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Date:	Mon, 27 Sep 2010 16:09:56 +0200
From:	Lukas Czerner <lczerner@...hat.com>
To:	linux-ext4@...r.kernel.org
Cc:	tytso@....edu, rwheeler@...hat.com, sandeen@...hat.com,
	adilger@...ger.ca, lczerner@...hat.com
Subject: [PATCH 0/4 v. 9] Ext3/Ext4 Batched discard support

Hi,

just some minor changes here. As Andreas pointed out it is better to
have special structure to pass FITRIM arguments into ioctl, instead
os just an array of "noname" elements. So I have introduced this
structure:

struct fstrim_range {
	uint64_t start;
	uint64_t len;
	uint64_t minlen;
};

Also the tool which uses FSTRIM ioctl gets updated.


SHORT DESCRIPTION:
==================

Batched discard adds ability to discard free space on mounded filesystem,
in order to avoid using current discard implementation which discards
recently freed blocks. This approach may on some devices (it depends on
how efficient is the device wear-leveling algorithm) result in huge
performance loss.

Batched discard can be invoked from user-space through FITRIM ioctl on
the whole, or just a part, of file system. With this approach we are
searching for continuous free blocks bigger than defined through ioctl
to discard them. So, since we are searching for big continuous extents
it is much more efficient than current approach and it gives user fine
grained control over how much disk space will be reclaimed for
wear-leveling and what impact will it have on performance.


I have attached source code for example application which uses FITRIM
to discard just a part or whole filesystem. Since FITRIM is filesystem
independent ioctl it can be used by any filesystem which supports it.

Usage: fstrim [-s start] [-l length] [-m minimum-extent] [-v] {mountpoint}
        -s Starting Byte to discard from
        -l Number of Bytes to discard from the start
        -m Minimum extent length to discard
        -v Verbose - number of discarded bytes

---
bd6a5a3 ext3: Add batched discard support for ext3
9dcabb2 ext4: Add batched discard support for ext4
9c8c3a5 Add ioctl FITRIM.
787dbea ext4: Use return value from sb_issue_discard()

 fs/ext3/balloc.c        |  256 +++++++++++++++++++++++++++++++++++++++++++++++
 fs/ext3/super.c         |    1 +
 fs/ext4/ext4.h          |    2 +
 fs/ext4/mballoc.c       |  194 +++++++++++++++++++++++++++++++++++-
 fs/ext4/super.c         |    1 +
 fs/ioctl.c              |   39 +++++++
 include/linux/ext3_fs.h |    1 +
 include/linux/fs.h      |    8 ++
 8 files changed, 501 insertions(+), 1 deletions(-)
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