fs/fs_struct.c

Source file repositories/reference/linux-study-clean/fs/fs_struct.c

File Facts

System
Linux kernel
Corpus path
fs/fs_struct.c
Extension
.c
Size
3151 bytes
Lines
156
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

if (fs) {
			int hits = 0;
			write_seqlock(&fs->seq);
			hits += replace_path(&fs->root, old_root, new_root);
			hits += replace_path(&fs->pwd, old_root, new_root);
			while (hits--) {
				count++;
				path_get(new_root);
			}
			write_sequnlock(&fs->seq);
		}
		task_unlock(p);
	}
	read_unlock(&tasklist_lock);
	while (count--)
		path_put(old_root);
}

void free_fs_struct(struct fs_struct *fs)
{
	path_put(&fs->root);
	path_put(&fs->pwd);
	kmem_cache_free(fs_cachep, fs);
}

void exit_fs(struct task_struct *tsk)
{
	struct fs_struct *fs = tsk->fs;

	if (fs) {
		int kill;
		task_lock(tsk);
		read_seqlock_excl(&fs->seq);
		tsk->fs = NULL;
		kill = !--fs->users;
		read_sequnlock_excl(&fs->seq);
		task_unlock(tsk);
		if (kill)
			free_fs_struct(fs);
	}
}

struct fs_struct *copy_fs_struct(struct fs_struct *old)
{
	struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL);
	/* We don't need to lock fs - think why ;-) */
	if (fs) {
		fs->users = 1;
		fs->in_exec = 0;
		seqlock_init(&fs->seq);
		fs->umask = old->umask;

		read_seqlock_excl(&old->seq);
		fs->root = old->root;
		path_get(&fs->root);
		fs->pwd = old->pwd;
		path_get(&fs->pwd);
		read_sequnlock_excl(&old->seq);
	}
	return fs;
}

int unshare_fs_struct(void)
{
	struct fs_struct *fs = current->fs;
	struct fs_struct *new_fs = copy_fs_struct(fs);
	int kill;

	if (!new_fs)
		return -ENOMEM;

	task_lock(current);
	read_seqlock_excl(&fs->seq);
	kill = !--fs->users;
	current->fs = new_fs;
	read_sequnlock_excl(&fs->seq);
	task_unlock(current);

	if (kill)
		free_fs_struct(fs);

	return 0;
}
EXPORT_SYMBOL_GPL(unshare_fs_struct);

/* to be mentioned only in INIT_TASK */
struct fs_struct init_fs = {
	.users		= 1,
	.seq		= __SEQLOCK_UNLOCKED(init_fs.seq),
	.umask		= 0022,

Annotation

Implementation Notes