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

[Christian Brauner]

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 <brau...@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);