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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* https://www.huawei.com/
* Copyright (C) 2022, Alibaba Cloud
*/
#include "xattr.h"
#include <trace/events/erofs.h>
struct erofs_qstr {
const unsigned char *name;
const unsigned char *end;
};
/* based on the end of qn is accurate and it must have the trailing '\0' */
static inline int erofs_dirnamecmp(const struct erofs_qstr *qn,
const struct erofs_qstr *qd,
unsigned int *matched)
{
unsigned int i = *matched;
/*
* on-disk error, let's only BUG_ON in the debugging mode.
* otherwise, it will return 1 to just skip the invalid name
* and go on (in consideration of the lookup performance).
*/
DBG_BUGON(qd->name > qd->end);
/* qd could not have trailing '\0' */
/* However it is absolutely safe if < qd->end */
while (qd->name + i < qd->end && qd->name[i] != '\0') {
if (qn->name[i] != qd->name[i]) {
*matched = i;
return qn->name[i] > qd->name[i] ? 1 : -1;
}
++i;
}
*matched = i;
/* See comments in __d_alloc on the terminating NUL character */
return qn->name[i] == '\0' ? 0 : 1;
}
#define nameoff_from_disk(off, sz) (le16_to_cpu(off) & ((sz) - 1))
static struct erofs_dirent *find_target_dirent(struct erofs_qstr *name,
u8 *data,
unsigned int dirblksize,
const int ndirents)
{
int head, back;
unsigned int startprfx, endprfx;
struct erofs_dirent *const de = (struct erofs_dirent *)data;
/* since the 1st dirent has been evaluated previously */
head = 1;
back = ndirents - 1;
startprfx = endprfx = 0;
while (head <= back) {
const int mid = head + (back - head) / 2;
const int nameoff = nameoff_from_disk(de[mid].nameoff,
dirblksize);
unsigned int matched = min(startprfx, endprfx);
struct erofs_qstr dname = {
.name = data + nameoff,
.end = mid >= ndirents - 1 ?
data + dirblksize :
data + nameoff_from_disk(de[mid + 1].nameoff,
dirblksize)
};
/* string comparison without already matched prefix */
int ret = erofs_dirnamecmp(name, &dname, &matched);
if (!ret) {
return de + mid;
} else if (ret > 0) {
head = mid + 1;
startprfx = matched;
} else {
back = mid - 1;
endprfx = matched;
}
}
return ERR_PTR(-ENOENT);
}
static void *erofs_find_target_block(struct erofs_buf *target,
struct inode *dir, struct erofs_qstr *name, int *_ndirents)
{
unsigned int bsz = i_blocksize(dir);
int head = 0, back = erofs_iblks(dir) - 1;
unsigned int startprfx = 0, endprfx = 0;
void *candidate = ERR_PTR(-ENOENT);
while (head <= back) {
const int mid = head + (back - head) / 2;
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct erofs_dirent *de;
buf.inode = dir;
de = erofs_bread(&buf, mid, EROFS_KMAP);
if (!IS_ERR(de)) {
const int nameoff = nameoff_from_disk(de->nameoff, bsz);
const int ndirents = nameoff / sizeof(*de);
int diff;
unsigned int matched;
struct erofs_qstr dname;
if (!ndirents) {
erofs_put_metabuf(&buf);
erofs_err(dir->i_sb,
"corrupted dir block %d @ nid %llu",
mid, EROFS_I(dir)->nid);
DBG_BUGON(1);
de = ERR_PTR(-EFSCORRUPTED);
goto out;
}
matched = min(startprfx, endprfx);
dname.name = (u8 *)de + nameoff;
if (ndirents == 1)
dname.end = (u8 *)de + bsz;
else
dname.end = (u8 *)de +
nameoff_from_disk(de[1].nameoff, bsz);
/* string comparison without already matched prefix */
diff = erofs_dirnamecmp(name, &dname, &matched);
if (!diff) {
*_ndirents = 0;
goto out;
} else if (diff > 0) {
head = mid + 1;
startprfx = matched;
if (!IS_ERR(candidate))
erofs_put_metabuf(target);
*target = buf;
candidate = de;
*_ndirents = ndirents;
} else {
erofs_put_metabuf(&buf);
back = mid - 1;
endprfx = matched;
}
continue;
}
out: /* free if the candidate is valid */
if (!IS_ERR(candidate))
erofs_put_metabuf(target);
return de;
}
return candidate;
}
int erofs_namei(struct inode *dir, const struct qstr *name, erofs_nid_t *nid,
unsigned int *d_type)
{
int ndirents;
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct erofs_dirent *de;
struct erofs_qstr qn;
if (!dir->i_size)
return -ENOENT;
qn.name = name->name;
qn.end = name->name + name->len;
buf.inode = dir;
ndirents = 0;
de = erofs_find_target_block(&buf, dir, &qn, &ndirents);
if (IS_ERR(de))
return PTR_ERR(de);
if (ndirents)
de = find_target_dirent(&qn, (u8 *)de, i_blocksize(dir),
ndirents);
if (!IS_ERR(de)) {
*nid = le64_to_cpu(de->nid);
*d_type = de->file_type;
}
erofs_put_metabuf(&buf);
return PTR_ERR_OR_ZERO(de);
}
static struct dentry *erofs_lookup(struct inode *dir, struct dentry *dentry,
unsigned int flags)
{
int err;
erofs_nid_t nid;
unsigned int d_type;
struct inode *inode;
trace_erofs_lookup(dir, dentry, flags);
if (dentry->d_name.len > EROFS_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
err = erofs_namei(dir, &dentry->d_name, &nid, &d_type);
if (err == -ENOENT)
/* negative dentry */
inode = NULL;
else if (err)
inode = ERR_PTR(err);
else
inode = erofs_iget(dir->i_sb, nid);
return d_splice_alias(inode, dentry);
}
const struct inode_operations erofs_dir_iops = {
.lookup = erofs_lookup,
.getattr = erofs_getattr,
.listxattr = erofs_listxattr,
.get_inode_acl = erofs_get_acl,
.fiemap = erofs_fiemap,
};
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