71 lines
1.6 KiB
C
71 lines
1.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2026 Christian Brauner <brauner@kernel.org> */
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#include <linux/fs/super_types.h>
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#include <linux/fs_context.h>
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#include <linux/magic.h>
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static const struct super_operations nullfs_super_operations = {
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.statfs = simple_statfs,
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};
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static int nullfs_fs_fill_super(struct super_block *s, struct fs_context *fc)
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{
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struct inode *inode;
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s->s_maxbytes = MAX_LFS_FILESIZE;
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s->s_blocksize = PAGE_SIZE;
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s->s_blocksize_bits = PAGE_SHIFT;
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s->s_magic = NULL_FS_MAGIC;
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s->s_op = &nullfs_super_operations;
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s->s_export_op = NULL;
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s->s_xattr = NULL;
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s->s_time_gran = 1;
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s->s_d_flags = 0;
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inode = new_inode(s);
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if (!inode)
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return -ENOMEM;
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/* nullfs is permanently empty... */
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make_empty_dir_inode(inode);
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simple_inode_init_ts(inode);
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inode->i_ino = 1;
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/* ... and immutable. */
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inode->i_flags |= S_IMMUTABLE;
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s->s_root = d_make_root(inode);
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if (!s->s_root)
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return -ENOMEM;
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return 0;
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}
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/*
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* For now this is a single global instance. If needed we can make it
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* mountable by userspace at which point we will need to make it
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* multi-instance.
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*/
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static int nullfs_fs_get_tree(struct fs_context *fc)
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{
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return get_tree_single(fc, nullfs_fs_fill_super);
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}
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static const struct fs_context_operations nullfs_fs_context_ops = {
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.get_tree = nullfs_fs_get_tree,
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};
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static int nullfs_init_fs_context(struct fs_context *fc)
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{
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fc->ops = &nullfs_fs_context_ops;
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fc->global = true;
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fc->sb_flags = SB_NOUSER;
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fc->s_iflags = SB_I_NOEXEC | SB_I_NODEV;
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return 0;
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}
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struct file_system_type nullfs_fs_type = {
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.name = "nullfs",
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.init_fs_context = nullfs_init_fs_context,
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.kill_sb = kill_anon_super,
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};
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