This commit adds functions that transfer names to inodes. Signed-off-by: Miao Xie <miaoxie@xxxxxxxxxx> Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx> Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx> --- drivers/staging/erofs/namei.c | 243 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 243 insertions(+) create mode 100644 drivers/staging/erofs/namei.c diff --git a/drivers/staging/erofs/namei.c b/drivers/staging/erofs/namei.c new file mode 100644 index 0000000..39db643 --- /dev/null +++ b/drivers/staging/erofs/namei.c @@ -0,0 +1,243 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/drivers/staging/erofs/namei.c + * + * Copyright (C) 2017-2018 HUAWEI, Inc. + * http://www.huawei.com/ + * Created by Gao Xiang <gaoxiang25@xxxxxxxxxx> + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of the Linux + * distribution for more details. + */ +#include "internal.h" + +/* based on the value of qn->len is accurate */ +static inline int dirnamecmp(struct qstr *qn, + struct qstr *qd, unsigned *matched) +{ + unsigned i = *matched, len = min(qn->len, qd->len); +loop: + if (unlikely(i >= len)) { + *matched = i; + if (qn->len < qd->len) { + /* + * actually (qn->len == qd->len) + * when qd->name[i] == '\0' + */ + return qd->name[i] == '\0' ? 0 : -1; + } + return (qn->len > qd->len); + } + + if (qn->name[i] != qd->name[i]) { + *matched = i; + return qn->name[i] > qd->name[i] ? 1 : -1; + } + + ++i; + goto loop; +} + +static struct erofs_dirent *find_target_dirent( + struct qstr *name, + u8 *data, int maxsize) +{ + unsigned ndirents, head, back; + unsigned startprfx, endprfx; + struct erofs_dirent *const de = (struct erofs_dirent *)data; + + /* make sure that maxsize is valid */ + BUG_ON(maxsize < sizeof(struct erofs_dirent)); + + ndirents = le16_to_cpu(de->nameoff) / sizeof(*de); + + /* corrupted dir (may be unnecessary...) */ + BUG_ON(!ndirents); + + head = 0; + back = ndirents - 1; + startprfx = endprfx = 0; + + while (head <= back) { + unsigned mid = head + (back - head) / 2; + unsigned nameoff = le16_to_cpu(de[mid].nameoff); + unsigned matched = min(startprfx, endprfx); + + struct qstr dname = QSTR_INIT(data + nameoff, + unlikely(mid >= ndirents - 1) ? + maxsize - nameoff : + le16_to_cpu(de[mid + 1].nameoff) - nameoff); + + /* string comparison without already matched prefix */ + int ret = dirnamecmp(name, &dname, &matched); + + if (unlikely(!ret)) + return de + mid; + else if (ret > 0) { + head = mid + 1; + startprfx = matched; + } else if (unlikely(mid < 1)) /* fix "mid" overflow */ + break; + else { + back = mid - 1; + endprfx = matched; + } + } + + return ERR_PTR(-ENOENT); +} + +static struct page *find_target_block_classic( + struct inode *dir, + struct qstr *name, int *_diff) +{ + unsigned startprfx, endprfx; + unsigned head, back; + struct address_space *const mapping = dir->i_mapping; + struct page *candidate = ERR_PTR(-ENOENT); + + startprfx = endprfx = 0; + head = 0; + back = inode_datablocks(dir) - 1; + + while (head <= back) { + unsigned mid = head + (back - head) / 2; + struct page *page = read_mapping_page(mapping, mid, NULL); + + if (IS_ERR(page)) { +exact_out: + if (!IS_ERR(candidate)) /* valid candidate */ + put_page(candidate); + return page; + } else { + int diff; + unsigned ndirents, matched; + struct qstr dname; + struct erofs_dirent *de = kmap_atomic(page); + unsigned nameoff = le16_to_cpu(de->nameoff); + + ndirents = nameoff / sizeof(*de); + + /* corrupted dir (should have one entry at least) */ + BUG_ON(!ndirents || nameoff > PAGE_SIZE); + + matched = min(startprfx, endprfx); + + dname.name = (u8 *)de + nameoff; + dname.len = ndirents == 1 ? + /* since the rest of the last page is 0 */ + EROFS_BLKSIZ - nameoff + : le16_to_cpu(de[1].nameoff) - nameoff; + + /* string comparison without already matched prefix */ + diff = dirnamecmp(name, &dname, &matched); + kunmap_atomic(de); + + if (unlikely(!diff)) { + *_diff = 0; + goto exact_out; + } else if (diff > 0) { + head = mid + 1; + startprfx = matched; + + if (likely(!IS_ERR(candidate))) + put_page(candidate); + candidate = page; + } else { + put_page(page); + + if (unlikely(mid < 1)) /* fix "mid" overflow */ + break; + + back = mid - 1; + endprfx = matched; + } + } + } + *_diff = 1; + return candidate; +} + +int erofs_namei(struct inode *dir, + struct qstr *name, + erofs_nid_t *nid, unsigned *d_type) +{ + int diff; + struct page *page; + u8 *data; + struct erofs_dirent *de; + + if (unlikely(!dir->i_size)) + return -ENOENT; + + diff = 1; + page = find_target_block_classic(dir, name, &diff); + + if (unlikely(IS_ERR(page))) + return PTR_ERR(page); + + data = kmap_atomic(page); + /* the target page has been mapped */ + de = likely(diff) ? + /* since the rest of the last page is 0 */ + find_target_dirent(name, data, EROFS_BLKSIZ) : + (struct erofs_dirent *)data; + + if (likely(!IS_ERR(de))) { + *nid = le64_to_cpu(de->nid); + *d_type = de->file_type; + } + + kunmap_atomic(data); + put_page(page); + + return IS_ERR(de) ? PTR_ERR(de) : 0; +} + +/* 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 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)); + + /* file name exceeds fs limit */ + if (unlikely(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; + goto negative_out; + } else if (unlikely(err)) + return ERR_PTR(err); + + debugln("%s, %s (nid %llu) found, d_type %u", __func__, + dentry->d_name.name, nid, d_type); + + inode = erofs_iget(dir->i_sb, nid, d_type == EROFS_FT_DIR); + if (IS_ERR(inode)) + return ERR_CAST(inode); + +negative_out: + return d_splice_alias(inode, dentry); +} + +const struct inode_operations erofs_dir_iops = { + .lookup = erofs_lookup, +}; + +const struct inode_operations erofs_dir_xattr_iops = { + .lookup = erofs_lookup, +}; + -- 1.9.1 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
