kernfs: invoke kernfs_unmap_bin_file() directly from kernfs_deactivate()

kernfs_unmap_bin_file() is supposed to unmap all memory mappings of
the target file before kernfs_remove() finishes; however, it currently
is being called from kernfs_addrm_finish() and has the same race
problem as the original implementation of deactivation when there are
multiple removers - only the remover which snatches the node to its
addrm_cxt->removed list is guaranteed to wait for its completion
before returning.

It can be easily fixed by moving kernfs_unmap_bin_file() invocation
from kernfs_addrm_finish() to kernfs_deactivated().  The function may
be called multiple times but that shouldn't do any harm.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 3ac93737174a..9603c06550a0 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -177,9 +177,10 @@ void kernfs_put_active(struct kernfs_node *kn)
  *      kernfs_deactivate - deactivate kernfs_node
  *      @kn: kernfs_node to deactivate
  *
- *      Deny new active references and drain existing ones.  Mutiple
- *      removers may invoke this function concurrently on @kn and all will
- *      return after deactivation and draining are complete.
+ *      Deny new active references, drain existing ones and nuke all
+ *      existing mmaps.  Mutiple removers may invoke this function
+ *      concurrently on @kn and all will return after deactivation and
+ *      draining are complete.
  */
 static void kernfs_deactivate(struct kernfs_node *kn)
         __releases(&kernfs_mutex) __acquires(&kernfs_mutex)
@@ -213,6 +214,8 @@ static void kernfs_deactivate(struct kernfs_node *kn)
                 rwsem_release(&kn->dep_map, 1, _RET_IP_);
         }
 
+        kernfs_unmap_bin_file(kn);
+
         mutex_lock(&kernfs_mutex);
 }
 
@@ -493,7 +496,6 @@ void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)
 
                 acxt->removed = kn->u.removed_list;
 
-                kernfs_unmap_bin_file(kn);
                 kernfs_put(kn);
         }
 }