diff options
Diffstat (limited to 'fs/libfs.c')
-rw-r--r-- | fs/libfs.c | 549 |
1 files changed, 549 insertions, 0 deletions
diff --git a/fs/libfs.c b/fs/libfs.c new file mode 100644 index 00000000000..f90b2959592 --- /dev/null +++ b/fs/libfs.c @@ -0,0 +1,549 @@ +/* + * fs/libfs.c + * Library for filesystems writers. + */ + +#include <linux/module.h> +#include <linux/pagemap.h> +#include <linux/mount.h> +#include <linux/vfs.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 super_block *sb, struct kstatfs *buf) +{ + buf->f_type = 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 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_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) +{ + down(&file->f_dentry->d_inode->i_sem); + switch (origin) { + case 1: + offset += file->f_pos; + case 0: + if (offset >= 0) + break; + default: + up(&file->f_dentry->d_inode->i_sem); + 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_child); + p = file->f_dentry->d_subdirs.next; + while (n && p != &file->f_dentry->d_subdirs) { + struct dentry *next; + next = list_entry(p, struct dentry, d_child); + if (!d_unhashed(next) && next->d_inode) + n--; + p = p->next; + } + list_add_tail(&cursor->d_child, p); + spin_unlock(&dcache_lock); + } + } + up(&file->f_dentry->d_inode->i_sem); + 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_dentry; + struct dentry *cursor = filp->private_data; + struct list_head *p, *q = &cursor->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_del(q); + list_add(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_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_del(q); + list_add(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; +} + +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, +}; + +struct inode_operations simple_dir_inode_operations = { + .lookup = simple_lookup, +}; + +/* + * Common helper for pseudo-filesystems (sockfs, pipefs, bdev - stuff that + * will never be mountable) + */ +struct super_block * +get_sb_pseudo(struct file_system_type *fs_type, char *name, + struct super_operations *ops, unsigned long magic) +{ + struct super_block *s = sget(fs_type, NULL, set_anon_super, NULL); + static struct super_operations default_ops = {.statfs = simple_statfs}; + struct dentry *dentry; + struct inode *root; + struct qstr d_name = {.name = name, .len = strlen(name)}; + + if (IS_ERR(s)) + return s; + + s->s_flags = MS_NOUSER; + s->s_maxbytes = ~0ULL; + s->s_blocksize = 1024; + s->s_blocksize_bits = 10; + s->s_magic = magic; + s->s_op = ops ? ops : &default_ops; + s->s_time_gran = 1; + root = new_inode(s); + if (!root) + goto Enomem; + root->i_mode = S_IFDIR | S_IRUSR | S_IWUSR; + root->i_uid = root->i_gid = 0; + 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; + return s; + +Enomem: + up_write(&s->s_umount); + deactivate_super(s); + return ERR_PTR(-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; + inode->i_nlink++; + 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_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; + inode->i_nlink--; + dput(dentry); + return 0; +} + +int simple_rmdir(struct inode *dir, struct dentry *dentry) +{ + if (!simple_empty(dentry)) + return -ENOTEMPTY; + + dentry->d_inode->i_nlink--; + simple_unlink(dir, dentry); + dir->i_nlink--; + 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) + old_dir->i_nlink--; + } else if (they_are_dirs) { + old_dir->i_nlink--; + new_dir->i_nlink++; + } + + 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) +{ + void *kaddr; + + if (PageUptodate(page)) + goto out; + + kaddr = kmap_atomic(page, KM_USER0); + memset(kaddr, 0, PAGE_CACHE_SIZE); + kunmap_atomic(kaddr, KM_USER0); + flush_dcache_page(page); + SetPageUptodate(page); +out: + 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) { + void *kaddr = kmap_atomic(page, KM_USER0); + memset(kaddr, 0, from); + memset(kaddr + to, 0, PAGE_CACHE_SIZE - to); + flush_dcache_page(page); + kunmap_atomic(kaddr, KM_USER0); + } + SetPageUptodate(page); + } + return 0; +} + +int simple_commit_write(struct file *file, struct page *page, + unsigned offset, unsigned to) +{ + struct inode *inode = page->mapping->host; + loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to; + + /* + * No need to use i_size_read() here, the i_size + * cannot change under us because we hold the i_sem. + */ + if (pos > inode->i_size) + i_size_write(inode, pos); + set_page_dirty(page); + return 0; +} + +int simple_fill_super(struct super_block *s, int magic, struct tree_descr *files) +{ + static struct super_operations s_ops = {.statfs = simple_statfs}; + 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 = &s_ops; + s->s_time_gran = 1; + + inode = new_inode(s); + if (!inode) + return -ENOMEM; + inode->i_mode = S_IFDIR | 0755; + inode->i_uid = inode->i_gid = 0; + inode->i_blksize = PAGE_CACHE_SIZE; + inode->i_blocks = 0; + inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; + inode->i_op = &simple_dir_inode_operations; + inode->i_fop = &simple_dir_operations; + 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; + 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_uid = inode->i_gid = 0; + inode->i_blksize = PAGE_CACHE_SIZE; + inode->i_blocks = 0; + 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(char *name, struct vfsmount **mount, int *count) +{ + struct vfsmount *mnt = NULL; + spin_lock(&pin_fs_lock); + if (unlikely(!*mount)) { + spin_unlock(&pin_fs_lock); + mnt = do_kern_mount(name, 0, 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); +} + +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; +} + +/* + * 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. + */ +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; +} + +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_commit_write); +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_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(simple_transaction_get); +EXPORT_SYMBOL(simple_transaction_read); +EXPORT_SYMBOL(simple_transaction_release); |