/* * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code * * Matt Mackall <mpm@selenic.com> January, 2004 * derived from mm/shmem.c and fs/ramfs/inode.c * * This is intended for small system where the benefits of the full * shmem code (swap-backed and resource-limited) are outweighed by * their complexity. On systems without swap this code should be * effectively equivalent, but much lighter weight. */ #include <linux/fs.h> #include <linux/init.h> #include <linux/devfs_fs_kernel.h> #include <linux/vfs.h> #include <linux/mount.h> #include <linux/file.h> #include <linux/mm.h> #include <linux/module.h> #include <linux/swap.h> #include <linux/ramfs.h> static struct file_system_type tmpfs_fs_type = { .name = "tmpfs", .get_sb = ramfs_get_sb, .kill_sb = kill_litter_super, }; static struct vfsmount *shm_mnt; static int __init init_tmpfs(void) { BUG_ON(register_filesystem(&tmpfs_fs_type) != 0); #ifdef CONFIG_TMPFS devfs_mk_dir("shm"); #endif shm_mnt = kern_mount(&tmpfs_fs_type); BUG_ON(IS_ERR(shm_mnt)); return 0; } module_init(init_tmpfs) /* * shmem_file_setup - get an unlinked file living in tmpfs * * @name: name for dentry (to be seen in /proc/<pid>/maps * @size: size to be set for the file * */ struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags) { int error; struct file *file; struct inode *inode; struct dentry *dentry, *root; struct qstr this; if (IS_ERR(shm_mnt)) return (void *)shm_mnt; error = -ENOMEM; this.name = name; this.len = strlen(name); this.hash = 0; /* will go */ root = shm_mnt->mnt_root; dentry = d_alloc(root, &this); if (!dentry) goto put_memory; error = -ENFILE; file = get_empty_filp(); if (!file) goto put_dentry; error = -ENOSPC; inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0); if (!inode) goto close_file; d_instantiate(dentry, inode); inode->i_nlink = 0; /* It is unlinked */ file->f_vfsmnt = mntget(shm_mnt); file->f_dentry = dentry; file->f_mapping = inode->i_mapping; file->f_op = &ramfs_file_operations; file->f_mode = FMODE_WRITE | FMODE_READ; /* notify everyone as to the change of file size */ error = do_truncate(dentry, size, file); if (error < 0) goto close_file; return file; close_file: put_filp(file); put_dentry: dput(dentry); put_memory: return ERR_PTR(error); } /* * shmem_zero_setup - setup a shared anonymous mapping * * @vma: the vma to be mmapped is prepared by do_mmap_pgoff */ int shmem_zero_setup(struct vm_area_struct *vma) { struct file *file; loff_t size = vma->vm_end - vma->vm_start; file = shmem_file_setup("dev/zero", size, vma->vm_flags); if (IS_ERR(file)) return PTR_ERR(file); if (vma->vm_file) fput(vma->vm_file); vma->vm_file = file; vma->vm_ops = &generic_file_vm_ops; return 0; } int shmem_unuse(swp_entry_t entry, struct page *page) { return 0; } int shmem_mmap(struct file *file, struct vm_area_struct *vma) { file_accessed(file); #ifndef CONFIG_MMU return ramfs_nommu_mmap(file, vma); #else return 0; #endif } #ifndef CONFIG_MMU unsigned long shmem_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags) { return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags); } #endif