• Steven Rostedt (Red Hat)'s avatar
    tracing: Have mkdir and rmdir be part of tracefs · eae47358
    Steven Rostedt (Red Hat) authored
    The tracing "instances" directory can create sub tracing buffers
    with mkdir, and remove them with rmdir. As a mkdir will also create
    all the files and directories that control the sub buffer the inode
    mutexes need to be released before this is done, to avoid deadlocks.
    It is better to let the tracing system unlock the inode mutexes before
    calling the functions that create the files within the new directory
    (or deletes the files from the one being destroyed).
    
    Now that tracing has been converted over to tracefs, the tracefs file
    system can be modified to accommodate this feature. It still releases
    the locks, but the filesystem itself can take care of the ugly
    business and let the user just do what it needs.
    
    The tracing system now attaches a descriptor to the directory dentry
    that can have userspace create or remove sub directories. If this
    descriptor does not exist for a dentry, then that dentry can not be
    used to create other directories. This descriptor holds a mkdir and
    rmdir method that only takes a character string as an argument.
    
    The tracefs file system will first make a copy of the dentry name
    before releasing the locks. Then it will pass the copied name to the
    methods. It is up to the tracing system that supplied the methods to
    handle races with duplicate names and such as all the inode mutexes
    would be released when the functions are called.
    
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
    eae47358
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