linux-ext4 - Re: [PATCH] ext4: Fix scheduling in atomic on group checksum failure

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Date:	Wed, 10 Feb 2016 09:52:46 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Ted Tso <tytso@....edu>, Dmitry Vyukov <dvyukov@...gle.com>,
	linux-ext4@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] ext4: Fix scheduling in atomic on group checksum failure

On Wed, Feb 10, 2016 at 02:58:30PM +0100, Jan Kara wrote:
> When block group checksum is wrong, we call ext4_error() while holding
> group spinlock from ext4_init_block_bitmap() or
> ext4_init_inode_bitmap() which results in scheduling while in atomic.
> Fix the issue by calling ext4_error() later after dropping the spinlock.
> 
> CC: stable@...r.kernel.org
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Jan Kara <jack@...e.cz>

Looks ok, so
Reviewed-by: Darrick J. Wong <darrick.wong@...cle.com>

--D

> ---
>  fs/ext4/balloc.c | 7 ++++---
>  fs/ext4/ialloc.c | 6 ++++--
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index ec0668a60678..fe1f50fe764f 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -191,7 +191,6 @@ static int ext4_init_block_bitmap(struct super_block *sb,
>  	/* If checksum is bad mark all blocks used to prevent allocation
>  	 * essentially implementing a per-group read-only flag. */
>  	if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) {
> -		ext4_error(sb, "Checksum bad for group %u", block_group);
>  		grp = ext4_get_group_info(sb, block_group);
>  		if (!EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
>  			percpu_counter_sub(&sbi->s_freeclusters_counter,
> @@ -442,14 +441,16 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
>  	}
>  	ext4_lock_group(sb, block_group);
>  	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
> -
>  		err = ext4_init_block_bitmap(sb, bh, block_group, desc);
>  		set_bitmap_uptodate(bh);
>  		set_buffer_uptodate(bh);
>  		ext4_unlock_group(sb, block_group);
>  		unlock_buffer(bh);
> -		if (err)
> +		if (err) {
> +			ext4_error(sb, "Failed to init block bitmap for group "
> +				   "%u: %d", block_group, err);
>  			goto out;
> +		}
>  		goto verify;
>  	}
>  	ext4_unlock_group(sb, block_group);
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index 3fcfd50a2e8a..acc0ad56bf2f 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -76,7 +76,6 @@ static int ext4_init_inode_bitmap(struct super_block *sb,
>  	/* If checksum is bad mark all blocks and inodes use to prevent
>  	 * allocation, essentially implementing a per-group read-only flag. */
>  	if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) {
> -		ext4_error(sb, "Checksum bad for group %u", block_group);
>  		grp = ext4_get_group_info(sb, block_group);
>  		if (!EXT4_MB_GRP_BBITMAP_CORRUPT(grp))
>  			percpu_counter_sub(&sbi->s_freeclusters_counter,
> @@ -191,8 +190,11 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
>  		set_buffer_verified(bh);
>  		ext4_unlock_group(sb, block_group);
>  		unlock_buffer(bh);
> -		if (err)
> +		if (err) {
> +			ext4_error(sb, "Failed to init inode bitmap for group "
> +				   "%u: %d", block_group, err);
>  			goto out;
> +		}
>  		return bh;
>  	}
>  	ext4_unlock_group(sb, block_group);
> -- 
> 2.6.2
> 
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