dir.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2017-2018 HUAWEI, Inc.
  4 *             https://www.huawei.com/
  5 * Copyright (C) 2022, Alibaba Cloud
  6 */
  7#include "internal.h"
  8
  9static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
 10			       void *dentry_blk, struct erofs_dirent *de,
 11			       unsigned int nameoff0, unsigned int maxsize)
 12{
 13	const struct erofs_dirent *end = dentry_blk + nameoff0;
 14
 15	while (de < end) {
 16		unsigned char d_type = fs_ftype_to_dtype(de->file_type);
 17		unsigned int nameoff = le16_to_cpu(de->nameoff);
 18		const char *de_name = (char *)dentry_blk + nameoff;
 19		unsigned int de_namelen;
 20
 21		/* the last dirent in the block? */
 22		if (de + 1 >= end)
 23			de_namelen = strnlen(de_name, maxsize - nameoff);
 24		else
 25			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
 26
 27		/* a corrupted entry is found */
 28		if (nameoff + de_namelen > maxsize ||
 29		    de_namelen > EROFS_NAME_LEN) {
 30			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
 31				  EROFS_I(dir)->nid);
 32			DBG_BUGON(1);
 33			return -EFSCORRUPTED;
 34		}
 35
 36		if (!dir_emit(ctx, de_name, de_namelen,
 37			      erofs_nid_to_ino64(EROFS_SB(dir->i_sb),
 38						 le64_to_cpu(de->nid)), d_type))
 39			return 1;
 40		++de;
 41		ctx->pos += sizeof(struct erofs_dirent);
 42	}
 43	return 0;
 44}
 45
 46static int erofs_readdir(struct file *f, struct dir_context *ctx)
 47{
 48	struct inode *dir = file_inode(f);
 49	struct erofs_buf buf = __EROFS_BUF_INITIALIZER;
 50	struct super_block *sb = dir->i_sb;
 51	struct file_ra_state *ra = &f->f_ra;
 52	unsigned long bsz = sb->s_blocksize;
 53	unsigned int ofs = erofs_blkoff(sb, ctx->pos);
 54	pgoff_t ra_pages = DIV_ROUND_UP_POW2(
 55			EROFS_I_SB(dir)->dir_ra_bytes, PAGE_SIZE);
 56	pgoff_t nr_pages = DIV_ROUND_UP_POW2(dir->i_size, PAGE_SIZE);
 57	int err = 0;
 58	bool initial = true;
 59
 60	buf.mapping = dir->i_mapping;
 61	while (ctx->pos < dir->i_size) {
 62		erofs_off_t dbstart = ctx->pos - ofs;
 63		struct erofs_dirent *de;
 64		unsigned int nameoff, maxsize;
 65
 66		if (fatal_signal_pending(current)) {
 67			err = -ERESTARTSYS;
 68			break;
 69		}
 70
 71		/* readahead blocks to enhance performance for large directories */
 72		if (ra_pages) {
 73			pgoff_t idx = DIV_ROUND_UP_POW2(ctx->pos, PAGE_SIZE);
 74			pgoff_t pages = min(nr_pages - idx, ra_pages);
 75
 76			if (pages > 1 && !ra_has_index(ra, idx))
 77				page_cache_sync_readahead(dir->i_mapping, ra,
 78							  f, idx, pages);
 79		}
 80
 81		de = erofs_bread(&buf, dbstart, true);
 82		if (IS_ERR(de)) {
 83			erofs_err(sb, "failed to readdir of logical block %llu of nid %llu",
 84				  erofs_blknr(sb, dbstart), EROFS_I(dir)->nid);
 85			err = PTR_ERR(de);
 86			break;
 87		}
 88
 89		nameoff = le16_to_cpu(de->nameoff);
 90		if (nameoff < sizeof(struct erofs_dirent) || nameoff >= bsz) {
 91			erofs_err(sb, "invalid de[0].nameoff %u @ nid %llu",
 92				  nameoff, EROFS_I(dir)->nid);
 93			err = -EFSCORRUPTED;
 94			break;
 95		}
 96
 97		maxsize = min_t(unsigned int, dir->i_size - dbstart, bsz);
 98		/* search dirents at the arbitrary position */
 99		if (initial) {
100			initial = false;
101			ofs = roundup(ofs, sizeof(struct erofs_dirent));
102			ctx->pos = dbstart + ofs;
103		}
104
105		err = erofs_fill_dentries(dir, ctx, de, (void *)de + ofs,
106					  nameoff, maxsize);
107		if (err)
108			break;
109		ctx->pos = dbstart + maxsize;
110		ofs = 0;
111		cond_resched();
112	}
113	erofs_put_metabuf(&buf);
114	if (EROFS_I(dir)->dot_omitted && ctx->pos == dir->i_size) {
115		if (!dir_emit_dot(f, ctx))
116			return 0;
117		++ctx->pos;
118	}
119	return err < 0 ? err : 0;
120}
121
122const struct file_operations erofs_dir_fops = {
123	.llseek		= generic_file_llseek,
124	.read		= generic_read_dir,
125	.iterate_shared	= erofs_readdir,
126	.unlocked_ioctl = erofs_ioctl,
127#ifdef CONFIG_COMPAT
128	.compat_ioctl   = erofs_compat_ioctl,
129#endif
130};