@ -24,6 +25,8 @@ struct mtd_blktrans_dev {
int devnum;
unsigned long size;
int readonly;
+ int open;
+ struct kref ref;
struct gendisk *disk;
struct task_struct *thread;
struct request_queue *rq;
--
1.6.3.3

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