// 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 folio *folio, loff_t pos, unsigned len)
{
struct address_space *mapping = folio->mapping;
struct inode *dir = mapping->host;
block_write_end(NULL, mapping, pos, len, len, folio, NULL);
if (pos+len > dir->i_size) {
i_size_write(dir, pos+len);
mark_inode_dirty(dir);
}
folio_unlock(folio);
}
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_folio()/folio_release_kmap() 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_folio()
* and must be treated accordingly for nesting purposes.
*/
static void *dir_get_folio(struct inode *dir, unsigned long n,
struct folio **foliop)
{
struct folio *folio = read_mapping_folio(dir->i_mapping, n, NULL);
if (IS_ERR(folio))
return ERR_CAST(folio);
*foliop = folio;
return kmap_local_folio(folio, 0);
}
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 folio *folio;
kaddr = dir_get_folio(inode, n, &folio);
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)) {
folio_release_kmap(folio, kaddr);
return 0;
}
}
folio_release_kmap(folio, 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 does NOT read the inode of the
* entry - you'll have to do that yourself if you want to.
*
* On Success folio_release_kmap() should be called on *foliop.
*
* sysv_find_entry() acts as a call to dir_get_folio() and must be treated
* accordingly for nesting purposes.
*/
struct sysv_dir_entry *sysv_find_entry(struct dentry *dentry, struct folio **foliop)
{
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 sysv_dir_entry *de;
start = SYSV_I(dir)->i_dir_start_lookup;
if (start >= npages)
start = 0;
n = start;
do {
char *kaddr = dir_get_folio(dir, n, foliop);
if (!IS_ERR(kaddr)) {
de = (struct sysv_dir_entry *)kaddr;
kaddr += folio_size(*foliop) - SYSV_DIRSIZE;
for ( ; (char *) de <= kaddr ; de++) {
if (!de->inode)
continue;
if (namecompare(namelen, SYSV_NAMELEN,
name, de->name))
goto found;
}
folio_release_kmap(*foliop, kaddr);
}
if (++n >= npages)
n = 0;
} while (n != start);
return NULL;
found:
SYSV_I(dir)->i_dir_start_lookup = n;
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 folio *folio = 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_folio(dir, n, &folio);
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_folio;
de++;
}
folio_release_kmap(folio, kaddr);
}
BUG();
return -EINVAL;
got_it:
pos = folio_pos(folio) + offset_in_folio(folio, de);
folio_lock(folio);
err = sysv_prepare_chunk(folio, 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(folio, pos, SYSV_DIRSIZE);
inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
mark_inode_dirty(dir);
err = sysv_handle_dirsync(dir);
out_folio:
folio_release_kmap(folio, kaddr);
return err;
out_unlock:
folio_unlock(folio);
goto out_folio;
}
int sysv_delete_entry(struct sysv_dir_entry *de, struct folio *folio)
{
struct inode *inode = folio->mapping->host;
loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
int err;
folio_lock(folio);
err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);
if (err) {
folio_unlock(folio);
return err;
}
de->inode = 0;
dir_commit_chunk(folio, 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 folio *folio = filemap_grab_folio(inode->i_mapping, 0);
struct sysv_dir_entry * de;
char *kaddr;
int err;
if (IS_ERR(folio))
return PTR_ERR(folio);
err = sysv_prepare_chunk(folio, 0, 2 * SYSV_DIRSIZE);
if (err) {
folio_unlock(folio);
goto fail;
}
kaddr = kmap_local_folio(folio, 0);
memset(kaddr, 0, folio_size(folio));
de = (struct sysv_dir_entry *)kaddr;
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(kaddr);
dir_commit_chunk(folio, 0, 2 * SYSV_DIRSIZE);
err = sysv_handle_dirsync(inode);
fail:
folio_put(folio);
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 folio *folio = NULL;
unsigned long i, npages = dir_pages(inode);
char *kaddr;
for (i = 0; i < npages; i++) {
struct sysv_dir_entry *de;
kaddr = dir_get_folio(inode, i, &folio);
if (IS_ERR(kaddr))
continue;
de = (struct sysv_dir_entry *)kaddr;
kaddr += folio_size(folio) - 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;
}
folio_release_kmap(folio, kaddr);
}
return 1;
not_empty:
folio_release_kmap(folio, kaddr);
return 0;
}
/* Releases the page */
int sysv_set_link(struct sysv_dir_entry *de, struct folio *folio,
struct inode *inode)
{
struct inode *dir = folio->mapping->host;
loff_t pos = folio_pos(folio) + offset_in_folio(folio, de);
int err;
folio_lock(folio);
err = sysv_prepare_chunk(folio, pos, SYSV_DIRSIZE);
if (err) {
folio_unlock(folio);
return err;
}
de->inode = cpu_to_fs16(SYSV_SB(inode->i_sb), inode->i_ino);
dir_commit_chunk(folio, 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_folio()/folio_release_kmap() must be nested according to the
* rules documented in mm/highmem.rst.
*
* sysv_dotdot() acts as a call to dir_get_folio() and must be treated
* accordingly for nesting purposes.
*/
struct sysv_dir_entry *sysv_dotdot(struct inode *dir, struct folio **foliop)
{
struct sysv_dir_entry *de = dir_get_folio(dir, 0, foliop);
if (IS_ERR(de))
return NULL;
/* ".." is the second directory entry */
return de + 1;
}
ino_t sysv_inode_by_name(struct dentry *dentry)
{
struct folio *folio;
struct sysv_dir_entry *de = sysv_find_entry (dentry, &folio);
ino_t res = 0;
if (de) {
res = fs16_to_cpu(SYSV_SB(dentry->d_sb), de->inode);
folio_release_kmap(folio, de);
}
return res;
}
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