On Tue, 22 Mar 2022, Eric Wheeler wrote: > On Mon, 21 Mar 2022, Ming Lei wrote: > > On Sat, Mar 19, 2022 at 10:14:29AM -0700, Eric Wheeler wrote: > > > Hello all, > > > > > > In loop.c do_req_filebacked() for REQ_OP_FLUSH, lo_req_flush() is called: > > > it does not appear that lo_req_flush() does anything to make sure > > > ki_complete has been called for pending work, it just calls vfs_fsync(). > > > > > > Is this a consistency problem? > > > > No. What FLUSH command provides is just flushing cache in device side to > > storage medium, so it is nothing to do with pending request. > > If a flush follows a series of writes, would it be best if the flush > happened _after_ those writes complete? Then then the storage medium will > be sure to flush what was intended to be written. > > It seems that this series of events could lead to inconsistent data: > loop -> filesystem > write a > write b > flush > write a > flush > write b > crash, b is lost > > If write+flush ordering is _not_ important, then can you help me > understand why? > Hi Ming, just checking in: did you see the message above? Do you really mean to say that reordering writes around a flush is safe in the presence of a crash? -- Eric Wheeler > -Eric > > > > > > > > > Thanks, > > Ming > > > > >
