On 6/17/20 8:45 PM, 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).
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.
OK, I will try that and run my test. If it pass, I will post a new patch
with the suggested change.
Thanks,
Longman
