Merge remote-tracking branch 'torvalds/master' into perf-tools-next

To pick up fixes sent via perf-tools, by Namhyung Kim.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 20 insertions, 5 deletions

diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 034a617cb1a5..a40da0065433 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -751,13 +751,28 @@ static void __debugfs_file_removed(struct dentry *dentry)
 	if ((unsigned long)fsd & DEBUGFS_FSDATA_IS_REAL_FOPS_BIT)
 		return;
 
-	/* if we hit zero, just wait for all to finish */
-	if (!refcount_dec_and_test(&fsd->active_users)) {
-		wait_for_completion(&fsd->active_users_drained);
+	/* if this was the last reference, we're done */
+	if (refcount_dec_and_test(&fsd->active_users))
 		return;
-	}
 
-	/* if we didn't hit zero, try to cancel any we can */
+	/*
+	 * If there's still a reference, the code that obtained it can
+	 * be in different states:
+	 *  - The common case of not using cancellations, or already
+	 *    after debugfs_leave_cancellation(), where we just need
+	 *    to wait for debugfs_file_put() which signals the completion;
+	 *  - inside a cancellation section, i.e. between
+	 *    debugfs_enter_cancellation() and debugfs_leave_cancellation(),
+	 *    in which case we need to trigger the ->cancel() function,
+	 *    and then wait for debugfs_file_put() just like in the
+	 *    previous case;
+	 *  - before debugfs_enter_cancellation() (but obviously after
+	 *    debugfs_file_get()), in which case we may not see the
+	 *    cancellation in the list on the first round of the loop,
+	 *    but debugfs_enter_cancellation() signals the completion
+	 *    after adding it, so this code gets woken up to call the
+	 *    ->cancel() function.
+	 */
 	while (refcount_read(&fsd->active_users)) {
 		struct debugfs_cancellation *c;