[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>

1 files changed, 26 insertions, 6 deletions

diff --git a/ipc/shm.c b/ipc/shm.c
index 3d0eb7940e9c..4fefbad7096d 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -285,21 +285,41 @@ static int shm_release(struct inode *ino, struct file *file)
         return 0;
 }
 
-#ifndef CONFIG_MMU
+static int shm_fsync(struct file *file, struct dentry *dentry, int datasync)
+{
+        int (*fsync) (struct file *, struct dentry *, int datasync);
+        struct shm_file_data *sfd = shm_file_data(file);
+        int ret = -EINVAL;
+
+        fsync = sfd->file->f_op->fsync;
+        if (fsync)
+                ret = fsync(sfd->file, sfd->file->f_path.dentry, datasync);
+        return ret;
+}
+
 static unsigned long shm_get_unmapped_area(struct file *file,
         unsigned long addr, unsigned long len, unsigned long pgoff,
         unsigned long flags)
 {
         struct shm_file_data *sfd = shm_file_data(file);
-        return sfd->file->f_op->get_unmapped_area(sfd->file, addr, len, pgoff,
-                                                        flags);
+        return get_unmapped_area(sfd->file, addr, len, pgoff, flags);
+}
+
+int is_file_shm_hugepages(struct file *file)
+{
+        int ret = 0;
+
+        if (file->f_op == &shm_file_operations) {
+                struct shm_file_data *sfd;
+                sfd = shm_file_data(file);
+                ret = is_file_hugepages(sfd->file);
+        }
+        return ret;
 }
-#else
-#define shm_get_unmapped_area NULL
-#endif
 
 static const struct file_operations shm_file_operations = {
         .mmap           = shm_mmap,
+        .fsync          = shm_fsync,
         .release        = shm_release,
         .get_unmapped_area      = shm_get_unmapped_area,
 };