[PATCH 04/12] kernfs: invoke kernfs_unmap_bin_file() directly from kernfs_deactivate()

From: Tejun Heo
Date: Tue Jan 07 2014 - 13:00:31 EST


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@xxxxxxxxxx>
---
fs/kernfs/dir.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index a73caa6..ff633d2 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)
@@ -209,6 +210,8 @@ static void kernfs_deactivate(struct kernfs_node *kn)
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);

+ kernfs_unmap_bin_file(kn);
+
mutex_lock(&kernfs_mutex);
}

@@ -477,7 +480,6 @@ void kernfs_addrm_finish(struct kernfs_addrm_cxt *acxt)

acxt->removed = kn->u.removed_list;

- kernfs_unmap_bin_file(kn);
kernfs_put(kn);
}
}
--
1.8.4.2

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