Initial Spring 2016 commit.

kern/fs/semfs/semfs_fsops.c

@@ -0,0 +1,226 @@
+/*
+ * Copyright (c) 2014
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <types.h>
+#include <kern/errno.h>
+#include <synch.h>
+#include <vfs.h>
+#include <fs.h>
+#include <vnode.h>
+
+#include "semfs.h"
+
+////////////////////////////////////////////////////////////
+// fs-level operations
+
+/*
+ * Sync doesn't need to do anything.
+ */
+static
+int
+semfs_sync(struct fs *fs)
+{
+	(void)fs;
+	return 0;
+}
+
+/*
+ * We have only one volume name and it's hardwired.
+ */
+static
+const char *
+semfs_getvolname(struct fs *fs)
+{
+	(void)fs;
+	return "sem";
+}
+
+/*
+ * Get the root directory vnode.
+ */
+static
+int
+semfs_getroot(struct fs *fs, struct vnode **ret)
+{
+	struct semfs *semfs = fs->fs_data;
+	struct vnode *vn;
+	int result;
+
+	result = semfs_getvnode(semfs, SEMFS_ROOTDIR, &vn);
+	if (result) {
+		kprintf("semfs: couldn't load root vnode: %s\n",
+			strerror(result));
+		return result;
+	}
+	*ret = vn;
+	return 0;
+}
+
+////////////////////////////////////////////////////////////
+// mount and unmount logic
+
+
+/*
+ * Destructor for struct semfs.
+ */
+static
+void
+semfs_destroy(struct semfs *semfs)
+{
+	struct semfs_sem *sem;
+	struct semfs_direntry *dent;
+	unsigned i, num;
+
+	num = semfs_semarray_num(semfs->semfs_sems);
+	for (i=0; i<num; i++) {
+		sem = semfs_semarray_get(semfs->semfs_sems, i);
+		semfs_sem_destroy(sem);
+	}
+	semfs_semarray_setsize(semfs->semfs_sems, 0);
+
+	num = semfs_direntryarray_num(semfs->semfs_dents);
+	for (i=0; i<num; i++) {
+		dent = semfs_direntryarray_get(semfs->semfs_dents, i);
+		semfs_direntry_destroy(dent);
+	}
+	semfs_direntryarray_setsize(semfs->semfs_dents, 0);
+
+	semfs_direntryarray_destroy(semfs->semfs_dents);
+	lock_destroy(semfs->semfs_dirlock);
+	semfs_semarray_destroy(semfs->semfs_sems);
+	vnodearray_destroy(semfs->semfs_vnodes);
+	lock_destroy(semfs->semfs_tablelock);
+	kfree(semfs);
+}
+
+/*
+ * Unmount routine. XXX: Since semfs is attached at boot and can't be
+ * remounted, maybe unmounting it shouldn't be allowed.
+ */
+static
+int
+semfs_unmount(struct fs *fs)
+{
+	struct semfs *semfs = fs->fs_data;
+
+	lock_acquire(semfs->semfs_tablelock);
+	if (vnodearray_num(semfs->semfs_vnodes) > 0) {
+		lock_release(semfs->semfs_tablelock);
+		return EBUSY;
+	}
+
+	lock_release(semfs->semfs_tablelock);
+	semfs_destroy(semfs);
+
+	return 0;
+}
+
+/*
+ * Operations table.
+ */
+static const struct fs_ops semfs_fsops = {
+	.fsop_sync = semfs_sync,
+	.fsop_getvolname = semfs_getvolname,
+	.fsop_getroot = semfs_getroot,
+	.fsop_unmount = semfs_unmount,
+};
+
+/*
+ * Constructor for struct semfs.
+ */
+static
+struct semfs *
+semfs_create(void)
+{
+	struct semfs *semfs;
+
+	semfs = kmalloc(sizeof(*semfs));
+	if (semfs == NULL) {
+		goto fail_total;
+	}
+
+	semfs->semfs_tablelock = lock_create("semfs_table");
+	if (semfs->semfs_tablelock == NULL) {
+		goto fail_semfs;
+	}
+	semfs->semfs_vnodes = vnodearray_create();
+	if (semfs->semfs_vnodes == NULL) {
+		goto fail_tablelock;
+	}
+	semfs->semfs_sems = semfs_semarray_create();
+	if (semfs->semfs_sems == NULL) {
+		goto fail_vnodes;
+	}
+
+	semfs->semfs_dirlock = lock_create("semfs_dir");
+	if (semfs->semfs_dirlock == NULL) {
+		goto fail_sems;
+	}
+	semfs->semfs_dents = semfs_direntryarray_create();
+	if (semfs->semfs_dents == NULL) {
+		goto fail_dirlock;
+	}
+
+	semfs->semfs_absfs.fs_data = semfs;
+	semfs->semfs_absfs.fs_ops = &semfs_fsops;
+	return semfs;
+
+ fail_dirlock:
+	lock_destroy(semfs->semfs_dirlock);
+ fail_sems:
+	semfs_semarray_destroy(semfs->semfs_sems);
+ fail_vnodes:
+	vnodearray_destroy(semfs->semfs_vnodes);
+ fail_tablelock:
+	lock_destroy(semfs->semfs_tablelock);
+ fail_semfs:
+	kfree(semfs);
+ fail_total:
+	return NULL;
+}
+
+/*
+ * Create the semfs. There is only one semfs and it's attached as
+ * "sem:" during bootup.
+ */
+void
+semfs_bootstrap(void)
+{
+	struct semfs *semfs;
+	int result;
+
+	semfs = semfs_create();
+	if (semfs == NULL) {
+		panic("Out of memory creating semfs\n");
+	}
+	result = vfs_addfs("sem", &semfs->semfs_absfs);
+	if (result) {
+		panic("Attaching semfs: %s\n", strerror(result));
+	}
+}