linux/fs/erofs/namei.c
Hongnan Li 3e917cc305 erofs: make filesystem exportable
Implement export operations in order to make EROFS support accessing
inodes with filehandles so that it can be exported via NFS and used
by overlayfs.

Without this patch, 'exportfs -rv' will report:
exportfs: /root/erofs_mp does not support NFS export

Also tested with unionmount-testsuite and the testcase below passes now:
./run --ov --erofs --verify hard-link

For more details about the testcase, see:
https://github.com/amir73il/unionmount-testsuite/pull/6

Signed-off-by: Hongnan Li <hongnan.li@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20220425040712.91685-1-hongnan.li@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
2022-05-17 23:48:54 +08:00

243 lines
5.8 KiB
C

// 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 *find_target_block_classic(struct erofs_buf *target,
struct inode *dir,
struct erofs_qstr *name,
int *_ndirents)
{
unsigned int startprfx, endprfx;
int head, back;
void *candidate = ERR_PTR(-ENOENT);
startprfx = endprfx = 0;
head = 0;
back = erofs_inode_datablocks(dir) - 1;
while (head <= back) {
const int mid = head + (back - head) / 2;
struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
struct erofs_dirent *de;
de = erofs_bread(&buf, dir, mid, EROFS_KMAP);
if (!IS_ERR(de)) {
const int nameoff = nameoff_from_disk(de->nameoff,
EROFS_BLKSIZ);
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 + EROFS_BLKSIZ;
else
dname.end = (u8 *)de +
nameoff_from_disk(de[1].nameoff,
EROFS_BLKSIZ);
/* 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;
ndirents = 0;
de = find_target_block_classic(&buf, dir, &qn, &ndirents);
if (IS_ERR(de))
return PTR_ERR(de);
/* the target page has been mapped */
if (ndirents)
de = find_target_dirent(&qn, (u8 *)de, EROFS_BLKSIZ, 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);
}
/* NOTE: i_mutex is already held by vfs */
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;
DBG_BUGON(!d_really_is_negative(dentry));
/* dentry must be unhashed in lookup, no need to worry about */
DBG_BUGON(!d_unhashed(dentry));
trace_erofs_lookup(dir, dentry, flags);
/* file name exceeds fs limit */
if (dentry->d_name.len > EROFS_NAME_LEN)
return ERR_PTR(-ENAMETOOLONG);
/* false uninitialized warnings on gcc 4.8.x */
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 {
erofs_dbg("%s, %pd (nid %llu) found, d_type %u", __func__,
dentry, nid, d_type);
inode = erofs_iget(dir->i_sb, nid, d_type == FT_DIR);
}
return d_splice_alias(inode, dentry);
}
const struct inode_operations erofs_dir_iops = {
.lookup = erofs_lookup,
.getattr = erofs_getattr,
.listxattr = erofs_listxattr,
.get_acl = erofs_get_acl,
.fiemap = erofs_fiemap,
};