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>

2 files changed, 7 insertions, 8 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;
 
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index bc737261f234..d6488674d916 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -810,7 +810,8 @@ static void gfs2_dirty_inode(struct inode *inode, int flags)
                         return;
                 }
                 need_unlock = 1;
-        }
+        } else if (WARN_ON_ONCE(ip->i_gl->gl_state != LM_ST_EXCLUSIVE))
+                return;
 
         if (current->journal_info == NULL) {
                 ret = gfs2_trans_begin(sdp, RES_DINODE, 0);