mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-05-20 14:35:06 +02:00
Gao Xiang
e9dfe33aea
There's no need to record "." dirents in the directory data (while they could be used for sanity checks, they aren't very useful.) Omitting "." dirents also improves directory data deduplication. Use a per-inode (instead of per-sb) flag to indicate if the "." dirent is omitted or not, ensuring compatibility with incremental builds. It also reuses EROFS_I_NLINK_1_BIT, as it has very limited use cases for directories with `nlink = 1`. Emit the "." entry as the last virtual dirent in the directory because it is _much_ less frequently used than the ".." dirent. It also keeps `f_pos` meaningful, as it strictly follows the directory data when it's less than i_size. Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com> Acked-by: Chao Yu <chao@kernel.org> Link: https://lore.kernel.org/r/20250310095459.2620647-6-hsiangkao@linux.alibaba.com
106 lines
2.8 KiB
C
106 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2017-2018 HUAWEI, Inc.
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* https://www.huawei.com/
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* Copyright (C) 2022, Alibaba Cloud
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*/
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#include "internal.h"
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static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
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void *dentry_blk, struct erofs_dirent *de,
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unsigned int nameoff0, unsigned int maxsize)
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{
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const struct erofs_dirent *end = dentry_blk + nameoff0;
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while (de < end) {
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unsigned char d_type = fs_ftype_to_dtype(de->file_type);
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unsigned int nameoff = le16_to_cpu(de->nameoff);
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const char *de_name = (char *)dentry_blk + nameoff;
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unsigned int de_namelen;
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/* the last dirent in the block? */
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if (de + 1 >= end)
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de_namelen = strnlen(de_name, maxsize - nameoff);
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else
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de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
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/* a corrupted entry is found */
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if (nameoff + de_namelen > maxsize ||
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de_namelen > EROFS_NAME_LEN) {
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erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
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EROFS_I(dir)->nid);
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DBG_BUGON(1);
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return -EFSCORRUPTED;
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}
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if (!dir_emit(ctx, de_name, de_namelen,
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le64_to_cpu(de->nid), d_type))
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return 1;
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++de;
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ctx->pos += sizeof(struct erofs_dirent);
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}
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return 0;
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}
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static int erofs_readdir(struct file *f, struct dir_context *ctx)
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{
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struct inode *dir = file_inode(f);
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struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
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struct super_block *sb = dir->i_sb;
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unsigned long bsz = sb->s_blocksize;
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unsigned int ofs = erofs_blkoff(sb, ctx->pos);
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int err = 0;
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bool initial = true;
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buf.mapping = dir->i_mapping;
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while (ctx->pos < dir->i_size) {
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erofs_off_t dbstart = ctx->pos - ofs;
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struct erofs_dirent *de;
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unsigned int nameoff, maxsize;
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de = erofs_bread(&buf, dbstart, true);
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if (IS_ERR(de)) {
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erofs_err(sb, "failed to readdir of logical block %llu of nid %llu",
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erofs_blknr(sb, dbstart), EROFS_I(dir)->nid);
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err = PTR_ERR(de);
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break;
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}
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nameoff = le16_to_cpu(de->nameoff);
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if (nameoff < sizeof(struct erofs_dirent) || nameoff >= bsz) {
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erofs_err(sb, "invalid de[0].nameoff %u @ nid %llu",
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nameoff, EROFS_I(dir)->nid);
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err = -EFSCORRUPTED;
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break;
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}
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maxsize = min_t(unsigned int, dir->i_size - dbstart, bsz);
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/* search dirents at the arbitrary position */
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if (initial) {
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initial = false;
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ofs = roundup(ofs, sizeof(struct erofs_dirent));
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ctx->pos = dbstart + ofs;
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}
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err = erofs_fill_dentries(dir, ctx, de, (void *)de + ofs,
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nameoff, maxsize);
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if (err)
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break;
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ctx->pos = dbstart + maxsize;
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ofs = 0;
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}
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erofs_put_metabuf(&buf);
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if (EROFS_I(dir)->dot_omitted && ctx->pos == dir->i_size) {
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if (!dir_emit_dot(f, ctx))
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return 0;
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++ctx->pos;
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}
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return err < 0 ? err : 0;
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}
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const struct file_operations erofs_dir_fops = {
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.llseek = generic_file_llseek,
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.read = generic_read_dir,
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.iterate_shared = erofs_readdir,
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};
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