From bb3b2cfeb206f5b10b859e134651b54120e3f530 Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Tue, 30 Jun 2026 18:05:56 +0100 Subject: ARM: 9480/1: entry: expand comment in __switch_to As per discussion between the developers in the mail thread linked, expand the comment in __switch_to so that readers of the code understand what is going on. Suggested-by: Mark Rutland Acked-by: Mark Rutland Signed-off-by: Linus Walleij > Signed-off-by: Russell King --- fs/nullfs.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 fs/nullfs.c (limited to 'fs/nullfs.c') diff --git a/fs/nullfs.c b/fs/nullfs.c new file mode 100644 index 000000000..fdbd3e5d3 --- /dev/null +++ b/fs/nullfs.c @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2026 Christian Brauner */ +#include +#include +#include + +static const struct super_operations nullfs_super_operations = { + .statfs = simple_statfs, +}; + +static int nullfs_fs_fill_super(struct super_block *s, struct fs_context *fc) +{ + struct inode *inode; + + s->s_maxbytes = MAX_LFS_FILESIZE; + s->s_blocksize = PAGE_SIZE; + s->s_blocksize_bits = PAGE_SHIFT; + s->s_magic = NULL_FS_MAGIC; + s->s_op = &nullfs_super_operations; + s->s_export_op = NULL; + s->s_xattr = NULL; + s->s_time_gran = 1; + s->s_d_flags = 0; + + inode = new_inode(s); + if (!inode) + return -ENOMEM; + + /* nullfs is permanently empty... */ + make_empty_dir_inode(inode); + simple_inode_init_ts(inode); + inode->i_ino = 1; + /* ... and immutable. */ + inode->i_flags |= S_IMMUTABLE; + + s->s_root = d_make_root(inode); + if (!s->s_root) + return -ENOMEM; + + return 0; +} + +/* + * For now this is a single global instance. If needed we can make it + * mountable by userspace at which point we will need to make it + * multi-instance. + */ +static int nullfs_fs_get_tree(struct fs_context *fc) +{ + return get_tree_single(fc, nullfs_fs_fill_super); +} + +static const struct fs_context_operations nullfs_fs_context_ops = { + .get_tree = nullfs_fs_get_tree, +}; + +static int nullfs_init_fs_context(struct fs_context *fc) +{ + fc->ops = &nullfs_fs_context_ops; + fc->global = true; + fc->sb_flags = SB_NOUSER; + fc->s_iflags = SB_I_NOEXEC | SB_I_NODEV; + return 0; +} + +struct file_system_type nullfs_fs_type = { + .name = "nullfs", + .init_fs_context = nullfs_init_fs_context, + .kill_sb = kill_anon_super, +}; -- cgit v1.3.1