Re: [PATCH 4/4] reiserfs: on-demand bitmap loading

[Jeff Mahoney <jeffm@suse.com>]

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Hans Reiser wrote:
> Are you saying that you allow bitmaps to be unloaded?  If yes, how about
> making that a separate option, and not the default?

They're released, yes. Whether or not they're unloaded is up to the rest
of the system, vm pressure, etc to determine. This isn't any different
than the patch I posted before, which you ultimately approved in September.

If the bitmaps are to be pinned at all, I'd prefer to make *that* the
option. ReiserFS's behavior with respect to bitmaps is inconsistent with
every other Linux file system. I'd prefer to make the dynamic bitmaps
the default, and if you really must, add an option to continue to pin them.

The fact remains that the bitmap blocks are infrequently accessed in
comparison with other bits of metadata that we don't pin. They're not
accessed at all in a read-only environment, and barely accessed in a
light-write workload. If the bitmaps are truly in demand for heavy
writing, the caches should keep those blocks in memory, the same as they
do on other file systems. If another file system, application, or kernel
subsystem needs that memory more, it should be available for it to claim.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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