On Sat, 26 Jan 2013, Dave Chinner wrote: > Date: Sat, 26 Jan 2013 12:00:55 +1100 > From: Dave Chinner <david@xxxxxxxxxxxxx> > To: Theodore Ts'o <tytso@xxxxxxx> > Cc: Lukáš Czerner <lczerner@xxxxxxxxxx>, linux-ext4@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2] ext4: call WARN_ON after the debug message > > On Fri, Jan 25, 2013 at 10:09:48AM -0500, Theodore Ts'o wrote: > > On Fri, Jan 25, 2013 at 10:22:44AM +0100, Lukáš Czerner wrote: > > > > > > we can get the EIO error from ext4_map_blocks not only in the case > > > of hardware error. The extent tree might not be in consistent state, > > > or we could even ask for blocks outside the file system itself (I > > > believe I've seen this before) and I think that in those cases it > > > might be worth to all WARN_ON. > > > > Sure, but in those cases, the file system is corrupt, and we should > > have thrown an ext4_error() in ext4_map_blocks(). The point is that a > > WARN_ON is only useful if there is a potential programming bug. If we > > know for sure that it's caused by a file system corruption, then we > > don't want to throw a WARN_ON. > > FWIW, XFS handles this problem with an error level sysctl. For > situations like this, the default level doesn't throw stack traces > (just the error message), but there are situations where diagnosis > requires emitting the stack trace. > > Hence if it is necessary for bug triage, users can then turn the > sysctl up to 11 and the stack trace will be emitted after the > warning message. CONFIG_XFS_DEBUG sets the default log level to 11, > because developers always want to know where an error came from ;) > > Cheers, > > Dave. > That might actually be very useful. Thanks Dave! -Lukas
