On Tue, Mar 16, 2021 at 03:23:14PM +0000, Christoph Hellwig wrote:
> On Mon, Mar 15, 2021 at 04:25:09PM +0300, Sergei Shtepa wrote:
> > The 03/14/2021 12:30, Christoph Hellwig wrote:
> > > On Fri, Mar 12, 2021 at 06:44:55PM +0300, Sergei Shtepa wrote:
> > > > DM_INTERPOSED_FLAG allow to create DM targets on "the fly".
> > > > Underlying block device opens without a flag FMODE_EXCL.
> > > > DM target receives bio from the original device via
> > > > bdev_interposer.
> > >
> > > This is more of a philopical comment, but the idea of just letting the
> > > interposed reopen the device by itself seems like a bad idea. I think
> > > that is probably better hidden in the block layer interposer attachment
> > > function, which could do the extra blkdev_get_by_dev for the caller.
> >
> > I suppose this cannot be implemented, since we need to change the behavior
> > for block devices that already have been opened.
>
> That's not what I mean. Take a look at the patch relative to your
> series to let me know what you think. The new blkdev_interposer_attach
> now takes a dev_t + mode for the original device and opens it on
> behalf of the interposer. It also moves the queue freezing into the
> API, which should address the concerns about the helper and adds a few
> more sanity checks.
And now actually with the diff:
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2f188a865024ac..d4d7c1caa43966 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -161,19 +161,6 @@ int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);
-bool blk_mq_is_queue_frozen(struct request_queue *q)
-{
- bool frozen;
-
- mutex_lock(&q->mq_freeze_lock);
- frozen = percpu_ref_is_dying(&q->q_usage_counter) &&
- percpu_ref_is_zero(&q->q_usage_counter);
- mutex_unlock(&q->mq_freeze_lock);
-
- return frozen;
-}
-EXPORT_SYMBOL_GPL(blk_mq_is_queue_frozen);
-
/*
* Guarantee no request is in use, so we can change any data structure of
* the queue afterward.
diff --git a/block/genhd.c b/block/genhd.c
index fa406b972371ae..64d6338b08cc87 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1944,51 +1944,70 @@ static void disk_release_events(struct gendisk *disk)
kfree(disk->ev);
}
-int bdev_interposer_attach(struct block_device *original,
+struct block_device *blkdev_interposer_attach(dev_t dev, fmode_t mode,
struct block_device *interposer)
{
+ struct block_device *bdev;
int ret = 0;
- if (WARN_ON(((!original) || (!interposer))))
- return -EINVAL;
- /*
- * interposer should be simple, no a multi-queue device
- */
- if (!interposer->bd_disk->fops->submit_bio)
- return -EINVAL;
+ if (WARN_ON_ONCE(!bdev_is_partition(interposer)))
+ return ERR_PTR(-EINVAL);
+ if (WARN_ON_ONCE(!queue_is_mq(interposer->bd_disk->queue)))
+ return ERR_PTR(-EINVAL);
- if (WARN_ON(!blk_mq_is_queue_frozen(original->bd_disk->queue)))
- return -EPERM;
+ bdev = blkdev_get_by_dev(dev, mode, NULL);
+ if (IS_ERR(bdev))
+ return bdev;
- mutex_lock(&bdev_interposer_attach_lock);
+ ret = -EINVAL;
+ if (WARN_ON_ONCE(bdev_nr_sectors(bdev) != bdev_nr_sectors(interposer)))
+ goto out;
- if (bdev_has_interposer(original))
- ret = -EBUSY;
- else {
- original->bd_interposer = bdgrab(interposer);
- if (!original->bd_interposer)
- ret = -ENODEV;
- }
+ blk_mq_freeze_queue(bdev->bd_disk->queue);
+ blk_mq_quiesce_queue(bdev->bd_disk->queue);
+ mutex_lock(&bdev_interposer_attach_lock);
+ ret = -EBUSY;
+ if (bdev_has_interposer(bdev))
+ goto out_unlock;
+ ret = -ENODEV;
+ bdev->bd_interposer = bdgrab(interposer);
+ if (!bdev->bd_interposer)
+ goto out_unlock;
+ ret = 0;
+out_unlock:
mutex_unlock(&bdev_interposer_attach_lock);
- return ret;
+ blk_mq_unquiesce_queue(bdev->bd_disk->queue);
+ blk_mq_unfreeze_queue(bdev->bd_disk->queue);
+out:
+ if (ret) {
+ blkdev_put(bdev, mode);
+ bdev = ERR_PTR(ret);
+ }
+
+ return bdev;
}
-EXPORT_SYMBOL_GPL(bdev_interposer_attach);
+EXPORT_SYMBOL_GPL(blkdev_interposer_attach);
-void bdev_interposer_detach(struct block_device *original)
+void blkdev_interposer_detach(struct block_device *bdev, fmode_t mode)
{
- if (WARN_ON(!original))
- return;
+ struct block_device *interposer;
- if (WARN_ON(!blk_mq_is_queue_frozen(original->bd_disk->queue)))
+ if (WARN_ON_ONCE(!bdev_has_interposer(bdev)))
return;
+ blk_mq_freeze_queue(bdev->bd_disk->queue);
+ blk_mq_quiesce_queue(bdev->bd_disk->queue);
+
mutex_lock(&bdev_interposer_attach_lock);
- if (bdev_has_interposer(original)) {
- bdput(original->bd_interposer);
- original->bd_interposer = NULL;
- }
+ interposer = bdev->bd_interposer;
+ bdev->bd_interposer = NULL;
mutex_unlock(&bdev_interposer_attach_lock);
+
+ blk_mq_unquiesce_queue(bdev->bd_disk->queue);
+ blk_mq_unfreeze_queue(bdev->bd_disk->queue);
+
+ blkdev_put(interposer, mode);
}
-EXPORT_SYMBOL_GPL(bdev_interposer_detach);
+EXPORT_SYMBOL_GPL(blkdev_interposer_detach);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f6e2eb3f894940..fde57bb5105025 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -359,18 +359,6 @@ dev_t dm_get_dev_t(const char *path)
}
EXPORT_SYMBOL_GPL(dm_get_dev_t);
-static inline void dm_disk_freeze(struct gendisk *disk)
-{
- blk_mq_freeze_queue(disk->queue);
- blk_mq_quiesce_queue(disk->queue);
-}
-
-static inline void dm_disk_unfreeze(struct gendisk *disk)
-{
- blk_mq_unquiesce_queue(disk->queue);
- blk_mq_unfreeze_queue(disk->queue);
-}
-
/*
* Add a device to the list, or just increment the usage count if
* it's already present.
@@ -418,29 +406,11 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
refcount_inc(&dd->count);
}
- if (t->md->is_interposed) {
- struct block_device *original = dd->dm_dev->bdev;
- struct block_device *interposer = t->md->disk->part0;
-
- if ((ti->begin != 0) || (ti->len < bdev_nr_sectors(original))) {
- dm_put_device(ti, dd->dm_dev);
- DMERR("The interposer device should not be less than the original.");
- return -EINVAL;
- }
-
- /*
- * Attach mapped interposer device to original.
- * It is quite convenient that device mapper creates
- * one disk for one block device.
- */
- dm_disk_freeze(original->bd_disk);
- r = bdev_interposer_attach(original, interposer);
- dm_disk_unfreeze(original->bd_disk);
- if (r) {
- dm_put_device(ti, dd->dm_dev);
- DMERR("Failed to attach dm interposer.");
- return r;
- }
+ if (t->md->is_interposed &&
+ (ti->begin != 0 || ti->len < bdev_nr_sectors(dd->dm_dev->bdev))) {
+ dm_put_device(ti, dd->dm_dev);
+ DMERR("The interposer device should not be less than the original.");
+ return -EINVAL;
}
*result = dd->dm_dev;
@@ -496,11 +466,6 @@ void dm_put_device(struct dm_target *ti, struct dm_dev *d)
dm_device_name(md), d->name);
return;
}
- if (md->is_interposed) {
- dm_disk_freeze(d->bdev->bd_disk);
- bdev_interposer_detach(d->bdev);
- dm_disk_unfreeze(d->bdev->bd_disk);
- }
if (refcount_dec_and_test(&dd->count)) {
dm_put_table_device(md, d);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c488e9554aa000..532ce17064b1c1 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -763,10 +763,12 @@ static int open_table_device(struct table_device *td, dev_t dev,
BUG_ON(td->dm_dev.bdev);
if (md->is_interposed) {
-
- bdev = blkdev_get_by_dev(dev, td->dm_dev.mode, NULL);
- if (IS_ERR(bdev))
+ bdev = blkdev_interposer_attach(dev, td->dm_dev.mode,
+ md->disk->part0);
+ if (IS_ERR(bdev)) {
+ DMERR("Failed to attach dm interposer.");
return PTR_ERR(bdev);
+ }
} else {
bdev = blkdev_get_by_dev(dev, td->dm_dev.mode | FMODE_EXCL, _dm_claim_ptr);
if (IS_ERR(bdev))
@@ -793,9 +795,9 @@ static void close_table_device(struct table_device *td, struct mapped_device *md
if (!td->dm_dev.bdev)
return;
- if (td->dm_dev.is_interposed)
- blkdev_put(td->dm_dev.bdev, td->dm_dev.mode);
- else {
+ if (td->dm_dev.is_interposed) {
+ blkdev_interposer_detach(td->dm_dev.bdev, td->dm_dev.mode);
+ } else {
bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
}
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 6f01971abf7b9b..2c473c9b899089 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -533,7 +533,6 @@ void blk_freeze_queue_start(struct request_queue *q);
void blk_mq_freeze_queue_wait(struct request_queue *q);
int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
unsigned long timeout);
-bool blk_mq_is_queue_frozen(struct request_queue *q);
int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 90f62b4197da91..fbc510162c3827 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -2036,8 +2036,8 @@ static inline bool bdev_has_interposer(struct block_device *bdev)
return (bdev->bd_interposer != NULL);
};
-int bdev_interposer_attach(struct block_device *original,
+struct block_device *blkdev_interposer_attach(dev_t dev, fmode_t mode,
struct block_device *interposer);
-void bdev_interposer_detach(struct block_device *original);
+void blkdev_interposer_detach(struct block_device *bdev, fmode_t mode);
#endif /* _LINUX_BLKDEV_H */
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