Messages in this thread | | | Date | Tue, 3 Jul 2018 19:43:31 -0400 | From | "Theodore Y. Ts'o" <> | Subject | Re: [PATCH 1/2] fs: ext4: use BUG_ON if writepage call comes from direct reclaim |
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On Tue, Jul 03, 2018 at 10:05:04AM -0700, Yang Shi wrote: > I'm not sure if it is a good choice to let filesystem handle such vital VM > regression. IMHO, writing out filesystem page from direct reclaim context is > a vital VM bug. It means something is definitely wrong in VM. It should > never happen.
If it does happen, it should happen reliably; this isn't the sort of thing where some linked list had gotten corrupted. This would be a structural problem in the VM code.
So presumably, if the WARN_ON triggered, it should be be noticed by VM developers, and they should fix it.
In general, though, BUG_ON's should be avoided unless there really is no way to recover.
> It sounds ok to have filesystem throw out warning and handle it, but I'm not > sure if someone will just ignore the warning, but it should *never* be > ignored.
If a kernel develper (a VM developer in this case) ignores a warning, that's just simply professional malpractice. In general WARN_ON's should only be used as a sign of a kernel bug. So they should never be ignored.
- Ted
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