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authorRasmus Villemoes <rasmus.villemoes@prevas.dk>2018-07-10 14:03:34 +0200
committerRichard Purdie <richard.purdie@linuxfoundation.org>2018-08-16 09:50:38 +0100
commit7ae93cf40ab91965147055100432961436bce46c (patch)
treec8bb389ce8328efb76b1a65db57128ef7a71e15a
parent99d9e4389e1f1d78d17a23ee078fe3f4a12cb31d (diff)
downloadbitbake-contrib-7ae93cf40ab91965147055100432961436bce46c.tar.gz
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 <rasmus.villemoes@prevas.dk> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
-rw-r--r--lib/bb/utils.py17
1 files changed, 17 insertions, 0 deletions
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).