[PATCH 7/7] fs: Fix a confusing error about overlapping regions

[Tom Rini]

On Tue, Sep 05, 2023 at 12:16:56PM -0600, Simon Glass wrote:
> Hi Tom,
> 
> On Sun, 3 Sept 2023 at 13:25, Tom Rini <trini at konsulko.com> wrote:
> >
> > On Sun, Sep 03, 2023 at 12:06:13PM -0600, Simon Glass wrote:
> > > Hi Tom,
> > >
> > > On Sun, 3 Sept 2023 at 10:42, Tom Rini <trini at konsulko.com> wrote:
> > > >
> > > > On Thu, Aug 31, 2023 at 06:15:19PM -0600, Simon Glass wrote:
> > > > > Hi Tom,
> > > > >
> > > > > On Wed, 23 Aug 2023 at 09:14, Tom Rini <trini at konsulko.com> wrote:
> > > > > >
> > > > > > On Wed, Aug 23, 2023 at 07:42:03AM -0600, Simon Glass wrote:
> > > > > >
> > > > > > > When lmb runs out of space in its internal tables, it gives
> errors on
> > > > > > > every fs load operation. This is horribly confusing, as the
> poor user
> > > > > > > tries different memory regions one at a time.
> > > > > > >
> > > > > > > Use the updated API to check the error code and print a helpful
> message.
> > > > > > > Also, allow the operation to proceed.
> > > > > > >
> > > > > > > Update the tests accordingly.
> > > > > > >
> > > > > > > Signed-off-by: Simon Glass <sjg at chromium.org>
> > > > > > [snip]
> > > > > > > +     if (ret == -E2BIG) {
> > > > > > > +             log_warning("Reservation tables exhausted: see
> CONFIG_LMB_USE_MAX_REGIONS\n");
> > > > > > > +             return 0;
> > > > > > > +     }
> > > > > >
> > > > > > This isn't the right option.  Everyone has
> CONFIG_LMB_USE_MAX_REGIONS
> > > > > > set.  You would want to increase CONFIG_LMB_MAX_REGIONS.
> > > > > >
> > > > > > But it sounds like what you've found and fixed is an underlying
> problem
> > > > > > as to why 16 regions isn't enough in some common cases now?  So
> we could
> > > > >
> > > > > I don't think I have fixed anything. But I'll send v2 and perhaps it
> > > > > will be clearer what is going on here.
> > > > >
> > > > > > possibly avoid the string size growth here and have a comment
> that also
> > > > > > matches up with the help under LMB_MAX_REGIONS?
> > > > >
> > > > > I don't know, sorry. The size of struct(lmb) on 64-bit sandbox is
> > > > > about 400 bytes. There seems to be a lot of code to save not much
> > > > > memory.
> > > >
> > > > What do you mean here?  The alternative is not unlimited ranges but
> > > > instead to define the limit of memory regions and limit of reserved
> > > > ranges.
> > >
> > > A better alternative would be not to limit the number of regions, IMO,
> > > i.e. have an array of regions that can grow as needed.
> >
> > That's not something that we have in the code today, however.
> 
> No, I do have an arraylist thing that I plan to upstream, which could
> handle that.
> 
> But for this series, what do you think of the memregion idea? I am still
> unsure of the saming we should use - see Heinrich's comments too.

My biggest worry here is that we're papering over a real issue, and
should either dig at that and see what's going on (should something be
coalescing adjacent allocations? Were many platforms just right at the
previous limit?) or just bump the default from 16 to "64 if EFI_LOADER"
and then see if anything else really needs tweaking / cleaning up in the
code itself.  I know Heinrich has previously said the LMB system could
be better (or something to that effect, I'm going from memory, sorry if
I'm mis-stating things) and I don't object to replacing what we have
with something more robust/smarter/etc.

-- 
Tom
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