On Thu, Jun 18, 2020 at 10:45:05AM +1000, Dave Chinner wrote: > On Wed, Jun 17, 2020 at 01:53:10PM -0400, Waiman Long wrote: > > fs/xfs/xfs_log.c | 9 +++++++++ > > fs/xfs/xfs_trans.c | 31 +++++++++++++++++++++++++++---- > > 2 files changed, 36 insertions(+), 4 deletions(-) > > > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > > index 00fda2e8e738..33244680d0d4 100644 > > --- a/fs/xfs/xfs_log.c > > +++ b/fs/xfs/xfs_log.c > > @@ -830,8 +830,17 @@ xlog_unmount_write( > > xfs_lsn_t lsn; > > uint flags = XLOG_UNMOUNT_TRANS; > > int error; > > + unsigned long pflags; > > > > + /* > > + * xfs_log_reserve() allocates memory. This can lead to fs reclaim > > + * which may conflicts with the unmount process. To avoid that, > > + * disable fs reclaim for this allocation. > > + */ > > + current_set_flags_nested(&pflags, PF_MEMALLOC_NOFS); > > error = xfs_log_reserve(mp, 600, 1, &tic, XFS_LOG, 0); > > + current_restore_flags_nested(&pflags, PF_MEMALLOC_NOFS); > > + > > if (error) > > goto out_err; > > The more I look at this, the more I think Darrick is right and I > somewhat misinterpretted what he meant by "the top of the freeze > path". > > i.e. setting PF_MEMALLOC_NOFS here is out of place - only one caller > of xlog_unmount_write requires PF_MEMALLOC_NOFS > context. That context should be set in the caller that requires this > context, and in this case it is xfs_fs_freeze(). This is top of the > final freeze state processing (what I think Darrick meant), not the > top of the freeze syscall call chain (what I thought he meant). Aha! Yes, that's exactly what I meant. Sorry we all kinda muddled around for a few days. :/ --D > So if set PF_MEMALLOC_NOFS setting in xfs_fs_freeze(), it covers all > the allocations in this problematic path, and it should obliviates > the need for the first patch in the series altogether. > > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
