linux-ext4 - Re: [PATCH v2] ext2: fix sleeping in atomic bugs on error

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Date:   Wed, 22 Sep 2021 13:05:41 +0200
From:   Jan Kara <jack@...e.cz>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] ext2: fix sleeping in atomic bugs on error

On Tue 21-09-21 23:32:33, Dan Carpenter wrote:
> The ext2_error() function syncs the filesystem so it sleeps.  The caller
> is holding a spinlock so it's not allowed to sleep.
> 
>    ext2_statfs() <- disables preempt
>    -> ext2_count_free_blocks()
>       -> ext2_get_group_desc()
> 
> Fix this by using WARN() to print an error message and a stack trace
> instead of using ext2_error().
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Thanks! I've added the patch to my tree.

								Honza

> ---
> v2: The first version disabled the sync in ext2_error()
> 
>  fs/ext2/balloc.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c
> index 1f3f4326bf3c..c17ccc19b938 100644
> --- a/fs/ext2/balloc.c
> +++ b/fs/ext2/balloc.c
> @@ -48,10 +48,9 @@ struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
>  	struct ext2_sb_info *sbi = EXT2_SB(sb);
>  
>  	if (block_group >= sbi->s_groups_count) {
> -		ext2_error (sb, "ext2_get_group_desc",
> -			    "block_group >= groups_count - "
> -			    "block_group = %d, groups_count = %lu",
> -			    block_group, sbi->s_groups_count);
> +		WARN(1, "block_group >= groups_count - "
> +		     "block_group = %d, groups_count = %lu",
> +		     block_group, sbi->s_groups_count);
>  
>  		return NULL;
>  	}
> @@ -59,10 +58,9 @@ struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
>  	group_desc = block_group >> EXT2_DESC_PER_BLOCK_BITS(sb);
>  	offset = block_group & (EXT2_DESC_PER_BLOCK(sb) - 1);
>  	if (!sbi->s_group_desc[group_desc]) {
> -		ext2_error (sb, "ext2_get_group_desc",
> -			    "Group descriptor not loaded - "
> -			    "block_group = %d, group_desc = %lu, desc = %lu",
> -			     block_group, group_desc, offset);
> +		WARN(1, "Group descriptor not loaded - "
> +		     "block_group = %d, group_desc = %lu, desc = %lu",
> +		      block_group, group_desc, offset);
>  		return NULL;
>  	}
>  
> -- 
> 2.20.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR