Date: Tue, 5 Apr 2011 17:16:31 +0300 From: Kostik Belousov <kostikbel@gmail.com> To: freebsd-fs@freebsd.org Subject: Knob to turn off _POSIX_NO_TRUNC Message-ID: <20110405141631.GA78089@deviant.kiev.zoral.com.ua>
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From very old and gloomy SysV times I remembered filesystem behaviour
that silently truncated the file name components to the NAME_MAX limit,
that was, AFAIR, 14. To much of my dismay, I met some usermode software
recently that blindly tried to create the file from externally provided
name, and sometimes failed with ENAMETOOLONG in similar situation.
The authors are not cooperative.
I ended up with the following hack, which almost turns off the
_POSIX_NO_TRUNC behaviour, globally on the system. Patch allowed me
to proceed. The cost in the default case is a single check, which is
performed only on ENAMETOOLONG path.
I am too chicken to commit it without prior discussion.
diff --git a/sys/kern/vfs_lookup.c b/sys/kern/vfs_lookup.c
index 50a2570..e9e7697 100644
--- a/sys/kern/vfs_lookup.c
+++ b/sys/kern/vfs_lookup.c
@@ -99,6 +99,11 @@ SYSCTL_INT(_vfs, OID_AUTO, lookup_shared, CTLFLAG_RW, &lookup_shared, 0,
"Enables/Disables shared locks for path name translation");
TUNABLE_INT("vfs.lookup_shared", &lookup_shared);
+static int lookup_trim;
+SYSCTL_INT(_vfs, OID_AUTO, lookup_trim, CTLFLAG_RW, &lookup_trim, 0,
+ "Enables/Disables trim of the long path component instead of ENAMETOOLONG");
+TUNABLE_INT("vfs.lookup_trim", &lookup_trim);
+
/*
* Convert a pathname into a pointer to a locked vnode.
*
@@ -514,8 +519,14 @@ dirloop:
continue;
cnp->cn_namelen = cp - cnp->cn_nameptr;
if (cnp->cn_namelen > NAME_MAX) {
- error = ENAMETOOLONG;
- goto bad;
+ if (!lookup_trim) {
+ error = ENAMETOOLONG;
+ goto bad;
+ }
+ ndp->ni_pathlen -= cnp->cn_namelen - NAME_MAX;
+ cnp->cn_namelen = NAME_MAX;
+ strcpy(cnp->cn_nameptr + cnp->cn_namelen, cp);
+ cp = cnp->cn_nameptr + cnp->cn_namelen;
}
#ifdef NAMEI_DIAGNOSTIC
{ char c = *cp;
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