kernfs: invoke kernfs_unmap_bin_file() directly from kernfs_deactivate() (ccf02aaf) · Commits · 戴 / test

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>

fs/kernfs/dir.c

+6 −4

Original line number	Diff line number	Diff line
		@@ -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);
		}
		}

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