GFS2: Don't call file_accessed() with a shared glock

file_accessed() was being called by gfs2_mmap() with a shared glock. If it
needed to update the atime, it was crashing because it dirtied the inode in
gfs2_dirty_inode() without holding an exclusive lock. gfs2_dirty_inode()
checked if the caller was already holding a glock, but it didn't make sure that
the glock was in the exclusive state. Now, instead of calling file_accessed()
while holding the shared lock in gfs2_mmap(), file_accessed() is called after
grabbing and releasing the glock to update the inode.  If file_accessed() needs
to update the atime, it will grab an exclusive lock in gfs2_dirty_inode().

gfs2_dirty_inode() now also checks to make sure that if the calling process has
already locked the glock, it has an exclusive lock.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 5 insertions, 7 deletions

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 377a68dbd066..e056b4ce4877 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -516,15 +516,13 @@ static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
 		struct gfs2_holder i_gh;
 		int error;
 
-		gfs2_holder_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY, &i_gh);
-		error = gfs2_glock_nq(&i_gh);
-		if (error == 0) {
-			file_accessed(file);
-			gfs2_glock_dq(&i_gh);
-		}
-		gfs2_holder_uninit(&i_gh);
+		error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
+					   &i_gh);
 		if (error)
 			return error;
+		/* grab lock to update inode */
+		gfs2_glock_dq_uninit(&i_gh);
+		file_accessed(file);
 	}
 	vma->vm_ops = &gfs2_vm_ops;