[PATCH 1/3] mm/hugetlb: Define hugetlb_falloc structure for hole punch race

[Mike Kravetz <mike.kravetz@oracle.com>]

A hugetlb_falloc structure is pointed to by i_private during fallocate
hole punch operations.  Page faults check this structure and if they are
in the hole, wait for the operation to finish.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 685c262..4be35b9 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -42,6 +42,16 @@ struct resv_map {
 extern struct resv_map *resv_map_alloc(void);
 void resv_map_release(struct kref *ref);
 
+/*
+ * hugetlb_falloc is used to prevent page faults during falloc hole punch
+ * operations.  During hole punch, inode->i_private points to this struct.
+ */
+struct hugetlb_falloc {
+	wait_queue_head_t *waitq;	/* Page faults waiting on hole punch */
+	pgoff_t start;			/* Start of fallocate hole */
+	pgoff_t end;			/* End of fallocate hole */
+};
+
 extern spinlock_t hugetlb_lock;
 extern int hugetlb_max_hstate __read_mostly;
 #define for_each_hstate(h) \
-- 
2.4.3

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