From: Phillip Susi <psusi@ubuntu.com>
To: Sankar P <sankar.curiosity@gmail.com>
Cc: Kernelnewbies@kernelnewbies.org, linux-fsdevel@vger.kernel.org
Subject: Re: How defragmentation works in linux filesystems ?
Date: Tue, 15 Jan 2013 16:23:51 -0500 [thread overview]
Message-ID: <50F5C8E7.8030607@ubuntu.com> (raw)
In-Reply-To: <CAMSEaH71w-4o2JP-6+4NjZbzP0drhpVysprsAPCHetuRtF7CzQ@mail.gmail.com>
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On 1/7/2013 4:27 AM, Sankar P wrote:
> Hi,
>
> Is there any technical article explaining how defragmentation works
> in linux filesystems, say btrfs or ext4 ?
>
> Do they recreate the file data blocks and change the root pointer
> to the new extent ? Or do they do some kind of moving blocks around
> ? Or is it based on some other strategy ? Partial defragmentation
> (based on either byte offset or extents) is also supported by any
> of the file systems ?
e4defrag uses an ioctl to allocate a new donor inode with enough
contiguous blocks to hold the original, then atomically copy the
blocks and swap the pointers.
> Is there a standard way to trigger a defragmentation operation (an
> ioctl ?) that my filesystem could implement so that any user space
> tool that work with other fs will work with mine too ? (Like, how
> FIEBMAP ioctl can help in giving the extent information for a file
> from the userspace)
No.
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prev parent reply other threads:[~2013-01-15 21:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-07 9:27 How defragmentation works in linux filesystems ? Sankar P
2013-01-15 21:23 ` Phillip Susi [this message]
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