Re: [RFC][PATCH 0/5] Fiemap, an extent mapping ioctl

[Joel Becker <Joel.Becker@oracle.com>]

On Thu, May 29, 2008 at 03:41:23PM -0600, Andreas Dilger wrote:
> So, to clarify, you are suggesting that FIEMAP_FLAG_NUM_EXTENTS isn't
> needed, and returning the extent count should just be detected by calling
> FIEMAP with fm_extent_count == 0?  I'm OK with that also, since calling
> it with fm_extent_count == 0 doesn't make sense otherwise.

	I'd always set fm_extent_count to whatever covers the range.
So, like snprintf(3), you always know when you were truncated and by how
much.  Then, passing fm_extent_count=0 in is just a special case of it.
Like estimating a printf buffer with len = snprintf(NULL, 0, fmt, ...);

Joel

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Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127