Re: hundreds of mount --bind mountpoints?

From: Alexander Viro (
Date: Tue Apr 24 2001 - 13:49:23 EST

On Tue, 24 Apr 2001, Andreas Dilger wrote:

> One thing to watch out for is that the current code zeros the u. struct
> for us (as you pointed out to me previously), but allocating from the
> slab cache will not... This could be an interesting source of bugs for
> some filesystems that assume zero'd inode_info structs.

True, but easy to catch.
> Well, if we get rid of NFS (50 x __u32) and HFS (44 * __u32) (sizes are
> approximate for 32-bit arches - I was just counting by hand and not
> strictly checking alignment), then almost all other filesystems are below
> 25 * __u32 (i.e. half of the previous size).

Yeah, but NFS suddenly takes 25+50 words... That's the type of complaints
I'm thinking about.
> Maybe the size of the union can depend on CONFIG_*_FS? There should be
> an absolute minimum size (16 * __u32 or so), but then people who want
> reiserfs as their primary fs do not need to pay the memory penalty of ext2.
> For ext2 (the next largest and most common fs), we could make it part of
> the union if it is compiled in, and on a slab cache if it is a module?

NO. Sorry about shouting, but that's the way to madness. I can understand
code depending on SMP vs. UP and similar beasts, but presense of specific
filesystems.... <shudder>

> Should uncommon-but-widely-used things like socket and shmem have their
> own slab cache, or should they just allocate from the generic size-32 slab?

That's pretty interesting - especially for sockets. I wonder whether
we would get problems with separate allocation of these - we don't
go from inode to socket all that often, but...

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This archive was generated by hypermail 2b29 : Mon Apr 30 2001 - 21:00:12 EST