autofs-5.0.5 - fix cache_init() on source re-read

From: Ian Kent <raven@themaw.net>

The master map entry cache is released and re-allocated for each

map source upon master map re-read. This is done without holding

the master map entry write lock and, when there are many master

map entries, could lead to a race because other activities can be

underway concurrently. In this case then we must either use

additional expensive exclusive locking or not do the cache

re-recreate.

So the question really becomes what do we have to gain by releasing

and re-creating the cache since we spend a fairly significant amount

of effort on pruning stale entries during ongoing operation already.

This patch moves the allocation of the map entry cache (belonging to

the map source) into the function used to add the map source to the

master map entry and does not release and re-create the cache if the

source already exists for the given master map entry.

---

 CHANGELOG              |    1 +

 lib/master.c           |    6 ++++++

 lib/master_parse.y     |   10 ----------

 modules/mount_autofs.c |    8 --------

 4 files changed, 7 insertions(+), 18 deletions(-)

--- autofs-5.0.5.orig/CHANGELOG

+++ autofs-5.0.5/CHANGELOG

@@ -38,6 +38,7 @@

 - fix parse_sun() module init.

 - dont check null cache on expire.

 - fix null cache race.

+- fix cache_init() on source re-read.

 03/09/2009 autofs-5.0.5

 -----------------------

--- autofs-5.0.5.orig/lib/master.c

+++ autofs-5.0.5/lib/master.c

@@ -188,6 +188,12 @@ master_add_map_source(struct master_mape

 	source->argc = argc;

 	source->argv = tmpargv;

+	source->mc = cache_init(entry->ap, source);

+	if (!source->mc) {

+		master_free_map_source(source, 0);

+		return NULL;

+	}

+

 	master_source_writelock(entry);

 	if (!entry->maps) {

--- autofs-5.0.5.orig/lib/master_parse.y

+++ autofs-5.0.5/lib/master_parse.y

@@ -830,16 +830,6 @@ int master_parse_entry(const char *buffe

 		return 0;

 	}

-	if (!source->mc) {

-		source->mc = cache_init(entry->ap, source);

-		if (!source->mc) {

-			error(m_logopt, "failed to init source cache");

-			if (new)

-				master_free_mapent(new);

-			local_free_vars();

-			return 0;

-		}

-	}

 	source->master_line = lineno;

 	entry->age = age;

--- autofs-5.0.5.orig/modules/mount_autofs.c

+++ autofs-5.0.5/modules/mount_autofs.c

@@ -200,14 +200,6 @@ int mount_mount(struct autofs_point *ap,

 	}

 	free_map_type_info(info);

-	source->mc = cache_init(entry->ap, source);

-	if (!source->mc) {

-		error(ap->logopt, MODPREFIX "failed to init source cache");

-		master_free_map_source(source, 0);

-		master_free_mapent(entry);

-		return 1;

-	}

-

 	mounts_mutex_lock(ap);

 	if (handle_mounts_startup_cond_init(&suc)) {