Re: [PATCH 0/4] Fiemap, an extent mapping ioctl - round 2

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Andreas Dilger wrote:
> On Jun 27, 2008  23:21 -0500, Eric Sandeen wrote:
> > even w/ metadata out of the way the ext4 extent format is still
> > capped at 128M per extent right, even if they're contiguous.  Which led
> > me to the little though experiment about hm, is this 1G file 1 extent or
> > 8 and what should fiemap return...
> 
> The current FIEMAP code will return 8 extents, which mirrors the number
> of physical extents on disk.  This could be important to the person
> looking at the file, as it will be clear that there are too many
> extents to fit into the inode and the extent tree will include an index
> block.
> 
> I was a bit on the fence about this, but I agree with David that if
> userspace has more information (e.g. all of the on-disk extent data)
> it can always merge it, but it can't "un-merge" the data returned
> from the kernel.

Ok, wouldn't be appropriate to include the extent of the index block
as well, somewhere, so that userspace can see which parts of the disk
must be read to read the file?

(As you say, more information...)

-- Jamie
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