1/* 2 * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code 3 * 4 * Matt Mackall <mpm@selenic.com> January, 2004 5 * derived from mm/shmem.c and fs/ramfs/inode.c 6 * 7 * This is intended for small system where the benefits of the full 8 * shmem code (swap-backed and resource-limited) are outweighed by 9 * their complexity. On systems without swap this code should be 10 * effectively equivalent, but much lighter weight. 11 */ 12 13#include <linux/fs.h> 14#include <linux/init.h> 15#include <linux/vfs.h> 16#include <linux/mount.h> 17#include <linux/file.h> 18#include <linux/mm.h> 19#include <linux/module.h> 20#include <linux/swap.h> 21#include <linux/ramfs.h> 22 23static struct file_system_type tmpfs_fs_type = { 24 .name = "tmpfs", 25 .get_sb = ramfs_get_sb, 26 .kill_sb = kill_litter_super, 27}; 28 29static struct vfsmount *shm_mnt; 30 31static int __init init_tmpfs(void) 32{ 33 BUG_ON(register_filesystem(&tmpfs_fs_type) != 0); 34 35 shm_mnt = kern_mount(&tmpfs_fs_type); 36 BUG_ON(IS_ERR(shm_mnt)); 37 38 return 0; 39} 40module_init(init_tmpfs) 41 42/* 43 * shmem_file_setup - get an unlinked file living in tmpfs 44 * 45 * @name: name for dentry (to be seen in /proc/<pid>/maps 46 * @size: size to be set for the file 47 * 48 */ 49struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags) 50{ 51 int error; 52 struct file *file; 53 struct inode *inode; 54 struct dentry *dentry, *root; 55 struct qstr this; 56 57 if (IS_ERR(shm_mnt)) 58 return (void *)shm_mnt; 59 60 error = -ENOMEM; 61 this.name = name; 62 this.len = strlen(name); 63 this.hash = 0; /* will go */ 64 root = shm_mnt->mnt_root; 65 dentry = d_alloc(root, &this); 66 if (!dentry) 67 goto put_memory; 68 69 error = -ENFILE; 70 file = get_empty_filp(); 71 if (!file) 72 goto put_dentry; 73 74 error = -ENOSPC; 75 inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0); 76 if (!inode) 77 goto close_file; 78 79 d_instantiate(dentry, inode); 80 inode->i_nlink = 0; /* It is unlinked */ 81 82 file->f_path.mnt = mntget(shm_mnt); 83 file->f_path.dentry = dentry; 84 file->f_mapping = inode->i_mapping; 85 file->f_op = &ramfs_file_operations; 86 file->f_mode = FMODE_WRITE | FMODE_READ; 87 88 /* notify everyone as to the change of file size */ 89 error = do_truncate(dentry, size, 0, file); 90 if (error < 0) 91 goto close_file; 92 93 return file; 94 95close_file: 96 put_filp(file); 97put_dentry: 98 dput(dentry); 99put_memory: 100 return ERR_PTR(error); 101} 102 103/* 104 * shmem_zero_setup - setup a shared anonymous mapping 105 * 106 * @vma: the vma to be mmapped is prepared by do_mmap_pgoff 107 */ 108int shmem_zero_setup(struct vm_area_struct *vma) 109{ 110 struct file *file; 111 loff_t size = vma->vm_end - vma->vm_start; 112 113 file = shmem_file_setup("dev/zero", size, vma->vm_flags); 114 if (IS_ERR(file)) 115 return PTR_ERR(file); 116 117 if (vma->vm_file) 118 fput(vma->vm_file); 119 vma->vm_file = file; 120 vma->vm_ops = &generic_file_vm_ops; 121 return 0; 122} 123 124int shmem_unuse(swp_entry_t entry, struct page *page) 125{ 126 return 0; 127} 128 129 130#ifndef CONFIG_MMU 131unsigned long shmem_get_unmapped_area(struct file *file, 132 unsigned long addr, 133 unsigned long len, 134 unsigned long pgoff, 135 unsigned long flags) 136{ 137 return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags); 138} 139#endif 140