From: Dominique Martinet <dominique.marti...@atmark-techno.com>
Checking st_dev fails to identify bind mounts as mount points if the
bind mount target is in the same filesystem as its parent directory,
for example (simple 'mountpoint' command is util-linux's):
```
cd $(mktemp -d)
mkdir src target
mount --bind src target
busybox mountpoint target; echo $?
# target is not a mountpoint
# 1
mountpoint target; echo $?
# target is a mountpoint
# 0
umount target
rm -rf $PWD
```
Parsing /proc/mounts with getmntent (like util-linux implementation
does) fixes the issue.
function old new delta
.rodata 79535 79529 -6
mountpoint_main 469 424 -45
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-51) Total: -51 bytes
---
FWIW I've been working around this problem with a awk one-liner instead:
```
is_mountpoint() {
! awk -v dir="$1" '$5 == dir { exit 1 }' < /proc/self/mountinfo
}
```
But this bit us somewhere else that wasn't using my wrapper, so figured
I'd try to fix this here... and it turns out to be a size saving as well
because we have a helper for mntent (find_mount_point).
I'll submit it to alpine in a few weeks depending on initial feedback.
util-linux/mountpoint.c | 40 +++++++++++++++-------------------------
1 file changed, 15 insertions(+), 25 deletions(-)
diff --git a/util-linux/mountpoint.c b/util-linux/mountpoint.c
index 87f4cc60d8c5..0a6df5160399 100644
--- a/util-linux/mountpoint.c
+++ b/util-linux/mountpoint.c
@@ -69,33 +69,23 @@ int mountpoint_main(int argc UNUSED_PARAM, char **argv)
errno = ENOTDIR;
if (S_ISDIR(st.st_mode)) {
- dev_t st_dev = st.st_dev;
- ino_t st_ino = st.st_ino;
- char *p = xasprintf("%s/..", arg);
-
- if (stat(p, &st) == 0) {
- //int is_mnt = (st_dev != st.st_dev) || (st_dev ==
st.st_dev && st_ino == st.st_ino);
- int is_not_mnt = (st_dev == st.st_dev) && (st_ino !=
st.st_ino);
-
- if (opt & OPT_d)
- printf("%u:%u\n", major(st_dev), minor(st_dev));
- if (opt & OPT_n) {
- const char *d = find_block_device(arg);
- /* name is undefined, but device is mounted ->
anonymous superblock! */
- /* happens with btrfs */
- if (!d) {
- d = "UNKNOWN";
- /* TODO: iterate /proc/mounts, or
/proc/self/mountinfo
- * to find out the device name */
- }
- printf("%s %s\n", d, arg);
+ bool is_not_mnt = find_mount_point(arg, 0) == NULL;
+ if (opt & OPT_d)
+ printf("%u:%u\n", major(st.st_dev), minor(st.st_dev));
+ if (opt & OPT_n) {
+ const char *d = find_block_device(arg);
+ /* name is undefined, but device is mounted ->
anonymous superblock! */
+ /* happens with btrfs */
+ if (!d) {
+ d = "UNKNOWN";
+ /* TODO: iterate /proc/mounts, or
/proc/self/mountinfo
+ * to find out the device name */
}
- if (!(opt & (OPT_q | OPT_d | OPT_n)))
- printf("%s is %sa mountpoint\n", arg,
is_not_mnt ? "not " : "");
- return is_not_mnt;
+ printf("%s %s\n", d, arg);
}
- arg = p;
- /* else: stat had set errno, just fall through */
+ if (!(opt & (OPT_q | OPT_d | OPT_n)))
+ printf("%s is %sa mountpoint\n", arg, is_not_mnt ? "not
" : "");
+ return is_not_mnt;
}
err:
--
2.39.2
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