linux-kernel - Re: [PATCH 13/22] staging: erofs: kill CONFIG_EROFS_FS_USE_VM_MAP

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Date:   Wed, 31 Jul 2019 16:27:07 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Gao Xiang <gaoxiang25@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <devel@...verdev.osuosl.org>
CC:     <linux-erofs@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>, <weidu.du@...wei.com>,
        Miao Xie <miaoxie@...wei.com>
Subject: Re: [PATCH 13/22] staging: erofs: kill CONFIG_EROFS_FS_USE_VM_MAP_RAM

On 2019/7/29 14:51, Gao Xiang wrote:
> Turn into a module parameter ("use_vmap") as it
> can be set at runtime.
> 
> Suggested-by: David Sterba <dsterba@...e.cz>
> Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
> ---
>  drivers/staging/erofs/Kconfig        |  8 ------
>  drivers/staging/erofs/decompressor.c | 37 +++++++++++++++-------------
>  2 files changed, 20 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/staging/erofs/Kconfig b/drivers/staging/erofs/Kconfig
> index 747e9eebfaa5..788beebf3f7d 100644
> --- a/drivers/staging/erofs/Kconfig
> +++ b/drivers/staging/erofs/Kconfig
> @@ -63,14 +63,6 @@ config EROFS_FS_SECURITY
>  
>  	  If you are not using a security module, say N.
>  
> -config EROFS_FS_USE_VM_MAP_RAM
> -	bool "EROFS VM_MAP_RAM Support"
> -	depends on EROFS_FS
> -	help
> -	  use vm_map_ram/vm_unmap_ram instead of vmap/vunmap.
> -
> -	  If you don't know what these are, say N.
> -
>  config EROFS_FAULT_INJECTION
>  	bool "EROFS fault injection facility"
>  	depends on EROFS_FS
> diff --git a/drivers/staging/erofs/decompressor.c b/drivers/staging/erofs/decompressor.c
> index 744c43a456e9..5352a50981cb 100644
> --- a/drivers/staging/erofs/decompressor.c
> +++ b/drivers/staging/erofs/decompressor.c
> @@ -7,6 +7,7 @@
>   * Created by Gao Xiang <gaoxiang25@...wei.com>
>   */
>  #include "compress.h"
> +#include <linux/module.h>
>  #include <linux/lz4.h>
>  
>  #ifndef LZ4_DISTANCE_MAX	/* history window size */
> @@ -29,6 +30,10 @@ struct z_erofs_decompressor {
>  	char *name;
>  };
>  
> +static bool use_vmap;
> +module_param(use_vmap, bool, 0444);
> +MODULE_PARM_DESC(use_vmap, "Use vmap() instead of vm_map_ram() (default 0)");

This should be documented in erofs.txt simply.

> +
>  static int lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
>  				 struct list_head *pagepool)
>  {
> @@ -219,29 +224,27 @@ static void copy_from_pcpubuf(struct page **out, const char *dst,
>  
>  static void *erofs_vmap(struct page **pages, unsigned int count)
>  {
> -#ifdef CONFIG_EROFS_FS_USE_VM_MAP_RAM
> -	int i = 0;
> -
> -	while (1) {
> -		void *addr = vm_map_ram(pages, count, -1, PAGE_KERNEL);
> -		/* retry two more times (totally 3 times) */
> -		if (addr || ++i >= 3)
> -			return addr;
> -		vm_unmap_aliases();
> +	if (!use_vmap) {

Minor thing.

if (use_vmap)
	return vmap(pages, count, VM_MAP, PAGE_KERNEL);

while (1) {
}

return NULL;

Otherwise, it looks good to me.

Reviewed-by: Chao Yu <yuchao0@...wei.com>

Thanks,

> +		int i = 0;
> +
> +		while (1) {
> +			void *addr = vm_map_ram(pages, count, -1, PAGE_KERNEL);
> +			/* retry two more times (totally 3 times) */
> +			if (addr || ++i >= 3)
> +				return addr;
> +			vm_unmap_aliases();
> +		}
> +		return NULL;
>  	}
> -	return NULL;
> -#else
>  	return vmap(pages, count, VM_MAP, PAGE_KERNEL);
> -#endif
>  }
>  
>  static void erofs_vunmap(const void *mem, unsigned int count)
>  {
> -#ifdef CONFIG_EROFS_FS_USE_VM_MAP_RAM
> -	vm_unmap_ram(mem, count);
> -#else
> -	vunmap(mem);
> -#endif
> +	if (!use_vmap)
> +		vm_unmap_ram(mem, count);
> +	else
> +		vunmap(mem);
>  }
>  
>  static int decompress_generic(struct z_erofs_decompress_req *rq,
>