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author | Rasmus Villemoes <rasmus.villemoes@prevas.dk> | 2018-07-10 14:03:34 +0200 |
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committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2018-08-16 09:50:38 +0100 |
commit | 7ae93cf40ab91965147055100432961436bce46c (patch) | |
tree | c8bb389ce8328efb76b1a65db57128ef7a71e15a /lib/bb/utils.py | |
parent | 99d9e4389e1f1d78d17a23ee078fe3f4a12cb31d (diff) | |
download | bitbake-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>
Diffstat (limited to 'lib/bb/utils.py')
-rw-r--r-- | lib/bb/utils.py | 17 |
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). |