linux-ext4 - Re: [PATCH 05/10] e2fsck: Allow to fix some superblock corruptions

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Message-Id: <044B6117-0D0F-4FAC-BCB4-724FB7CEB70C@dilger.ca>
Date:   Sun, 3 Jun 2018 22:31:29 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 05/10] e2fsck: Allow to fix some superblock corruptions

On May 30, 2018, at 6:51 AM, Jan Kara <jack@...e.cz> wrote:
> 
> Add a flag to ext2fs_open() which allows to open a filesystem even if
> superblock is somewhat inconsistent. Use this flag from e2fsck as a last
> resort to try to fix the superblok.
> 
> Currently, the flag does nothing. We'll relax checks in ext2fs_open()
> once e2fsck is able to handle corresponding corruption gracefully.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>

I'd think this patch would go at the end once ext2fs_open() checks for
this flag and handles it, but either way...

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

> ---
> e2fsck/unix.c       | 22 +++++++++++++++++++++-
> lib/ext2fs/ext2fs.h |  1 +
> 2 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/e2fsck/unix.c b/e2fsck/unix.c
> index cbe5ec5034cb..55e21ea0aeac 100644
> --- a/e2fsck/unix.c
> +++ b/e2fsck/unix.c
> @@ -1364,7 +1364,7 @@ int main (int argc, char *argv[])
> 	const char	*lib_ver_date;
> 	int		my_ver, lib_ver;
> 	e2fsck_t	ctx;
> -	blk64_t		orig_superblock;
> +	blk64_t		orig_superblock = ~(blk64_t)0;
> 	struct problem_context pctx;
> 	int flags, run_result, was_changed;
> 	int journal_size;
> @@ -1571,6 +1571,26 @@ failure:
> 					     "check of the device.\n"));
> #endif
> 		else {
> +			/*
> +			 * Let's try once more will less consistency checking
> +			 * so that we are able to recover from more errors
> +			 * (e.g. some tool messing up some value in the sb).
> +			 */
> +			if (!(flags & EXT2_FLAG_IGNORE_SB_ERRORS)) {
> +				if (fs)
> +					ext2fs_close_free(&fs);
> +				log_out(ctx, _("%s: Trying to load superblock "
> +					"despite errors...\n"),
> +					ctx->program_name);
> +				flags |= EXT2_FLAG_IGNORE_SB_ERRORS;
> +				/*
> +				 * If we tried backup sb, revert to the
> +				 * original one now.
> +				 */
> +				if (orig_superblock != ~(blk64_t)0)
> +					ctx->superblock = orig_superblock;
> +				goto restart;
> +			}
> 			fix_problem(ctx, PR_0_SB_CORRUPT, &pctx);
> 			if (retval == EXT2_ET_BAD_MAGIC)
> 				check_plausibility(ctx->filesystem_name,
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 6774e32c91c2..250fd174cd48 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -195,6 +195,7 @@ typedef struct ext2_file *ext2_file_t;
> #define EXT2_FLAG_DIRECT_IO		0x80000
> #define EXT2_FLAG_SKIP_MMP		0x100000
> #define EXT2_FLAG_IGNORE_CSUM_ERRORS	0x200000
> +#define EXT2_FLAG_IGNORE_SB_ERRORS	0x400000
> 
> /*
>  * Special flag in the ext2 inode i_flag field that means that this is
> --
> 2.13.6
> 


Cheers, Andreas






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