On Thu, Sep 28, 2017 at 08:39:33AM -0400, Mimi Zohar wrote: > Don't attempt to take the i_rwsem, if it has already been taken > exclusively. > > Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx> That's bloody awful. The locking in filesystem IO paths is already complex enough without adding a new IO path semantic that says "caller has already locked the i_rwsem in some order and some dependencies that we have no idea about". Instead of having well defined locking in a small amount of self contained code, we've now got to search through completely unfamiliar code to analyse any sort of filesystem lockdep report or deadlock to determine if that somethign else has screwed up the filesystem IO path locking. It also seems to have an undocumented semantic of not updating access times on the inode, which effectively makes this invisible IO and means we're assuming that timestamp updates will be done by correctly callers outside the filesystem IO path. That's almost certainly going to be a source of bugs in the future. This seems like a recipe for future disasters to me.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
