Re: [PATCH v11 7/8] xfs: Implement ->notify_failure() for XFS

[Shiyang Ruan]

在 2022/3/30 14:00, Christoph Hellwig 写道:
> > @@ -1892,6 +1893,8 @@ xfs_free_buftarg(
> >   	list_lru_destroy(&btp->bt_lru);
> >   
> >   	blkdev_issue_flush(btp->bt_bdev);
> > +	if (btp->bt_daxdev)
> > +		dax_unregister_holder(btp->bt_daxdev, btp->bt_mount);
> >   	fs_put_dax(btp->bt_daxdev);
> >   
> >   	kmem_free(btp);
> > @@ -1939,6 +1942,7 @@ xfs_alloc_buftarg(
> >   	struct block_device	*bdev)
> >   {
> >   	xfs_buftarg_t		*btp;
> > +	int			error;
> >   
> >   	btp = kmem_zalloc(sizeof(*btp), KM_NOFS);
> >   
> > @@ -1946,6 +1950,14 @@ xfs_alloc_buftarg(
> >   	btp->bt_dev =  bdev->bd_dev;
> >   	btp->bt_bdev = bdev;
> >   	btp->bt_daxdev = fs_dax_get_by_bdev(bdev, &btp->bt_dax_part_off);
> > +	if (btp->bt_daxdev) {
> > +		error = dax_register_holder(btp->bt_daxdev, mp,
> > +				&xfs_dax_holder_operations);
> > +		if (error) {
> > +			xfs_err(mp, "DAX device already in use?!");
> > +			goto error_free;
> > +		}
> > +	}
>
> It seems to me that just passing the holder and holder ops to
> fs_dax_get_by_bdev and the holder to dax_unregister_holder would
> significantly simply the interface here.
>
> Dan, what do you think?

Hi Dan,

Could you give some advise on this API?  Is it needed to move 
dax_register_holder's job into fs_dax_get_by_bdev()?


--
Thanks,
Ruan

> > +#if IS_ENABLED(CONFIG_MEMORY_FAILURE) && IS_ENABLED(CONFIG_FS_DAX)
>
> No real need for the IS_ENABLED.  Also any reason to even build this
> file if the options are not set?  It seems like
> xfs_dax_holder_operations should just be defined to NULL and the
> whole file not supported if we can't support the functionality.
>
> Dan: not for this series, but is there any reason not to require
> MEMORY_FAILURE for DAX to start with?
>
> > +
> > +	ddev_start = mp->m_ddev_targp->bt_dax_part_off;
> > +	ddev_end = ddev_start +
> > +		(mp->m_ddev_targp->bt_bdev->bd_nr_sectors << SECTOR_SHIFT) - 1;
>
> This should use bdev_nr_bytes.
>
> But didn't we say we don't want to support notifications on partitioned
> devices and thus don't actually need all this?
>
> > +
> > +	/* Ignore the range out of filesystem area */
> > +	if ((offset + len) < ddev_start)
>
> No need for the inner braces.
>
> > +	if ((offset + len) > ddev_end)
>
> No need for the braces either.
>
> > diff --git a/fs/xfs/xfs_notify_failure.h b/fs/xfs/xfs_notify_failure.h
> > new file mode 100644
> > index 000000000000..76187b9620f9
> > --- /dev/null
> > +++ b/fs/xfs/xfs_notify_failure.h
> > @@ -0,0 +1,10 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2022 Fujitsu.  All Rights Reserved.
> > + */
> > +#ifndef __XFS_NOTIFY_FAILURE_H__
> > +#define __XFS_NOTIFY_FAILURE_H__
> > +
> > +extern const struct dax_holder_operations xfs_dax_holder_operations;
> > +
> > +#endif  /* __XFS_NOTIFY_FAILURE_H__ */
>
> Dowe really need a new header for this vs just sequeezing it into
> xfs_super.h or something like that?
>
> > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> > index e8f37bdc8354..b8de6ed2c888 100644
> > --- a/fs/xfs/xfs_super.c
> > +++ b/fs/xfs/xfs_super.c
> > @@ -353,6 +353,12 @@ xfs_setup_dax_always(
> >   		return -EINVAL;
> >   	}
> >   
> > +	if (xfs_has_reflink(mp) && !xfs_has_rmapbt(mp)) {
> > +		xfs_alert(mp,
> > +			"need rmapbt when both DAX and reflink enabled.");
> > +		return -EINVAL;
> > +	}
>
> Right now we can't even enable reflink with DAX yet, so adding this
> here seems premature - it should go into the patch allowing DAX+reflink.