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). 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 da...@fromorbit.com
