linux-ext4 - Re: [PATCH V2] e2fsck: fix multiply-claimed block quota accounting when deleting files

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Date:   Thu, 11 May 2017 10:32:17 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Eric Whitney <enwlinux@...il.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu
Subject: Re: [PATCH V2] e2fsck: fix multiply-claimed block quota accounting
 when deleting files


> On May 11, 2017, at 9:46 AM, Eric Whitney <enwlinux@...il.com> wrote:
> 
> As e2fsck processes each file in pass1, the actual file system quota is
> increased by the number of blocks discovered in the file.  This can
> include both non-multiply-claimed and multiply-claimed blocks, if the
> latter exist.  However, if a file containing multiply-claimed blocks
> is then deleted in pass1b, those blocks are not taken into account when
> decreasing the actual quota.  In this case, the new quota values written
> to the file system by e2fsck overstate the space actually consumed.
> And, e2fsck must be run twice on the file system to fully correct
> quota.
> 
> Fix this by counting multiply-claimed blocks as a debit to quota when
> deleting files in pass1b.
> 
> [V2] Correct a dangling else bug in the original patch.
> 
> Signed-off-by: Eric Whitney <enwlinux@...il.com>

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> ---
> e2fsck/pass1b.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/e2fsck/pass1b.c b/e2fsck/pass1b.c
> index b40f026..d22cffd 100644
> --- a/e2fsck/pass1b.c
> +++ b/e2fsck/pass1b.c
> @@ -637,9 +637,11 @@ static int delete_file_block(ext2_filsys fs,
> 	if (ext2fs_test_block_bitmap2(ctx->block_dup_map, *block_nr)) {
> 		n = dict_lookup(&clstr_dict, INT_TO_VOIDPTR(c));
> 		if (n) {
> -			p = (struct dup_cluster *) dnode_get(n);
> -			if (lc != pb->cur_cluster)
> +			if (lc != pb->cur_cluster) {
> +				p = (struct dup_cluster *) dnode_get(n);
> 				decrement_badcount(ctx, *block_nr, p);
> +				pb->dup_blocks++;
> +			}
> 		} else
> 			com_err("delete_file_block", 0,
> 			    _("internal error: can't find dup_blk for %llu\n"),

My preference would be to have {} around the else clause as well, and I
believe that checkpatch.pl agrees "braces {} should be used on all arms
of this statement".  That said, this is a pre-existing condition and is
only code style, while your patch fixes a real bug.

Cheers, Andreas






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