linux-ext4 - Re: [PATCH] ext4: don't work without procfs

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Date:	Tue, 4 Oct 2011 11:20:36 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Yargil <yargil@...e.fr>
cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: don't work without procfs

On Mon, 3 Oct 2011, Yargil wrote:

> Regression from commit dd68314ccf3fb918c1fb6471817edbc60ece4b52

Hi,

the commit you've mentioned does not have anything to do with procfs.
Maybe you meant commit 

c9de560ded61faa5b754137b7753da252391c55a
	ext4: Add multi block allocator for ext4

which adds multi block allocator for ext4 (mballoc.c) and has been added
in Jan 29 2008.

> ---
>  fs/ext4/super.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 44d0c8d..8e7298d 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -53,7 +53,9 @@
>  #define CREATE_TRACE_POINTS
>  #include <trace/events/ext4.h>
>  
> +#ifdef CONFIG_PROC_FS
>  static struct proc_dir_entry *ext4_proc_root;
> +#endif

This is not needed I think, since proc_dir_entry is defined in
linux/proc_fs.h even if CONFIG_PROC_FS is not defined.

>  static struct kset *ext4_kset;
>  static struct ext4_lazy_init *ext4_li_info;
>  static struct mutex ext4_li_mtx;
> @@ -812,9 +814,11 @@ static void ext4_put_super(struct super_block *sb)
>  		es->s_state = cpu_to_le16(sbi->s_mount_state);
>  		ext4_commit_super(sb, 1);
>  	}
> +#ifdef CONFIG_PROC_FS
>  	if (sbi->s_proc) {
>  		remove_proc_entry(sb->s_id, ext4_proc_root);

This function exists even if CONFIG_PROC_FS is not defined.

#define remove_proc_entry(name, parent) do {} while (0)


>  	}
> +#endif
>  	kobject_del(&sbi->s_kobj);
>  
>  	for (i = 0; i < sbi->s_gdb_count; i++)
> @@ -4984,9 +4988,11 @@ static int __init ext4_init_fs(void)
>  	ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj);
>  	if (!ext4_kset)
>  		goto out6;
> +#ifdef CONFIG_PROC_FS
>  	ext4_proc_root = proc_mkdir("fs/ext4", NULL);

The same here

static inline struct proc_dir_entry *proc_mkdir(const char *name,
	struct proc_dir_entry *parent) {return NULL;}


>  	if (!ext4_proc_root)
>  		goto out5;
However this is wrong, because in case that procfs is not compiled in
ext4_proc_root will be NULL, but there is no reason to error out in this
case.

The question is whether we should error out in case that it fails even
if we have procfs compiled in. I am slightly in favour of just printing
a warning in !CONFIG_PROC_FS case.

Also this is probably why you blame commit
dd68314ccf3fb918c1fb6471817edbc60ece4b52 for the regression, since this
check was added with this commit. But I think that there is no reasong
to #ifdef everything procfs related.


> +#endif
>  
>  	err = ext4_init_feat_adverts();
>  	if (err)
> @@ -5022,8 +5028,10 @@ out2:
>  out3:
>  	ext4_exit_feat_adverts();
>  out4:
> +#ifdef CONFIG_PROC_FS
>  	remove_proc_entry("fs/ext4", NULL);

same here.

>  out5:
> +#endif
>  	kset_unregister(ext4_kset);
>  out6:
>  	ext4_exit_system_zone();
> 

-Lukas
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