dir.c
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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* https://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*/
#include "internal.h"
static void debug_one_dentry(unsigned char d_type, const char *de_name,
unsigned int de_namelen)
{
#ifdef CONFIG_EROFS_FS_DEBUG
/* since the on-disk name could not have the trailing '\0' */
unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
memcpy(dbg_namebuf, de_name, de_namelen);
dbg_namebuf[de_namelen] = '\0';
erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
de_namelen, d_type);
#endif
}
static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
void *dentry_blk, unsigned int *ofs,
unsigned int nameoff, unsigned int maxsize)
{
struct erofs_dirent *de = dentry_blk + *ofs;
const struct erofs_dirent *end = dentry_blk + nameoff;
while (de < end) {
const char *de_name;
unsigned int de_namelen;
unsigned char d_type;
d_type = fs_ftype_to_dtype(de->file_type);
nameoff = le16_to_cpu(de->nameoff);
de_name = (char *)dentry_blk + nameoff;
/* the last dirent in the block? */
if (de + 1 >= end)
de_namelen = strnlen(de_name, maxsize - nameoff);
else
de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
/* a corrupted entry is found */
if (nameoff + de_namelen > maxsize ||
de_namelen > EROFS_NAME_LEN) {
erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
EROFS_I(dir)->nid);
DBG_BUGON(1);
return -EFSCORRUPTED;
}
debug_one_dentry(d_type, de_name, de_namelen);
if (!dir_emit(ctx, de_name, de_namelen,
le64_to_cpu(de->nid), d_type))
/* stopped by some reason */
return 1;
++de;
*ofs += sizeof(struct erofs_dirent);
}
*ofs = maxsize;
return 0;
}
static int erofs_readdir(struct file *f, struct dir_context *ctx)
{
struct inode *dir = file_inode(f);
struct address_space *mapping = dir->i_mapping;
const size_t dirsize = i_size_read(dir);
unsigned int i = ctx->pos / EROFS_BLKSIZ;
unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
int err = 0;
bool initial = true;
while (ctx->pos < dirsize) {
struct page *dentry_page;
struct erofs_dirent *de;
unsigned int nameoff, maxsize;
dentry_page = read_mapping_page(mapping, i, NULL);
if (dentry_page == ERR_PTR(-ENOMEM)) {
err = -ENOMEM;
break;
} else if (IS_ERR(dentry_page)) {
erofs_err(dir->i_sb,
"fail to readdir of logical block %u of nid %llu",
i, EROFS_I(dir)->nid);
err = -EFSCORRUPTED;
break;
}
de = (struct erofs_dirent *)kmap(dentry_page);
nameoff = le16_to_cpu(de->nameoff);
if (nameoff < sizeof(struct erofs_dirent) ||
nameoff >= PAGE_SIZE) {
erofs_err(dir->i_sb,
"invalid de[0].nameoff %u @ nid %llu",
nameoff, EROFS_I(dir)->nid);
err = -EFSCORRUPTED;
goto skip_this;
}
maxsize = min_t(unsigned int,
dirsize - ctx->pos + ofs, PAGE_SIZE);
/* search dirents at the arbitrary position */
if (initial) {
initial = false;
ofs = roundup(ofs, sizeof(struct erofs_dirent));
if (ofs >= nameoff)
goto skip_this;
}
err = erofs_fill_dentries(dir, ctx, de, &ofs,
nameoff, maxsize);
skip_this:
kunmap(dentry_page);
put_page(dentry_page);
ctx->pos = blknr_to_addr(i) + ofs;
if (err)
break;
++i;
ofs = 0;
}
return err < 0 ? err : 0;
}
const struct file_operations erofs_dir_fops = {
.llseek = generic_file_llseek,
.read = generic_read_dir,
.iterate_shared = erofs_readdir,
};