The PF_MEMALLOC_NORECLAIM flag was introduced in commit eab0af905bfc
("mm: introduce PF_MEMALLOC_NORECLAIM, PF_MEMALLOC_NOWARN"). To complement
this, let's add two helper functions, memalloc_nowait_{save,restore}, which
will be useful in scenarios where we want to avoid waiting for memory
reclamation.
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
---
include/linux/sched/mm.h | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 91546493c43d..4fbae0013166 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -484,6 +484,36 @@ static inline void memalloc_pin_restore(unsigned int flags)
memalloc_flags_restore(flags);
}
+/**
+ * memalloc_nowait_save - Marks implicit ~__GFP_DIRECT_RECLAIM allocation scope.
+ *
+ * This functions marks the beginning of the ~__GFP_DIRECT_RECLAIM allocation
+ * scope. All further allocations will implicitly drop __GFP_DIRECT_RECLAIM flag
+ * and so they are won't wait for direct memory reclaiming. Use
+ * memalloc_nowait_restore to end the scope with flags returned by this
+ * function.
+ *
+ * Context: This function is safe to be used from any context.
+ * Return: The saved flags to be passed to memalloc_nowait_restore.
+ */
+static inline unsigned int memalloc_nowait_save(void)
+{
+ return memalloc_flags_save(PF_MEMALLOC_NORECLAIM);
+}
+
+/**
+ * memalloc_nofs_restore - Ends the implicit ~__GFP_DIRECT_RECLAIM scope.
+ * @flags: Flags to restore.
+ *
+ * Ends the implicit ~__GFP_DIRECT_RECLAIM scope started by memalloc_nowait_save
+ * function. Always make sure that the given flags is the return value from the
+ * pairing memalloc_nowait_save call.
+ */
+static inline void memalloc_nowait_restore(unsigned int flags)
+{
+ memalloc_flags_restore(flags);
+}
+
#ifdef CONFIG_MEMCG
DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
/**
--
2.43.5
