linux-ext4 - Re: [PATCH 1/3] Add ioctl FITRIM.

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Date:	Thu, 05 Aug 2010 11:00:19 +0400
From:	Dmitry Monakhov <dmonakhov@...nvz.org>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org, jmoyer@...hat.com, rwheeler@...hat.com,
	eshishki@...hat.com, sandeen@...hat.com, jack@...e.cz,
	tytso@....edu
Subject: Re: [PATCH 1/3] Add ioctl FITRIM.

Lukas Czerner <lczerner@...hat.com> writes:

> On Wed, 4 Aug 2010, Dmitry Monakhov wrote:
>
>> Lukas Czerner <lczerner@...hat.com> writes:
>> 
>> > Adds an filesystem independent ioctl to allow implementation of file
>> > system batched discard support.
>> >
>> > Signed-off-by: Lukas Czerner <lczerner@...hat.com>
>> > ---
>> >  fs/ioctl.c         |   31 +++++++++++++++++++++++++++++++
>> >  include/linux/fs.h |    2 ++
>> >  2 files changed, 33 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/fs/ioctl.c b/fs/ioctl.c
>> > index 2d140a7..6c01c3c 100644
>> > --- a/fs/ioctl.c
>> > +++ b/fs/ioctl.c
>> > @@ -540,6 +540,33 @@ static int ioctl_fsthaw(struct file *filp)
>> >  	return thaw_super(sb);
>> >  }
>> >  
>> > +static int ioctl_fstrim(struct file *filp, unsigned long arg)
>> BTW why do we have to trim fs in one shot ?
>> IMHO it is much suitable to provide start,len parameters as we 
>> do in most functions(truncate, bdevdiscard, getdents).
>> It allow userspace caller to implement a fancy looking progress bars.
>
> Hi,
>
> do you think it is really needed when even with todays SSD's it takes
> just a couple of seconds ? And I suppose it will improve in future. But
> generally I think we can do that..I would like to hear some more
> opinions before I start looking at this.
Hi, Lukas
we may face a really long delays due to bad layouts and slow devices
Please read my response to Ted
I'm agree with you what this interface is important, BTW i already
enabled FITRIM support on my notebook, my speed difference is about 2-3%.
But let's provide right user interface from very beginning.
>
> Thanks.
>
> -Lukas.
>
>> > +{
>> > +	struct super_block *sb = filp->f_path.dentry->d_inode->i_sb;
>> > +	unsigned int minlen;
>> > +	int err;
>> > +
>> > +	if (!capable(CAP_SYS_ADMIN))
>> > +		return -EPERM;
>> > +
>> > +	/* If filesystem doesn't support trim feature, return. */
>> > +	if (sb->s_op->trim_fs == NULL)
>> > +		return -EOPNOTSUPP;
>> > +
>> > +	/* If a blockdevice-backed filesystem isn't specified, return EINVAL. */
>> > +	if (sb->s_bdev == NULL)
>> > +		return -EINVAL;
>> > +
>> > +	err = get_user(minlen, (unsigned int __user *) arg);
>> > +	if (err)
>> > +		return err;
>> > +
>> > +	err = sb->s_op->trim_fs(minlen, sb);
>> > +	if (err)
>> > +		return err;
>> > +	return 0;
>> > +}
>> > +
>> >  /*
>> >   * When you add any new common ioctls to the switches above and below
>> >   * please update compat_sys_ioctl() too.
>> > @@ -590,6 +617,10 @@ int do_vfs_ioctl(struct file *filp, unsigned int fd, unsigned int cmd,
>> >  		error = ioctl_fsthaw(filp);
>> >  		break;
>> >  
>> > +	case FITRIM:
>> > +		error = ioctl_fstrim(filp, arg);
>> > +		break;
>> > +
>> >  	case FS_IOC_FIEMAP:
>> >  		return ioctl_fiemap(filp, arg);
>> >  
>> > diff --git a/include/linux/fs.h b/include/linux/fs.h
>> > index 68ca1b0..01632e4 100644
>> > --- a/include/linux/fs.h
>> > +++ b/include/linux/fs.h
>> > @@ -315,6 +315,7 @@ struct inodes_stat_t {
>> >  #define FIGETBSZ   _IO(0x00,2)	/* get the block size used for bmap */
>> >  #define FIFREEZE	_IOWR('X', 119, int)	/* Freeze */
>> >  #define FITHAW		_IOWR('X', 120, int)	/* Thaw */
>> > +#define FITRIM		_IOWR('X', 121, int)	/* Trim */
>> >  
>> >  #define	FS_IOC_GETFLAGS			_IOR('f', 1, long)
>> >  #define	FS_IOC_SETFLAGS			_IOW('f', 2, long)
>> > @@ -1580,6 +1581,7 @@ struct super_operations {
>> >  	ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
>> >  #endif
>> >  	int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
>> > +	int (*trim_fs) (unsigned int, struct super_block *);
>> >  };
>> >  
>> >  /*
>> --
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