Re: fiemap is broken for sparse file in ext4?

From: Tao Ma
Date: Fri Jun 11 2010 - 19:47:25 EST

Hi Eric,
Eric Sandeen wrote:
Greg Freemyer wrote:
On Fri, Jun 11, 2010 at 11:46 AM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
Tao Ma wrote:

What are you using to call fiemap? Here it seems to be working:
I just wrote a simple test program by calling ioctl. It is attached.
btw, you need to call it immediately after dd so that we have a chance
that ext4 don't have time to allocate extents. ;)
OK I take it back, I do see it. *cough* too many different filesystems
on this box ... ;)

Yes, it does look like a bug.

I'm not clear how this is supposed to work.

Is this just a userspace bug in that FIEMAP_FLAG_SYNC is needed in the
fiemap call, or is there a kernel bug as well?

The flag is optional, though maybe filefrag should use it.

Without it, we should get the proper logical offset and a delalloc-flagged
extent returned

If fiemap is called with the FIEMAP_FLAG_SYNC flag is there currently a problem?

yep, we should get one delalloc extent in the results and we don't.
With FIEMAP_FLAG_SYNC set, my test shows that we get one extent without dealloc flags. So no problem with it.
We have another different test result? ;)


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at