On Mon, Mar 03, 2014 at 04:40:21PM +0100, Lukáš Czerner wrote:
>
> are you going to take this in ?
>
> > It's better to use the resize_inode for file systems that are smaller
> > than 16TB, even if the 64-bit flag is enabled, since using the meta_bg
> > style resizing spreads out the block group descriptors, which
> > increases the time to mount the file system. Using the resize_inode
> > will defer the need to go to the meta_bg-style resizing until we cross
> > the 16TB boundary.
See my comments above.
If we create a file system which is say, 1T but with the 64-bit flag,
we do want the resize_inode feature to be used until we cross over the
32-bit boundary, because keeping block group descriptors contiguous
speeds up the mount time.
If I were to accept this patch, and/or Red Hat were to ship with it, I
will predict that you will get angry customer support calls about file
system mount times getting slow after doing a resize.
At some point what we may want to lazily load the block group
descriptors at mount time, to mitigate the slow mount time issue when
using meta_bg. We have a lot of assumptions in the code that the
block group descriptors are always available, though.
- Ted
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