linux-kernel - Re: defrag deployment status (was Re: [PATCH] ext4: allow defrag (EXT4_IOC_MOVE

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Message-Id: <201003080853.42978.borntraeger@de.ibm.com>
Date:	Mon, 8 Mar 2010 08:53:42 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	Akira Fujita <a-fujita@...jp.nec.com>
Subject: Re: defrag deployment status (was Re: [PATCH] ext4: allow defrag (EXT4_IOC_MOVE_EXT) in 32bit compat mode)

Am Montag 08 März 2010 00:27:58 schrieb Jeff Garzik:
> I'm curious, what is the overall deployment status of ext4 defragging? 
> I actually worked on this problem years ago[1], and am hopeful that I 
> will see defragging in a Linux distribution sometime in my lifetime!  ;-)

I had to make the following patch. (There was the same patch already on the
e2fsprogs mailing list, but I cannot find that at the moment. Would be good
if this patch can make it into the next version).

--- a/misc/e4defrag.c
+++ b/misc/e4defrag.c
@@ -1605,7 +1605,7 @@ static int file_defrag(const char *file, const struct stat64 *buf,
                return 0;
        }

-       fd = open64(file, O_RDONLY);
+       fd = open64(file, O_RDWR);
        if (fd < 0) {
                if (mode_flag & DETAIL) {
                        PRINT_FILE_NAME(file);


I did use it on two machines and it does not seem to break anything. 
Some bigger things are missing in the e4defrag tool:
- make the indirect to extend change for old files - e.g. converted ext3
  file systems. Adding the MIGRATE ioctl does not look very hard, but who knows?
- defragging directories (and also remove deleted entries)
- free space optimization is only done as a side effect
- overall layout considerations (e.g. putting files close to its directory or
  use the atime to move often used files to the beginning of a disk etc.)
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