[PATCH] Fix get_unmapped_area and fsync for hugetlb shm segments

This patch provides the following hugetlb-related fixes to the recent stacked
shm files changes:
 - Update is_file_hugepages() so it will reconize hugetlb shm segments.
 - get_unmapped_area must be called with the nested file struct to handle
   the sfd->file->f_ops->get_unmapped_area == NULL case.
 - The fsync f_op must be wrapped since it is specified in the hugetlbfs
   f_ops.

This is based on proposed fixes from Eric Biederman that were debugged and
tested by me.  Without it, attempting to use hugetlb shared memory segments
on powerpc (and likely ia64) will kill your box.

Signed-off-by: Adam Litke <agl@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: William Irwin <bill.irwin@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index a60995a..3f3e7a6 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -4,6 +4,7 @@
 #ifdef CONFIG_HUGETLB_PAGE
 
 #include <linux/mempolicy.h>
+#include <linux/shm.h>
 #include <asm/tlbflush.h>
 
 struct ctl_table;
@@ -168,7 +169,12 @@ void hugetlb_put_quota(struct address_space *mapping);
 
 static inline int is_file_hugepages(struct file *file)
 {
-	return file->f_op == &hugetlbfs_file_operations;
+	if (file->f_op == &hugetlbfs_file_operations)
+		return 1;
+	if (is_file_shm_hugepages(file))
+		return 1;
+
+	return 0;
 }
 
 static inline void set_file_hugepages(struct file *file)
diff --git a/include/linux/shm.h b/include/linux/shm.h
index a2c896a..ad2e3af 100644
--- a/include/linux/shm.h
+++ b/include/linux/shm.h
@@ -96,12 +96,17 @@ struct shmid_kernel /* private to the kernel */
 
 #ifdef CONFIG_SYSVIPC
 long do_shmat(int shmid, char __user *shmaddr, int shmflg, unsigned long *addr);
+extern int is_file_shm_hugepages(struct file *file);
 #else
 static inline long do_shmat(int shmid, char __user *shmaddr,
 				int shmflg, unsigned long *addr)
 {
 	return -ENOSYS;
 }
+static inline int is_file_shm_hugepages(struct file *file)
+{
+	return 0;
+}
 #endif
 
 #endif /* __KERNEL__ */