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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /fs/filesystems.c
downloadlinux-linaro-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'fs/filesystems.c')
-rw-r--r--fs/filesystems.c236
1 files changed, 236 insertions, 0 deletions
diff --git a/fs/filesystems.c b/fs/filesystems.c
new file mode 100644
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+++ b/fs/filesystems.c
@@ -0,0 +1,236 @@
+/*
+ * linux/fs/filesystems.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * table of configured filesystems
+ */
+
+#include <linux/syscalls.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/kmod.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+/*
+ * Handling of filesystem drivers list.
+ * Rules:
+ * Inclusion to/removals from/scanning of list are protected by spinlock.
+ * During the unload module must call unregister_filesystem().
+ * We can access the fields of list element if:
+ * 1) spinlock is held or
+ * 2) we hold the reference to the module.
+ * The latter can be guaranteed by call of try_module_get(); if it
+ * returned 0 we must skip the element, otherwise we got the reference.
+ * Once the reference is obtained we can drop the spinlock.
+ */
+
+static struct file_system_type *file_systems;
+static DEFINE_RWLOCK(file_systems_lock);
+
+/* WARNING: This can be used only if we _already_ own a reference */
+void get_filesystem(struct file_system_type *fs)
+{
+ __module_get(fs->owner);
+}
+
+void put_filesystem(struct file_system_type *fs)
+{
+ module_put(fs->owner);
+}
+
+static struct file_system_type **find_filesystem(const char *name)
+{
+ struct file_system_type **p;
+ for (p=&file_systems; *p; p=&(*p)->next)
+ if (strcmp((*p)->name,name) == 0)
+ break;
+ return p;
+}
+
+/**
+ * register_filesystem - register a new filesystem
+ * @fs: the file system structure
+ *
+ * Adds the file system passed to the list of file systems the kernel
+ * is aware of for mount and other syscalls. Returns 0 on success,
+ * or a negative errno code on an error.
+ *
+ * The &struct file_system_type that is passed is linked into the kernel
+ * structures and must not be freed until the file system has been
+ * unregistered.
+ */
+
+int register_filesystem(struct file_system_type * fs)
+{
+ int res = 0;
+ struct file_system_type ** p;
+
+ if (!fs)
+ return -EINVAL;
+ if (fs->next)
+ return -EBUSY;
+ INIT_LIST_HEAD(&fs->fs_supers);
+ write_lock(&file_systems_lock);
+ p = find_filesystem(fs->name);
+ if (*p)
+ res = -EBUSY;
+ else
+ *p = fs;
+ write_unlock(&file_systems_lock);
+ return res;
+}
+
+EXPORT_SYMBOL(register_filesystem);
+
+/**
+ * unregister_filesystem - unregister a file system
+ * @fs: filesystem to unregister
+ *
+ * Remove a file system that was previously successfully registered
+ * with the kernel. An error is returned if the file system is not found.
+ * Zero is returned on a success.
+ *
+ * Once this function has returned the &struct file_system_type structure
+ * may be freed or reused.
+ */
+
+int unregister_filesystem(struct file_system_type * fs)
+{
+ struct file_system_type ** tmp;
+
+ write_lock(&file_systems_lock);
+ tmp = &file_systems;
+ while (*tmp) {
+ if (fs == *tmp) {
+ *tmp = fs->next;
+ fs->next = NULL;
+ write_unlock(&file_systems_lock);
+ return 0;
+ }
+ tmp = &(*tmp)->next;
+ }
+ write_unlock(&file_systems_lock);
+ return -EINVAL;
+}
+
+EXPORT_SYMBOL(unregister_filesystem);
+
+static int fs_index(const char __user * __name)
+{
+ struct file_system_type * tmp;
+ char * name;
+ int err, index;
+
+ name = getname(__name);
+ err = PTR_ERR(name);
+ if (IS_ERR(name))
+ return err;
+
+ err = -EINVAL;
+ read_lock(&file_systems_lock);
+ for (tmp=file_systems, index=0 ; tmp ; tmp=tmp->next, index++) {
+ if (strcmp(tmp->name,name) == 0) {
+ err = index;
+ break;
+ }
+ }
+ read_unlock(&file_systems_lock);
+ putname(name);
+ return err;
+}
+
+static int fs_name(unsigned int index, char __user * buf)
+{
+ struct file_system_type * tmp;
+ int len, res;
+
+ read_lock(&file_systems_lock);
+ for (tmp = file_systems; tmp; tmp = tmp->next, index--)
+ if (index <= 0 && try_module_get(tmp->owner))
+ break;
+ read_unlock(&file_systems_lock);
+ if (!tmp)
+ return -EINVAL;
+
+ /* OK, we got the reference, so we can safely block */
+ len = strlen(tmp->name) + 1;
+ res = copy_to_user(buf, tmp->name, len) ? -EFAULT : 0;
+ put_filesystem(tmp);
+ return res;
+}
+
+static int fs_maxindex(void)
+{
+ struct file_system_type * tmp;
+ int index;
+
+ read_lock(&file_systems_lock);
+ for (tmp = file_systems, index = 0 ; tmp ; tmp = tmp->next, index++)
+ ;
+ read_unlock(&file_systems_lock);
+ return index;
+}
+
+/*
+ * Whee.. Weird sysv syscall.
+ */
+asmlinkage long sys_sysfs(int option, unsigned long arg1, unsigned long arg2)
+{
+ int retval = -EINVAL;
+
+ switch (option) {
+ case 1:
+ retval = fs_index((const char __user *) arg1);
+ break;
+
+ case 2:
+ retval = fs_name(arg1, (char __user *) arg2);
+ break;
+
+ case 3:
+ retval = fs_maxindex();
+ break;
+ }
+ return retval;
+}
+
+int get_filesystem_list(char * buf)
+{
+ int len = 0;
+ struct file_system_type * tmp;
+
+ read_lock(&file_systems_lock);
+ tmp = file_systems;
+ while (tmp && len < PAGE_SIZE - 80) {
+ len += sprintf(buf+len, "%s\t%s\n",
+ (tmp->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
+ tmp->name);
+ tmp = tmp->next;
+ }
+ read_unlock(&file_systems_lock);
+ return len;
+}
+
+struct file_system_type *get_fs_type(const char *name)
+{
+ struct file_system_type *fs;
+
+ read_lock(&file_systems_lock);
+ fs = *(find_filesystem(name));
+ if (fs && !try_module_get(fs->owner))
+ fs = NULL;
+ read_unlock(&file_systems_lock);
+ if (!fs && (request_module("%s", name) == 0)) {
+ read_lock(&file_systems_lock);
+ fs = *(find_filesystem(name));
+ if (fs && !try_module_get(fs->owner))
+ fs = NULL;
+ read_unlock(&file_systems_lock);
+ }
+ return fs;
+}
+
+EXPORT_SYMBOL(get_fs_type);