fuser: rework string comparison

This one is a patch that reworks the string comparision for file name
space in fuser. It makes the usage of this configurable with
--enable-mountinfo-list at build time as well as at runtime with
--inode. Also it uses shared memory maps to reduce the load on
write/read the stat buffers.

References:
  https://sourceforge.net/p/psmisc/patches/36/

8 files changed, 351 insertions, 171 deletions

diff --git a/ChangeLog b/ChangeLog
index 14e8df6..aa97e56 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 Changes in 22.22
 ================
+	* Make usage of linked lists of devices found in
+	  /proc/self/mountinfo optional
+	* Make timeout() in timeout.c work with shared mmap to
+	  reduce the load due write/read the stat buffers
+	* Add list_sort() to lists.h to be able to sort lists
 	* fuser: Fixed typo for  -M flag. Debian #740275
 	* pstree: by default doesn't show threadnames, use -t to show
 	  as it disables compaction. SF [#33]
diff --git a/configure.ac b/configure.ac
index 20549f6..4a159b4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -42,6 +42,17 @@ if test "$enable_timeout_stat" = "static"; then
 fi
 AM_CONDITIONAL([WANT_TIMEOUT_STAT], [test "$enable_timeout_stat" = "static"])
 
+# Use string search for network based file systems but only if the system
+# has /proc/self/mountinfo
+AC_SUBST([WITH_MOUNTINFO_LIST])
+AC_ARG_ENABLE([mountinfo_list],
+  [AS_HELP_STRING([--enable-mountinfo-list], [Use the list in /proc/self/mountinfo to replace stat(2) syscall on network file systems shares])],
+  [enable_mountinfo_list="yes"],
+  [enable_mountinfo_list="no"])
+if test "$enable_mountinfo_list" = "yes" -a -e /proc/self/mountinfo ; then
+  AC_DEFINE([WITH_MOUNTINFO_LIST], [1], [Use list in /proc/self/mountinfo to replace stat calls])
+fi
+
 # Enable hardened compile and link flags
 AC_ARG_ENABLE([harden_flags],
   [AS_HELP_STRING([--disable-harden-flags], [disable hardened compilier and linker flags])],
diff --git a/doc/fuser.1 b/doc/fuser.1
index f95e8d8..9f150da 100644
--- a/doc/fuser.1
+++ b/doc/fuser.1
@@ -120,6 +120,12 @@ silently ignored if
 .B \-k
 is not present too.
 .TP
+\fB\-I\fR, \fB\-\-inode\fR
+For the name space
+.B file
+let all comparisions be based on the inodes of the specified file(s)
+and never on the file names even on network based file systems.
+.TP
 \fB\-l\fR, \fB\-\-list\-signals\fR
 List all known signal names.
 .TP
diff --git a/src/fuser.c b/src/fuser.c
index 4eeac7d..da94d22 100644
--- a/src/fuser.c
+++ b/src/fuser.c
@@ -58,6 +58,7 @@
 #include "fuser.h"
 #include "signals.h"
 #include "i18n.h"
+#include "timeout.h"
 
 //#define DEBUG 1
 
@@ -104,25 +105,14 @@ static void debug_match_lists(struct names *names_head,
 			      struct device_list *dev_head);
 #endif
 
-#ifdef _LISTS_H
+#if defined(WITH_MOUNTINFO_LIST)
 static void clear_mntinfo(void) __attribute__ ((__destructor__));
 static void init_mntinfo(void) __attribute__ ((__constructor__));
-static dev_t device(const char *path);
+static int mntstat(const char *path, struct stat *buf);
 #endif
+static stat_t thestat = stat;
 static char *expandpath(const char *path);
 
-#ifdef WITH_TIMEOUT_STAT
-#if (WITH_TIMEOUT_STAT == 2)
-#include "timeout.h"
-#else
-typedef int (*stat_t) (const char *, struct stat *);
-static int timeout(stat_t func, const char *path, struct stat *buf,
-		   unsigned int seconds);
-#endif
-#else
-#define timeout(func,path,buf,dummy) (func)((path),(buf))
-#endif				/* WITH_TIMEOUT_STAT */
-
 static void usage(const char *errormsg)
 {
 	if (errormsg != NULL)
@@ -135,6 +125,7 @@ static void usage(const char *errormsg)
 		 "Show which processes use the named files, sockets, or filesystems.\n\n"
 		 "  -a,--all              display unused files too\n"
 		 "  -i,--interactive      ask before killing (ignored without -k)\n"
+		 "  -I,--inode            use always inodes to compare files\n"
 		 "  -k,--kill             kill processes accessing the named file\n"
 		 "  -l,--list-signals     list available signal names\n"
 		 "  -m,--mount            show all processes using the named filesystems or block device\n"
@@ -191,10 +182,6 @@ scan_procs(struct names *names_head, struct inode_list *ino_head,
 		struct stat *cwd_stat = NULL;
 		struct stat *exe_stat = NULL;
 		struct stat *root_stat = NULL;
-#ifdef _LISTS_H
-		char path[256] = "/proc/", *slash;
-		ssize_t len;
-#endif
 
 		if (topproc_dent->d_name[0] < '0' || topproc_dent->d_name[0] > '9')	/* Not a process */
 			continue;
@@ -204,30 +191,12 @@ scan_procs(struct names *names_head, struct inode_list *ino_head,
 			continue;
 		uid = getpiduid(pid);
 
-#ifdef _LISTS_H
-		strcpy(&path[6], topproc_dent->d_name);
-		len = strlen(path);
-		slash = &path[len];
-
-		*slash = '\0';
-		strcat(slash, "/cwd");
-		cwd_dev = device(path);
-
-		*slash = '\0';
-		strcat(slash, "/exe");
-		exe_dev = device(path);
-
-		*slash = '\0';
-		strcat(slash, "/root");
-		root_dev = device(path);
-#else
 		cwd_stat = get_pidstat(pid, "cwd");
 		exe_stat = get_pidstat(pid, "exe");
 		root_stat = get_pidstat(pid, "root");
 		cwd_dev = cwd_stat ? cwd_stat->st_dev : 0;
 		exe_dev = exe_stat ? exe_stat->st_dev : 0;
 		root_dev = root_stat ? root_stat->st_dev : 0;
-#endif
 
 		/* Scan the devices */
 		for (dev_tmp = dev_head; dev_tmp != NULL;
@@ -463,7 +432,7 @@ add_special_proc(struct names *name_list, const char ptype, const uid_t uid,
 }
 
 int parse_file(struct names *this_name, struct inode_list **ino_list,
-	       const char opts)
+	       const opt_type opts)
 {
 	char *new = expandpath(this_name->filename);
 	if (new) {
@@ -471,8 +440,7 @@ int parse_file(struct names *this_name, struct inode_list **ino_list,
 			free(this_name->filename);
 		this_name->filename = strdup(new);
 	}
-
-	if (timeout(stat, this_name->filename, &(this_name->st), 5) != 0) {
+	if (timeout(thestat, this_name->filename, &(this_name->st), 5) != 0) {
 		if (errno == ENOENT)
 			fprintf(stderr,
 				_("Specified filename %s does not exist.\n"),
@@ -514,7 +482,7 @@ parse_unixsockets(struct names *this_name, struct inode_list **ino_list,
 
 int
 parse_mounts(struct names *this_name, struct device_list **dev_list,
-	     const char opts)
+	     const opt_type opts)
 {
 	dev_t match_device;
 
@@ -953,6 +921,7 @@ int main(int argc, char *argv[])
 		{"all", 0, NULL, 'a'},
 		{"kill", 0, NULL, 'k'},
 		{"interactive", 0, NULL, 'i'},
+		{"inode", 0, NULL, 'I'},
 		{"list-signals", 0, NULL, 'l'},
 		{"mount", 0, NULL, 'm'},
 		{"ismountpoint", 0, NULL, 'M'},
@@ -1029,6 +998,7 @@ int main(int argc, char *argv[])
 					break;
 				case 'c':
 					opts |= OPT_MOUNTS;
+					read_proc_mounts(&mounts);
 					break;
 				case 'f':
 					/* ignored */
@@ -1039,6 +1009,11 @@ int main(int argc, char *argv[])
 				case 'i':
 					opts |= OPT_INTERACTIVE;
 					break;
+				case 'I':
+#if defined(WITH_MOUNTINFO_LIST)
+					opts |= OPT_ALWAYSSTAT;
+#endif
+					break;
 				case 'k':
 					opts |= OPT_KILL;
 					break;
@@ -1112,6 +1087,10 @@ int main(int argc, char *argv[])
 			continue;
 		}
 
+#if defined(WITH_MOUNTINFO_LIST)
+		if ((opts & OPT_ALWAYSSTAT) == 0)
+			thestat = mntstat;
+#endif
 		/* an option */
 		/* Not an option, must be a file specification */
 		if ((this_name = malloc(sizeof(struct names))) == NULL)
@@ -1416,7 +1395,7 @@ static struct stat *get_pidstat(const pid_t pid, const char *filename)
 	if ((st = (struct stat *)malloc(sizeof(struct stat))) == NULL)
 		return NULL;
 	snprintf(pathname, 256, "/proc/%d/%s", pid, filename);
-	if (timeout(stat, pathname, st, 5) != 0) {
+	if (timeout(thestat, pathname, st, 5) != 0) {
 		free(st);
 		return NULL;
 	}
@@ -1448,7 +1427,7 @@ check_dir(const pid_t pid, const char *dirname, struct device_list *dev_head,
 		snprintf(filepath, MAX_PATHNAME, "/proc/%d/%s/%s",
 			 pid, dirname, direntry->d_name);
 
-		if (timeout(stat, filepath, &st, 5) != 0) {
+		if (timeout(thestat, filepath, &st, 5) != 0) {
 			if (errno != ENOENT && errno != ENOTDIR) {
 				fprintf(stderr, _("Cannot stat file %s: %s\n"),
 					filepath, strerror(errno));
@@ -1487,7 +1466,7 @@ check_dir(const pid_t pid, const char *dirname, struct device_list *dev_head,
 				if (thedev != ino_tmp->device)
 					continue;
 				if (!st.st_ino
-				    && timeout(stat, filepath, &st, 5) != 0) {
+				    && timeout(thestat, filepath, &st, 5) != 0) {
 					fprintf(stderr,
 						_("Cannot stat file %s: %s\n"),
 						filepath, strerror(errno));
@@ -1557,7 +1536,7 @@ static uid_t getpiduid(const pid_t pid)
 
 	if (snprintf(pathname, MAX_PATHNAME, "/proc/%d", pid) < 0)
 		return 0;
-	if (timeout(stat, pathname, &st, 5) != 0)
+	if (timeout(thestat, pathname, &st, 5) != 0)
 		return 0;
 	return st.st_uid;
 }
@@ -1593,7 +1572,7 @@ void fill_unix_cache(struct unixsocket_list **unixsocket_head)
 		path = scanned_path;
 		if (*scanned_path == '@')
 			scanned_path++;
-		if (timeout(stat, scanned_path, &st, 5) < 0) {
+		if (timeout(thestat, scanned_path, &st, 5) < 0) {
 			free(path);
 			continue;
 		}
@@ -1738,7 +1717,7 @@ scan_knfsd(struct names *names_head, struct inode_list *ino_head,
 		if ((find_space = strpbrk(line, " \t")) == NULL)
 			continue;
 		*find_space = '\0';
-		if (timeout(stat, line, &st, 5) != 0) {
+		if (timeout(thestat, line, &st, 5) != 0) {
 			continue;
 		}
 		/* Scan the devices */
@@ -1782,7 +1761,7 @@ scan_mounts(struct names *names_head, struct inode_list *ino_head,
 		if ((find_space = strchr(find_mountp, ' ')) == NULL)
 			continue;
 		*find_space = '\0';
-		if (timeout(stat, find_mountp, &st, 5) != 0) {
+		if (timeout(thestat, find_mountp, &st, 5) != 0) {
 			continue;
 		}
 		/* Scan the devices */
@@ -1829,7 +1808,7 @@ scan_swaps(struct names *names_head, struct inode_list *ino_head,
 			if (*find_space == '\0')
 				continue;
 		}
-		if (timeout(stat, line, &st, 5) != 0) {
+		if (timeout(thestat, line, &st, 5) != 0) {
 			continue;
 		}
 		/* Scan the devices */
@@ -1850,73 +1829,7 @@ scan_swaps(struct names *names_head, struct inode_list *ino_head,
 	fclose(fp);
 }
 
-/*
- * Execute stat(2) system call with timeout to avoid deadlock
- * on network based file systems.
- */
-#if defined(WITH_TIMEOUT_STAT) && (WITH_TIMEOUT_STAT == 1)
-
-static sigjmp_buf jenv;
-
-static void sigalarm(int sig)
-{
-	if (sig == SIGALRM)
-		siglongjmp(jenv, 1);
-}
-
-static int
-timeout(stat_t func, const char *path, struct stat *buf, unsigned int seconds)
-{
-	pid_t pid = 0;
-	int ret = 0, pipes[4];
-	ssize_t len;
-
-	if (pipe(&pipes[0]) < 0)
-		goto err;
-	switch ((pid = fork())) {
-	case -1:
-		close(pipes[0]);
-		close(pipes[1]);
-		goto err;
-	case 0:
-		(void)signal(SIGALRM, SIG_DFL);
-		close(pipes[0]);
-		if ((ret = func(path, buf)) == 0)
-			do
-				len = write(pipes[1], buf, sizeof(struct stat));
-			while (len < 0 && errno == EINTR);
-		close(pipes[1]);
-		exit(ret);
-	default:
-		close(pipes[1]);
-		if (sigsetjmp(jenv, 1)) {
-			(void)alarm(0);
-			(void)signal(SIGALRM, SIG_DFL);
-			if (waitpid(0, (int *)0, WNOHANG) == 0)
-				kill(pid, SIGKILL);
-			errno = ETIMEDOUT;
-			seconds = 1;
-			goto err;
-		}
-		(void)signal(SIGALRM, sigalarm);
-		(void)alarm(seconds);
-		if (read(pipes[0], buf, sizeof(struct stat)) == 0) {
-			errno = EFAULT;
-			ret = -1;
-		}
-		(void)alarm(0);
-		(void)signal(SIGALRM, SIG_DFL);
-		close(pipes[0]);
-		waitpid(pid, NULL, 0);
-		break;
-	}
-	return ret;
- err:
-	return -1;
-}
-#endif				/* WITH_TIMEOUT_STAT */
-
-#ifdef _LISTS_H
+#if defined(WITH_MOUNTINFO_LIST)
 /*
  * Use /proc/self/mountinfo of modern linux system to determine
  * the device numbers of the mount points. Use this to avoid the
@@ -2005,42 +1918,46 @@ static void init_mntinfo(void)
 /*
  * Determine device of links below /proc/
  */
-static dev_t device(const char *path)
+static int mntstat(const char *path, struct stat *buf)
 {
 	char name[PATH_MAX + 1];
 	const char *use;
 	ssize_t nlen;
 	list_t *ptr;
 
-	if ((nlen = readlink(path, name, PATH_MAX)) < 0) {
-		nlen = strlen(path);
-		use = &path[0];
-	} else {
-		name[nlen] = '\0';
-		use = &name[0];
-	}
-
-	if (*use != '/') {	/* special file (socket, pipe, inotify) */
-		struct stat st;
-		if (timeout(stat, path, &st, 5) != 0)
-			return (dev_t) - 1;
-		return st.st_dev;
+	if ((use = realpath(path, name)) == NULL || *use != '/')
+	{
+		if (errno == ENOENT)
+			return -1;
+		/*
+		 * Could be a special file (socket, pipe, inotify)
+		 */
+		errno = 0;
+		return stat(path, buf);
 	}
 
+	nlen = strlen(use);
 	list_for_each(ptr, &mntinfo) {
 		mntinfo_t *mnt = list_entry(ptr, mntinfo_t);
 		if (nlen < mnt->nlen)
 			continue;
-		if (mnt->nlen == 1)	/* root fs is the last entry */
-			return mnt->dev;
+		if (mnt->nlen == 1) {	/* root fs is the last entry */
+			buf->st_dev = mnt->dev;
+			buf->st_ino = 0;
+			return 0;
+		}
 		if (use[mnt->nlen] != '\0' && use[mnt->nlen] != '/')
 			continue;
-		if (strncmp(use, mnt->mpoint, mnt->nlen) == 0)
-			return mnt->dev;
+		if (strncmp(use, mnt->mpoint, mnt->nlen) == 0) {
+			buf->st_dev = mnt->dev;
+			buf->st_ino = 0;
+			return 0;
+		}
 	}
-	return (dev_t) - 1;
+	errno = ENOENT;
+	return -1;
 }
-#endif				/* _LISTS_H */
+#endif				/* WITH_MOUNTINFO_LIST */
 
 /*
  * Somehow the realpath(3) glibc function call, nevertheless
diff --git a/src/fuser.h b/src/fuser.h
index 242ce19..a4df711 100644
--- a/src/fuser.h
+++ b/src/fuser.h
@@ -11,6 +11,7 @@ typedef unsigned short opt_type;
 #define OPT_USER 64
 #define OPT_ISMOUNTPOINT 128
 #define OPT_WRITE 256
+#define OPT_ALWAYSSTAT 512
 
 struct procs {
 	pid_t pid;
@@ -86,7 +87,7 @@ struct mount_list {
 	struct mount_list *next;
 };
 
-#if defined (__GNUC__) && defined(__OPTIMIZE__) && !defined (__CYGWIN__)
+#if defined (__GNUC__) && defined(WITH_MOUNTINFO_LIST)
 # include "lists.h"
 typedef struct mntinfo_s {
     list_t   this;
@@ -95,6 +96,8 @@ typedef struct mntinfo_s {
     size_t   nlen;
     char  *mpoint;
 } mntinfo_t;
+#else
+# undef WITH_MOUNTINFO_LIST
 #endif
 
 #define NAMESPACE_FILE 0
diff --git a/src/lists.h b/src/lists.h
index ae8929e..bd371a4 100644
--- a/src/lists.h
+++ b/src/lists.h
@@ -1,10 +1,10 @@
 /*
- * lists.h	Simple doubly linked list implementation,
- *		based on <linux/list.h> and <linux/prefetch.h>.
+ * lists.h	Simple doubly linked list implementation, based on
+ *		<linux/list.h>, <linux/prefetch.h>, and lib/list_sort.c
  *
- * Version:	0.1 01-Feb-2011 Fink
+ * Version:	0.2 11-Dec-2012 Fink
  *
- * Copyright 2011 Werner Fink, 2005 SUSE LINUX Products GmbH, Germany.
+ * Copyright 2011,2012 Werner Fink, 2005,2012 SUSE LINUX Products GmbH, Germany.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -246,4 +246,128 @@ static inline void move_tail(list_t *restrict entry, list_t *restrict head)
 #define np_list_for_each_prev(pos, head)	\
 	for (pos = (head)->prev; pos != (head); pos = pos->prev)
 
+#define MAX_LIST_LENGTH_BITS 20
+
+/*
+ * Returns a list organized in an intermediate format suited
+ * to chaining of merge() calls: null-terminated, no reserved or
+ * sentinel head node, "prev" links not maintained.
+ */
+static inline list_t *merge(int (*cmp)(list_t *a, list_t *b), list_t *a, list_t *b)
+{
+    list_t head, *tail = &head;
+    while (a && b) {
+	/* if equal, take 'a' -- important for sort stability */
+	if ((*cmp)(a, b) <= 0) {
+	    tail->next = a;
+	    a = a->next;
+	} else {
+	    tail->next = b;
+	    b = b->next;
+	}
+	tail = tail->next;
+    }
+    tail->next = a ? a : b;
+    return head.next;
+}
+
+/*
+ * Combine final list merge with restoration of standard doubly-linked
+ * list structure.  This approach duplicates code from merge(), but
+ * runs faster than the tidier alternatives of either a separate final
+ * prev-link restoration pass, or maintaining the prev links
+ * throughout.
+ */
+static inline void merge_and_restore_back_links(int (*cmp)(list_t *a, list_t *b), list_t *head, list_t *a, list_t *b)
+{
+    list_t *tail = head;
+
+    while (a && b) {
+	/* if equal, take 'a' -- important for sort stability */
+	if ((*cmp)(a, b) <= 0) {
+	    tail->next = a;
+	    a->prev = tail;
+	    a = a->next;
+	} else {
+	    tail->next = b;
+	    b->prev = tail;
+	    b = b->next;
+	}
+	tail = tail->next;
+    }
+    tail->next = a ? a : b;
+
+    do {
+	/*
+	 * In worst cases this loop may run many iterations.
+	 * Continue callbacks to the client even though no
+	 * element comparison is needed, so the client's cmp()
+	 * routine can invoke cond_resched() periodically.
+	 */
+	(*cmp)(tail->next, tail->next);
+
+	tail->next->prev = tail;
+	tail = tail->next;
+    } while (tail->next);
+
+    tail->next = head;
+    head->prev = tail;
+}
+
+
+/**
+ * list_sort - sort a list
+ * @head: the list to sort
+ * @cmp: the elements comparison function
+ *
+ * This function implements "merge sort", which has O(nlog(n))
+ * complexity.
+ *
+ * The comparison function @cmp must return a negative value if @a
+ * should sort before @b, and a positive value if @a should sort after
+ * @b. If @a and @b are equivalent, and their original relative
+ * ordering is to be preserved, @cmp must return 0.
+ */
+static inline void list_sort(list_t *head, int (*cmp)(list_t *a, list_t *b))
+{
+    list_t *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists
+						-- last slot is a sentinel */
+    size_t lev;  /* index into part[] */
+    size_t max_lev = 0;
+    list_t *list;
+
+    if (list_empty(head))
+	return;
+
+    memset(part, 0, sizeof(part));
+
+    head->prev->next = NULL;
+    list = head->next;
+
+    while (list) {
+	list_t *cur = list;
+	list = list->next;
+	cur->next = NULL;
+
+	for (lev = 0; part[lev]; lev++) {
+	    cur = merge(cmp, part[lev], cur);
+	    part[lev] = NULL;
+	}
+	if (lev > max_lev) {
+	    /* list passed to list_sort() too long for efficiency */
+	    if (lev >= MAX_LIST_LENGTH_BITS)
+		lev--;
+	    max_lev = lev;
+	}
+	part[lev] = cur;
+    }
+
+    for (lev = 0; lev < max_lev; lev++) {
+	if (part[lev])
+	    list = merge(cmp, part[lev], list);
+    }
+
+    merge_and_restore_back_links(cmp, head, part[max_lev], list);
+}
+
 #endif /* _LISTS_H */
diff --git a/src/timeout.c b/src/timeout.c
index 1fe0354..ca4a7cd 100644
--- a/src/timeout.c
+++ b/src/timeout.c
@@ -2,9 +2,9 @@
  * timout.c	Advanced timeout handling for file system calls
  *		to avoid deadlocks on remote file shares.
  *
- * Version:	0.1 07-Sep-2011 Fink
+ * Version:	0.2 11-Dec-2012 Fink
  *
- * Copyright 2011 Werner Fink, 2011 SUSE LINUX Products GmbH, Germany.
+ * Copyright 2011,2012 Werner Fink, 2011,2012 SUSE LINUX Products GmbH, Germany.
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -18,26 +18,29 @@
 # define _GNU_SOURCE
 #endif
 
-#ifndef USE_SOCKETPAIR
-# define USE_SOCKETPAIR		1
-#endif
-
 #ifdef _FEATURES_H
 # error Include local config.h before any system header file
 #endif
-#include "config.h"		/* For _FILE_OFFSET_BITS */
+#include "config.h"
+
+#ifndef WITH_TIMEOUT_STAT
+# define WITH_TIMEOUT_STAT	0
+#endif
+
+#ifndef USE_SOCKETPAIR
+# define USE_SOCKETPAIR		1
+#endif
 
 #include <errno.h>
-#include <pthread.h>
 #include <setjmp.h>
 #include <signal.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/mman.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <sys/select.h>
 #include <sys/stat.h>
-
 #include <unistd.h>
 #if USE_SOCKETPAIR
 # include <sys/socket.h>
@@ -86,6 +89,15 @@
 # define strcpy(d,s)		__builtin_strcpy((d),(s))   /* Without boundary check please */
 #endif
 
+#if WITH_TIMEOUT_STAT
+static sigjmp_buf jenv;
+static void sigjump(int sig attribute((unused)))
+{
+	siglongjmp(jenv, 1);
+}
+#endif
+
+#if WITH_TIMEOUT_STAT == 2
 /*
  * The structure used for communication between the processes
  */
@@ -106,7 +118,8 @@ typedef struct _handle {
 
 static volatile pid_t active;
 static int pipes[4] = {-1, -1, -1, -1};
-static char buf[PATH_MAX + sizeof(handle_t) + 1];
+static handle_t *restrict handle;
+static const size_t buflen = PATH_MAX+sizeof(handle_t)+1;
 
 static void sigchild(int sig attribute((unused)))
 {
@@ -122,6 +135,7 @@ static void attribute((constructor)) start(void)
 {
 	sigset_t sigset, oldset;
 	struct sigaction act;
+	char sync[1];
 	ssize_t in;
 
 	if (pipes[1] >= 0) close(pipes[1]);
@@ -138,6 +152,12 @@ static void attribute((constructor)) start(void)
 	act.sa_handler = sigchild;
 	sigaction(SIGCHLD, &act, 0);
 
+	if (!handle)
+		handle = mmap(NULL, buflen, PROT_READ|PROT_WRITE,
+			      MAP_ANONYMOUS|MAP_SHARED, -1, 0);
+	if (handle == MAP_FAILED)
+		goto error;
+
 	if ((active = fork()) < 0)
 		goto error;
 
@@ -164,16 +184,22 @@ static void attribute((constructor)) start(void)
 	pipes[1] = pipes[2] = -1;
 	pipes[0] = pipes[3] = -1;
 
-	{
-		handle_t *restrict handle = (void*)&buf[0];
-
-		while ((in = read(STDIN_FILENO, handle, sizeof(buf))) > sizeof(handle_t)) {
-			if (handle->function(handle->path, &handle->argument) < 0)
-					handle->errcode = errno;
-			write(STDOUT_FILENO, &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument));
-			memset(handle, 0, sizeof(handle_t));
+	while ((in = read(STDIN_FILENO, &sync, sizeof(sync))) != 0) {
+		ssize_t out;
+		if (in < 0) {
+			if (errno == EINTR)
+				continue;
+			break;
 		}
+		if (!handle)
+			break;
+		if (handle->function(handle->path, &handle->argument) < 0)
+				handle->errcode = errno;
+		do
+			out = write(STDOUT_FILENO, &sync, sizeof(sync));
+		while (out < 0 && errno == EINTR);
 	}
+
 	sigprocmask(SIG_SETMASK, &oldset, NULL);
 	exit(0);
 error:
@@ -181,6 +207,9 @@ error:
 	if (pipes[1] >= 0) close(pipes[1]);
 	if (pipes[2] >= 0) close(pipes[2]);
 	if (pipes[3] >= 0) close(pipes[3]);
+	if (handle && handle != MAP_FAILED)
+		munmap(handle, buflen);
+	handle = NULL;
 }
 
 static void /* attribute((destructor)) */ stop(void)
@@ -189,24 +218,24 @@ static void /* attribute((destructor)) */ stop(void)
 		kill(active, SIGKILL);
 }
 
-static sigjmp_buf jenv;
-static void sigjump(int sig attribute((unused)))
-{
-	siglongjmp(jenv, 1);
-}
-
 /*
  * External routine
+ *
+ * Execute stat(2) system call with timeout to avoid deadlock
+ * on network based file systems.
+ *
  */
-int timeout(stat_t function, const char *path, struct stat *restrict argument, time_t seconds)
+int
+timeout(stat_t function, const char *path, struct stat *restrict argument, time_t seconds)
 {
-	handle_t *restrict handle = (void*)&buf[0];
 	struct sigaction alrm_act, pipe_act, new_act;
 	sigset_t sigset, oldset;
+	char sync[1] = "x";
 
 	if (active <= 0)	/* Oops, last one failed therefore clear status and restart */
 		start();
-
+	if (!handle)		/* No shared memory area */
+		return function(path, argument);
 	memset(handle, 0, sizeof(handle_t));
 	handle->len = strlen(path) + 1;
 	if (handle->len >= PATH_MAX) {
@@ -235,8 +264,8 @@ int timeout(stat_t function, const char *path, struct stat *restrict argument, t
 	sigaction(SIGPIPE, &new_act, &pipe_act);
 	alarm(seconds);
 
-	write(pipes[1], handle, sizeof(handle_t)+handle->len);
-	read(pipes[2], &handle->errcode, sizeof(handle->errcode)+sizeof(handle->argument));
+	write(pipes[1], &sync, sizeof(sync));
+	read(pipes[2], &sync, sizeof(sync));
 
 	alarm(0);
 	sigaction(SIGPIPE, &pipe_act, NULL);
@@ -261,6 +290,82 @@ timed:
 error:
 	return -1;
 }
+#elif WITH_TIMEOUT_STAT == 1
+/*
+ * External routine
+ *
+ * Execute stat(2) system call with timeout to avoid deadlock
+ * on network based file systems.
+ *
+ */
+int
+timeout(stat_t function, const char *path, struct stat *restrict argument, time_t seconds)
+{
+	struct sigaction alrm_act, pipe_act, new_act;
+	sigset_t sigset, oldset;
+	int ret = 0, pipes[4];
+	pid_t pid = 0;
+	ssize_t len;
+
+	if (pipe(&pipes[0]) < 0)
+		goto error;
+	switch ((pid = fork())) {
+	case -1:
+		close(pipes[0]);
+		close(pipes[1]);
+		goto error;
+	case 0:
+		new_act.sa_handler = SIG_DFL;
+		sigaction(SIGALRM, &new_act, NULL);
+		close(pipes[0]);
+		if ((ret = function(path, argument)) == 0)
+			do
+				len = write(pipes[1], argument, sizeof(struct stat));
+			while (len < 0 && errno == EINTR);
+		close(pipes[1]);
+		exit(ret);
+	default:
+		close(pipes[1]);
+
+		sigemptyset(&sigset);
+		sigaddset(&sigset, SIGALRM);
+		sigaddset(&sigset, SIGPIPE);
+		sigprocmask(SIG_UNBLOCK, &sigset, &oldset);
+
+		memset(&new_act, 0, sizeof(new_act));
+		sigemptyset(&new_act.sa_mask);
+
+		if (sigsetjmp(jenv, 1))
+			goto timed;
+
+		new_act.sa_handler = sigjump;
+		sigaction(SIGALRM, &new_act, &alrm_act);
+		sigaction(SIGPIPE, &new_act, &pipe_act);
+		alarm(seconds);
+		if (read(pipes[0], argument, sizeof(struct stat)) == 0) {
+			errno = EFAULT;
+			ret = -1;
+		}
+		(void)alarm(0);
+		sigaction(SIGPIPE, &pipe_act, NULL);
+		sigaction(SIGALRM, &alrm_act, NULL);
+
+		close(pipes[0]);
+		waitpid(pid, NULL, 0);
+		break;
+	}
+	return ret;
+timed:
+	(void)alarm(0);
+	sigaction(SIGPIPE, &pipe_act, NULL);
+	sigaction(SIGALRM, &alrm_act, NULL);
+	if (waitpid(0, NULL, WNOHANG) == 0)
+		kill(pid, SIGKILL);
+	errno = ETIMEDOUT;
+error:
+	return -1;
+}
+#endif
 
 /*
  * End of timeout.c
diff --git a/src/timeout.h b/src/timeout.h
index 546c13b..f372297 100644
--- a/src/timeout.h
+++ b/src/timeout.h
@@ -17,7 +17,11 @@
 #ifndef _TIMEOUT_H
 #define _TIMEOUT_H
 
-#include "config.h"		/* For _FILE_OFFSET_BITS */
+#include "config.h"
+
+#ifndef WITH_TIMEOUT_STAT
+# define WITH_TIMEOUT_STAT 0
+#endif
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -30,7 +34,12 @@
 # endif
 #endif
 
-typedef int (*stat_t)(const char *, struct stat *restrict);
+typedef int (*stat_t)(const char *, struct stat *);
+
+#if WITH_TIMEOUT_STAT > 0
 extern int timeout(stat_t, const char *, struct stat *restrict, time_t);
+#else
+# define timeout(func,path,buf,dummy)	(func)((path),(buf))
+#endif
 
 #endif