On Thu, Apr 04, 2024 at 10:33:07AM +0200, Dmitry Vyukov wrote:
> On Thu, 4 Apr 2024 at 01:59, Kent Overstreet <[email protected]> 
> wrote:
> >
> > Hi - what would it take to get syzbot going for bcachefs?
> 
> Hi Kent,
> 
> There are 2 parts:
> 
> The easy one: we need to enable it in syzbot configs. Should we
> configure it as follows?
> 
> CONFIG_BCACHEFS_FS=y
> CONFIG_BCACHEFS_QUOTA=y
> CONFIG_BCACHEFS_ERASURE_CODING=y
> CONFIG_BCACHEFS_POSIX_ACL=y
> CONFIG_BCACHEFS_DEBUG=y
> # CONFIG_BCACHEFS_TESTS is not set
> # CONFIG_BCACHEFS_LOCK_TIME_STATS is not set
> # CONFIG_BCACHEFS_NO_LATENCY_ACCT is not set
> CONFIG_BCACHEFS_SIX_OPTIMISTIC_SPIN=y
> 
> In particular, I am interested in CONFIG_BCACHEFS_DEBUG. Does it
> really add more debug checks rather than lots of console printing w/o
> checks? Some "DEBUG" kernel configs are misleading here. Checks will
> be useful on syzbot, lots of printing not so much.

CONFIG_BCACHEFS_DEBUG adds piles of assertions and no extra console
printing :)

> Second part: syzbot will need to exercise the fs in some useful way.
> Is it just a "normal" fs with files, or something special?

It's a normal - but multi device - filesystem, similar featureset to
btrfs.

> Is it mounted from an image, or an image-less fs? If it needs images,
> how can they be created?

apt install bcachefs-tools
mkfs.bcachefs <dev>
mount <dev> /mnt

...

> "find tools/testing/ Documentation/ -name "*bcachefs*"" does not give
> me anything useful.

https://bcachefs.org/ has some docs, and the tools have a man page

Anything else you'd be interested in? Thomas was interested in working
on on-disk-image error injection, is that something that would be
useful?

Ariel's also probably going to be working on adding full image creation
to mkfs, i.e. pass it a directory - is that something that would be
useful as well?

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