findmnt: use mnt_cache_set_targets() for non-kernel table

findmnt compares the user-supplied path <target> with each entry in the
parsed table. To do this comparison, libmount attempts to canonicalize
the target path of each table entry, when the entry does not originate
from the kernel (kernel supplied target paths are already
canonicalized). However, if one of these entries is an active mount
point, stat(2) or readlink(2) on the mount target path can hang (e.g.
unreachable NFS server).

If the main table is not a kernel table, we parse /proc/self/mountinfo
into a secondary table and call mnt_cache_set_targets(). This allows
libmount to check that the target path of each entry in the main table
is not an active mount point, so it can avoid canonicalizing it.

Signed-off-by: Eric Rannaud <e@nanocritical.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/misc-utils/findmnt.c b/misc-utils/findmnt.c
index 445a9b3f1..0b3e380fb 100644
--- a/misc-utils/findmnt.c
+++ b/misc-utils/findmnt.c
@@ -833,6 +833,36 @@ static struct libmnt_table *parse_tabfiles(char **files,
 	return tb;
 }
 
+/*
+ * Parses mountinfo and calls mnt_cache_set_targets(cache, mtab). Only
+ * necessary if @tb in main() was read from a non-kernel source.
+ */
+static void cache_set_targets(struct libmnt_cache *cache)
+{
+	struct libmnt_table *tb = NULL;
+	char *path = NULL;
+	int rc = 0;
+
+	tb = mnt_new_table();
+	if (!tb)
+		goto done;
+
+	path = access(_PATH_PROC_MOUNTINFO, R_OK) == 0 ?
+		_PATH_PROC_MOUNTINFO :
+		_PATH_PROC_MOUNTS;
+
+	rc = mnt_table_parse_file(tb, path);
+	if (rc)
+		goto done;
+
+	rc = mnt_cache_set_targets(cache, tb);
+	if (rc)
+		goto done;
+
+done:
+	mnt_unref_table(tb);
+}
+
 /* checks if @tb contains parent->child relations */
 static int tab_is_tree(struct libmnt_table *tb)
 {
@@ -1471,6 +1501,9 @@ int main(int argc, char *argv[])
 			goto leave;
 		}
 		mnt_table_set_cache(tb, cache);
+
+		if (tabtype != TABTYPE_KERNEL)
+			cache_set_targets(cache);
 	}
 
 	if (flags & FL_UNIQ)