Re: Are there limitation to the number of named pipes/FIFO's supported by F2FS?

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 09/05, Patrick Doyle wrote:
> On Wed, Sep 5, 2018 at 11:57 AM Chao Yu <chao@kernel.org> wrote:
> > If there is any chance to retry f2fs, let f2fs guys know anything we can help. :)
> >
> Thank you.  If I have the opportunity to do that, I'll let you know.
> 
> As far as opportunities are concerned, I could just buy (have my
> employer buy) another 1TB SSD, stick it in my system, format it with
> F2FS, and see if I run into these sorts of issues again.  All that
> would take is time, which is in short supply right now.  But it's not
> out of the question.
> 
> > >
> > > For your own reference, I am running my production system on Ubuntu
> > > 16.04 LTS with a "4.15.0-33-generic" kernel.
> >
> > Large nat bitmap feature was supported in 4.17, old kernel can not recognize the
> > feature flag set in mkfs, to make sure, are you porting last f2fs to 4.15?
> What is the "Large nat bitmap feature"? (Now you've got me curious).
> 
> Would that have been turned on by default with the 1.11.0 version of
> mkfs.f2fs I used to gain access to the "-i" option?

I'm quite surprised that there was a case requiring over 10M files. I'm
little bit hesitate to enable this by default due to old kernel issue and
runtime checkpoint overheads given more data writes.

df -i:
         w/o -i       w/ -i
256GB   12812797    12346877
512GB   11800957    24926717
1TB     10017277    48688637

> 
> >
> > To Jaegeuk,
> >
> > Anyway, I think we'd better to add some warn info during formatting with an
> > upgraded mkfs, so that it can reduce the possiblity of encountering incompatible
> > issue between new mkfs and old kernel.
> I think it would also be worthwhile also to submit patches to the LTS
> kernels that would check for an inhibit mounting of F2FS filesystems
> that have features unsupported by the kernel.  If that is already in
> place, then I shouldn't have been able to mount my f2fs partition if
> it had the "Large nat bitmap feature" enabled.

Agreed, but I haven't taken a look at how ubuntu maintains their kernels.
BTW, 4.17-stable is EOL, and next -stable is 4.18.6.

> 
> --wpd

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