383 lines
9.1 KiB
C
383 lines
9.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/sysv/dir.c
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*
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* minix/dir.c
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* coh/dir.c
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* Copyright (C) 1993 Pascal Haible, Bruno Haible
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*
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* sysv/dir.c
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* Copyright (C) 1993 Bruno Haible
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*
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* SystemV/Coherent directory handling functions
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*/
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/swap.h>
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#include "sysv.h"
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static int sysv_readdir(struct file *, struct dir_context *);
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const struct file_operations sysv_dir_operations = {
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.llseek = generic_file_llseek,
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.read = generic_read_dir,
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.iterate_shared = sysv_readdir,
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.fsync = generic_file_fsync,
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};
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static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
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{
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struct address_space *mapping = page->mapping;
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struct inode *dir = mapping->host;
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block_write_end(NULL, mapping, pos, len, len, page, NULL);
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if (pos+len > dir->i_size) {
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i_size_write(dir, pos+len);
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mark_inode_dirty(dir);
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}
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unlock_page(page);
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}
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static int sysv_handle_dirsync(struct inode *dir)
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{
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int err;
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err = filemap_write_and_wait(dir->i_mapping);
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if (!err)
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err = sync_inode_metadata(dir, 1);
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return err;
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}
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/*
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* Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
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* rules documented in mm/highmem.rst.
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*
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* NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
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* and must be treated accordingly for nesting purposes.
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*/
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static void *dir_get_page(struct inode *dir, unsigned long n, struct page **p)
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{
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struct address_space *mapping = dir->i_mapping;
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struct page *page = read_mapping_page(mapping, n, NULL);
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if (IS_ERR(page))
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return ERR_CAST(page);
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*p = page;
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return kmap_local_page(page);
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}
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static int sysv_readdir(struct file *file, struct dir_context *ctx)
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{
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unsigned long pos = ctx->pos;
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struct inode *inode = file_inode(file);
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struct super_block *sb = inode->i_sb;
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unsigned long npages = dir_pages(inode);
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unsigned offset;
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unsigned long n;
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ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
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if (pos >= inode->i_size)
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return 0;
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offset = pos & ~PAGE_MASK;
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n = pos >> PAGE_SHIFT;
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for ( ; n < npages; n++, offset = 0) {
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char *kaddr, *limit;
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struct sysv_dir_entry *de;
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struct page *page;
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kaddr = dir_get_page(inode, n, &page);
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if (IS_ERR(kaddr))
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continue;
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de = (struct sysv_dir_entry *)(kaddr+offset);
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limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
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for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
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char *name = de->name;
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if (!de->inode)
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continue;
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if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
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fs16_to_cpu(SYSV_SB(sb), de->inode),
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DT_UNKNOWN)) {
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unmap_and_put_page(page, kaddr);
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return 0;
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}
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}
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unmap_and_put_page(page, kaddr);
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}
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return 0;
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}
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/* compare strings: name[0..len-1] (not zero-terminated) and
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* buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
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*/
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static inline int namecompare(int len, int maxlen,
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const char * name, const char * buffer)
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{
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if (len < maxlen && buffer[len])
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return 0;
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return !memcmp(name, buffer, len);
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}
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/*
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* sysv_find_entry()
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*
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* finds an entry in the specified directory with the wanted name. It
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* returns the cache buffer in which the entry was found, and the entry
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* itself (as a parameter - res_dir). It does NOT read the inode of the
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* entry - you'll have to do that yourself if you want to.
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*
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* On Success unmap_and_put_page() should be called on *res_page.
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*
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* sysv_find_entry() acts as a call to dir_get_page() and must be treated
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* accordingly for nesting purposes.
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*/
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struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
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{
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const char * name = dentry->d_name.name;
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int namelen = dentry->d_name.len;
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struct inode * dir = d_inode(dentry->d_parent);
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unsigned long start, n;
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unsigned long npages = dir_pages(dir);
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struct page *page = NULL;
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struct sysv_dir_entry *de;
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*res_page = NULL;
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start = SYSV_I(dir)->i_dir_start_lookup;
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if (start >= npages)
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start = 0;
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n = start;
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do {
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char *kaddr = dir_get_page(dir, n, &page);
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if (!IS_ERR(kaddr)) {
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de = (struct sysv_dir_entry *)kaddr;
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kaddr += PAGE_SIZE - SYSV_DIRSIZE;
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for ( ; (char *) de <= kaddr ; de++) {
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if (!de->inode)
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continue;
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if (namecompare(namelen, SYSV_NAMELEN,
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name, de->name))
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goto found;
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}
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unmap_and_put_page(page, kaddr);
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}
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if (++n >= npages)
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n = 0;
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} while (n != start);
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return NULL;
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found:
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SYSV_I(dir)->i_dir_start_lookup = n;
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*res_page = page;
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return de;
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}
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int sysv_add_link(struct dentry *dentry, struct inode *inode)
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{
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struct inode *dir = d_inode(dentry->d_parent);
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const char * name = dentry->d_name.name;
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int namelen = dentry->d_name.len;
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struct page *page = NULL;
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struct sysv_dir_entry * de;
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unsigned long npages = dir_pages(dir);
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unsigned long n;
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char *kaddr;
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loff_t pos;
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int err;
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/* We take care of directory expansion in the same loop */
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for (n = 0; n <= npages; n++) {
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kaddr = dir_get_page(dir, n, &page);
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if (IS_ERR(kaddr))
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return PTR_ERR(kaddr);
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de = (struct sysv_dir_entry *)kaddr;
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kaddr += PAGE_SIZE - SYSV_DIRSIZE;
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while ((char *)de <= kaddr) {
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if (!de->inode)
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goto got_it;
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err = -EEXIST;
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if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
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goto out_page;
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de++;
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}
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unmap_and_put_page(page, kaddr);
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}
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BUG();
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return -EINVAL;
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got_it:
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pos = page_offset(page) + offset_in_page(de);
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lock_page(page);
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err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
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if (err)
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goto out_unlock;
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memcpy (de->name, name, namelen);
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memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
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de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
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dir_commit_chunk(page, pos, SYSV_DIRSIZE);
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dir->i_mtime = dir->i_ctime = current_time(dir);
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mark_inode_dirty(dir);
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err = sysv_handle_dirsync(dir);
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out_page:
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unmap_and_put_page(page, kaddr);
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return err;
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out_unlock:
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unlock_page(page);
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goto out_page;
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}
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int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
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{
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struct inode *inode = page->mapping->host;
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loff_t pos = page_offset(page) + offset_in_page(de);
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int err;
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lock_page(page);
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err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
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if (err) {
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unlock_page(page);
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return err;
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}
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de->inode = 0;
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dir_commit_chunk(page, pos, SYSV_DIRSIZE);
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inode->i_ctime = inode->i_mtime = current_time(inode);
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mark_inode_dirty(inode);
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return sysv_handle_dirsync(inode);
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}
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int sysv_make_empty(struct inode *inode, struct inode *dir)
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{
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struct page *page = grab_cache_page(inode->i_mapping, 0);
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struct sysv_dir_entry * de;
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char *base;
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int err;
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if (!page)
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return -ENOMEM;
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err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
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if (err) {
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unlock_page(page);
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goto fail;
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}
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base = kmap_local_page(page);
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memset(base, 0, PAGE_SIZE);
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de = (struct sysv_dir_entry *) base;
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de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
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strcpy(de->name,".");
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de++;
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de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
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strcpy(de->name,"..");
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kunmap_local(base);
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dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
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err = sysv_handle_dirsync(inode);
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fail:
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put_page(page);
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return err;
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}
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/*
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* routine to check that the specified directory is empty (for rmdir)
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*/
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int sysv_empty_dir(struct inode * inode)
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{
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struct super_block *sb = inode->i_sb;
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struct page *page = NULL;
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unsigned long i, npages = dir_pages(inode);
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char *kaddr;
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for (i = 0; i < npages; i++) {
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struct sysv_dir_entry *de;
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kaddr = dir_get_page(inode, i, &page);
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if (IS_ERR(kaddr))
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continue;
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de = (struct sysv_dir_entry *)kaddr;
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kaddr += PAGE_SIZE-SYSV_DIRSIZE;
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for ( ;(char *)de <= kaddr; de++) {
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if (!de->inode)
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continue;
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/* check for . and .. */
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if (de->name[0] != '.')
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goto not_empty;
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if (!de->name[1]) {
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if (de->inode == cpu_to_fs16(SYSV_SB(sb),
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inode->i_ino))
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continue;
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goto not_empty;
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}
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if (de->name[1] != '.' || de->name[2])
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goto not_empty;
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}
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unmap_and_put_page(page, kaddr);
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}
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return 1;
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not_empty:
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unmap_and_put_page(page, kaddr);
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return 0;
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}
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/* Releases the page */
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int sysv_set_link(struct sysv_dir_entry *de, struct page *page,
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struct inode *inode)
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{
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struct inode *dir = page->mapping->host;
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loff_t pos = page_offset(page) + offset_in_page(de);
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int err;
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lock_page(page);
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err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
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if (err) {
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unlock_page(page);
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return err;
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}
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de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
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dir_commit_chunk(page, pos, SYSV_DIRSIZE);
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dir->i_mtime = dir->i_ctime = current_time(dir);
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mark_inode_dirty(dir);
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return sysv_handle_dirsync(inode);
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}
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/*
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* Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
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* rules documented in mm/highmem.rst.
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*
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* sysv_dotdot() acts as a call to dir_get_page() and must be treated
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* accordingly for nesting purposes.
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*/
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struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct page **p)
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{
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struct sysv_dir_entry *de = dir_get_page(dir, 0, p);
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if (IS_ERR(de))
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return NULL;
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/* ".." is the second directory entry */
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return de + 1;
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}
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ino_t sysv_inode_by_name(struct dentry *dentry)
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{
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struct page *page;
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struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
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ino_t res = 0;
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if (de) {
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res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
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unmap_and_put_page(page, de);
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}
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return res;
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}
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