diff mercurial/util.py @ 13204:5b83ab614dab stable

checknlink: use two testfiles (issue2543) Preventing file loss repository corruption (e.g. vanished changelog.i) when Mercurial pushes to repositories on Windows shares served by Samba. This is a workaround for Samba bug 7863, which is present in current latest stable Samba 3.5.6 and various prior versions down to 3.0.26a (the oldest one I tested). Of course this should be fixed in Samba, but there probably aren't that many other applications who use hardlinks that extensively and keep files open like Mercurial, so the pressure to fix this on Samba is probably not that high. And even if the Samba project should be able to fix their bug within a month or two, it will take quite some time until users upgrade their Samba installs.
author Adrian Buehlmann <adrian@cadifra.com>
date Mon, 13 Dec 2010 22:38:06 +0100
parents 6c9345f9edca
children 18f0084a97c8 5d0a30fad7de
line wrap: on
line diff
--- a/mercurial/util.py	Sun Dec 19 21:49:54 2010 -0500
+++ b/mercurial/util.py	Mon Dec 13 22:38:06 2010 +0100
@@ -717,21 +717,37 @@
 
 def checknlink(testfile):
     '''check whether hardlink count reporting works properly'''
-    f = testfile + ".hgtmp"
 
+    # testfile may be open, so we need a separate file for checking to
+    # work around issue2543 (or testfile may get lost on Samba shares)
+    f1 = testfile + ".hgtmp1"
+    if os.path.lexists(f1):
+        return False
     try:
-        os_link(testfile, f)
-    except OSError:
+        posixfile(f1, 'w').close()
+    except IOError:
         return False
 
+    f2 = testfile + ".hgtmp2"
+    fd = None
     try:
+        try:
+            os_link(f1, f2)
+        except OSError:
+            return False
+
         # nlinks() may behave differently for files on Windows shares if
         # the file is open.
-        fd = open(f)
-        return nlinks(f) > 1
+        fd = open(f2)
+        return nlinks(f2) > 1
     finally:
-        fd.close()
-        os.unlink(f)
+        if fd is not None:
+            fd.close()
+        for f in (f1, f2):
+            try:
+                os.unlink(f)
+            except OSError:
+                pass
 
     return False