fs/sysv/dir.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/sysv/dir.c
  *
  *  minix/dir.c
  *  Copyright (C) 1991, 1992  Linus Torvalds
  *
  *  coh/dir.c
  *  Copyright (C) 1993  Pascal Haible, Bruno Haible
  *
  *  sysv/dir.c
  *  Copyright (C) 1993  Bruno Haible
  *
  *  SystemV/Coherent directory handling functions
  */

 #include <linux/pagemap.h>
 #include <linux/highmem.h>
 #include <linux/swap.h>
 #include "sysv.h"

 static int sysv_readdir(struct file *, struct dir_context *);

 const struct file_operations sysv_dir_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.iterate_shared	= sysv_readdir,
 	.fsync		= generic_file_fsync,
 };

 static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
 {
 	struct address_space *mapping = page->mapping;
 	struct inode *dir = mapping->host;

 	block_write_end(NULL, mapping, pos, len, len, page, NULL);
 	if (pos+len > dir->i_size) {
 		i_size_write(dir, pos+len);
 		mark_inode_dirty(dir);
 	}
 	unlock_page(page);
 }

 static int sysv_handle_dirsync(struct inode *dir)
 {
 	int err;

 	err = filemap_write_and_wait(dir->i_mapping);
 	if (!err)
 		err = sync_inode_metadata(dir, 1);
 	return err;
 }

 /*
  * Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
  * rules documented in mm/highmem.rst.
  *
  * NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
  * and must be treated accordingly for nesting purposes.
  */
 static void *dir_get_page(struct inode *dir, unsigned long n, struct page **p)
 {
 	struct address_space *mapping = dir->i_mapping;
 	struct page *page = read_mapping_page(mapping, n, NULL);
 	if (IS_ERR(page))
 		return ERR_CAST(page);
 	*p = page;
 	return kmap_local_page(page);
 }

 static int sysv_readdir(struct file *file, struct dir_context *ctx)
 {
 	unsigned long pos = ctx->pos;
 	struct inode *inode = file_inode(file);
 	struct super_block *sb = inode->i_sb;
 	unsigned long npages = dir_pages(inode);
 	unsigned offset;
 	unsigned long n;

 	ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
 	if (pos >= inode->i_size)
 		return 0;

 	offset = pos & ~PAGE_MASK;
 	n = pos >> PAGE_SHIFT;

 	for ( ; n < npages; n++, offset = 0) {
 		char *kaddr, *limit;
 		struct sysv_dir_entry *de;
 		struct page *page;

 		kaddr = dir_get_page(inode, n, &page);
 		if (IS_ERR(kaddr))
 			continue;
 		de = (struct sysv_dir_entry *)(kaddr+offset);
 		limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
 		for ( ;(char*)de <= limit; de++, ctx->pos += sizeof(*de)) {
 			char *name = de->name;

 			if (!de->inode)
 				continue;

 			if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
 					fs16_to_cpu(SYSV_SB(sb), de->inode),
 					DT_UNKNOWN)) {
 				unmap_and_put_page(page, kaddr);
 				return 0;
 			}
 		}
 		unmap_and_put_page(page, kaddr);
 	}
 	return 0;
 }

 /* compare strings: name[0..len-1] (not zero-terminated) and
  * buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
  */
 static inline int namecompare(int len, int maxlen,
 	const char * name, const char * buffer)
 {
 	if (len < maxlen && buffer[len])
 		return 0;
 	return !memcmp(name, buffer, len);
 }

 /*
  *	sysv_find_entry()
  *
  * finds an entry in the specified directory with the wanted name. It
  * returns the cache buffer in which the entry was found, and the entry
  * itself (as a parameter - res_dir). It does NOT read the inode of the
  * entry - you'll have to do that yourself if you want to.
  *
  * On Success unmap_and_put_page() should be called on *res_page.
  *
  * sysv_find_entry() acts as a call to dir_get_page() and must be treated
  * accordingly for nesting purposes.
  */
 struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct page **res_page)
 {
 	const char * name = dentry->d_name.name;
 	int namelen = dentry->d_name.len;
 	struct inode * dir = d_inode(dentry->d_parent);
 	unsigned long start, n;
 	unsigned long npages = dir_pages(dir);
 	struct page *page = NULL;
 	struct sysv_dir_entry *de;

 	*res_page = NULL;

 	start = SYSV_I(dir)->i_dir_start_lookup;
 	if (start >= npages)
 		start = 0;
 	n = start;

 	do {
 		char *kaddr = dir_get_page(dir, n, &page);

 		if (!IS_ERR(kaddr)) {
 			de = (struct sysv_dir_entry *)kaddr;
 			kaddr += PAGE_SIZE - SYSV_DIRSIZE;
 			for ( ; (char *) de <= kaddr ; de++) {
 				if (!de->inode)
 					continue;
 				if (namecompare(namelen, SYSV_NAMELEN,
 							name, de->name))
 					goto found;
 			}
 			unmap_and_put_page(page, kaddr);
 		}

 		if (++n >= npages)
 			n = 0;
 	} while (n != start);

 	return NULL;

 found:
 	SYSV_I(dir)->i_dir_start_lookup = n;
 	*res_page = page;
 	return de;
 }

 int sysv_add_link(struct dentry *dentry, struct inode *inode)
 {
 	struct inode *dir = d_inode(dentry->d_parent);
 	const char * name = dentry->d_name.name;
 	int namelen = dentry->d_name.len;
 	struct page *page = NULL;
 	struct sysv_dir_entry * de;
 	unsigned long npages = dir_pages(dir);
 	unsigned long n;
 	char *kaddr;
 	loff_t pos;
 	int err;

 	/* We take care of directory expansion in the same loop */
 	for (n = 0; n <= npages; n++) {
 		kaddr = dir_get_page(dir, n, &page);
 		if (IS_ERR(kaddr))
 			return PTR_ERR(kaddr);
 		de = (struct sysv_dir_entry *)kaddr;
 		kaddr += PAGE_SIZE - SYSV_DIRSIZE;
 		while ((char *)de <= kaddr) {
 			if (!de->inode)
 				goto got_it;
 			err = -EEXIST;
 			if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
 				goto out_page;
 			de++;
 		}
 		unmap_and_put_page(page, kaddr);
 	}
 	BUG();
 	return -EINVAL;

 got_it:
 	pos = page_offset(page) + offset_in_page(de);
 	lock_page(page);
 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	if (err)
 		goto out_unlock;
 	memcpy (de->name, name, namelen);
 	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	mark_inode_dirty(dir);
 	err = sysv_handle_dirsync(dir);
 out_page:
 	unmap_and_put_page(page, kaddr);
 	return err;
 out_unlock:
 	unlock_page(page);
 	goto out_page;
 }

 int sysv_delete_entry(struct sysv_dir_entry *de, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	loff_t pos = page_offset(page) + offset_in_page(de);
 	int err;

 	lock_page(page);
 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	if (err) {
 		unlock_page(page);
 		return err;
 	}
 	de->inode = 0;
 	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
 	mark_inode_dirty(inode);
 	return sysv_handle_dirsync(inode);
 }

 int sysv_make_empty(struct inode *inode, struct inode *dir)
 {
 	struct page *page = grab_cache_page(inode->i_mapping, 0);
 	struct sysv_dir_entry * de;
 	char *base;
 	int err;

 	if (!page)
 		return -ENOMEM;
 	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
 	if (err) {
 		unlock_page(page);
 		goto fail;
 	}
 	base = kmap_local_page(page);
 	memset(base, 0, PAGE_SIZE);

 	de = (struct sysv_dir_entry *) base;
 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 	strcpy(de->name,".");
 	de++;
 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
 	strcpy(de->name,"..");

 	kunmap_local(base);
 	dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
 	err = sysv_handle_dirsync(inode);
 fail:
 	put_page(page);
 	return err;
 }

 /*
  * routine to check that the specified directory is empty (for rmdir)
  */
 int sysv_empty_dir(struct inode * inode)
 {
 	struct super_block *sb = inode->i_sb;
 	struct page *page = NULL;
 	unsigned long i, npages = dir_pages(inode);
 	char *kaddr;

 	for (i = 0; i < npages; i++) {
 		struct sysv_dir_entry *de;

 		kaddr = dir_get_page(inode, i, &page);
 		if (IS_ERR(kaddr))
 			continue;

 		de = (struct sysv_dir_entry *)kaddr;
 		kaddr += PAGE_SIZE-SYSV_DIRSIZE;

 		for ( ;(char *)de <= kaddr; de++) {
 			if (!de->inode)
 				continue;
 			/* check for . and .. */
 			if (de->name[0] != '.')
 				goto not_empty;
 			if (!de->name[1]) {
 				if (de->inode == cpu_to_fs16(SYSV_SB(sb),
 							inode->i_ino))
 					continue;
 				goto not_empty;
 			}
 			if (de->name[1] != '.' || de->name[2])
 				goto not_empty;
 		}
 		unmap_and_put_page(page, kaddr);
 	}
 	return 1;

 not_empty:
 	unmap_and_put_page(page, kaddr);
 	return 0;
 }

 /* Releases the page */
 int sysv_set_link(struct sysv_dir_entry *de, struct page *page,
 	struct inode *inode)
 {
 	struct inode *dir = page->mapping->host;
 	loff_t pos = page_offset(page) + offset_in_page(de);
 	int err;

 	lock_page(page);
 	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
 	if (err) {
 		unlock_page(page);
 		return err;
 	}
 	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
 	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	mark_inode_dirty(dir);
 	return sysv_handle_dirsync(inode);
 }

 /*
  * Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
  * rules documented in mm/highmem.rst.
  *
  * sysv_dotdot() acts as a call to dir_get_page() and must be treated
  * accordingly for nesting purposes.
  */
 struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct page **p)
 {
 	struct sysv_dir_entry *de = dir_get_page(dir, 0, p);

 	if (IS_ERR(de))
 		return NULL;
 	/* ".." is the second directory entry */
 	return de + 1;
 }

 ino_t sysv_inode_by_name(struct dentry *dentry)
 {
 	struct page *page;
 	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
 	ino_t res = 0;

 	if (de) {
 		res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
 		unmap_and_put_page(page, de);
 	}
 	return res;
 }
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/fs/sysv/dir.c
	*
	* minix/dir.c
	* Copyright (C) 1991, 1992 Linus Torvalds
	*
	* coh/dir.c
	* Copyright (C) 1993 Pascal Haible, Bruno Haible
	*
	* sysv/dir.c
	* Copyright (C) 1993 Bruno Haible
	*
	* SystemV/Coherent directory handling functions
	*/

	#include <linux/pagemap.h>
	#include <linux/highmem.h>
	#include <linux/swap.h>
	#include "sysv.h"

	static int sysv_readdir(struct file , struct dir_context );

	const struct file_operations sysv_dir_operations = {
	.llseek = generic_file_llseek,
	.read = generic_read_dir,
	.iterate_shared = sysv_readdir,
	.fsync = generic_file_fsync,
	};

	static void dir_commit_chunk(struct page *page, loff_t pos, unsigned len)
	{
	struct address_space *mapping = page->mapping;
	struct inode *dir = mapping->host;

	block_write_end(NULL, mapping, pos, len, len, page, NULL);
	if (pos+len > dir->i_size) {
	i_size_write(dir, pos+len);
	mark_inode_dirty(dir);
	}
	unlock_page(page);
	}

	static int sysv_handle_dirsync(struct inode *dir)
	{
	int err;

	err = filemap_write_and_wait(dir->i_mapping);
	if (!err)
	err = sync_inode_metadata(dir, 1);
	return err;
	}

	/*
	* Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
	* rules documented in mm/highmem.rst.
	*
	* NOTE: sysv_find_entry() and sysv_dotdot() act as calls to dir_get_page()
	* and must be treated accordingly for nesting purposes.
	*/
	static void dir_get_page(struct inode dir, unsigned long n, struct page **p)
	{
	struct address_space *mapping = dir->i_mapping;
	struct page *page = read_mapping_page(mapping, n, NULL);
	if (IS_ERR(page))
	return ERR_CAST(page);
	*p = page;
	return kmap_local_page(page);
	}

	static int sysv_readdir(struct file file, struct dir_context ctx)
	{
	unsigned long pos = ctx->pos;
	struct inode *inode = file_inode(file);
	struct super_block *sb = inode->i_sb;
	unsigned long npages = dir_pages(inode);
	unsigned offset;
	unsigned long n;

	ctx->pos = pos = (pos + SYSV_DIRSIZE-1) & ~(SYSV_DIRSIZE-1);
	if (pos >= inode->i_size)
	return 0;

	offset = pos & ~PAGE_MASK;
	n = pos >> PAGE_SHIFT;

	for ( ; n < npages; n++, offset = 0) {
	char kaddr, limit;
	struct sysv_dir_entry *de;
	struct page *page;

	kaddr = dir_get_page(inode, n, &page);
	if (IS_ERR(kaddr))
	continue;
	de = (struct sysv_dir_entry *)(kaddr+offset);
	limit = kaddr + PAGE_SIZE - SYSV_DIRSIZE;
	for ( ;(char)de <= limit; de++, ctx->pos += sizeof(de)) {
	char *name = de->name;

	if (!de->inode)
	continue;

	if (!dir_emit(ctx, name, strnlen(name,SYSV_NAMELEN),
	fs16_to_cpu(SYSV_SB(sb), de->inode),
	DT_UNKNOWN)) {
	unmap_and_put_page(page, kaddr);
	return 0;
	}
	}
	unmap_and_put_page(page, kaddr);
	}
	return 0;
	}

	/* compare strings: name[0..len-1] (not zero-terminated) and
	* buffer[0..] (filled with zeroes up to buffer[0..maxlen-1])
	*/
	static inline int namecompare(int len, int maxlen,
	const char * name, const char * buffer)
	{
	if (len < maxlen && buffer[len])
	return 0;
	return !memcmp(name, buffer, len);
	}

	/*
	* sysv_find_entry()
	*
	* finds an entry in the specified directory with the wanted name. It
	* returns the cache buffer in which the entry was found, and the entry
	* itself (as a parameter - res_dir). It does NOT read the inode of the
	* entry - you'll have to do that yourself if you want to.
	*
	* On Success unmap_and_put_page() should be called on *res_page.
	*
	* sysv_find_entry() acts as a call to dir_get_page() and must be treated
	* accordingly for nesting purposes.
	*/
	struct sysv_dir_entry sysv_find_entry(struct dentry dentry, struct page **res_page)
	{
	const char * name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct inode * dir = d_inode(dentry->d_parent);
	unsigned long start, n;
	unsigned long npages = dir_pages(dir);
	struct page *page = NULL;
	struct sysv_dir_entry *de;

	*res_page = NULL;

	start = SYSV_I(dir)->i_dir_start_lookup;
	if (start >= npages)
	start = 0;
	n = start;

	do {
	char *kaddr = dir_get_page(dir, n, &page);

	if (!IS_ERR(kaddr)) {
	de = (struct sysv_dir_entry *)kaddr;
	kaddr += PAGE_SIZE - SYSV_DIRSIZE;
	for ( ; (char *) de <= kaddr ; de++) {
	if (!de->inode)
	continue;
	if (namecompare(namelen, SYSV_NAMELEN,
	name, de->name))
	goto found;
	}
	unmap_and_put_page(page, kaddr);
	}

	if (++n >= npages)
	n = 0;
	} while (n != start);

	return NULL;

	found:
	SYSV_I(dir)->i_dir_start_lookup = n;
	*res_page = page;
	return de;
	}

	int sysv_add_link(struct dentry dentry, struct inode inode)
	{
	struct inode *dir = d_inode(dentry->d_parent);
	const char * name = dentry->d_name.name;
	int namelen = dentry->d_name.len;
	struct page *page = NULL;
	struct sysv_dir_entry * de;
	unsigned long npages = dir_pages(dir);
	unsigned long n;
	char *kaddr;
	loff_t pos;
	int err;

	/* We take care of directory expansion in the same loop */
	for (n = 0; n <= npages; n++) {
	kaddr = dir_get_page(dir, n, &page);
	if (IS_ERR(kaddr))
	return PTR_ERR(kaddr);
	de = (struct sysv_dir_entry *)kaddr;
	kaddr += PAGE_SIZE - SYSV_DIRSIZE;
	while ((char *)de <= kaddr) {
	if (!de->inode)
	goto got_it;
	err = -EEXIST;
	if (namecompare(namelen, SYSV_NAMELEN, name, de->name))
	goto out_page;
	de++;
	}
	unmap_and_put_page(page, kaddr);
	}
	BUG();
	return -EINVAL;

	got_it:
	pos = page_offset(page) + offset_in_page(de);
	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	if (err)
	goto out_unlock;
	memcpy (de->name, name, namelen);
	memset (de->name + namelen, 0, SYSV_DIRSIZE - namelen - 2);
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
	mark_inode_dirty(dir);
	err = sysv_handle_dirsync(dir);
	out_page:
	unmap_and_put_page(page, kaddr);
	return err;
	out_unlock:
	unlock_page(page);
	goto out_page;
	}

	int sysv_delete_entry(struct sysv_dir_entry de, struct page page)
	{
	struct inode *inode = page->mapping->host;
	loff_t pos = page_offset(page) + offset_in_page(de);
	int err;

	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	if (err) {
	unlock_page(page);
	return err;
	}
	de->inode = 0;
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
	mark_inode_dirty(inode);
	return sysv_handle_dirsync(inode);
	}

	int sysv_make_empty(struct inode inode, struct inode dir)
	{
	struct page *page = grab_cache_page(inode->i_mapping, 0);
	struct sysv_dir_entry * de;
	char *base;
	int err;

	if (!page)
	return -ENOMEM;
	err = sysv_prepare_chunk(page, 0, 2 * SYSV_DIRSIZE);
	if (err) {
	unlock_page(page);
	goto fail;
	}
	base = kmap_local_page(page);
	memset(base, 0, PAGE_SIZE);

	de = (struct sysv_dir_entry *) base;
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	strcpy(de->name,".");
	de++;
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), dir->i_ino);
	strcpy(de->name,"..");

	kunmap_local(base);
	dir_commit_chunk(page, 0, 2 * SYSV_DIRSIZE);
	err = sysv_handle_dirsync(inode);
	fail:
	put_page(page);
	return err;
	}

	/*
	* routine to check that the specified directory is empty (for rmdir)
	*/
	int sysv_empty_dir(struct inode * inode)
	{
	struct super_block *sb = inode->i_sb;
	struct page *page = NULL;
	unsigned long i, npages = dir_pages(inode);
	char *kaddr;

	for (i = 0; i < npages; i++) {
	struct sysv_dir_entry *de;

	kaddr = dir_get_page(inode, i, &page);
	if (IS_ERR(kaddr))
	continue;

	de = (struct sysv_dir_entry *)kaddr;
	kaddr += PAGE_SIZE-SYSV_DIRSIZE;

	for ( ;(char *)de <= kaddr; de++) {
	if (!de->inode)
	continue;
	/* check for . and .. */
	if (de->name[0] != '.')
	goto not_empty;
	if (!de->name[1]) {
	if (de->inode == cpu_to_fs16(SYSV_SB(sb),
	inode->i_ino))
	continue;
	goto not_empty;
	}
	if (de->name[1] != '.' \|\| de->name[2])
	goto not_empty;
	}
	unmap_and_put_page(page, kaddr);
	}
	return 1;

	not_empty:
	unmap_and_put_page(page, kaddr);
	return 0;
	}

	/* Releases the page */
	int sysv_set_link(struct sysv_dir_entry de, struct page page,
	struct inode *inode)
	{
	struct inode *dir = page->mapping->host;
	loff_t pos = page_offset(page) + offset_in_page(de);
	int err;

	lock_page(page);
	err = sysv_prepare_chunk(page, pos, SYSV_DIRSIZE);
	if (err) {
	unlock_page(page);
	return err;
	}
	de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
	dir_commit_chunk(page, pos, SYSV_DIRSIZE);
	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
	mark_inode_dirty(dir);
	return sysv_handle_dirsync(inode);
	}

	/*
	* Calls to dir_get_page()/unmap_and_put_page() must be nested according to the
	* rules documented in mm/highmem.rst.
	*
	* sysv_dotdot() acts as a call to dir_get_page() and must be treated
	* accordingly for nesting purposes.
	*/
	struct sysv_dir_entry sysv_dotdot(struct inode dir, struct page **p)
	{
	struct sysv_dir_entry *de = dir_get_page(dir, 0, p);

	if (IS_ERR(de))
	return NULL;
	/* ".." is the second directory entry */
	return de + 1;
	}

	ino_t sysv_inode_by_name(struct dentry *dentry)
	{
	struct page *page;
	struct sysv_dir_entry *de = sysv_find_entry (dentry, &page);
	ino_t res = 0;

	if (de) {
	res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
	unmap_and_put_page(page, de);
	}
	return res;
	}