[DEBUG PATCH 2/2] silent warnings which we cannot do anything about

[Michal Hocko]

From: Michal Hocko <mhocko at suse.com>

THIS PATCH IS FOR TESTING ONLY AND NOT MEANT TO HIT LINUS TREE

There are some code paths used by all the filesystems which we cannot
change to drop the GFP_NOFS, yet they generate a lot of warnings.
Provide {disable,enable}_scope_gfp_check to silence those.
alloc_page_buffers and grow_dev_page are silenced right away.

Signed-off-by: Michal Hocko <mhocko at suse.com>
---
 fs/buffer.c           |  4 ++++
 include/linux/sched.h | 11 +++++++++++
 mm/page_alloc.c       |  3 +++
 3 files changed, 18 insertions(+)

diff --git a/fs/buffer.c b/fs/buffer.c
index d21771fcf7d3..d27e8f05f736 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -873,7 +873,9 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 	head = NULL;
 	offset = PAGE_SIZE;
 	while ((offset -= size) >= 0) {
+		disable_scope_gfp_check();
 		bh = alloc_buffer_head(GFP_NOFS);
+		enable_scope_gfp_check();
 		if (!bh)
 			goto no_grow;
 
@@ -1003,7 +1005,9 @@ grow_dev_page(struct block_device *bdev, sector_t block,
 	 */
 	gfp_mask |= __GFP_NOFAIL;
 
+	disable_scope_gfp_check();
 	page = find_or_create_page(inode->i_mapping, index, gfp_mask);
+	enable_scope_gfp_check();
 	if (!page)
 		return ret;
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 288946bfc326..b379ef9ed464 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1988,6 +1988,7 @@ struct task_struct {
 	/* A live task holds one reference. */
 	atomic_t stack_refcount;
 #endif
+	bool disable_scope_gfp_warn;
 	unsigned long nofs_caller;
 	unsigned long noio_caller;
 /* CPU-specific state of this task */
@@ -2390,6 +2391,16 @@ static inline unsigned int __memalloc_nofs_save(unsigned long caller)
 	return flags;
 }
 
+static inline void disable_scope_gfp_check(void)
+{
+	current->disable_scope_gfp_warn = true;
+}
+
+static inline void enable_scope_gfp_check(void)
+{
+	current->disable_scope_gfp_warn = false;
+}
+
 #define memalloc_nofs_save()	__memalloc_nofs_save(_RET_IP_)
 
 static inline void memalloc_nofs_restore(unsigned int flags)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9e35fb2a8681..7ecae58abf74 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3758,6 +3758,9 @@ void debug_scope_gfp_context(gfp_t gfp_mask)
 	if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
 		return;
 
+	if (current->disable_scope_gfp_warn)
+		return;
+
 	if (current->flags & PF_MEMALLOC_NOIO)
 		restrict_mask = __GFP_IO;
 	else if ((current->flags & PF_MEMALLOC_NOFS) && (gfp_mask & __GFP_IO))
-- 
2.10.2