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authorSang-Heon Jeon <ekffu200098@gmail.com>2026-08-24 01:18:14 +0900
committerJulia Lawall <Julia.Lawall@inria.fr>2026-08-23 22:12:11 +0200
commit2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c (patch)
treedcc4da1d99f17541c5590ac63c77da4bf372a4ab /fs/filesystems.c
downloadlinux-stable-2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c.tar.gz
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coccinelle: alloc_cast: drop removed allocatorsgrafted
- pci_alloc_consistent() and pci_zalloc_consistent() were removed by commit 7968778914e5 ("PCI: Remove the deprecated "pci-dma-compat.h" API") - kmem_alloc() was removed by commit f078d4ea8276 ("xfs: convert kmem_alloc() to kmalloc()") - kmem_zalloc() was removed by commit 10634530f7ba ("xfs: convert kmem_zalloc() to kzalloc()") - kmem_zone_alloc() and kmem_zone_zalloc() were removed by commit bae633a4a283 ("xfs: remove xfs_zone_{alloc,zalloc} helpers") So drop them from the rules. No functional change. Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Diffstat (limited to 'fs/filesystems.c')
-rw-r--r--fs/filesystems.c413
1 files changed, 413 insertions, 0 deletions
diff --git a/fs/filesystems.c b/fs/filesystems.c
new file mode 100644
index 000000000..3083d904d
--- /dev/null
+++ b/fs/filesystems.c
@@ -0,0 +1,413 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/filesystems.c
+ *
+ * Copyright (C) 1991, 1992 Linus Torvalds
+ *
+ * table of configured filesystems
+ */
+
+#include <linux/syscalls.h>
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/kmod.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/fs_parser.h>
+#include <linux/rculist.h>
+
+/*
+ * Read-mostly filesystem drivers list.
+ *
+ * Readers walk under rcu_read_lock(); writers take file_systems_lock
+ * and publish via _rcu hlist primitives. unregister_filesystem()
+ * synchronize_rcu()s after unlock so the embedded file_system_type
+ * can't go away under a reader. To keep using a filesystem after
+ * the RCU section ends, take a module reference via try_module_get().
+ */
+static HLIST_HEAD(file_systems);
+static DEFINE_SPINLOCK(file_systems_lock);
+
+#ifdef CONFIG_PROC_FS
+/*
+ * Cache a stringified version of the filesystem list.
+ *
+ * The fs list gets queried a lot by userspace because of libselinux, including
+ * rather surprising programs (would you guess *sed* is on the list?). In order
+ * to reduce the overhead we cache the resulting string, which normally hangs
+ * around below 512 bytes in size.
+ *
+ * As the list almost never changes, its creation is not particularly optimized
+ * to keep things simple.
+ *
+ * We sort it out on read in order to not introduce a failure point for fs
+ * registration (in principle we may be unable to alloc memory for the list).
+ */
+struct file_systems_string {
+ struct rcu_head rcu;
+ unsigned long gen;
+ size_t len;
+ char string[];
+};
+
+static unsigned long file_systems_gen;
+static struct file_systems_string __read_mostly __rcu *file_systems_string;
+
+static void invalidate_filesystems_string(void);
+#else
+static inline void invalidate_filesystems_string(void) { }
+#endif
+
+/* WARNING: This can be used only if we _already_ own a reference */
+struct file_system_type *get_filesystem(struct file_system_type *fs)
+{
+ __module_get(fs->owner);
+ return fs;
+}
+
+void put_filesystem(struct file_system_type *fs)
+{
+ module_put(fs->owner);
+}
+
+static struct file_system_type *find_filesystem(const char *name, unsigned len)
+{
+ struct file_system_type *fs;
+
+ hlist_for_each_entry_rcu(fs, &file_systems, list,
+ lockdep_is_held(&file_systems_lock))
+ if (strncmp(fs->name, name, len) == 0 && !fs->name[len])
+ return fs;
+ return NULL;
+}
+
+/**
+ * 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)
+{
+ if (fs->parameters &&
+ !fs_validate_description(fs->name, fs->parameters))
+ return -EINVAL;
+
+ BUG_ON(strchr(fs->name, '.'));
+ if (!hlist_unhashed_lockless(&fs->list))
+ return -EBUSY;
+
+ guard(spinlock)(&file_systems_lock);
+ if (find_filesystem(fs->name, strlen(fs->name)))
+ return -EBUSY;
+ hlist_add_tail_rcu(&fs->list, &file_systems);
+ invalidate_filesystems_string();
+ return 0;
+}
+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)
+{
+ scoped_guard(spinlock, &file_systems_lock) {
+ if (hlist_unhashed(&fs->list))
+ return -EINVAL;
+ hlist_del_init_rcu(&fs->list);
+ invalidate_filesystems_string();
+ }
+ synchronize_rcu();
+ return 0;
+}
+EXPORT_SYMBOL(unregister_filesystem);
+
+#ifdef CONFIG_SYSFS_SYSCALL
+static int fs_index(const char __user *__name)
+{
+ struct file_system_type *p;
+ char *name __free(kfree) = strndup_user(__name, PATH_MAX);
+ int index = 0;
+
+ if (IS_ERR(name))
+ return PTR_ERR(name);
+
+ guard(rcu)();
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ if (strcmp(p->name, name) == 0)
+ return index;
+ index++;
+ }
+ return -EINVAL;
+}
+
+static int fs_name(unsigned int index, char __user *buf)
+{
+ struct file_system_type *p, *found = NULL;
+ int len, res;
+
+ scoped_guard(rcu) {
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ if (index--)
+ continue;
+ if (try_module_get(p->owner))
+ found = p;
+ break;
+ }
+ }
+ if (!found)
+ return -EINVAL;
+
+ /* OK, we got the reference, so we can safely block */
+ len = strlen(found->name) + 1;
+ res = copy_to_user(buf, found->name, len) ? -EFAULT : 0;
+ put_filesystem(found);
+ return res;
+}
+
+static int fs_maxindex(void)
+{
+ struct file_system_type *p;
+ int index = 0;
+
+ guard(rcu)();
+ hlist_for_each_entry_rcu(p, &file_systems, list)
+ index++;
+ return index;
+}
+
+/*
+ * Whee.. Weird sysv syscall.
+ */
+SYSCALL_DEFINE3(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;
+}
+#endif
+
+int __init list_bdev_fs_names(char *buf, size_t size)
+{
+ struct file_system_type *p;
+ size_t len;
+ int count = 0;
+
+ guard(rcu)();
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ if (!(p->fs_flags & FS_REQUIRES_DEV))
+ continue;
+ len = strlen(p->name) + 1;
+ if (len > size) {
+ pr_warn("%s: truncating file system list\n", __func__);
+ break;
+ }
+ memcpy(buf, p->name, len);
+ buf += len;
+ size -= len;
+ count++;
+ }
+ return count;
+}
+
+#ifdef CONFIG_PROC_FS
+static void invalidate_filesystems_string(void)
+{
+ struct file_systems_string *old;
+
+ lockdep_assert_held_write(&file_systems_lock);
+ file_systems_gen++;
+ old = rcu_replace_pointer(file_systems_string, NULL,
+ lockdep_is_held(&file_systems_lock));
+ if (old)
+ kfree_rcu(old, rcu);
+}
+
+static __cold noinline int regen_filesystems_string(void)
+{
+ struct file_system_type *p;
+ struct file_systems_string *old, *new;
+ size_t newlen, usedlen;
+ unsigned long gen;
+
+retry:
+ newlen = 0;
+
+ /* pre-calc space for each fs */
+ spin_lock(&file_systems_lock);
+ gen = file_systems_gen;
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ if (!(p->fs_flags & FS_REQUIRES_DEV))
+ newlen += strlen("nodev");
+ newlen += strlen("\t") + strlen(p->name) + strlen("\n");
+ }
+ spin_unlock(&file_systems_lock);
+
+ new = kmalloc(offsetof(struct file_systems_string, string) + newlen + 1,
+ GFP_KERNEL);
+ if (!new)
+ return -ENOMEM;
+
+ new->gen = gen;
+ new->len = newlen;
+ new->string[newlen] = '\0';
+
+ spin_lock(&file_systems_lock);
+ old = file_systems_string;
+
+ /*
+ * Did someone beat us to it?
+ */
+ if (old && old->gen == file_systems_gen) {
+ spin_unlock(&file_systems_lock);
+ kfree(new);
+ return 0;
+ }
+
+ /*
+ * Did the list change in the meantime?
+ */
+ if (gen != file_systems_gen) {
+ spin_unlock(&file_systems_lock);
+ kfree(new);
+ goto retry;
+ }
+
+ /*
+ * Populate the string.
+ *
+ * We know we have just enough space because we calculated the right
+ * size the previous time we had the lock and confirmed the list has
+ * not changed after reacquiring it.
+ */
+ usedlen = 0;
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ usedlen += sprintf(&new->string[usedlen], "%s\t%s\n",
+ (p->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
+ p->name);
+ }
+
+ if (WARN_ON_ONCE(new->len != strlen(new->string))) {
+ /*
+ * Should never happen of course, keep this in case someone changes string
+ * generation above and messes it up.
+ */
+ spin_unlock(&file_systems_lock);
+ kfree(new);
+ return -EINVAL;
+ }
+
+ rcu_assign_pointer(file_systems_string, new);
+ spin_unlock(&file_systems_lock);
+ if (old)
+ kfree_rcu(old, rcu);
+ return 0;
+}
+
+static __cold noinline int filesystems_proc_show_fallback(struct seq_file *m, void *v)
+{
+ struct file_system_type *p;
+
+ guard(rcu)();
+ hlist_for_each_entry_rcu(p, &file_systems, list) {
+ seq_printf(m, "%s\t%s\n",
+ (p->fs_flags & FS_REQUIRES_DEV) ? "" : "nodev",
+ p->name);
+ }
+ return 0;
+}
+
+static int filesystems_proc_show(struct seq_file *m, void *v)
+{
+ struct file_systems_string *fss;
+
+ for (;;) {
+ scoped_guard(rcu) {
+ fss = rcu_dereference(file_systems_string);
+ if (likely(fss)) {
+ seq_write(m, fss->string, fss->len);
+ return 0;
+ }
+ }
+
+ int err = regen_filesystems_string();
+ if (unlikely(err))
+ return filesystems_proc_show_fallback(m, v);
+ }
+}
+
+static int __init proc_filesystems_init(void)
+{
+ struct proc_dir_entry *pde;
+
+ pde = proc_create_single("filesystems", 0, NULL, filesystems_proc_show);
+ if (!pde)
+ return -ENOMEM;
+ proc_make_permanent(pde);
+ return 0;
+}
+module_init(proc_filesystems_init);
+#endif
+
+static struct file_system_type *__get_fs_type(const char *name, int len)
+{
+ struct file_system_type *fs;
+
+ guard(rcu)();
+ fs = find_filesystem(name, len);
+ if (fs && !try_module_get(fs->owner))
+ fs = NULL;
+ return fs;
+}
+
+struct file_system_type *get_fs_type(const char *name)
+{
+ struct file_system_type *fs;
+ const char *dot = strchr(name, '.');
+ int len = dot ? dot - name : strlen(name);
+
+ fs = __get_fs_type(name, len);
+ if (!fs && (request_module("fs-%.*s", len, name) == 0)) {
+ fs = __get_fs_type(name, len);
+ if (!fs)
+ pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n",
+ len, name);
+ }
+
+ if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) {
+ put_filesystem(fs);
+ fs = NULL;
+ }
+ return fs;
+}
+EXPORT_SYMBOL(get_fs_type);