swapon/swapoff: size reduction, cleanup, fixes, improvements

1) real swapon/swapoff handles also devices on the commandline with -a;
2) xstat(device)  in  swap_enable_disable aborts on error when cycling through
   fstab so some devices  are not handled;
3) duplicated code for ENABLE_FEATURE_SWAPON_DISCARD and
   ENABLE_FEATURE_SWAPON_PRI was moved to functions.
4) silence some error messages with -a;
5) minor cleanups and code refactoring reduced the size as per bloat-check:
6) I also added support for /proc/swaps handling to swapoff:
"When the -a flag is given, swapping is disabled on all known  swap  devices
 and  files  (as  found  in  /proc/swaps  or /etc/fstab)."
So now swapoff first cycles through  /proc/swaps and then through fstab
to swapoff all devices.

function                                             old     new   delta
set_discard_flag                                       -     106    +106
swap_enable_disable                                  147     238     +91
set_priority_flag                                      -      79     +79
retrieve_file_data                                   470     467      -3
swap_on_off_main                                     638     418    -220
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 1/2 up/down: 276/-223)           Total: 53 bytes

Signed-off-by: Tito Ragusa <farmatito@tiscali.it>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 161 insertions, 115 deletions

diff --git a/util-linux/swaponoff.c b/util-linux/swaponoff.c
index a7ad6db79..acdb67729 100644
--- a/util-linux/swaponoff.c
+++ b/util-linux/swaponoff.c
@@ -63,90 +63,142 @@ struct globals {
 } FIX_ALIASING;
 #define G (*(struct globals*)&bb_common_bufsiz1)
 #define g_flags (G.flags)
+#define save_g_flags()    int save_g_flags = g_flags
+#define restore_g_flags() g_flags = save_g_flags
 #else
 #define g_flags 0
+#define save_g_flags()    ((void)0)
+#define restore_g_flags() ((void)0)
 #endif
 #define INIT_G() do { } while (0)
 
+#define do_swapoff   (applet_name[5] == 'f')
+
+/* Command line options */
+enum {
+        OPTBIT_a,                              /* -a all      */
+        IF_FEATURE_SWAPON_DISCARD( OPTBIT_d ,) /* -d discard  */
+        IF_FEATURE_SWAPON_PRI    ( OPTBIT_p ,) /* -p priority */
+        OPT_a = 1 << OPTBIT_a,
+        OPT_d = IF_FEATURE_SWAPON_DISCARD((1 << OPTBIT_d)) + 0,
+        OPT_p = IF_FEATURE_SWAPON_PRI    ((1 << OPTBIT_p)) + 0,
+};
+
+#define OPT_ALL      (option_mask32 & OPT_a)
+#define OPT_DISCARD  (option_mask32 & OPT_d)
+#define OPT_PRIO     (option_mask32 & OPT_p)
+
 static int swap_enable_disable(char *device)
 {
-        int status;
+        int err = 0;
+        int quiet = 0;
         struct stat st;
 
         resolve_mount_spec(&device);
-        xstat(device, &st);
-
-#if ENABLE_DESKTOP
-        /* test for holes */
-        if (S_ISREG(st.st_mode))
-                if (st.st_blocks * (off_t)512 < st.st_size)
-                        bb_error_msg("warning: swap file has holes");
-#endif
 
-        if (applet_name[5] == 'n')
-                status = swapon(device, g_flags);
-        else
-                status = swapoff(device);
+        if (do_swapoff) {
+                err = swapoff(device);
+                /* Don't complain on OPT_ALL if not a swap device or if it doesn't exist */
+                quiet = (OPT_ALL && (errno == EINVAL || errno == ENOENT));
+        } else {
+                /* swapon */
+                err = stat(device, &st);
+                if (!err) {
+                        if (ENABLE_DESKTOP && S_ISREG(st.st_mode)) {
+                                if (st.st_blocks * (off_t)512 < st.st_size) {
+                                        bb_error_msg("%s: file has holes", device);
+                                        return 1;
+                                }
+                        }
+                        err = swapon(device, g_flags);
+                        /* Don't complain on swapon -a if device is already in use */
+                        quiet = (OPT_ALL && errno == EBUSY);
+                }
+        }
 
-        if (status != 0) {
-                bb_simple_perror_msg(device);
+        if (err) {
+                if (!quiet)
+                        bb_simple_perror_msg(device);
                 return 1;
         }
-
         return 0;
 }
 
-static int do_em_all(void)
+#if ENABLE_FEATURE_SWAPON_DISCARD
+static void set_discard_flag(char *s)
 {
-        struct mntent *m;
-        FILE *f;
-        int err;
-#ifdef G
-        int cl_flags = g_flags;
+        /* Unset the flag first to allow fstab options to override */
+        /* options set on the command line */
+        g_flags = (g_flags & ~SWAP_FLAG_DISCARD_MASK) | SWAP_FLAG_DISCARD;
+
+        if (!s) /* No optional policy value on the commandline */
+                return;
+        /* Skip prepended '=' */
+        if (*s == '=')
+                s++;
+        /* For fstab parsing: remove other appended options */
+        *strchrnul(s, ',') = '\0';
+
+        if (strcmp(s, "once") == 0)
+                g_flags |= SWAP_FLAG_DISCARD_ONCE;
+        if  (strcmp(s, "pages") == 0)
+                g_flags |= SWAP_FLAG_DISCARD_PAGES;
+}
+#else
+#define set_discard_flag(s) ((void)0)
+#endif
+
+#if ENABLE_FEATURE_SWAPON_PRI
+static void set_priority_flag(char *s)
+{
+        unsigned prio;
+
+        /* For fstab parsing: remove other appended options */
+        *strchrnul(s, ',') = '\0';
+        /* Max allowed 32767 (== SWAP_FLAG_PRIO_MASK) */
+        prio = bb_strtou(s, NULL, 10);
+        if (!errno) {
+                /* Unset the flag first to allow fstab options to override */
+                /* options set on the command line */
+                g_flags = (g_flags & ~SWAP_FLAG_PRIO_MASK) | SWAP_FLAG_PREFER |
+                                        MIN(prio, SWAP_FLAG_PRIO_MASK);
+        }
+}
+#else
+#define set_priority_flag(s) ((void)0)
 #endif
 
-        f = setmntent("/etc/fstab", "r");
-        if (f == NULL)
-                bb_perror_msg_and_die("/etc/fstab");
+static int do_em_all_in_fstab(void)
+{
+        struct mntent *m;
+        int err = 0;
+        FILE *f = xfopen_for_read("/etc/fstab");
 
-        err = 0;
         while ((m = getmntent(f)) != NULL) {
                 if (strcmp(m->mnt_type, MNTTYPE_SWAP) == 0) {
                         /* swapon -a should ignore entries with noauto,
-                         * but swapoff -a should process them */
-                        if (applet_name[5] != 'n'
-                         || hasmntopt(m, MNTOPT_NOAUTO) == NULL
-                        ) {
-#if ENABLE_FEATURE_SWAPON_DISCARD || ENABLE_FEATURE_SWAPON_PRI
-                                char *p;
-                                g_flags = cl_flags; /* each swap space might have different flags */
-#if ENABLE_FEATURE_SWAPON_DISCARD
-                                p = hasmntopt(m, "discard");
-                                if (p) {
-                                        if (p[7] == '=') {
-                                                if (strncmp(p + 8, "once", 4) == 0 && (p[12] == ',' || p[12] == '\0'))
-                                                        g_flags = (g_flags & ~SWAP_FLAG_DISCARD_MASK) | SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE;
-                                                else if (strncmp(p + 8, "pages", 5) == 0 && (p[13] == ',' || p[13] == '\0'))
-                                                        g_flags = (g_flags & ~SWAP_FLAG_DISCARD_MASK) | SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_PAGES;
+                         * but swapoff -a should process them
+                         */
+                        if (do_swapoff || hasmntopt(m, MNTOPT_NOAUTO) == NULL) {
+                                /* each swap space might have different flags */
+                                /* save global flags for the next round */
+                                save_g_flags();
+                                if (ENABLE_FEATURE_SWAPON_DISCARD) {
+                                        char *p = hasmntopt(m, "discard");
+                                        if (p) {
+                                                /* move to '=' or to end of string */
+                                                p += 7;
+                                                set_discard_flag(p);
                                         }
-                                        else if (p[7] == ',' || p[7] == '\0')
-                                                g_flags = (g_flags & ~SWAP_FLAG_DISCARD_MASK) | SWAP_FLAG_DISCARD;
                                 }
-#endif
-#if ENABLE_FEATURE_SWAPON_PRI
-                                p = hasmntopt(m, "pri");
-                                if (p) {
-                                        /* Max allowed 32767 (== SWAP_FLAG_PRIO_MASK) */
-                                        unsigned prio = bb_strtou(p + 4, NULL, 10);
-                                        /* We want to allow "NNNN,foo", thus errno == EINVAL is allowed too */
-                                        if (errno != ERANGE) {
-                                                g_flags = (g_flags & ~SWAP_FLAG_PRIO_MASK) | SWAP_FLAG_PREFER |
-                                                        MIN(prio, SWAP_FLAG_PRIO_MASK);
+                                if (ENABLE_FEATURE_SWAPON_PRI) {
+                                        char *p = hasmntopt(m, "pri");
+                                        if (p) {
+                                                set_priority_flag(p + 4);
                                         }
                                 }
-#endif
-#endif
-                                err += swap_enable_disable(m->mnt_fsname);
+                                err |= swap_enable_disable(m->mnt_fsname);
+                                restore_g_flags();
                         }
                 }
         }
@@ -157,74 +209,68 @@ static int do_em_all(void)
         return err;
 }
 
+static int do_all_in_proc_swaps(void)
+{
+        char *line;
+        int err = 0;
+        FILE *f = fopen_for_read("/proc/swaps");
+        /* Don't complain if missing */
+        if (f) {
+                while ((line = xmalloc_fgetline(f)) != NULL) {
+                        if (line[0] == '/') {
+                                *strchrnul(line, ' ') = '\0';
+                                err |= swap_enable_disable(line);
+                        }
+                        free(line);
+                }
+                if (ENABLE_FEATURE_CLEAN_UP)
+                        fclose(f);
+        }
+
+        return err;
+}
+
+#define OPTSTR_SWAPON "a" \
+        IF_FEATURE_SWAPON_DISCARD("d::") \
+        IF_FEATURE_SWAPON_PRI("p:")
+
 int swap_on_off_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int swap_on_off_main(int argc UNUSED_PARAM, char **argv)
 {
-        int ret;
-#if ENABLE_FEATURE_SWAPON_DISCARD
-        char *discard = NULL;
-#endif
-#if ENABLE_FEATURE_SWAPON_PRI
-        unsigned prio;
-#endif
+        IF_FEATURE_SWAPON_PRI(char *prio;)
+        IF_FEATURE_SWAPON_DISCARD(char *discard = NULL;)
+        int ret = 0;
 
         INIT_G();
 
-#if !ENABLE_FEATURE_SWAPON_DISCARD && !ENABLE_FEATURE_SWAPON_PRI
-        ret = getopt32(argv, "a");
-#else
-#if ENABLE_FEATURE_SWAPON_PRI
-        if (applet_name[5] == 'n')
-                opt_complementary = "p+";
-#endif
-        ret = getopt32(argv, (applet_name[5] == 'n') ?
-#if ENABLE_FEATURE_SWAPON_DISCARD
-                "d::"
-#endif
-#if ENABLE_FEATURE_SWAPON_PRI
-                "p:"
-#endif
-                "a" : "a"
-#if ENABLE_FEATURE_SWAPON_DISCARD
-                , &discard
-#endif
-#if ENABLE_FEATURE_SWAPON_PRI
-                , &prio
-#endif
-                );
-#endif
-
-#if ENABLE_FEATURE_SWAPON_DISCARD
-        if (ret & 1) { // -d
-                if (!discard)
-                        g_flags |= SWAP_FLAG_DISCARD;
-                else if (strcmp(discard, "once") == 0)
-                        g_flags |= SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE;
-                else if (strcmp(discard, "pages") == 0)
-                        g_flags |= SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_PAGES;
-                else
-                        bb_show_usage();
-        }
-        ret >>= 1;
-#endif
-#if ENABLE_FEATURE_SWAPON_PRI
-        if (ret & 1) // -p
-                g_flags |= SWAP_FLAG_PREFER |
-                        MIN(prio, SWAP_FLAG_PRIO_MASK);
-        ret >>= 1;
-#endif
-
-        if (ret /* & 1: not needed */) // -a
-                return do_em_all();
+        getopt32(argv, do_swapoff ? "a" : OPTSTR_SWAPON
+                        IF_FEATURE_SWAPON_DISCARD(, &discard)
+                        IF_FEATURE_SWAPON_PRI(, &prio)
+        );
 
         argv += optind;
-        if (!*argv)
-                bb_show_usage();
 
-        /* ret = 0; redundant */
-        do {
-                ret += swap_enable_disable(*argv);
-        } while (*++argv);
+        if (OPT_DISCARD) {
+                set_discard_flag(discard);
+        }
+        if (OPT_PRIO) {
+                set_priority_flag(prio);
+        }
 
+        if (OPT_ALL) {
+                /* swapoff -a does also /proc/swaps */
+                if (do_swapoff)
+                        ret = do_all_in_proc_swaps();
+                ret |= do_em_all_in_fstab();
+        } else if (!*argv) {
+                /* if not -a we need at least one arg */
+                bb_show_usage();
+        }
+        /* Unset -a now to allow for more messages in swap_enable_disable */
+        option_mask32 = option_mask32 & ~OPT_a;
+        /* Now process devices on the commandline if any */
+        while (*argv) {
+                ret |= swap_enable_disable(*argv++);
+        }
         return ret;
 }