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, 2 insertions, 1 deletions

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index bc73726..d648867 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);