linux-kernel - Re: [PATCH] dax: add set_dax_nomc() and set_dax

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Date: Fri, 16 Feb 2024 15:26:57 -0500
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Arnd Bergmann <arnd@...nel.org>, Dan Williams <dan.j.williams@...el.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>, kernel test robot <lkp@...el.com>,
 Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
 Jane Chu <jane.chu@...cle.com>, linux-fsdevel@...r.kernel.org,
 nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dax: add set_dax_nomc() and set_dax_nocache() stub
 helpers

On 2024-02-16 15:22, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> In some randconfig builds, the IS_ERR() check appears to not get completely
> eliminated, resulting in the compiler to insert references to these two
> functions that cause a link failure:
> 
> ERROR: modpost: "set_dax_nocache" [drivers/md/dm-mod.ko] undefined!
> ERROR: modpost: "set_dax_nomc" [drivers/md/dm-mod.ko] undefined!
> 
> Add more stub functions for the dax-disabled case here to make it build again.

Hi Arnd,

Note that this is a duplicate of:

https://lore.kernel.org/lkml/20240215144633.96437-2-mathieu.desnoyers@efficios.com/

now present in Andrew's tree.

The only differences are the subject, commit message and a newline between "set_dax_nomc"
and "set_dax_synchronous" in your change.

Thanks,

Mathieu

> 
> Fixes: d888f6b0a766 ("dm: treat alloc_dax() -EOPNOTSUPP failure as non-fatal")
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202402160420.e4QKwoGO-lkp@intel.com/
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>   include/linux/dax.h | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index df2d52b8a245..4527c10016fb 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -64,6 +64,9 @@ void dax_write_cache(struct dax_device *dax_dev, bool wc);
>   bool dax_write_cache_enabled(struct dax_device *dax_dev);
>   bool dax_synchronous(struct dax_device *dax_dev);
>   void set_dax_synchronous(struct dax_device *dax_dev);
> +void set_dax_nocache(struct dax_device *dax_dev);
> +void set_dax_nomc(struct dax_device *dax_dev);
> +
>   size_t dax_recovery_write(struct dax_device *dax_dev, pgoff_t pgoff,
>   		void *addr, size_t bytes, struct iov_iter *i);
>   /*
> @@ -108,6 +111,12 @@ static inline bool dax_synchronous(struct dax_device *dax_dev)
>   static inline void set_dax_synchronous(struct dax_device *dax_dev)
>   {
>   }
> +static inline void set_dax_nocache(struct dax_device *dax_dev)
> +{
> +}
> +static inline void set_dax_nomc(struct dax_device *dax_dev)
> +{
> +}
>   static inline bool daxdev_mapping_supported(struct vm_area_struct *vma,
>   				struct dax_device *dax_dev)
>   {
> @@ -120,9 +129,6 @@ static inline size_t dax_recovery_write(struct dax_device *dax_dev,
>   }
>   #endif
>   
> -void set_dax_nocache(struct dax_device *dax_dev);
> -void set_dax_nomc(struct dax_device *dax_dev);
> -
>   struct writeback_control;
>   #if defined(CONFIG_BLOCK) && defined(CONFIG_FS_DAX)
>   int dax_add_host(struct dax_device *dax_dev, struct gendisk *disk);

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com