From 7ae93cf40ab91965147055100432961436bce46c Mon Sep 17 00:00:00 2001 From: Rasmus Villemoes Date: Tue, 10 Jul 2018 14:03:34 +0200 Subject: bb/utils.py: add break_hardlinks helper bb.utils.copyfile is called in a few places with identical src and dst in order to create an st_nlinks==1 version of the file. That that even works relies on an implementation detail of copyfile (namely, that it creates a temporary file and then does a rename). Moreover, it's a waste of time if the file already has st_nlinks==1. So create a helper that optimizes away the copy in the st_nlinks==1 case. Of course, this helper relies on the same implementation detail, but that's now contained within bb.utils itself. To test that we do at least sometimes hit the no-copy path, I tested locally with if sstat[stat.ST_NLINK] == 1: + bb.note("Woohoo, 2*%d bytes I/O avoided" % sstat[stat.ST_SIZE]) return True (and the obvious places in oe-core patched), and the do_package log files are indeed filled with woohoo notes. Signed-off-by: Rasmus Villemoes Signed-off-by: Richard Purdie --- lib/bb/utils.py | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/lib/bb/utils.py b/lib/bb/utils.py index b20cdabcf..56894f130 100644 --- a/lib/bb/utils.py +++ b/lib/bb/utils.py @@ -906,6 +906,23 @@ def copyfile(src, dest, newmtime = None, sstat = None): newmtime = sstat[stat.ST_MTIME] return newmtime +def break_hardlinks(src, sstat = None): + """ + Ensures src is the only hardlink to this file. Other hardlinks, + if any, are not affected (other than in their st_nlink value, of + course). Returns true on success and false on failure. + + """ + try: + if not sstat: + sstat = os.lstat(src) + except Exception as e: + logger.warning("break_hardlinks: stat of %s failed (%s)" % (src, e)) + return False + if sstat[stat.ST_NLINK] == 1: + return True + return copyfile(src, src, sstat=sstat) + def which(path, item, direction = 0, history = False, executable=False): """ Locate `item` in the list of paths `path` (colon separated string like $PATH). -- cgit 1.2.3-korg