libmount: add support for mount -a --fork

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

6 files changed, 217 insertions, 28 deletions

diff --git a/libmount/samples/mount.c b/libmount/samples/mount.c
index 2d995fd18..08b92332b 100644
--- a/libmount/samples/mount.c
+++ b/libmount/samples/mount.c
@@ -136,10 +136,8 @@ static void print_all(struct libmnt_context *cxt, char *pattern, int show_label)
 
 /*
  * mount -a [-F]
- * ... -F is not supported yet (TODO)
  */
-static int mount_all(struct libmnt_context *cxt,
-		     int forkme __attribute__((unused)))
+static int mount_all(struct libmnt_context *cxt)
 {
 	struct libmnt_iter *itr;
 	struct libmnt_fs *fs;
@@ -160,24 +158,39 @@ static int mount_all(struct libmnt_context *cxt,
 				printf(ignored == 1 ? _("%-25s: ignored\n") :
 						      _("%-25s: already mounted\n"),
 						tgt);
-		} else if (!mnt_context_get_status(cxt)) {
-			if (mntrc > 0) {
-				errno = mntrc;
-				printf(_("%-25s: failed: %s\n"), tgt,
-						strerror(mntrc));
-				rc |= EX_FAIL;
-			} else {
-				printf(_("%-25s: failed\n"), tgt);
-				rc |= EX_SYSERR;
-			}
+
+		} else if (mnt_context_is_fork(cxt)) {
+			printf("%-25s: mount successfully forked\n", tgt);
+
 		} else {
-			if (mnt_context_is_verbose(cxt))
-				printf("%-25s: successfully mounted\n", tgt);
+			if (!mnt_context_get_status(cxt)) {
+				if (mntrc > 0) {
+					errno = mntrc;
+					printf(_("%-25s: failed: %s\n"), tgt,
+							strerror(mntrc));
+					rc |= EX_FAIL;
+				} else {
+					printf(_("%-25s: failed\n"), tgt);
+					rc |= EX_SYSERR;
+				}
+			} else {
+				if (mnt_context_is_verbose(cxt))
+					printf("%-25s: successfully mounted\n", tgt);
 
-			rc |= EX_SOMEOK;
+				rc |= EX_SOMEOK;
+			}
 		}
 	}
 
+	if (mnt_context_is_parent(cxt)) {
+		/* wait for mount --fork children */
+		int nerrs = 0, nchildren = 0;
+
+		rc = mnt_context_wait_for_children(cxt, &nchildren, &nerrs);
+		if (!rc && nchildren)
+			rc = nchildren == nerrs ? EX_FAIL : EX_SOMEOK;
+	}
+
 	return rc;
 }
 
@@ -251,7 +264,7 @@ static void __attribute__((__noreturn__)) usage(FILE *out)
 
 int main(int argc, char **argv)
 {
-	int c, rc = EX_SUCCESS, all = 0, forkme = 0, show_labels = 0;
+	int c, rc = EX_SUCCESS, all = 0, show_labels = 0;
 	struct libmnt_context *cxt;
 	char *source = NULL, *srcbuf = NULL;
 	char *types = NULL;
@@ -332,7 +345,7 @@ int main(int argc, char **argv)
 			mnt_context_enable_fake(cxt, TRUE);
 			break;
 		case 'F':
-			forkme = 1;
+			mnt_context_enable_fork(cxt, TRUE);
 			break;
 		case 'h':
 			usage(stdout);
@@ -445,7 +458,7 @@ int main(int argc, char **argv)
 		/*
 		 * A) Mount all
 		 */
-		rc = mount_all(cxt, forkme);
+		rc = mount_all(cxt);
 		goto done;
 
 	} else if (argc == 0 && source) {
diff --git a/libmount/src/context.c b/libmount/src/context.c
index e971003cb..c61a14473 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -33,6 +33,8 @@
 
 #include "mountP.h"
 
+#include <sys/wait.h>
+
 /**
  * mnt_new_context:
  *
@@ -94,6 +96,8 @@ void mnt_free_context(struct libmnt_context *cxt)
 	mnt_free_lock(cxt->lock);
 	mnt_free_update(cxt->update);
 
+	free(cxt->children);
+
 	DBG(CXT, mnt_debug_h(cxt, "<---- free"));
 	free(cxt);
 }
@@ -161,6 +165,7 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	cxt->flags |= (fl & MNT_FL_NOHELPERS);
 	cxt->flags |= (fl & MNT_FL_LOOPDEL);
 	cxt->flags |= (fl & MNT_FL_LAZY);
+	cxt->flags |= (fl & MNT_FL_FORK);
 	cxt->flags |= (fl & MNT_FL_FORCE);
 	cxt->flags |= (fl & MNT_FL_NOCANONICALIZE);
 	cxt->flags |= (fl & MNT_FL_RDONLY_UMOUNT);
@@ -171,10 +176,13 @@ static int set_flag(struct libmnt_context *cxt, int flag, int enable)
 {
 	if (!cxt)
 		return -EINVAL;
-	if (enable)
+	if (enable) {
+		DBG(CXT, mnt_debug_h(cxt, "enabling flag %04x", flag));
 		cxt->flags |= flag;
-	else
+	} else {
+		DBG(CXT, mnt_debug_h(cxt, "disabling flag %04x", flag));
 		cxt->flags &= ~flag;
+	}
 	return 0;
 }
 
@@ -254,6 +262,21 @@ int mnt_context_enable_lazy(struct libmnt_context *cxt, int enable)
 }
 
 /**
+ * mnt_context_enable_fork:
+ * @cxt: mount context
+ * @enable: TRUE or FALSE
+ *
+ * Enable/disable fork(2) call in mnt_context_next_mount() (see mount(8) man
+ * page, option -F).
+ *
+ * Returns: 0 on success, negative number in case of error.
+ */
+int mnt_context_enable_fork(struct libmnt_context *cxt, int enable)
+{
+	return set_flag(cxt, MNT_FL_FORK, enable);
+}
+
+/**
  * mnt_context_is_lazy:
  * @cxt: mount context
  *
@@ -1683,6 +1706,116 @@ int mnt_context_is_fs_mounted(struct libmnt_context *cxt,
 	return 0;
 }
 
+static int mnt_context_add_child(struct libmnt_context *cxt, pid_t pid)
+{
+	pid_t *pids;
+
+	if (!cxt)
+		return -EINVAL;
+
+	pids = realloc(cxt->children, sizeof(pid_t) * cxt->nchildren + 1);
+	if (!pids)
+		return -ENOMEM;
+
+	DBG(CXT, mnt_debug_h(cxt, "add new child %d", pid));
+	cxt->children = pids;
+	cxt->children[cxt->nchildren++] = pid;
+
+	return 0;
+}
+
+int mnt_fork_context(struct libmnt_context *cxt)
+{
+	int rc = 0;
+	pid_t pid;
+
+	if (!mnt_context_is_parent(cxt))
+		return -EINVAL;
+
+	DBG(CXT, mnt_debug_h(cxt, "forking context"));
+
+	DBG_FLUSH;
+
+	pid = fork();
+
+	switch (pid) {
+	case -1: /* error */
+		DBG(CXT, mnt_debug_h(cxt, "fork failed %m"));
+		return -errno;
+
+	case 0: /* child */
+		cxt->pid = getpid();
+		cxt->flags &= ~MNT_FL_FORK;
+		DBG(CXT, mnt_debug_h(cxt, "child created"));
+		break;
+
+	default:
+		rc = mnt_context_add_child(cxt, pid);
+		break;
+	}
+
+	return rc;
+}
+
+int mnt_context_wait_for_children(struct libmnt_context *cxt,
+				  int *nchildren, int *nerrs)
+{
+	int i;
+
+	if (!cxt)
+		return -EINVAL;
+
+	assert(mnt_context_is_parent(cxt));
+
+	for (i = 0; i < cxt->nchildren; i++) {
+		pid_t pid = cxt->children[i];
+		int rc = 0, ret = 0;
+
+		if (!pid)
+			continue;
+		do {
+			DBG(CXT, mnt_debug_h(cxt,
+					"waiting for child (%d/%d): %d",
+					i + 1, cxt->nchildren, pid));
+			errno = 0;
+			rc = waitpid(pid, &ret, 0);
+
+		} while (rc == -1 && errno == EINTR);
+
+		if (nchildren)
+			(*nchildren)++;
+
+		if (rc != -1 && nerrs) {
+			if (WIFEXITED(ret))
+				(*nerrs) += WEXITSTATUS(ret) == 0 ? 0 : 1;
+			else
+				(*nerrs)++;
+		}
+		cxt->children[i] = 0;
+	}
+
+	cxt->nchildren = 0;
+	free(cxt->children);
+	cxt->children = NULL;
+	return 0;
+}
+
+int mnt_context_is_fork(struct libmnt_context *cxt)
+{
+	return cxt && (cxt->flags & MNT_FL_FORK);
+}
+
+
+int mnt_context_is_parent(struct libmnt_context *cxt)
+{
+	return mnt_context_is_fork(cxt) && cxt->pid == 0;
+}
+
+int mnt_context_is_child(struct libmnt_context *cxt)
+{
+	return !mnt_context_is_fork(cxt) && cxt->pid;
+}
+
 #ifdef TEST_PROGRAM
 
 struct libmnt_lock *lock;
diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index 7b4c0bae3..8fba9c6be 100644
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -762,12 +762,30 @@ int mnt_context_next_mount(struct libmnt_context *cxt,
 		return 0;
 	}
 
+	if (mnt_context_is_fork(cxt)) {
+		rc = mnt_fork_context(cxt);
+		if (rc)
+			return rc;		/* fork error */
+
+		if (mnt_context_is_parent(cxt)) {
+			return 0;		/* parent */
+		}
+	}
+
+	/* child or non-forked */
+
 	rc = mnt_context_set_fs(cxt, *fs);
-	if (rc)
-		return rc;
-	rc = mnt_context_mount(cxt);
-	if (mntrc)
-		*mntrc = rc;
+	if (!rc) {
+		rc = mnt_context_mount(cxt);
+		if (mntrc)
+			*mntrc = rc;
+	}
+
+	if (mnt_context_is_child(cxt)) {
+		DBG(CXT, mnt_debug_h(cxt, "next-mount: child exit [rc=%d]", rc));
+		DBG_FLUSH;
+		exit(rc);
+	}
 	return 0;
 }
 
diff --git a/libmount/src/libmount.h.in b/libmount/src/libmount.h.in
index c991764b9..95a710e2f 100644
--- a/libmount/src/libmount.h.in
+++ b/libmount/src/libmount.h.in
@@ -390,6 +390,7 @@ extern int mnt_context_disable_mtab(struct libmnt_context *cxt, int disable);
 extern int mnt_context_enable_force(struct libmnt_context *cxt, int enable);
 extern int mnt_context_enable_verbose(struct libmnt_context *cxt, int enable);
 extern int mnt_context_enable_loopdel(struct libmnt_context *cxt, int enable);
+extern int mnt_context_enable_fork(struct libmnt_context *cxt, int enable);
 
 extern int mnt_context_get_optsmode(struct libmnt_context *cxt);
 extern int mnt_context_is_lazy(struct libmnt_context *cxt);
@@ -400,6 +401,13 @@ extern int mnt_context_is_nomtab(struct libmnt_context *cxt);
 extern int mnt_context_is_force(struct libmnt_context *cxt);
 extern int mnt_context_is_verbose(struct libmnt_context *cxt);
 
+extern int mnt_context_is_fork(struct libmnt_context *cxt);
+extern int mnt_context_is_parent(struct libmnt_context *cxt);
+extern int mnt_context_is_child(struct libmnt_context *cxt);
+
+extern int mnt_context_wait_for_children(struct libmnt_context *cxt,
+                                  int *nchildren, int *nerrs);
+
 extern int mnt_context_is_fs_mounted(struct libmnt_context *cxt,
                               struct libmnt_fs *fs, int *mounted);
 
diff --git a/libmount/src/libmount.sym b/libmount/src/libmount.sym
index 6f4eda71d..6f4d1c02b 100644
--- a/libmount/src/libmount.sym
+++ b/libmount/src/libmount.sym
@@ -208,5 +208,10 @@ global:
 
 MOUNT_2.21 {
 global:
+	mnt_context_enable_fork;
+	mnt_context_is_child;
+	mnt_context_is_fork;
+	mnt_context_is_parent;
 	mnt_context_next_umount;
+	mnt_context_wait_for_children;
 } MOUNT_2.20;
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index cce4c5c35..9be3aabed 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -61,12 +61,16 @@
 
 # define DBG(m, x)	do { \
 				if ((MNT_DEBUG_ ## m) & libmount_debug_mask) { \
-					fprintf(stderr, "libmount: %8s: ", # m); \
+					fprintf(stderr, "%d: libmount: %8s: ", getpid(), # m); \
 					x; \
 				} \
 			} while (0)
 
-# define DBG_FLUSH	do { fflush(stderr); } while(0)
+# define DBG_FLUSH	do { \
+				if (libmount_debug_mask && \
+				    libmount_debug_mask != MNT_DEBUG_INIT) \
+					fflush(stderr); \
+			} while(0)
 
 extern int libmount_debug_mask;
 
@@ -299,6 +303,11 @@ struct libmnt_context
 
 	char	*orig_user;	/* original (non-fixed) user= option */
 
+	pid_t	*children;	/* "mount -a --fork" PIDs */
+	int	nchildren;	/* number of children */
+	pid_t	pid;		/* 0=parent; PID=child */
+
+
 	int	syscall_status;	/* 1: not called yet, 0: success, <0: -errno */
 };
 
@@ -313,6 +322,7 @@ struct libmnt_context
 #define MNT_FL_FORCE		(1 << 8)
 #define MNT_FL_NOCANONICALIZE	(1 << 9)
 #define MNT_FL_RDONLY_UMOUNT	(1 << 11)	/* remount,ro after EBUSY umount(2) */
+#define MNT_FL_FORK		(1 << 12)
 
 #define MNT_FL_EXTERN_FS	(1 << 15)	/* cxt->fs is not private */
 #define MNT_FL_EXTERN_FSTAB	(1 << 16)	/* cxt->fstab is not private */
@@ -370,6 +380,8 @@ extern int mnt_context_setup_loopdev(struct libmnt_context *cxt);
 extern int mnt_context_delete_loopdev(struct libmnt_context *cxt);
 extern int mnt_context_clear_loopdev(struct libmnt_context *cxt);
 
+extern int mnt_fork_context(struct libmnt_context *cxt);
+
 /* tab_update.c */
 extern struct libmnt_fs *mnt_update_get_fs(struct libmnt_update *upd);
 extern int mnt_update_set_filename(struct libmnt_update *upd,