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    Subject[PATCH v6 07/24] erofs: add directory operations
    Date
    This adds functions for directory, mainly readdir.

    Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
    ---
    fs/erofs/dir.c | 147 +++++++++++++++++++++++++++++++++++++++++++++++++
    1 file changed, 147 insertions(+)
    create mode 100644 fs/erofs/dir.c

    diff --git a/fs/erofs/dir.c b/fs/erofs/dir.c
    new file mode 100644
    index 000000000000..7cf7da8574c4
    --- /dev/null
    +++ b/fs/erofs/dir.c
    @@ -0,0 +1,147 @@
    +// SPDX-License-Identifier: GPL-2.0-only
    +/*
    + * linux/fs/erofs/dir.c
    + *
    + * Copyright (C) 2017-2018 HUAWEI, Inc.
    + * http://www.huawei.com/
    + * Created by Gao Xiang <gaoxiang25@huawei.com>
    + */
    +#include "internal.h"
    +
    +static const unsigned char erofs_filetype_table[EROFS_FT_MAX] = {
    + [EROFS_FT_UNKNOWN] = DT_UNKNOWN,
    + [EROFS_FT_REG_FILE] = DT_REG,
    + [EROFS_FT_DIR] = DT_DIR,
    + [EROFS_FT_CHRDEV] = DT_CHR,
    + [EROFS_FT_BLKDEV] = DT_BLK,
    + [EROFS_FT_FIFO] = DT_FIFO,
    + [EROFS_FT_SOCK] = DT_SOCK,
    + [EROFS_FT_SYMLINK] = DT_LNK,
    +};
    +
    +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';
    +
    + debugln("found dirent %s de_len %u d_type %d", dbg_namebuf,
    + de_namelen, d_type);
    +#endif
    +}
    +
    +static int erofs_fill_dentries(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;
    +
    + if (de->file_type < EROFS_FT_MAX)
    + d_type = erofs_filetype_table[de->file_type];
    + else
    + d_type = DT_UNKNOWN;
    +
    + 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 (unlikely(nameoff + de_namelen > maxsize ||
    + de_namelen > EROFS_NAME_LEN)) {
    + DBG_BUGON(1);
    + return -EIO;
    + }
    +
    + 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 (IS_ERR(dentry_page))
    + continue;
    +
    + de = (struct erofs_dirent *)kmap(dentry_page);
    +
    + nameoff = le16_to_cpu(de->nameoff);
    +
    + if (unlikely(nameoff < sizeof(struct erofs_dirent) ||
    + nameoff >= PAGE_SIZE)) {
    + errln("%s, invalid de[0].nameoff %u",
    + __func__, nameoff);
    +
    + err = -EIO;
    + goto skip_this;
    + }
    +
    + maxsize = min_t(unsigned int,
    + dirsize - ctx->pos + ofs, PAGE_SIZE);
    +
    + /* search dirents at the arbitrary position */
    + if (unlikely(initial)) {
    + initial = false;
    +
    + ofs = roundup(ofs, sizeof(struct erofs_dirent));
    + if (unlikely(ofs >= nameoff))
    + goto skip_this;
    + }
    +
    + err = erofs_fill_dentries(ctx, de, &ofs, nameoff, maxsize);
    +skip_this:
    + kunmap(dentry_page);
    +
    + put_page(dentry_page);
    +
    + ctx->pos = blknr_to_addr(i) + ofs;
    +
    + if (unlikely(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,
    +};
    +
    --
    2.17.1
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