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List: busybox
Subject: [PATCH v2] umount: Implement -O option to unmount by mount options
From: soeren () soeren-tempel ! net
Date: 2023-03-03 16:00:17
Message-ID: 20230303160016.4785-1-soeren () soeren-tempel ! net
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From: Sören Tempel <soeren@soeren-tempel.net>
This commit adds an implementation of the umount -O option, as provided
by util-linux's mount(8) implementation, to BusyBox. Similar to -t, the
option is intended to be used in conjunction with -a thereby allowing
users to filter which file systems are unmounted by mount options.
Multiple options can be specified with -O, all of which need to match.
Each option can be prefixed with `no` to indicate that no action should
be taken for a mount point with this mount option. The "no" prefix
interpretation can be disabled using the "+" prefix.
At Alpine, this feature is often requested by users as the OpenRC
netmount service uses `umount -a -O _netdev` to amount all network
file systems [1] [2].
This implementation is functionally equivalent to the util-linux
implementation with the exception that it implements no special handling
for `key="value"` mount options to keep the implementation simple.
Therefore, filesystems mounted with options like `foo="bar"` won't
be matched by `umount -a -O foo`.
[1]: https://gitlab.alpinelinux.org/alpine/aports/-/issues/9923
[2]: https://gitlab.alpinelinux.org/alpine/aports/-/issues/13789
Signed-off-by: Sören Tempel <soeren@soeren-tempel.net>
---
Changes since v1:
* Fix a typo during parsing of no keyword (n0 -> no)
* Treat alone "no" as an error (as done in util-linux)
* Implement support for the "+" prefix to bypass the "no" keyword
This version of the patch has been tested against the util-linux
implementation using KLEE: https://github.com/nmeum/umount-test-opts
include/libbb.h | 1 +
libbb/Kbuild.src | 1 +
libbb/match_fsopts.c | 69 ++++++++++++++++++++++++++++++++++++++++++++
util-linux/umount.c | 10 +++++--
4 files changed, 78 insertions(+), 3 deletions(-)
create mode 100644 libbb/match_fsopts.c
diff --git a/include/libbb.h b/include/libbb.h
index cca33a177..ad41adec8 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1586,6 +1586,7 @@ const struct hwtype *get_hwntype(int type) FAST_FUNC;
extern int fstype_matches(const char *fstype, const char *comma_list) FAST_FUNC;
+extern int fsopts_matches(const char *opts_list, const char *reqopts_list) \
FAST_FUNC; #ifdef HAVE_MNTENT_H
extern struct mntent *find_mount_point(const char *name, int subdir_too) FAST_FUNC;
#endif
diff --git a/libbb/Kbuild.src b/libbb/Kbuild.src
index 653025e56..4bb8260b9 100644
--- a/libbb/Kbuild.src
+++ b/libbb/Kbuild.src
@@ -120,6 +120,7 @@ lib-y += xrealloc_vector.o
lib-$(CONFIG_MOUNT) += match_fstype.o
lib-$(CONFIG_UMOUNT) += match_fstype.o
+lib-$(CONFIG_UMOUNT) += match_fsopts.o
lib-$(CONFIG_FEATURE_UTMP) += utmp.o
diff --git a/libbb/match_fsopts.c b/libbb/match_fsopts.c
new file mode 100644
index 000000000..b1cc85c3c
--- /dev/null
+++ b/libbb/match_fsopts.c
@@ -0,0 +1,69 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Match fsopts for use in mount unmount -O.
+ *
+ * Returns 1 for a match, otherwise 0.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+#include "libbb.h"
+
+static int fsopt_matches(const char *opts_list, const char *opt, size_t optlen)
+{
+ int match = 1;
+
+ if (optlen >= 2 && opt[0] == 'n' && opt[1] == 'o') {
+ match--;
+ opt += 2; optlen -= 2;
+ }
+
+ /* The alone "no" is an error, all matching ends with False. */
+ if (optlen == 0)
+ return 0;
+
+ /* The "no" prefix interpretation can be disabled by the "+" prefix. */
+ if (match && optlen > 1 && *opt == '+') {
+ opt++; optlen--;
+ }
+
+ while (1) {
+ if (strncmp(opts_list, opt, optlen) == 0) {
+ const char *after_opt = opts_list + optlen;
+ if (*after_opt == '\0' || *after_opt == ',')
+ return match;
+ }
+
+ opts_list = strchr(opts_list, ',');
+ if (!opts_list)
+ break;
+ opts_list++;
+ }
+
+ return !match;
+}
+
+/* This function implements the mnt_match_options function from libmount. */
+int FAST_FUNC fsopts_matches(const char *opts_list, const char *reqopts_list)
+{
+ if (!reqopts_list)
+ return 1; /* no options requested, match anything */
+
+ while (1) {
+ size_t len;
+ const char *comma = strchr(reqopts_list, ',');
+ if (!comma)
+ len = strlen(reqopts_list);
+ else
+ len = comma - reqopts_list;
+
+ if (len && !fsopt_matches(opts_list, reqopts_list, len))
+ return 0;
+
+ if (!comma)
+ break;
+ reqopts_list = ++comma;
+ }
+
+ return 1;
+}
diff --git a/util-linux/umount.c b/util-linux/umount.c
index 23da32868..7a54cafb0 100644
--- a/util-linux/umount.c
+++ b/util-linux/umount.c
@@ -41,7 +41,7 @@
//kbuild:lib-$(CONFIG_UMOUNT) += umount.o
//usage:#define umount_trivial_usage
-//usage: "[-rlf"IF_FEATURE_MTAB_SUPPORT("m")IF_FEATURE_MOUNT_LOOP("d")IF_FEATURE_UMOUNT_ALL("a")"] \
[-t FSTYPE] FILESYSTEM|DIRECTORY" +//usage: \
"[-rlf"IF_FEATURE_MTAB_SUPPORT("m")IF_FEATURE_MOUNT_LOOP("d")IF_FEATURE_UMOUNT_ALL("a")"] \
[-t FSTYPE] [-O FSOPT] FILESYSTEM|DIRECTORY" //usage:#define umount_full_usage \
"\n\n" //usage: "Unmount filesystems\n"
//usage: IF_FEATURE_UMOUNT_ALL(
@@ -57,6 +57,7 @@
//usage: "\n -d Free loop device if it has been used"
//usage: )
//usage: "\n -t FSTYPE[,...] Unmount only these filesystem type(s)"
+//usage: "\n -O FSOPT[,...] Unmount only filesystem mounted with the given \
options" //usage:
//usage:#define umount_example_usage
//usage: "$ umount /dev/hdc1\n"
@@ -82,7 +83,7 @@ static struct mntent *getmntent_r(FILE* stream, struct mntent* \
result, #endif
/* ignored: -c -v -i */
-#define OPTION_STRING "fldnrat:" "cvi"
+#define OPTION_STRING "fldnrat:O:" "cvi"
#define OPT_FORCE (1 << 0) // Same as MNT_FORCE
#define OPT_LAZY (1 << 1) // Same as MNT_DETACH
#define OPT_FREELOOP (1 << 2)
@@ -96,6 +97,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
int doForce;
struct mntent me;
FILE *fp;
+ char *opts = NULL;
char *fstype = NULL;
int status = EXIT_SUCCESS;
unsigned opt;
@@ -105,7 +107,7 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
struct mtab_list *next;
} *mtl, *m;
- opt = getopt32(argv, OPTION_STRING, &fstype);
+ opt = getopt32(argv, OPTION_STRING, &fstype, &opts);
//argc -= optind;
argv += optind;
@@ -133,6 +135,8 @@ int umount_main(int argc UNUSED_PARAM, char **argv)
/* Match fstype (fstype==NULL matches always) */
if (!fstype_matches(me.mnt_type, fstype))
continue;
+ if (!fsopts_matches(me.mnt_opts, opts))
+ continue;
m = xzalloc(sizeof(*m));
m->next = mtl;
m->device = xstrdup(me.mnt_fsname);
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