linux-ext4 - Re: [PATCH 5/7] mke2fs: Change -K option to discard/nodiscard

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Date:	Tue, 26 Oct 2010 13:41:34 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
CC:	linux-ext4@...r.kernel.org, tytso@....edu, adilger@...ger.ca
Subject: Re: [PATCH 5/7] mke2fs: Change -K option to discard/nodiscard

Lukas Czerner wrote:
> It would be nice to have consistent "discard" options in every system
> tool (mount, fsck, mkfs) taking advantage of discards. Also "discard"
> and "nodiscard" is more descriptive instead of just "-K" and can be
> easily defaulted and it is something we can not do with "-K".
> 
> With this commit you need to specify extended option like this:
> 
> ./mke2fs -T <fstype> -E nodiscard <device>
> 
> in order make a filesystem without discarding the device first. And
> 
> ./mke2fs -T <fstype> -E discard <device>
> 
> respectively.

Sadly, we probably need to map -K onto -E nodiscard and deprecate
it for now, rather than just removing it altogether?

-Eric

> Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> ---
>  misc/mke2fs.8.in |   18 +++++++++++-------
>  misc/mke2fs.c    |   13 ++++++++-----
>  2 files changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
> index b46e7e2..6b437bc 100644
> --- a/misc/mke2fs.8.in
> +++ b/misc/mke2fs.8.in
> @@ -45,9 +45,6 @@ mke2fs \- create an ext2/ext3/ext4 filesystem
>  .I journal-options
>  ]
>  [
> -.B \-K
> -]
> -[
>  .B \-N
>  .I number-of-inodes
>  ]
> @@ -240,6 +237,17 @@ enable lazy inode table initialization.
>  .B test_fs
>  Set a flag in the filesystem superblock indicating that it may be
>  mounted using experimental kernel code, such as the ext4dev filesystem.
> +.TP
> +.BI discard
> +Attempt to discard blocks at mkfs time (discarding blocks initially is useful
> +on solid state devices and sparse / thin-provisioned storage). When the device
> +advertise that discard also zeroes data (any subsequent read after the discard
> +and before write returns zero), then mark all not-yet-zeroed inode table as
> +zeroed. This significantly speeds up filesystem initialization. This is set
> +as default.
> +.TP
> +.BI nodiscard
> +Do not attempt to discard blocks at mkfs time.
>  .RE
>  .TP
>  .BI \-f " fragment-size"
> @@ -369,10 +377,6 @@ and may be no more than 102,400 filesystem blocks.
>  @JDEV@.BR size " or " device
>  @JDEV@...ions can be given for a filesystem.
>  .TP
> -.BI \-K
> -Keep, do not attempt to discard blocks at mkfs time (discarding blocks initially
> -is useful on solid state devices and sparse / thin-provisioned storage).
> -.TP
>  .BI \-l " filename"
>  Read the bad blocks list from
>  .IR filename .
> diff --git a/misc/mke2fs.c b/misc/mke2fs.c
> index 0980045..32e3a2b 100644
> --- a/misc/mke2fs.c
> +++ b/misc/mke2fs.c
> @@ -753,6 +753,10 @@ static void parse_extended_opts(struct ext2_super_block *param,
>  				lazy_itable_init = strtoul(arg, &p, 0);
>  			else
>  				lazy_itable_init = 1;
> +		} else if (!strcmp(token, "discard")) {
> +			discard = 1;
> +		} else if (!strcmp(token, "nodiscard")) {
> +			discard = 0;
>  		} else {
>  			r_usage++;
>  			badopt = token;
> @@ -768,7 +772,9 @@ static void parse_extended_opts(struct ext2_super_block *param,
>  			"\tstripe-width=<RAID stride * data disks in blocks>\n"
>  			"\tresize=<resize maximum size in blocks>\n"
>  			"\tlazy_itable_init=<0 to disable, 1 to enable>\n"
> -			"\ttest_fs\n\n"),
> +			"\ttest_fs\n"
> +			"\tdiscard\n"
> +			"\tnodiscard\n\n"),
>  			badopt ? badopt : "");
>  		free(buf);
>  		exit(1);
> @@ -1168,7 +1174,7 @@ static void PRS(int argc, char *argv[])
>  	}
>  
>  	while ((c = getopt (argc, argv,
> -		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:KL:M:N:O:R:ST:U:V")) != EOF) {
> +		    "b:cf:g:G:i:jl:m:no:qr:s:t:vE:FI:J:L:M:N:O:R:ST:U:V")) != EOF) {
>  		switch (c) {
>  		case 'b':
>  			blocksize = strtol(optarg, &tmp, 0);
> @@ -1247,9 +1253,6 @@ static void PRS(int argc, char *argv[])
>  		case 'J':
>  			parse_journal_opts(optarg);
>  			break;
> -		case 'K':
> -			discard = 0;
> -			break;
>  		case 'j':
>  			if (!journal_size)
>  				journal_size = -1;

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