linux-ext4 - Re: [PATCH v2 8/8] ext4: mark the group block bitmap as corrupted before reporting an error

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Date: Thu, 4 Jan 2024 11:51:51 +0100
From: Jan Kara <jack@...e.cz>
To: Baokun Li <libaokun1@...wei.com>
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
	jack@...e.cz, ritesh.list@...il.com, linux-kernel@...r.kernel.org,
	yi.zhang@...wei.com, yangerkun@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v2 8/8] ext4: mark the group block bitmap as corrupted
 before reporting an error

On Thu 21-12-23 23:05:58, Baokun Li wrote:
> Otherwise unlocking the group in ext4_grp_locked_error may allow other
> processes to modify the core block bitmap that is known to be corrupt.
> 
> Signed-off-by: Baokun Li <libaokun1@...wei.com>

I'm not opposed but I don't think this matters much.
ext4_grp_locked_error() unlocks the group only in errors=remount-ro case
these days and in that case we abort the journal so none of the changes
should make it to disk anyway. Anyway, in the name of defensive programming
feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

:)

								Honza

> ---
>  fs/ext4/mballoc.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index b862ca2750fd..c43eefebdaa3 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -564,14 +564,14 @@ static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b,
>  
>  			blocknr = ext4_group_first_block_no(sb, e4b->bd_group);
>  			blocknr += EXT4_C2B(EXT4_SB(sb), first + i);
> +			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> +					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			ext4_grp_locked_error(sb, e4b->bd_group,
>  					      inode ? inode->i_ino : 0,
>  					      blocknr,
>  					      "freeing block already freed "
>  					      "(bit %u)",
>  					      first + i);
> -			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> -					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  		}
>  		mb_clear_bit(first + i, e4b->bd_info->bb_bitmap);
>  	}
> @@ -1926,14 +1926,13 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,
>  		blocknr = ext4_group_first_block_no(sb, e4b->bd_group);
>  		blocknr += EXT4_C2B(sbi, block);
>  		if (!(sbi->s_mount_state & EXT4_FC_REPLAY)) {
> +			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> +					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			ext4_grp_locked_error(sb, e4b->bd_group,
>  					      inode ? inode->i_ino : 0,
>  					      blocknr,
>  					      "freeing already freed block (bit %u); block bitmap corrupt.",
>  					      block);
> -			ext4_mark_group_bitmap_corrupted(
> -				sb, e4b->bd_group,
> -				EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  		} else {
>  			mb_regenerate_buddy(e4b);
>  			goto check;
> @@ -2410,12 +2409,12 @@ void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,
>  
>  		k = mb_find_next_zero_bit(buddy, max, 0);
>  		if (k >= max) {
> +			ext4_mark_group_bitmap_corrupted(ac->ac_sb,
> +					e4b->bd_group,
> +					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			ext4_grp_locked_error(ac->ac_sb, e4b->bd_group, 0, 0,
>  				"%d free clusters of order %d. But found 0",
>  				grp->bb_counters[i], i);
> -			ext4_mark_group_bitmap_corrupted(ac->ac_sb,
> -					 e4b->bd_group,
> -					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			break;
>  		}
>  		ac->ac_found++;
> @@ -2466,12 +2465,12 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
>  			 * free blocks even though group info says we
>  			 * have free blocks
>  			 */
> +			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> +					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
>  					"%d free clusters as per "
>  					"group info. But bitmap says 0",
>  					free);
> -			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> -					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			break;
>  		}
>  
> @@ -2497,12 +2496,12 @@ void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,
>  		if (WARN_ON(ex.fe_len <= 0))
>  			break;
>  		if (free < ex.fe_len) {
> +			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> +					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
>  					"%d free clusters as per "
>  					"group info. But got %d blocks",
>  					free, ex.fe_len);
> -			ext4_mark_group_bitmap_corrupted(sb, e4b->bd_group,
> -					EXT4_GROUP_INFO_BBITMAP_CORRUPT);
>  			/*
>  			 * The number of free blocks differs. This mostly
>  			 * indicate that the bitmap is corrupt. So exit
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR