// SPDX-License-Identifier: GPL-2.0/* *  linux/fs/ext2/dir.c * * Copyright (C) 1992, 1993, 1994, 1995 * Remy Card (card@masi.ibp.fr) * Laboratoire MASI - Institut Blaise Pascal * Universite Pierre et Marie Curie (Paris VI) * *  from * *  linux/fs/minix/dir.c * *  Copyright (C) 1991, 1992  Linus Torvalds * *  ext2 directory handling functions * *  Big-endian to little-endian byte-swapping/bitmaps by *        David S. Miller (davem@caip.rutgers.edu), 1995 * * All code that works with directory layout had been switched to pagecache * and moved here. AV */ #include "ext2.h"#include <linux/buffer_head.h>#include <linux/pagemap.h>#include <linux/swap.h>#include <linux/iversion.h> typedef struct ext2_dir_entry_2 ext2_dirent; /* * Tests against MAX_REC_LEN etc were put in place for 64k block * sizes; if that is not possible on this arch, we can skip * those tests and speed things up. */static inline unsigned ext2_rec_len_from_disk(__le16 dlen){	unsigned len = le16_to_cpu(dlen); #if (PAGE_SIZE >= 65536)	if (len == EXT2_MAX_REC_LEN)		return 1 << 16;#endif	return len;} static inline __le16 ext2_rec_len_to_disk(unsigned len){#if (PAGE_SIZE >= 65536)	if (len == (1 << 16))		return cpu_to_le16(EXT2_MAX_REC_LEN);	else		BUG_ON(len > (1 << 16));#endif	return cpu_to_le16(len);} /* * ext2 uses block-sized chunks. Arguably, sector-sized ones would be * more robust, but we have what we have */static inline unsigned ext2_chunk_size(struct inode *inode){	return inode->i_sb->s_blocksize;} static inline void ext2_put_page(struct page *page){	kunmap(page);	put_page(page);} /* * Return the offset into page `page_nr' of the last valid * byte in that page, plus one. */static unsignedext2_last_byte(struct inode *inode, unsigned long page_nr){	unsigned last_byte = inode->i_size; 	last_byte -= page_nr << PAGE_SHIFT;	if (last_byte > PAGE_SIZE)		last_byte = PAGE_SIZE;	return last_byte;} static int ext2_commit_chunk(struct page *page, loff_t pos, unsigned len){	struct address_space *mapping = page->mapping;	struct inode *dir = mapping->host;	int err = 0; 	inode_inc_iversion(dir);	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);	} 	if (IS_DIRSYNC(dir)) {		err = write_one_page(page);		if (!err)			err = sync_inode_metadata(dir, 1);	} else {		unlock_page(page);	} 	return err;} static bool ext2_check_page(struct page *page, int quiet){	struct inode *dir = page->mapping->host;	struct super_block *sb = dir->i_sb;	unsigned chunk_size = ext2_chunk_size(dir);	char *kaddr = page_address(page);	u32 max_inumber = le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count);	unsigned offs, rec_len;	unsigned limit = PAGE_SIZE;	ext2_dirent *p;	char *error; 	if ((dir->i_size >> PAGE_SHIFT) == page->index) {		limit = dir->i_size & ~PAGE_MASK;		if (limit & (chunk_size - 1))			goto Ebadsize;		if (!limit)			goto out;	}	for (offs = 0; offs <= limit - EXT2_DIR_REC_LEN(1); offs += rec_len) {		p = (ext2_dirent *)(kaddr + offs);		rec_len = ext2_rec_len_from_disk(p->rec_len); 		if (unlikely(rec_len < EXT2_DIR_REC_LEN(1)))			goto Eshort;		if (unlikely(rec_len & 3))			goto Ealign;		if (unlikely(rec_len < EXT2_DIR_REC_LEN(p->name_len)))			goto Enamelen;		if (unlikely(((offs + rec_len - 1) ^ offs) & ~(chunk_size-1)))			goto Espan;		if (unlikely(le32_to_cpu(p->inode) > max_inumber))			goto Einumber;	}	if (offs != limit)		goto Eend;out:	SetPageChecked(page);	return true; 	/* Too bad, we had an error */ Ebadsize:	if (!quiet)		ext2_error(sb, __func__,			"size of directory #%lu is not a multiple "			"of chunk size", dir->i_ino);	goto fail;Eshort:	error = "rec_len is smaller than minimal";	goto bad_entry;Ealign:	error = "unaligned directory entry";	goto bad_entry;Enamelen:	error = "rec_len is too small for name_len";	goto bad_entry;Espan:	error = "directory entry across blocks";	goto bad_entry;Einumber:	error = "inode out of bounds";bad_entry:	if (!quiet)		ext2_error(sb, __func__, "bad entry in directory #%lu: : %s - "			"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",			dir->i_ino, error, (page->index<<PAGE_SHIFT)+offs,			(unsigned long) le32_to_cpu(p->inode),			rec_len, p->name_len);	goto fail;Eend:	if (!quiet) {		p = (ext2_dirent *)(kaddr + offs);		ext2_error(sb, "ext2_check_page",			"entry in directory #%lu spans the page boundary"			"offset=%lu, inode=%lu",			dir->i_ino, (page->index<<PAGE_SHIFT)+offs,			(unsigned long) le32_to_cpu(p->inode));	}fail:	SetPageError(page);	return false;} static struct page * ext2_get_page(struct inode *dir, unsigned long n,				   int quiet){	struct address_space *mapping = dir->i_mapping;	struct page *page = read_mapping_page(mapping, n, NULL);	if (!IS_ERR(page)) {		kmap(page);		if (unlikely(!PageChecked(page))) {			if (PageError(page) || !ext2_check_page(page, quiet))				goto fail;		}	}	return page; fail:	ext2_put_page(page);	return ERR_PTR(-EIO);} /* * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure. * * len <= EXT2_NAME_LEN and de != NULL are guaranteed by caller. */static inline int ext2_match (int len, const char * const name,					struct ext2_dir_entry_2 * de){	if (len != de->name_len)		return 0;	if (!de->inode)		return 0;	return !memcmp(name, de->name, len);} /* * p is at least 6 bytes before the end of page */static inline ext2_dirent *ext2_next_entry(ext2_dirent *p){	return (ext2_dirent *)((char *)p +			ext2_rec_len_from_disk(p->rec_len));} static inline unsigned ext2_validate_entry(char *base, unsigned offset, unsigned mask){	ext2_dirent *de = (ext2_dirent*)(base + offset);	ext2_dirent *p = (ext2_dirent*)(base + (offset&mask));	while ((char*)p < (char*)de) {		if (p->rec_len == 0)			break;		p = ext2_next_entry(p);	}	return (char *)p - base;} static inline void ext2_set_de_type(ext2_dirent *de, struct inode *inode){	if (EXT2_HAS_INCOMPAT_FEATURE(inode->i_sb, EXT2_FEATURE_INCOMPAT_FILETYPE))		de->file_type = fs_umode_to_ftype(inode->i_mode);	else		de->file_type = 0;} static intext2_readdir(struct file *file, struct dir_context *ctx){	loff_t pos = ctx->pos;	struct inode *inode = file_inode(file);	struct super_block *sb = inode->i_sb;	unsigned int offset = pos & ~PAGE_MASK;	unsigned long n = pos >> PAGE_SHIFT;	unsigned long npages = dir_pages(inode);	unsigned chunk_mask = ~(ext2_chunk_size(inode)-1);	bool need_revalidate = !inode_eq_iversion(inode, file->f_version);	bool has_filetype; 	if (pos > inode->i_size - EXT2_DIR_REC_LEN(1))		return 0; 	has_filetype =		EXT2_HAS_INCOMPAT_FEATURE(sb, EXT2_FEATURE_INCOMPAT_FILETYPE); 	for ( ; n < npages; n++, offset = 0) {		char *kaddr, *limit;		ext2_dirent *de;		struct page *page = ext2_get_page(inode, n, 0); 		if (IS_ERR(page)) {			ext2_error(sb, __func__,				   "bad page in #%lu",				   inode->i_ino);			ctx->pos += PAGE_SIZE - offset;			return PTR_ERR(page);		}		kaddr = page_address(page);		if (unlikely(need_revalidate)) {			if (offset) {				offset = ext2_validate_entry(kaddr, offset, chunk_mask);				ctx->pos = (n<<PAGE_SHIFT) + offset;			}			file->f_version = inode_query_iversion(inode);			need_revalidate = false;		}		de = (ext2_dirent *)(kaddr+offset);		limit = kaddr + ext2_last_byte(inode, n) - EXT2_DIR_REC_LEN(1);		for ( ;(char*)de <= limit; de = ext2_next_entry(de)) {			if (de->rec_len == 0) {				ext2_error(sb, __func__,					"zero-length directory entry");				ext2_put_page(page);				return -EIO;			}			if (de->inode) {				unsigned char d_type = DT_UNKNOWN; 				if (has_filetype)					d_type = fs_ftype_to_dtype(de->file_type); 				if (!dir_emit(ctx, de->name, de->name_len,						le32_to_cpu(de->inode),						d_type)) {					ext2_put_page(page);					return 0;				}			}			ctx->pos += ext2_rec_len_from_disk(de->rec_len);		}		ext2_put_page(page);	}	return 0;} /* *	ext2_find_entry() * * finds an entry in the specified directory with the wanted name. It * returns the page in which the entry was found (as a parameter - res_page), * and the entry itself. Page is returned mapped and unlocked. * Entry is guaranteed to be valid. */struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,			const struct qstr *child, struct page **res_page){	const char *name = child->name;	int namelen = child->len;	unsigned reclen = EXT2_DIR_REC_LEN(namelen);	unsigned long start, n;	unsigned long npages = dir_pages(dir);	struct page *page = NULL;	struct ext2_inode_info *ei = EXT2_I(dir);	ext2_dirent * de; 	if (npages == 0)		goto out; 	/* OFFSET_CACHE */	*res_page = NULL; 	start = ei->i_dir_start_lookup;	if (start >= npages)		start = 0;	n = start;	do {		char *kaddr;		page = ext2_get_page(dir, n, 0);		if (IS_ERR(page))			return ERR_CAST(page); 		kaddr = page_address(page);		de = (ext2_dirent *) kaddr;		kaddr += ext2_last_byte(dir, n) - reclen;		while ((char *) de <= kaddr) {			if (de->rec_len == 0) {				ext2_error(dir->i_sb, __func__,					"zero-length directory entry");				ext2_put_page(page);				goto out;			}			if (ext2_match(namelen, name, de))				goto found;			de = ext2_next_entry(de);		}		ext2_put_page(page); 		if (++n >= npages)			n = 0;		/* next page is past the blocks we've got */		if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {			ext2_error(dir->i_sb, __func__,				"dir %lu size %lld exceeds block count %llu",				dir->i_ino, dir->i_size,				(unsigned long long)dir->i_blocks);			goto out;		}	} while (n != start);out:	return ERR_PTR(-ENOENT); found:	*res_page = page;	ei->i_dir_start_lookup = n;	return de;} struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p){	struct page *page = ext2_get_page(dir, 0, 0);	ext2_dirent *de = NULL; 	if (!IS_ERR(page)) {		de = ext2_next_entry((ext2_dirent *) page_address(page));		*p = page;	}	return de;} int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino){	struct ext2_dir_entry_2 *de;	struct page *page;		de = ext2_find_entry(dir, child, &page);	if (IS_ERR(de))		return PTR_ERR(de); 	*ino = le32_to_cpu(de->inode);	ext2_put_page(page);	return 0;} static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len){	return __block_write_begin(page, pos, len, ext2_get_block);} /* Releases the page */void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,		   struct page *page, struct inode *inode, int update_times){	loff_t pos = page_offset(page) +			(char *) de - (char *) page_address(page);	unsigned len = ext2_rec_len_from_disk(de->rec_len);	int err; 	lock_page(page);	err = ext2_prepare_chunk(page, pos, len);	BUG_ON(err);	de->inode = cpu_to_le32(inode->i_ino);	ext2_set_de_type(de, inode);	err = ext2_commit_chunk(page, pos, len);	ext2_put_page(page);	if (update_times)		dir->i_mtime = dir->i_ctime = current_time(dir);	EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;	mark_inode_dirty(dir);} /* *	Parent is locked. */int ext2_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;	unsigned chunk_size = ext2_chunk_size(dir);	unsigned reclen = EXT2_DIR_REC_LEN(namelen);	unsigned short rec_len, name_len;	struct page *page = NULL;	ext2_dirent * 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.	 * This code plays outside i_size, so it locks the page	 * to protect that region.	 */	for (n = 0; n <= npages; n++) {		char *dir_end; 		page = ext2_get_page(dir, n, 0);		err = PTR_ERR(page);		if (IS_ERR(page))			goto out;		lock_page(page);		kaddr = page_address(page);		dir_end = kaddr + ext2_last_byte(dir, n);		de = (ext2_dirent *)kaddr;		kaddr += PAGE_SIZE - reclen;		while ((char *)de <= kaddr) {			if ((char *)de == dir_end) {				/* We hit i_size */				name_len = 0;				rec_len = chunk_size;				de->rec_len = ext2_rec_len_to_disk(chunk_size);				de->inode = 0;				goto got_it;

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