On Tue, Dec 07, 2021 at 11:19:35AM +0000, David Howells wrote: > Taking sb_writers whilst holding mmap_lock isn't allowed and will result in > a lockdep warning like that below. The problem comes from cachefiles > needing to take the sb_writers lock in order to do a write to the cache, > but being asked to do this by netfslib called from readpage, readahead or > write_begin[1]. Isn't it taking sb_writers _on a different filesystem_? So there's not a real deadlock here, just a need to tell lockdep that this is a different subclass of lock?
