linux-ext4 - Re: [PATCH v2 05/12] e4defrag: Add force option for e4defrag

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Date:	Wed, 17 Aug 2011 10:31:14 -0600
From:	Andreas Dilger <adilger@...ger.ca>
To:	Kazuya Mio <k-mio@...jp.nec.com>
Cc:	ext4 <linux-ext4@...r.kernel.org>, Theodore Tso <tytso@....edu>
Subject: Re: [PATCH v2 05/12] e4defrag: Add force option for e4defrag

On 2011-08-17, at 1:47 AM, Kazuya Mio <k-mio@...jp.nec.com> wrote:
> Currently, e4defrag calls EXT4_IOC_MOVE_EXT ioctl if the fragmentation score
> of a donor file is zero. However, it is difficult sometimes to create the file
> that has the average of 4096 blocks per extent. We can use e4defrag -F to defrag
> in this case.
> 
> Signed-off-by: Kazuya Mio <k-mio@...jp.nec.com>
> ---
> misc/e4defrag.8.in |    5 ++++-
> misc/e4defrag.c    |   14 ++++++++++----
> 2 files changed, 14 insertions(+), 5 deletions(-)
> diff --git a/misc/e4defrag.8.in b/misc/e4defrag.8.in
> index 81adc29..ede7455 100644
> --- a/misc/e4defrag.8.in
> +++ b/misc/e4defrag.8.in
> @@ -4,7 +4,7 @@ e4defrag \- online defragmenter for ext4 filesystem
> .SH SYNOPSIS
> .B e4defrag
> [
> -.B \-v
> +.B \-Fv
> ]
> .I target
> \&...
> @@ -31,6 +31,9 @@ gets the mount point of it and reduces fragmentation of all files in this mount
> point.
> .SH OPTIONS
> .TP
> +.B \-F
> +Force defrag if the fragmentation gets better.
> +.TP
> .B \-v
> Print error messages and the fragmentation count before and after defrag for
> each file.
> diff --git a/misc/e4defrag.c b/misc/e4defrag.c
> index 44d54f3..64b1474 100644
> --- a/misc/e4defrag.c
> +++ b/misc/e4defrag.c
> @@ -80,6 +80,7 @@
> 
> /* The mode of defrag */
> #define DETAIL            0x01
> +#define FORCE            0x02
> 
> #define DEVNAME            0
> #define DIRNAME            1
> @@ -107,7 +108,7 @@
> 
> /* The following macros are error message */
> #define MSG_USAGE        \
> -"Usage    : e4defrag [-v] file...| directory...| device...\n"
> +"Usage    : e4defrag [-Fv] file...| directory...| device...\n"
> 
> #define NGMSG_EXT4        "Filesystem is not ext4 filesystem"
> #define NGMSG_FILE_EXTENT    "Failed to get file extents"
> @@ -1153,7 +1154,8 @@ check_improvement:
>        extents_before_defrag += file_frags_start;
>    }
> 
> -    if (!orig_score || donor_score) {
> +    if (!orig_score || (donor_score && !(mode_flag & FORCE)) ||
> +            (orig_score <= donor_score && (mode_flag & FORCE))) {

It is confusing in conditionals like this when integer variables are treated as boolean values. It would be more clear to compare the orig_score and donor_score to zero.

        if (orig_score == 0 || (donor_score > 0 && !(mode_flag & FORCE)) ||
            (orig_score <= donor_score && (mode_flag & FORCE))) {

To be honest, I still can't understand the above logic. I would think it is enough to check:

        if (orig_score < donor_score && !(mode_flag & FORCE))) {

so that the file is not defragged if the score would get worse, but "force" means it is always moved.
 
> printf("\033[79;0H\033[K[%u/%u]%s:\t%3d%%",

It would be nice if the color terminal output was optional (maybe only on by default for tty output).  This is not typical for other e2fsprogs utilities, and makes a mess of logs being kept of the output. 

>            defraged_file_count, total_count, file, 100);
>        if (mode_flag & DETAIL)
> @@ -1231,8 +1233,12 @@ int main(int argc, char *argv[])
>    if (argc == 1)
>        goto out;
> 
> -    while ((opt = getopt(argc, argv, "v")) != EOF) {
> +    while ((opt = getopt(argc, argv, "Fv")) != EOF) {
>        switch (opt) {
> +        case 'F':
> +            /* Force defrag if the fragmentation gets better */
> +            mode_flag |= FORCE;

Should this comment be "Force defrag if the fragmentation gets _worse_"?

> +            break;
>        case 'v':
>            mode_flag |= DETAIL;
>            break;
> @@ -1245,7 +1251,7 @@ int main(int argc, char *argv[])
>        goto out;
> 
>    current_uid = getuid();
> -    threshold = DEFAULT_THRESHOLD;
> +    threshold = (mode_flag & FORCE) ? ~0U : DEFAULT_THRESHOLD;
> 
>    /* Main process */
>    for (i = optind; i < argc; i++) {
> --
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