Re: [PATCH v2 04/34] md: port block device access to file

Mike Snitzer
2024-04-15T13:56:31Z

On Mon, Apr 15 2024 at 8:35P -0400,
Christian Brauner <brauner@kernel.org> wrote:

> On Mon, Apr 15, 2024 at 05:26:19PM +0800, Ming Lei wrote:
> > Hello,
> >
> > On Tue, Jan 23, 2024 at 02:26:21PM +0100, Christian Brauner wrote:
> > > Signed-off-by: Christian Brauner <brauner@kernel.org>
> > > ---
> > > drivers/md/dm.c | 23 +++++++++++++----------
> > > drivers/md/md.c | 12 ++++++------
> > > drivers/md/md.h | 2 +-
> > > include/linux/device-mapper.h | 2 +-
> > > 4 files changed, 21 insertions(+), 18 deletions(-)
> > >
> > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> > > index 8dcabf84d866..87de5b5682ad 100644
> > > --- a/drivers/md/dm.c
> > > +++ b/drivers/md/dm.c
> >
> > ...
> >
> > > @@ -775,7 +778,7 @@ static void close_table_device(struct table_device *td, struct mapped_device *md
> > > {
> > > if (md->disk->slave_dir)
> > > bd_unlink_disk_holder(td->dm_dev.bdev, md->disk);
> > > - bdev_release(td->dm_dev.bdev_handle);
> > > + fput(td->dm_dev.bdev_file);
> >
> > The above change caused regression on 'dmsetup remove_all'.
> >
> > blkdev_release() is delayed because of fput(), so dm_lock_for_deletion
> > returns -EBUSY, then this dm disk is skipped in remove_all().
> >
> > Force to mark DMF_DEFERRED_REMOVE might solve it, but need our device
> > mapper guys to check if it is safe.
> >
> > Or other better solution?
>
> Yeah, I think there is. You can just switch all fput() instances in
> device mapper to bdev_fput() which is mainline now. This will yield the
> device and make it able to be reclaimed. Should be as simple as the
> patch below. Could you test this and send a patch based on this (I'm on
> a prolonged vacation so I don't have time right now.):
>
> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
> index 56aa2a8b9d71..0f681a1e70af 100644
> --- a/drivers/md/dm.c
> +++ b/drivers/md/dm.c
> @@ -765,7 +765,7 @@ static struct table_device *open_table_device(struct mapped_device *md,
> return td;
>
> out_blkdev_put:
> - fput(bdev_file);
> + bdev_fput(bdev_file);
> out_free_td:
> kfree(td);
> return ERR_PTR(r);
> @@ -778,7 +778,7 @@ static void close_table_device(struct table_device *td, struct mapped_device *md
> {
> if (md->disk->slave_dir)
> bd_unlink_disk_holder(td->dm_dev.bdev, md->disk);
> - fput(td->dm_dev.bdev_file);
> + bdev_fput(td->dm_dev.bdev_file);
> put_dax(td->dm_dev.dax_dev);
> list_del(&td->list);
> kfree(td);
>
>

Thanks. I'll work with Ming and others to take care of it. Have a great vacation!