Messages in this thread | | | Date | Mon, 26 Feb 2024 12:05:35 +0000 | From | Jonathan Cameron <> | Subject | Re: [RFC PATCH 02/20] dev_dax_iomap: Add fs_dax_get() func to prepare dax for fs-dax usage |
| |
On Fri, 23 Feb 2024 11:41:46 -0600 John Groves <John@Groves.net> wrote:
> This function should be called by fs-dax file systems after opening the > devdax device. This adds holder_operations. > > This function serves the same role as fs_dax_get_by_bdev(), which dax > file systems call after opening the pmem block device. > > Signed-off-by: John Groves <john@groves.net>
A few trivial comments form a first read to get my head around this.
Yeah, it is only an RFC, but who doesn't like tidy code? :)
> --- > drivers/dax/super.c | 38 ++++++++++++++++++++++++++++++++++++++ > include/linux/dax.h | 5 +++++ > 2 files changed, 43 insertions(+) > > diff --git a/drivers/dax/super.c b/drivers/dax/super.c > index f4b635526345..fc96362de237 100644 > --- a/drivers/dax/super.c > +++ b/drivers/dax/super.c > @@ -121,6 +121,44 @@ void fs_put_dax(struct dax_device *dax_dev, void *holder) > EXPORT_SYMBOL_GPL(fs_put_dax); > #endif /* CONFIG_BLOCK && CONFIG_FS_DAX */ > > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP) > + > +/** > + * fs_dax_get()
Smells like kernel doc but fairly sure it needs a short description. Have you sanity checked for warnings when running scripts/kerneldoc on it?
> + * > + * fs-dax file systems call this function to prepare to use a devdax device for fsdax. Trivial but lines too long. Keep under 80 chars unless there is a strong readability arguement for not doing so.
> + * This is like fs_dax_get_by_bdev(), but the caller already has struct dev_dax (and there > + * is no bdev). The holder makes this exclusive.
Not familiar with this area: what does exclusive mean here?
> + * > + * @dax_dev: dev to be prepared for fs-dax usage > + * @holder: filesystem or mapped device inside the dax_device > + * @hops: operations for the inner holder > + * > + * Returns: 0 on success, -1 on failure
Why not return < 0 and use somewhat useful return values?
> + */ > +int fs_dax_get( > + struct dax_device *dax_dev, > + void *holder, > + const struct dax_holder_operations *hops)
Match local style for indents - it's a bit inconsistent but probably...
int fs_dax_get(struct dad_device *dev_dax, void *holder, const struct dax_holder_operations *hops)
> +{ > + /* dax_dev->ops should have been populated by devm_create_dev_dax() */ > + if (WARN_ON(!dax_dev->ops)) > + return -1; > + > + if (!dax_dev || !dax_alive(dax_dev) || !igrab(&dax_dev->inode))
You dereferenced dax_dev on the line above so check is too late or unnecessary
> + return -1; > + > + if (cmpxchg(&dax_dev->holder_data, NULL, holder)) { > + pr_warn("%s: holder_data already set\n", __func__);
Perhaps nicer to use a pr_fmt() deal with the func name if you need it. or make it pr_debug and let dynamic debug control formatting if anyone wants the function name.
> + return -1; > + } > + dax_dev->holder_ops = hops; > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(fs_dax_get); > +#endif /* DEV_DAX_IOMAP */ > + > enum dax_device_flags { > /* !alive + rcu grace period == no new operations / mappings */ > DAXDEV_ALIVE, > diff --git a/include/linux/dax.h b/include/linux/dax.h > index b463502b16e1..e973289bfde3 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -57,7 +57,12 @@ struct dax_holder_operations { > > #if IS_ENABLED(CONFIG_DAX) > struct dax_device *alloc_dax(void *private, const struct dax_operations *ops); > + > +#if IS_ENABLED(CONFIG_DEV_DAX_IOMAP) > +int fs_dax_get(struct dax_device *dax_dev, void *holder, const struct dax_holder_operations *hops); line wrap < 80 chars
> +#endif > void *dax_holder(struct dax_device *dax_dev); > +struct dax_device *inode_dax(struct inode *inode);
Unrelated change?
> void put_dax(struct dax_device *dax_dev); > void kill_dax(struct dax_device *dax_dev); > void dax_write_cache(struct dax_device *dax_dev, bool wc);
| |