swapon/swapoff: size reduction, cleanup, fixes, improvements
authorTito Ragusa <farmatito@tiscali.it>
Mon, 31 Mar 2014 14:39:26 +0000 (16:39 +0200)
committerDenys Vlasenko <vda.linux@googlemail.com>
Mon, 31 Mar 2014 14:39:26 +0000 (16:39 +0200)
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>
util-linux/swaponoff.c

index a7ad6db793264ffa9bdc0de39ce1c0149bdf89f6..acdb67729fbdf245676cc72cb1e6845d8e90fb66 100644 (file)
@@ -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;
 }