linux-kernel - Re: [PATCH] nvdimm-btt: simplify code with the scope based resource management

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Message-ID: <8716bf72-e4ca-4f83-8a30-327baf459dbb@intel.com>
Date:   Mon, 11 Dec 2023 11:26:56 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Dinghao Liu <dinghao.liu@....edu.cn>
CC:     Vishal Verma <vishal.l.verma@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Ira Weiny <ira.weiny@...el.com>, <nvdimm@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvdimm-btt: simplify code with the scope based resource
 management



On 12/10/23 03:27, Dinghao Liu wrote:
> Use the scope based resource management (defined in
> linux/cleanup.h) to automate resource lifetime
> control on struct btt_sb *super in discover_arenas().
> 
> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
> ---
>  drivers/nvdimm/btt.c | 12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
> index d5593b0dc700..ff42778b51de 100644
> --- a/drivers/nvdimm/btt.c
> +++ b/drivers/nvdimm/btt.c
> @@ -16,6 +16,7 @@
>  #include <linux/fs.h>
>  #include <linux/nd.h>
>  #include <linux/backing-dev.h>
> +#include <linux/cleanup.h>
>  #include "btt.h"
>  #include "nd.h"
>  
> @@ -847,7 +848,7 @@ static int discover_arenas(struct btt *btt)
>  {
>  	int ret = 0;
>  	struct arena_info *arena;
> -	struct btt_sb *super;
> +	struct btt_sb *super __free(kfree) = NULL;
>  	size_t remaining = btt->rawsize;
>  	u64 cur_nlba = 0;
>  	size_t cur_off = 0;
> @@ -860,10 +861,8 @@ static int discover_arenas(struct btt *btt)
>  	while (remaining) {
>  		/* Alloc memory for arena */
>  		arena = alloc_arena(btt, 0, 0, 0);
> -		if (!arena) {
> -			ret = -ENOMEM;
> -			goto out_super;
> -		}
> +		if (!arena)
> +			return -ENOMEM;
>  
>  		arena->infooff = cur_off;
>  		ret = btt_info_read(arena, super);
> @@ -919,14 +918,11 @@ static int discover_arenas(struct btt *btt)
>  	btt->nlba = cur_nlba;
>  	btt->init_state = INIT_READY;
>  
> -	kfree(super);
>  	return ret;
>  
>   out:
>  	kfree(arena);
>  	free_arenas(btt);
> - out_super:
> -	kfree(super);
>  	return ret;
>  }
>  

I would do the allocation like something below for the first chunk. Otherwise the rest LGTM. 

diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index d5593b0dc700..143921e7f26c 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -16,6 +16,7 @@
 #include <linux/fs.h>
 #include <linux/nd.h>
 #include <linux/backing-dev.h>
+#include <linux/cleanup.h>
 #include "btt.h"
 #include "nd.h"
 
@@ -845,25 +846,23 @@ static void parse_arena_meta(struct arena_info *arena, struct btt_sb *super,
 
 static int discover_arenas(struct btt *btt)
 {
+       struct btt_sb *super __free(kfree) =
+               kzalloc(sizeof(*super), GFP_KERNEL);
        int ret = 0;
        struct arena_info *arena;
-       struct btt_sb *super;
        size_t remaining = btt->rawsize;
        u64 cur_nlba = 0;
        size_t cur_off = 0;
        int num_arenas = 0;
 
-       super = kzalloc(sizeof(*super), GFP_KERNEL);
        if (!super)
                return -ENOMEM;
 
        while (remaining) {
                /* Alloc memory for arena */
                arena = alloc_arena(btt, 0, 0, 0);
-               if (!arena) {
-                       ret = -ENOMEM;
-                       goto out_super;
-               }
+               if (!arena)
+                       return -ENOMEM;
 
                arena->infooff = cur_off;
                ret = btt_info_read(arena, super);