• Henry Wilson's avatar
    inotify: Add flag IN_MASK_CREATE for inotify_add_watch() · 4d97f7d5
    Henry Wilson authored
    The flag IN_MASK_CREATE is introduced as a flag for inotiy_add_watch()
    which prevents inotify from modifying any existing watches when invoked.
    If the pathname specified in the call has a watched inode associated
    with it and IN_MASK_CREATE is specified, fail with an errno of EEXIST.
    
    Use of IN_MASK_CREATE with IN_MASK_ADD is reserved for future use and
    will return EINVAL.
    
    RATIONALE
    
    In the current implementation, there is no way to prevent
    inotify_add_watch() from modifying existing watch descriptors. Even if
    the caller keeps a record of all watch descriptors collected, this is
    only sufficient to detect that an existing watch descriptor may have
    been modified.
    
    The assumption that a particular path will map to the same inode over
    multiple calls to inotify_add_watch() cannot be made as files can be
    renamed or deleted.  It is also not possible to assume that two distinct
    paths do no map to the same inode, due to hard-links or a dereferenced
    symbolic link. Further uses of inotify_add_watch() to revert the change
    may cause other watch descriptors to be modified or created, merely
    compunding the problem. There is currently no system call such as
    inotify_modify_watch() to explicity modify a watch descriptor, which
    would be able to revert unwanted changes. Thus the caller cannot
    guarantee to be able to revert any changes to existing watch decriptors.
    
    Additionally the caller cannot assume that the events that are
    associated with a watch descriptor are within the set requested, as any
    future calls to inotify_add_watch() may unintentionally modify a watch
    descriptor's mask. Thus it cannot currently be guaranteed that a watch
    descriptor will only generate events which have been requested. The
    program must filter events which come through its watch descriptor to
    within its expected range.
    Reviewed-by: Amir Goldstein's avatarAmir Goldstein <amir73il@gmail.com>
    Signed-off-by: default avatarHenry Wilson <henry.wilson@acentic.com>
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    4d97f7d5
inotify.h 713 Bytes