1 files changed, 382 insertions, 0 deletions
diff --git a/fs/sysv/dir.c b/fs/sysv/dir.c
new file mode 100644
index 0000000000..2f5ead88d0
--- /dev/null
+++ b/fs/sysv/dir.c
@@ -0,0 +1,382 @@
+// 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);
+	dir->i_mtime = 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->i_mtime = 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);
+	dir->i_mtime = 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;
+}