Date: Thu, 15 Jul 1999 16:45:10 +0100 From: Ian Dowse <iedowse@maths.tcd.ie> To: Jan Conrad <conrad@th.physik.uni-bonn.de> Cc: freebsd-hackers@freebsd.org Subject: Re: NFS problems due to getcwd/realpath Message-ID: <199907151645.aa25796@salmon.maths.tcd.ie> In-Reply-To: Your message of "Thu, 15 Jul 1999 14:10:52 %2B0200." <Pine.BSF.4.10.9907151329040.9501-100000@merlin.th.physik.uni-bonn.de>
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In message <Pine.BSF.4.10.9907151329040.9501-100000@merlin.th.physik.uni-bonn.d
e>, Jan Conrad writes:
>after wondering for two years why FreeBSD (2.2.x ... 3.2) might lock up
>when an NFS server is down, I think I have found one reason for that (see
>kern/12609 - I now know it doesn't belong to kern - sorry).
>
>It is the implementation of getcwd (src/lib/libc/gen/getcwd.c). When
>examining the parent dir of a mounted filesystem, getcwd lstats every
>directory entry prior to the mountpoint to find out the name of the
>mountpoint (but it would only need the inodes's device to do a rough
>check....).
This should no longer be an issue with FreeBSD 3.x, as the system normally
uses the new _getcwd syscall. The old code is still in getcwd.c, but is
only used if the syscall isn't present (e.g. if running a 3.x executable
on a 2.2 system).
We use the following patch on all our 2.2-stable machines, which works
around the problem. This was submitted as PR bin/6658, but it wasn't
committed, as a backport of 3.x's _getcwd (which never occurred) was
considered to be a more appropriate change.
Ian
--- getcwd.c.orig Tue Jun 30 15:38:44 1998
+++ getcwd.c Tue Jun 30 15:39:08 1998
@@ -36,6 +36,7 @@
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
+#include <sys/mount.h>
#include <sys/stat.h>
#include <errno.h>
@@ -169,7 +170,28 @@
if (dp->d_fileno == ino)
break;
}
- } else
+ } else {
+ struct statfs sfs;
+ char *dirname;
+
+ /*
+ * Try to get the directory name by using statfs on
+ * the mount point.
+ */
+ if (!statfs(up[3] ? up + 3 : ".", &sfs) &&
+ (dirname = rindex(sfs.f_mntonname, '/')))
+ while((dp = readdir(dir))) {
+ if (ISDOT(dp))
+ continue;
+ bcopy(dp->d_name, bup, dp->d_namlen+1);
+ if (!strcmp(dirname + 1, dp->d_name) &&
+ !lstat(up, &s) &&
+ s.st_dev == dev &&
+ s.st_ino == ino)
+ goto found;
+ }
+ rewinddir(dir);
+
for (;;) {
if (!(dp = readdir(dir)))
goto notfound;
@@ -187,7 +209,9 @@
if (s.st_dev == dev && s.st_ino == ino)
break;
}
+ }
+found:
/*
* Check for length of the current name, preceding slash,
* leading slash.
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