linux-ext4 - Re: [PATCH 1/2] Add discard/nodiscard mount option for ext3

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Date:	Mon, 12 Jul 2010 11:27:32 -0400
From:	Ric Wheeler <rwheeler@...hat.com>
To:	Jan Kara <jack@...e.cz>
CC:	Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
	jmoyer@...hat.com, eshishki@...hat.com, sandeen@...hat.com
Subject: Re: [PATCH 1/2] Add discard/nodiscard mount option for ext3

On 07/12/2010 11:19 AM, Jan Kara wrote:
>> Those mount option has the same meaning as in ext4 file system. It
>> provide a way to enable/disable file system's trim support. The trim
>> support is off by default, thus nodiscard option is not actually
>> necessary.
>    I kind of miss why ext3 should have a 'discard' mount option. When
> user calls DISCARD ioctl on the filesystem, then he probably wants
> discard to be performed.
>
> 								Honza


Did you see Lukas' second patch for batched discards in ext3?

Ric

>
>> Signed-off-by: Lukas Czerner<lczerner@...hat.com>
>> ---
>>   fs/ext3/super.c         |   14 +++++++++++++-
>>   include/linux/ext3_fs.h |    1 +
>>   2 files changed, 14 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/ext3/super.c b/fs/ext3/super.c
>> index 1bee604..6baf7ef 100644
>> --- a/fs/ext3/super.c
>> +++ b/fs/ext3/super.c
>> @@ -662,6 +662,9 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
>>   	if (test_opt(sb, DATA_ERR_ABORT))
>>   		seq_puts(seq, ",data_err=abort");
>>
>> +	if (test_opt(sb, DISCARD))
>> +		seq_puts(seq, ",discard");
>> +
>>   	if (test_opt(sb, NOLOAD))
>>   		seq_puts(seq, ",norecovery");
>>
>> @@ -811,7 +814,8 @@ enum {
>>   	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
>>   	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
>>   	Opt_noquota, Opt_ignore, Opt_barrier, Opt_err, Opt_resize,
>> -	Opt_usrquota, Opt_grpquota
>> +	Opt_usrquota, Opt_grpquota,
>> +	Opt_discard, Opt_nodiscard,
>>   };
>>
>>   static const match_table_t tokens = {
>> @@ -866,6 +870,8 @@ static const match_table_t tokens = {
>>   	{Opt_usrquota, "usrquota"},
>>   	{Opt_barrier, "barrier=%u"},
>>   	{Opt_resize, "resize"},
>> +	{Opt_discard, "discard"},
>> +	{Opt_nodiscard, "nodiscard"},
>>   	{Opt_err, NULL},
>>   };
>>
>> @@ -1242,6 +1248,12 @@ set_qf_format:
>>   		case Opt_bh:
>>   			clear_opt(sbi->s_mount_opt, NOBH);
>>   			break;
>> +		case Opt_discard:
>> +			set_opt(sbi->s_mount_opt, DISCARD);
>> +			break;
>> +		case Opt_nodiscard:
>> +			clear_opt(sbi->s_mount_opt, DISCARD);
>> +			break;
>>   		default:
>>   			ext3_msg(sb, KERN_ERR,
>>   				"error: unrecognized mount option \"%s\" "
>> diff --git a/include/linux/ext3_fs.h b/include/linux/ext3_fs.h
>> index 5f494b4..f3fdd94 100644
>> --- a/include/linux/ext3_fs.h
>> +++ b/include/linux/ext3_fs.h
>> @@ -406,6 +406,7 @@ struct ext3_inode {
>>   #define EXT3_MOUNT_GRPQUOTA		0x200000 /* "old" group quota */
>>   #define EXT3_MOUNT_DATA_ERR_ABORT	0x400000 /* Abort on file data write
>>   						  * error in ordered mode */
>> +#define EXT3_MOUNT_DISCARD		0x800000 /* Issue DISCARD requests */
>>
>>   /* Compatibility, for having both ext2_fs.h and ext3_fs.h included at once */
>>   #ifndef _LINUX_EXT2_FS_H
>> --
>> 1.6.6.1
>>
>> --
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