/* * fs/libfs.c * Library for filesystems writers. */ #include <linux/module.h> #include <linux/pagemap.h> #include <linux/mount.h> #include <linux/vfs.h> #include <linux/mutex.h> #include <linux/exportfs.h> #include <linux/writeback.h> #include <linux/buffer_head.h> #include <asm/uaccess.h> int simple_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) { struct inode *inode = dentry->d_inode; generic_fillattr(inode, stat); stat->blocks = inode->i_mapping->nrpages << (PAGE_CACHE_SHIFT - 9); return 0; } int simple_statfs(struct dentry *dentry, struct kstatfs *buf) { buf->f_type = dentry->d_sb->s_magic; buf->f_bsize = PAGE_CACHE_SIZE; buf->f_namelen = NAME_MAX; return 0; } /* * Retaining negative dentries for an in-memory filesystem just wastes * memory and lookup time: arrange for them to be deleted immediately. */ static int simple_delete_dentry(struct dentry *dentry) { return 1; } /* * Lookup the data. This is trivial - if the dentry didn't already * exist, we know it is negative. Set d_op to delete negative dentries. */ struct dentry *simple_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) { static const struct dentry_operations simple_dentry_operations = { .d_delete = simple_delete_dentry, }; if (dentry->d_name.len > NAME_MAX) return ERR_PTR(-ENAMETOOLONG); dentry->d_op = &simple_dentry_operations; d_add(dentry, NULL); return NULL; } int simple_sync_file(struct file * file, struct dentry *dentry, int datasync) { return 0; } int dcache_dir_open(struct inode *inode, struct file *file) { static struct qstr cursor_name = {.len = 1, .name = "."}; file->private_data = d_alloc(file->f_path.dentry, &cursor_name); return file->private_data ? 0 : -ENOMEM; } int dcache_dir_close(struct inode *inode, struct file *file) { dput(file->private_data); return 0; } loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin) { mutex_lock(&file->f_path.dentry->d_inode->i_mutex); switch (origin) { case 1: offset += file->f_pos; case 0: if (offset >= 0) break; default: mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); return -EINVAL; } if (offset != file->f_pos) { file->f_pos = offset; if (file->f_pos >= 2) { struct list_head *p; struct dentry *cursor = file->private_data; loff_t n = file->f_pos - 2; spin_lock(&dcache_lock); list_del(&cursor->d_u.d_child); p = file->f_path.dentry->d_subdirs.next; while (n && p != &file->f_path.dentry->d_subdirs) { struct dentry *next; next = list_entry(p, struct dentry, d_u.d_child); if (!d_unhashed(next) && next->d_inode) n--; p = p->next; } list_add_tail(&cursor->d_u.d_child, p); spin_unlock(&dcache_lock); } } mutex_unlock(&file->f_path.dentry->d_inode->i_mutex); return offset; } /* Relationship between i_mode and the DT_xxx types */ static inline unsigned char dt_type(struct inode *inode) { return (inode->i_mode >> 12) & 15; } /* * Directory is locked and all positive dentries in it are safe, since * for ramfs-type trees they can't go away without unlink() or rmdir(), * both impossible due to the lock on directory. */ int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir) { struct dentry *dentry = filp->f_path.dentry; struct dentry *cursor = filp->private_data; struct list_head *p, *q = &cursor->d_u.d_child; ino_t ino; int i = filp->f_pos; switch (i) { case 0: ino = dentry->d_inode->i_ino; if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0) break; filp->f_pos++; i++; /* fallthrough */ case 1: ino = parent_ino(dentry); if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0) break; filp->f_pos++; i++; /* fallthrough */ default: spin_lock(&dcache_lock); if (filp->f_pos == 2) list_move(q, &dentry->d_subdirs); for (p=q->next; p != &dentry->d_subdirs; p=p->next) { struct dentry *next; next = list_entry(p, struct dentry, d_u.d_child); if (d_unhashed(next) || !next->d_inode) continue; spin_unlock(&dcache_lock); if (filldir(dirent, next->d_name.name, next->d_name.len, filp->f_pos, next->d_inode->i_ino, dt_type(next->d_inode)) < 0) return 0; spin_lock(&dcache_lock); /* next is still alive */ list_move(q, p); p = q; filp->f_pos++; } spin_unlock(&dcache_lock); } return 0; } ssize_t generic_read_dir(struct file *filp, char __user *buf, size_t siz, loff_t *ppos) { return -EISDIR; } const struct file_operations simple_dir_operations = { .open = dcache_dir_open, .release = dcache_dir_close, .llseek = dcache_dir_lseek, .read = generic_read_dir, .readdir = dcache_readdir, .fsync = simple_sync_file, }; const struct inode_operations simple_dir_inode_operations = { .lookup = simple_lookup, }; static const struct super_operations simple_super_operations = { .statfs = simple_statfs, }; /* * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that * will never be mountable) */ int get_sb_pseudo(struct file_system_type *fs_type, char *name, const struct super_operations *ops, unsigned long magic, struct vfsmount *mnt) { struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); struct dentry *dentry; struct inode *root; struct qstr d_name = {.name = name, .len = strlen(name)}; if (IS_ERR(s)) return PTR_ERR(s); s->s_flags = MS_NOUSER; s->s_maxbytes = ~0ULL; s->s_blocksize = PAGE_SIZE; s->s_blocksize_bits = PAGE_SHIFT; s->s_magic = magic; s->s_op = ops ? ops : &simple_super_operations; s->s_time_gran = 1; root = new_inode(s); if (!root) goto Enomem; /* * since this is the first inode, make it number 1. New inodes created * after this must take care not to collide with it (by passing * max_reserved of 1 to iunique). */ root->i_ino = 1; root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; root->i_atime = root->i_mtime = root->i_ctime = CURRENT_TIME; dentry = d_alloc(NULL, &d_name); if (!dentry) { iput(root); goto Enomem; } dentry->d_sb = s; dentry->d_parent = dentry; d_instantiate(dentry, root); s->s_root = dentry; s->s_flags |= MS_ACTIVE; simple_set_mnt(mnt, s); return 0; Enomem: deactivate_locked_super(s); return -ENOMEM; } int simple_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry) { struct inode *inode = old_dentry->d_inode; inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; inc_nlink(inode); atomic_inc(&inode->i_count); dget(dentry); d_instantiate(dentry, inode); return 0; } static inline int simple_positive(struct dentry *dentry) { return dentry->d_inode && !d_unhashed(dentry); } int simple_empty(struct dentry *dentry) { struct dentry *child; int ret = 0; spin_lock(&dcache_lock); list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) if (simple_positive(child)) goto out; ret = 1; out: spin_unlock(&dcache_lock); return ret; } int simple_unlink(struct inode *dir, struct dentry *dentry) { struct inode *inode = dentry->d_inode; inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME; drop_nlink(inode); dput(dentry); return 0; } int simple_rmdir(struct inode *dir, struct dentry *dentry) { if (!simple_empty(dentry)) return -ENOTEMPTY; drop_nlink(dentry->d_inode); simple_unlink(dir, dentry); drop_nlink(dir); return 0; } int simple_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry) { struct inode *inode = old_dentry->d_inode; int they_are_dirs = S_ISDIR(old_dentry->d_inode->i_mode); if (!simple_empty(new_dentry)) return -ENOTEMPTY; if (new_dentry->d_inode) { simple_unlink(new_dir, new_dentry); if (they_are_dirs) drop_nlink(old_dir); } else if (they_are_dirs) { drop_nlink(old_dir); inc_nlink(new_dir); } old_dir->i_ctime = old_dir->i_mtime = new_dir->i_ctime = new_dir->i_mtime = inode->i_ctime = CURRENT_TIME; return 0; } int simple_readpage(struct file *file, struct page *page) { clear_highpage(page); flush_dcache_page(page); SetPageUptodate(page); unlock_page(page); return 0; } int simple_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to) { if (!PageUptodate(page)) { if (to - from != PAGE_CACHE_SIZE) zero_user_segments(page, 0, from, to, PAGE_CACHE_SIZE); } return 0; } int simple_write_begin(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned flags, struct page **pagep, void **fsdata) { struct page *page; pgoff_t index; unsigned from; index = pos >> PAGE_CACHE_SHIFT; from = pos & (PAGE_CACHE_SIZE - 1); page = grab_cache_page_write_begin(mapping, index, flags); if (!page) return -ENOMEM; *pagep = page; return simple_prepare_write(file, page, from, from+len); } static int simple_commit_write(struct file *file, struct page *page, unsigned from, unsigned to) { struct inode *inode = page->mapping->host; loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; if (!PageUptodate(page)) SetPageUptodate(page); /* * No need to use i_size_read() here, the i_size * cannot change under us because we hold the i_mutex. */ if (pos > inode->i_size) i_size_write(inode, pos); set_page_dirty(page); return 0; } int simple_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, struct page *page, void *fsdata) { unsigned from = pos & (PAGE_CACHE_SIZE - 1); /* zero the stale part of the page if we did a short copy */ if (copied < len) { void *kaddr = kmap_atomic(page, KM_USER0); memset(kaddr + from + copied, 0, len - copied); flush_dcache_page(page); kunmap_atomic(kaddr, KM_USER0); } simple_commit_write(file, page, from, from+copied); unlock_page(page); page_cache_release(page); return copied; } /* * the inodes created here are not hashed. If you use iunique to generate * unique inode values later for this filesystem, then you must take care * to pass it an appropriate max_reserved value to avoid collisions. */ int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files) { struct inode *inode; struct dentry *root; struct dentry *dentry; int i; s->s_blocksize = PAGE_CACHE_SIZE; s->s_blocksize_bits = PAGE_CACHE_SHIFT; s->s_magic = magic; s->s_op = &simple_super_operations; s->s_time_gran = 1; inode = new_inode(s); if (!inode) return -ENOMEM; /* * because the root inode is 1, the files array must not contain an * entry at index 1 */ inode->i_ino = 1; inode->i_mode = S_IFDIR | 0755; inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; inode->i_op = &simple_dir_inode_operations; inode->i_fop = &simple_dir_operations; inode->i_nlink = 2; root = d_alloc_root(inode); if (!root) { iput(inode); return -ENOMEM; } for (i = 0; !files->name || files->name[0]; i++, files++) { if (!files->name) continue; /* warn if it tries to conflict with the root inode */ if (unlikely(i == 1)) printk(KERN_WARNING "%s: %s passed in a files array" "with an index of 1!\n", __func__, s->s_type->name); dentry = d_alloc_name(root, files->name); if (!dentry) goto out; inode = new_inode(s); if (!inode) goto out; inode->i_mode = S_IFREG | files->mode; inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; inode->i_fop = files->ops; inode->i_ino = i; d_add(dentry, inode); } s->s_root = root; return 0; out: d_genocide(root); dput(root); return -ENOMEM; } static DEFINE_SPINLOCK(pin_fs_lock); int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count) { struct vfsmount *mnt = NULL; spin_lock(&pin_fs_lock); if (unlikely(!*mount)) { spin_unlock(&pin_fs_lock); mnt = vfs_kern_mount(type, 0, type->name, NULL); if (IS_ERR(mnt)) return PTR_ERR(mnt); spin_lock(&pin_fs_lock); if (!*mount) *mount = mnt; } mntget(*mount); ++*count; spin_unlock(&pin_fs_lock); mntput(mnt); return 0; } void simple_release_fs(struct vfsmount **mount, int *count) { struct vfsmount *mnt; spin_lock(&pin_fs_lock); mnt = *mount; if (!--*count) *mount = NULL; spin_unlock(&pin_fs_lock); mntput(mnt); } /** * simple_read_from_buffer - copy data from the buffer to user space * @to: the user space buffer to read to * @count: the maximum number of bytes to read * @ppos: the current position in the buffer * @from: the buffer to read from * @available: the size of the buffer * * The simple_read_from_buffer() function reads up to @count bytes from the * buffer @from at offset @ppos into the user space address starting at @to. * * On success, the number of bytes read is returned and the offset @ppos is * advanced by this number, or negative value is returned on error. **/ ssize_t simple_read_from_buffer(void __user *to, size_t count, loff_t *ppos, const void *from, size_t available) { loff_t pos = *ppos; if (pos < 0) return -EINVAL; if (pos >= available) return 0; if (count > available - pos) count = available - pos; if (copy_to_user(to, from + pos, count)) return -EFAULT; *ppos = pos + count; return count; } /** * memory_read_from_buffer - copy data from the buffer * @to: the kernel space buffer to read to * @count: the maximum number of bytes to read * @ppos: the current position in the buffer * @from: the buffer to read from * @available: the size of the buffer * * The memory_read_from_buffer() function reads up to @count bytes from the * buffer @from at offset @ppos into the kernel space address starting at @to. * * On success, the number of bytes read is returned and the offset @ppos is * advanced by this number, or negative value is returned on error. **/ ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos, const void *from, size_t available) { loff_t pos = *ppos; if (pos < 0) return -EINVAL; if (pos >= available) return 0; if (count > available - pos) count = available - pos; memcpy(to, from + pos, count); *ppos = pos + count; return count; } /* * Transaction based IO. * The file expects a single write which triggers the transaction, and then * possibly a read which collects the result - which is stored in a * file-local buffer. */ void simple_transaction_set(struct file *file, size_t n) { struct simple_transaction_argresp *ar = file->private_data; BUG_ON(n > SIMPLE_TRANSACTION_LIMIT); /* * The barrier ensures that ar->size will really remain zero until * ar->data is ready for reading. */ smp_mb(); ar->size = n; } char *simple_transaction_get(struct file *file, const char __user *buf, size_t size) { struct simple_transaction_argresp *ar; static DEFINE_SPINLOCK(simple_transaction_lock); if (size > SIMPLE_TRANSACTION_LIMIT - 1) return ERR_PTR(-EFBIG); ar = (struct simple_transaction_argresp *)get_zeroed_page(GFP_KERNEL); if (!ar) return ERR_PTR(-ENOMEM); spin_lock(&simple_transaction_lock); /* only one write allowed per open */ if (file->private_data) { spin_unlock(&simple_transaction_lock); free_page((unsigned long)ar); return ERR_PTR(-EBUSY); } file->private_data = ar; spin_unlock(&simple_transaction_lock); if (copy_from_user(ar->data, buf, size)) return ERR_PTR(-EFAULT); return ar->data; } ssize_t simple_transaction_read(struct file *file, char __user *buf, size_t size, loff_t *pos) { struct simple_transaction_argresp *ar = file->private_data; if (!ar) return 0; return simple_read_from_buffer(buf, size, pos, ar->data, ar->size); } int simple_transaction_release(struct inode *inode, struct file *file) { free_page((unsigned long)file->private_data); return 0; } /* Simple attribute files */ struct simple_attr { int (*get)(void *, u64 *); int (*set)(void *, u64); char get_buf[24]; /* enough to store a u64 and "\n\0" */ char set_buf[24]; void *data; const char *fmt; /* format for read operation */ struct mutex mutex; /* protects access to these buffers */ }; /* simple_attr_open is called by an actual attribute open file operation * to set the attribute specific access operations. */ int simple_attr_open(struct inode *inode, struct file *file, int (*get)(void *, u64 *), int (*set)(void *, u64), const char *fmt) { struct simple_attr *attr; attr = kmalloc(sizeof(*attr), GFP_KERNEL); if (!attr) return -ENOMEM; attr->get = get; attr->set = set; attr->data = inode->i_private; attr->fmt = fmt; mutex_init(&attr->mutex); file->private_data = attr; return nonseekable_open(inode, file); } int simple_attr_release(struct inode *inode, struct file *file) { kfree(file->private_data); return 0; } /* read from the buffer that is filled with the get function */ ssize_t simple_attr_read(struct file *file, char __user *buf, size_t len, loff_t *ppos) { struct simple_attr *attr; size_t size; ssize_t ret; attr = file->private_data; if (!attr->get) return -EACCES; ret = mutex_lock_interruptible(&attr->mutex); if (ret) return ret; if (*ppos) { /* continued read */ size = strlen(attr->get_buf); } else { /* first read */ u64 val; ret = attr->get(attr->data, &val); if (ret) goto out; size = scnprintf(attr->get_buf, sizeof(attr->get_buf), attr->fmt, (unsigned long long)val); } ret = simple_read_from_buffer(buf, len, ppos, attr->get_buf, size); out: mutex_unlock(&attr->mutex); return ret; } /* interpret the buffer as a number to call the set function with */ ssize_t simple_attr_write(struct file *file, const char __user *buf, size_t len, loff_t *ppos) { struct simple_attr *attr; u64 val; size_t size; ssize_t ret; attr = file->private_data; if (!attr->set) return -EACCES; ret = mutex_lock_interruptible(&attr->mutex); if (ret) return ret; ret = -EFAULT; size = min(sizeof(attr->set_buf) - 1, len); if (copy_from_user(attr->set_buf, buf, size)) goto out; ret = len; /* claim we got the whole input */ attr->set_buf[size] = '\0'; val = simple_strtol(attr->set_buf, NULL, 0); attr->set(attr->data, val); out: mutex_unlock(&attr->mutex); return ret; } /** * generic_fh_to_dentry - generic helper for the fh_to_dentry export operation * @sb: filesystem to do the file handle conversion on * @fid: file handle to convert * @fh_len: length of the file handle in bytes * @fh_type: type of file handle * @get_inode: filesystem callback to retrieve inode * * This function decodes @fid as long as it has one of the well-known * Linux filehandle types and calls @get_inode on it to retrieve the * inode for the object specified in the file handle. */ struct dentry *generic_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type, struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen)) { struct inode *inode = NULL; if (fh_len < 2) return NULL; switch (fh_type) { case FILEID_INO32_GEN: case FILEID_INO32_GEN_PARENT: inode = get_inode(sb, fid->i32.ino, fid->i32.gen); break; } return d_obtain_alias(inode); } EXPORT_SYMBOL_GPL(generic_fh_to_dentry); /** * generic_fh_to_dentry - generic helper for the fh_to_parent export operation * @sb: filesystem to do the file handle conversion on * @fid: file handle to convert * @fh_len: length of the file handle in bytes * @fh_type: type of file handle * @get_inode: filesystem callback to retrieve inode * * This function decodes @fid as long as it has one of the well-known * Linux filehandle types and calls @get_inode on it to retrieve the * inode for the _parent_ object specified in the file handle if it * is specified in the file handle, or NULL otherwise. */ struct dentry *generic_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len, int fh_type, struct inode *(*get_inode) (struct super_block *sb, u64 ino, u32 gen)) { struct inode *inode = NULL; if (fh_len <= 2) return NULL; switch (fh_type) { case FILEID_INO32_GEN_PARENT: inode = get_inode(sb, fid->i32.parent_ino, (fh_len > 3 ? fid->i32.parent_gen : 0)); break; } return d_obtain_alias(inode); } EXPORT_SYMBOL_GPL(generic_fh_to_parent); int simple_fsync(struct file *file, struct dentry *dentry, int datasync) { struct writeback_control wbc = { .sync_mode = WB_SYNC_ALL, .nr_to_write = 0, /* metadata-only; caller takes care of data */ }; struct inode *inode = dentry->d_inode; int err; int ret; ret = sync_mapping_buffers(inode->i_mapping); if (!(inode->i_state & I_DIRTY)) return ret; if (datasync && !(inode->i_state & I_DIRTY_DATASYNC)) return ret; err = sync_inode(inode, &wbc); if (ret == 0) ret = err; return ret; } EXPORT_SYMBOL(simple_fsync); EXPORT_SYMBOL(dcache_dir_close); EXPORT_SYMBOL(dcache_dir_lseek); EXPORT_SYMBOL(dcache_dir_open); EXPORT_SYMBOL(dcache_readdir); EXPORT_SYMBOL(generic_read_dir); EXPORT_SYMBOL(get_sb_pseudo); EXPORT_SYMBOL(simple_write_begin); EXPORT_SYMBOL(simple_write_end); EXPORT_SYMBOL(simple_dir_inode_operations); EXPORT_SYMBOL(simple_dir_operations); EXPORT_SYMBOL(simple_empty); EXPORT_SYMBOL(d_alloc_name); EXPORT_SYMBOL(simple_fill_super); EXPORT_SYMBOL(simple_getattr); EXPORT_SYMBOL(simple_link); EXPORT_SYMBOL(simple_lookup); EXPORT_SYMBOL(simple_pin_fs); EXPORT_UNUSED_SYMBOL(simple_prepare_write); EXPORT_SYMBOL(simple_readpage); EXPORT_SYMBOL(simple_release_fs); EXPORT_SYMBOL(simple_rename); EXPORT_SYMBOL(simple_rmdir); EXPORT_SYMBOL(simple_statfs); EXPORT_SYMBOL(simple_sync_file); EXPORT_SYMBOL(simple_unlink); EXPORT_SYMBOL(simple_read_from_buffer); EXPORT_SYMBOL(memory_read_from_buffer); EXPORT_SYMBOL(simple_transaction_set); EXPORT_SYMBOL(simple_transaction_get); EXPORT_SYMBOL(simple_transaction_read); EXPORT_SYMBOL(simple_transaction_release); EXPORT_SYMBOL_GPL(simple_attr_open); EXPORT_SYMBOL_GPL(simple_attr_release); EXPORT_SYMBOL_GPL(simple_attr_read); EXPORT_SYMBOL_GPL(simple_attr_write);