kernel: vfs: Simplify mounting logic

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 141 insertions, 0 deletions

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
new file mode 100644
index 0000000..53df6a2
--- /dev/null
+++ b/sys/kern/vfs_mount.c
@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2023-2024 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * 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 Hyra 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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 <sys/types.h>
+#include <sys/queue.h>
+#include <sys/mount.h>
+#include <sys/vfs.h>
+#include <sys/errno.h>
+#include <vm/dynalloc.h>
+#include <assert.h>
+
+/* TODO: Make this more flexible */
+#define MOUNTLIST_SIZE 8
+
+/* Mountlist entry */
+struct mountlist_entry {
+    TAILQ_HEAD(, mount) buckets;
+};
+
+static struct mountlist_entry *mountlist = NULL;
+
+static int
+vfs_create_mp(const char *path, int mntflags, struct mount **mp_out)
+{
+    struct mount *mp;
+
+    mp = dynalloc(sizeof(struct mount));
+    if (mp == NULL) {
+        return -ENOMEM;
+    }
+
+    mp->flags = mntflags;
+    *mp_out = mp;
+    return 0;
+}
+
+/*
+ * Mount a mountpoint
+ *
+ * @mp: Mountpoint to mount
+ * @path: Path this mountpoint belongs to
+ *
+ * If this mount entry already exists, -EEXIST
+ * will be returned.
+ */
+int
+vfs_mount(const char *path, int mntflags)
+{
+    size_t hash = vfs_hash_path(path);
+    int status;
+    struct mountlist_entry *entry;
+    struct mount *mp;
+
+    if ((status = vfs_create_mp(path, mntflags, &mp)) != 0) {
+        return status;
+    }
+    if (hash == 0) {
+        /* Something is wrong with the path */
+        return -EINVAL;
+    }
+
+    if (vfs_get_mp(path, NULL) == 0) {
+        /* mount hit, do not duplicate this entry */
+        return -EEXIST;
+    }
+
+    mp->phash = hash;
+    entry = &mountlist[hash % MOUNTLIST_SIZE];
+    TAILQ_INSERT_TAIL(&entry->buckets, mp, link);
+    return 0;
+}
+
+/*
+ * Fetch mountpoint
+ *
+ * @path: Path of target mountpoint
+ * @mp: Pointer of variable where mountpoint fetched will
+ *      be stored
+ *
+ * Returns 0 upon a mplist hit, on a mplist miss this
+ * function returns -ENOENT.
+ */
+int
+vfs_get_mp(const char *path, struct mount **mp)
+{
+    size_t hash = vfs_hash_path(path);
+    struct mountlist_entry *entry;
+    struct mount *mount_iter;
+
+    if (hash == 0) {
+        /* Something is wrong with the path */
+        return -EINVAL;
+    }
+
+    entry = &mountlist[hash % MOUNTLIST_SIZE];
+    TAILQ_FOREACH(mount_iter, &entry->buckets, link) {
+        if (mount_iter->phash == hash) {
+            if (mp != NULL) *mp = mount_iter;
+            return 0;
+        }
+    }
+
+    return -ENOENT;
+}
+
+void
+vfs_mount_init(void)
+{
+    mountlist = dynalloc(sizeof(struct mountlist_entry) * MOUNTLIST_SIZE);
+    __assert(mountlist != NULL);
+
+    for (size_t i = 0; i < MOUNTLIST_SIZE; ++i) {
+        TAILQ_INIT(&mountlist[i].buckets);
+    }
+}