the regular expression @var{regexp}
(@code{dired-mark-files-containing-regexp}). This command is like
@kbd{% m}, except that it searches the file contents instead of the file
-name.
+name. Note that if a file is visited in an Emacs buffer, this command
+will look in the buffer without revisiting the file, so the results
+might be inconsistent with the file on disk if its contents has changed
+since it was last visited. If you don't want this, you may wish
+reverting the files you have visited in your buffers, or turning on
+the @code{auto-revert} mode in those buffers, before invoking this
+command. @xref{Reverting}.
@item C-/
@itemx C-x u