/*
* Ideally this function should call VFS:do_last() in order to keep all its
* checkings. But it is very hard for aufs to regenerate several VFS internal
* structure such as nameidata. This is a second (or third) best approach.
* cf. linux/fs/namei.c:do_last(), lookup_open() and atomic_open().
*/
int vfsub_atomic_open(struct inode *dir, struct dentry *dentry,
struct vfsub_aopen_args *args, struct au_branch *br)
{
int err;
struct file *file = args->file;
/* copied from linux/fs/namei.c:atomic_open() */
struct dentry *const DENTRY_NOT_SET = (void *)-1UL;
IMustLock(dir);
AuDebugOn(!dir->i_op->atomic_open);
err = au_br_test_oflag(args->open_flag, br);
if (unlikely(err))
goto out;
args->file->f_path.dentry = DENTRY_NOT_SET;
args->file->f_path.mnt = au_br_mnt(br);
err = dir->i_op->atomic_open(dir, dentry, file, args->open_flag,
args->create_mode, args->opened);
if (err >= 0) {
/* some filesystems don't set FILE_CREATED while succeeded? */
if (*args->opened & FILE_CREATED)
fsnotify_create(dir, dentry);
} else
goto out;
if (!err) {
/* todo: call VFS:may_open() here */
err = open_check_o_direct(file);
/* todo: ima_file_check() too? */
if (!err && (args->open_flag & __FMODE_EXEC))
err = deny_write_access(file);
if (unlikely(err))
/* note that the file is created and still opened */
goto out;
}
atomic_inc(&br->br_count);
fsnotify_open(file);
out:
return err;
}
/* common functions to regular file and dir */
struct file *au_h_open(struct dentry *dentry, aufs_bindex_t bindex, int flags,
struct file *file, int force_wr)
{
struct file *h_file;
struct dentry *h_dentry;
struct inode *h_inode;
struct super_block *sb;
struct au_branch *br;
struct path h_path;
int err;
/* a race condition can happen between open and unlink/rmdir */
h_file = ERR_PTR(-ENOENT);
h_dentry = au_h_dptr(dentry, bindex);
if (au_test_nfsd() && !h_dentry)
goto out;
h_inode = h_dentry->d_inode;
if (au_test_nfsd() && !h_inode)
goto out;
spin_lock(&h_dentry->d_lock);
err = (!d_unhashed(dentry) && d_unlinked(h_dentry))
|| !h_inode
/* || !dentry->d_inode->i_nlink */
;
spin_unlock(&h_dentry->d_lock);
if (unlikely(err))
goto out;
sb = dentry->d_sb;
br = au_sbr(sb, bindex);
err = au_br_test_oflag(flags, br);
h_file = ERR_PTR(err);
if (unlikely(err))
goto out;
/* drop flags for writing */
if (au_test_ro(sb, bindex, dentry->d_inode)) {
if (force_wr && !(flags & O_WRONLY))
force_wr = 0;
flags = au_file_roflags(flags);
if (force_wr) {
h_file = ERR_PTR(-EROFS);
flags = au_file_roflags(flags);
if (unlikely(vfsub_native_ro(h_inode)
|| IS_APPEND(h_inode)))
goto out;
flags &= ~O_ACCMODE;
flags |= O_WRONLY;
}
}
flags &= ~O_CREAT;
atomic_inc(&br->br_count);
h_path.dentry = h_dentry;
h_path.mnt = au_br_mnt(br);
h_file = vfsub_dentry_open(&h_path, flags);
if (IS_ERR(h_file))
goto out_br;
if (flags & __FMODE_EXEC) {
err = deny_write_access(h_file);
if (unlikely(err)) {
fput(h_file);
h_file = ERR_PTR(err);
goto out_br;
}
}
fsnotify_open(h_file);
goto out; /* success */
out_br:
atomic_dec(&br->br_count);
out:
return h_file;
}