From 0f66811659aa8fd8b14ade8a80bfecd580962b2d Mon Sep 17 00:00:00 2001

From: Karel Zak <kzak@redhat.com>

Date: Tue, 10 Mar 2015 12:51:44 +0100

Subject: [PATCH 71/84] findmnt: don't rely on st_dev for --target

The overlay filesystem does not provide usable st_dev (in traditional

UNIX way). It's necessary to search in /proc/self/mountinfo to detect

which path element is mountpoint.

$ findmnt --target /mnt/merged/dir-a/foo

TARGET      SOURCE  FSTYPE  OPTIONS

/mnt/merged overlay overlay rw,relatime,lowerdir=/mnt/low,upperdir=/mnt/high/data,workdir=/mnt/high/work

Upstream: http://github.com/karelzak/util-linux/commit/cd41b385a06dde70bb45c3143d3459157bda58f8

Addresses: http://bugzilla.redhat.com/show_bug.cgi?id=587393

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 libmount/src/utils.c |  6 +++++-

 misc-utils/findmnt.8 |  8 ++++++--

 misc-utils/findmnt.c | 17 +++++++++++------

 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/libmount/src/utils.c b/libmount/src/utils.c

index 7c6f5b1..5783d88 100644

--- a/libmount/src/utils.c

+++ b/libmount/src/utils.c

@@ -859,7 +859,11 @@ int mnt_open_uniq_filename(const char *filename, char **name)

  * This function finds the mountpoint that a given path resides in. @path

  * should be canonicalized. The returned pointer should be freed by the caller.

  *

- * Returns: allocated string with target of the mounted device or NULL on error

+ * WARNING: the function compares st_dev of the @path elements. This traditional

+ * way maybe be insufficient on filesystems like Linux "overlay". See also

+ * mnt_table_find_target().

+ *

+ * Returns: allocated string with the target of the mounted device or NULL on error

  */

 char *mnt_get_mountpoint(const char *path)

 {

diff --git a/misc-utils/findmnt.8 b/misc-utils/findmnt.8

index 407636e..54739b7 100644

--- a/misc-utils/findmnt.8

+++ b/misc-utils/findmnt.8

@@ -179,8 +179,12 @@ Search in

 .IR /etc/fstab .

 The output is in the list format (see \fB--list\fR).

 .TP

-.BR \-T , " \-\-target \fIdir\fP"

-Explicitly define the mount target (mountpoint directory).

+.BR \-T , " \-\-target \fIpath\fP"

+Explicitly define the mount target (mountpoint directory). If the \fIpath\fR

+is not a mountpoint file or directory than

+.B findmnt

+checks \fIpath\fR elements in reverse order for get the mountpoint (this feature is 

+supported only if search in kernel files and unsupported for \fB\-\-fstab\fP).

 .TP

 .BR \-t , " \-\-types \fIlist\fP"

 Limit the set of printed filesystems.  More than one type may be

diff --git a/misc-utils/findmnt.c b/misc-utils/findmnt.c

index f16da91..fe899db 100644

--- a/misc-utils/findmnt.c

+++ b/misc-utils/findmnt.c

@@ -236,9 +236,12 @@ static void set_source_match(const char *data)

 		set_match(COL_SOURCE, data);

 }

-static void enable_extra_target_match(void)

+/* @tb has to be from kernel (so no fstab or so)! */

+static void enable_extra_target_match(struct libmnt_table *tb)

 {

-	char *cn = NULL, *mnt = NULL;

+	char *cn = NULL;

+	const char *tgt = NULL, *mnt = NULL;

+	struct libmnt_fs *fs;

 	/*

 	 * Check if match pattern is mountpoint, if not use the

@@ -248,9 +251,11 @@ static void enable_extra_target_match(void)

 	if (!cn)

 		return;

-	mnt = mnt_get_mountpoint(cn);

-	if (!mnt || strcmp(mnt, cn) == 0)

-		return;

+	fs = mnt_table_find_mountpoint(tb, tgt, MNT_ITER_BACKWARD);

+	if (fs)

+		mnt = mnt_fs_get_target(fs);

+	if (mnt && strcmp(mnt, tgt) != 0)

+		set_match(COL_TARGET, xstrdup(mnt));	/* replace the current setting */

 	/* replace the current setting with the real mountpoint */

 	set_match(COL_TARGET, mnt);

@@ -1484,7 +1489,7 @@ int main(int argc, char *argv[])

 			 * try it again with extra functionality for target

 			 * match

 			 */

-			enable_extra_target_match();

+			enable_extra_target_match(tb);

 			rc = add_matching_lines(tb, tt, direction);

 		}

 	}

-- 

2.7.4