[RFC 1/3] hugetlbfs: add reserved mount fields to subpool structure

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

Add a boolean to the subpool structure to indicate that the pages for
subpool have been reserved.  The hstate pointer in the subpool is
convenient to have when it comes time to unreserve the pages.
subool_reserved() is a handy way to check if reserved and take into
account a NULL subpool.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
---
 include/linux/hugetlb.h | 6 ++++++
 mm/hugetlb.c            | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 431b7fc..605c648 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -23,6 +23,8 @@ struct hugepage_subpool {
 	spinlock_t lock;
 	long count;
 	long max_hpages, used_hpages;
+	struct hstate *hstate;
+	bool reserved;
 };
 
 struct resv_map {
@@ -38,6 +40,10 @@ extern int hugetlb_max_hstate __read_mostly;
 #define for_each_hstate(h) \
 	for ((h) = hstates; (h) < &hstates[hugetlb_max_hstate]; (h)++)
 
+static inline bool subpool_reserved(struct hugepage_subpool *spool)
+{
+	return spool && spool->reserved;
+}
 struct hugepage_subpool *hugepage_new_subpool(long nr_blocks);
 void hugepage_put_subpool(struct hugepage_subpool *spool);
 
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 85032de..c6adf65 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -85,6 +85,8 @@ struct hugepage_subpool *hugepage_new_subpool(long nr_blocks)
 	spool->count = 1;
 	spool->max_hpages = nr_blocks;
 	spool->used_hpages = 0;
+	spool->hstate = NULL;
+	spool->reserved = false;
 
 	return spool;
 }
-- 
2.1.0

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