linux-ext4 - Re: [PATCH] e2fsck: skip extent optimization by default

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Date:   Tue, 22 Sep 2020 12:26:00 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     adilger@...mcloud.com
Cc:     tytso@....edu, linux-ext4@...r.kernel.org,
        Andreas Dilger <adilger@...ger.ca>
Subject: Re: [PATCH] e2fsck: skip extent optimization by default

On Mon, Sep 21, 2020 at 04:16:02PM -0600, adilger@...mcloud.com wrote:
> From: Andreas Dilger <adilger@...mcloud.com>
> 
> The e2fsck error message:
> 
>     inode nnn extent tree (at level 1) could be narrower. Optimize<y>?
> 
> can be fairly verbose at times, and leads users to think that there
> may be something wrong with the filesystem.  Basically, almost any
> message printed by e2fsck makes users nervous when they are facing
> other corruption, and a few thousand of these printed may hide other
> errors.  It also isn't clear that saving a few blocks optimizing the
> extent tree noticeably improves performance.
> 
> This message has previously been annoying enough for Ted to add the
> "-E no_optimize_extents" option to disable it.  Just enable this
> option by default, similar to the "-D" directory optimization option.

Hi Andreas,

it seem counterproductive to me that we would disable usefull (even if
just a little) optimization just because the way it is presented to the
user is inconvenient. I agree that messages during e2fsck often raise
alarms, as they should, but perfeps instead of disabling the feature we
can figure out a way to make the messaging better ?

Can we just not print the every message if the answer is going to be yes
anyway, either because of -y, -p, <a> or whatever when the user is not
involved in the decision anymore ? Maybe a log file can be created
for the purpose of storing the full log of changes. Or perhaps we can
print out a summary for each type of the problem and how many of the
instaces of a particular problem have been optimized/fixed after the
e2fsck is done pointing to that full log for details ?

-Lukas

> 
> Signed-off-by: Andreas Dilger <adilger@...ger.ca>
> ---
>  e2fsck/e2fsck.8.in | 4 ++--
>  e2fsck/unix.c      | 7 +++++++
>  2 files changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/e2fsck/e2fsck.8.in b/e2fsck/e2fsck.8.in
> index 4e3890b..4f5086a 100644
> --- a/e2fsck/e2fsck.8.in
> +++ b/e2fsck/e2fsck.8.in
> @@ -228,12 +228,12 @@ exactly the opposite of discard option. This is set as default.
>  .TP
>  .BI no_optimize_extents
>  Do not offer to optimize the extent tree by eliminating unnecessary
> -width or depth.  This can also be enabled in the options section of
> +width or depth.  This is the default unless otherwise specified in
>  .BR /etc/e2fsck.conf .
>  .TP
>  .BI optimize_extents
>  Offer to optimize the extent tree by eliminating unnecessary
> -width or depth.  This is the default unless otherwise specified in
> +width or depth.  This can also be enabled in the options section of
>  .BR /etc/e2fsck.conf .
>  .TP
>  .BI inode_count_fullmap
> diff --git a/e2fsck/unix.c b/e2fsck/unix.c
> index 1b7ccea..445f806 100644
> --- a/e2fsck/unix.c
> +++ b/e2fsck/unix.c
> @@ -840,6 +840,8 @@ static errcode_t PRS(int argc, char *argv[], e2fsck_t *ret_ctx)
>  	else
>  		ctx->program_name = "e2fsck";
>  
> +	ctx->options |= E2F_OPT_NOOPT_EXTENTS;
> +
>  	phys_mem_kb = get_memory_size() / 1024;
>  	ctx->readahead_kb = ~0ULL;
>  	while ((c = getopt(argc, argv, "panyrcC:B:dE:fvtFVM:b:I:j:P:l:L:N:SsDkz:")) != EOF)
> @@ -1051,6 +1053,11 @@ static errcode_t PRS(int argc, char *argv[], e2fsck_t *ret_ctx)
>  	if (c)
>  		ctx->options |= E2F_OPT_NOOPT_EXTENTS;
>  
> +	profile_get_boolean(ctx->profile, "options", "optimize_extents",
> +			    0, 0, &c);
> +	if (c)
> +		ctx->options &= ~E2F_OPT_NOOPT_EXTENTS;
> +
>  	profile_get_boolean(ctx->profile, "options", "inode_count_fullmap",
>  			    0, 0, &c);
>  	if (c)
> -- 
> 1.7.12.4
>