how to create file without using extent allocation

On 3/22/12, Greg Freemyer [off-list ref] wrote:

quoted

On 3/22/12, Vlad Dogaru [off-list ref] wrote:

quoted

On Thu, Mar 22, 2012 at 3:31 PM, Akshay Nehe [off-list ref]
wrote:

quoted

Hello,

Can we create file on ext4 file system which dose not uses extent
allocation?

Man page of mkfs.ext4 suggests using "-O ^feature" to disable an ext4
feature.  This seems to work:

$ dd if=/dev/zero of=test1 bs=4M count=20
[...]
$ mkfs.ext4 -F test1
[...]
$ file test1
test1: Linux rev 1.0 ext4 filesystem data,
UUID=408f6da2-c4ef-4335-9574-985f3a349ed2 (extents) (huge files)

$ mkfs -O ^extent -F test1
[...]
$ file test1
test1: Linux rev 1.0 ext4 filesystem data,
UUID=23c046d6-db7a-419d-a1d5-0cba3c5b52d0 (huge files)

Hope this helps,
Vlad

On Thu, Mar 22, 2012 at 9:59 AM, Akshay Nehe [off-list ref]
wrote:

quoted

Thanks for help, i find it useful.

--
Regards,
Akshay Nehe.

Akshay,

1) If you are going to participate in kernel mailinglists, you need to
be aware the appropriate netiquette is to bottom post all responses.
I have moved your reply to the bottom to make this flow better.

    Okay I got it, I will follow right method from now onwards.

2) I assume you see it is a mkfs option that controls this.  So you
can't control it on a file by file basis as far as I know.  I don't
think you can even control it by re-mounting.  Instead you have to
reformat, so it is a fundamental change.

    Actually I want to create files which uses indirect block mapping
on ext4 file-system. I have mounted loop device with ext4 file-system,
can I create files on it using indirect block mapping?

Greg

-- 
Regards,
Akshay Nehe.