gfs2: Fix mmap locking for write faults

When a write fault occurs, we need to take the inode glock of the underlying
inode in exclusive mode.  Otherwise, there's no guarantee that the dirty page
will be written back to disk.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 493a83e3f59061d59f163abb637e28a614b77e79..8a35a0196b6da9c0ec783c0a7aff9019db4d6e22 100644 (file)
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -540,9 +540,11 @@ static vm_fault_t gfs2_fault(struct vm_fault *vmf)
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_holder gh;
        vm_fault_t ret;
+       u16 state;
        int err;
 
-       gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
+       state = (vmf->flags & FAULT_FLAG_WRITE) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
+       gfs2_holder_init(ip->i_gl, state, 0, &gh);
        err = gfs2_glock_nq(&gh);
        if (err) {
                ret = block_page_mkwrite_return(err);