LXR linux/fs/qnx4/dir.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * QNX4 file system, Linux implementation.
   4 *
   5 * Version : 0.2.1
   6 *
   7 * Using parts of the xiafs filesystem.
   8 *
   9 * History :
  10 *
  11 * 28-05-1998 by Richard Frowijn : first release.
  12 * 20-06-1998 by Frank Denis : Linux 2.1.99+ & dcache support.
  13 */
  14
  15#include <linux/buffer_head.h>
  16#include "qnx4.h"
  17
  18/*
  19 * A qnx4 directory entry is an inode entry or link info
  20 * depending on the status field in the last byte. The
  21 * first byte is where the name start either way, and a
  22 * zero means it's empty.
  23 *
  24 * Also, due to a bug in gcc, we don't want to use the
  25 * real (differently sized) name arrays in the inode and
  26 * link entries, but always the 'de_name[]' one in the
  27 * fake struct entry.
  28 *
  29 * See
  30 *
  31 *   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
  32 *
  33 * for details, but basically gcc will take the size of the
  34 * 'name' array from one of the used union entries randomly.
  35 *
  36 * This use of 'de_name[]' (48 bytes) avoids the false positive
  37 * warnings that would happen if gcc decides to use 'inode.di_name'
  38 * (16 bytes) even when the pointer and size were to come from
  39 * 'link.dl_name' (48 bytes).
  40 *
  41 * In all cases the actual name pointer itself is the same, it's
  42 * only the gcc internal 'what is the size of this field' logic
  43 * that can get confused.
  44 */
  45union qnx4_directory_entry {
  46        struct {
  47                const char de_name[48];
  48                u8 de_pad[15];
  49                u8 de_status;
  50        };
  51        struct qnx4_inode_entry inode;
  52        struct qnx4_link_info link;
  53};
  54
  55static int qnx4_readdir(struct file *file, struct dir_context *ctx)
  56{
  57        struct inode *inode = file_inode(file);
  58        unsigned int offset;
  59        struct buffer_head *bh;
  60        unsigned long blknum;
  61        int ix, ino;
  62        int size;
  63
  64        QNX4DEBUG((KERN_INFO "qnx4_readdir:i_size = %ld\n", (long) inode->i_size));
  65        QNX4DEBUG((KERN_INFO "pos                 = %ld\n", (long) ctx->pos));
  66
  67        while (ctx->pos < inode->i_size) {
  68                blknum = qnx4_block_map(inode, ctx->pos >> QNX4_BLOCK_SIZE_BITS);
  69                bh = sb_bread(inode->i_sb, blknum);
  70                if (bh == NULL) {
  71                        printk(KERN_ERR "qnx4_readdir: bread failed (%ld)\n", blknum);
  72                        return 0;
  73                }
  74                ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
  75                for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
  76                        union qnx4_directory_entry *de;
  77
  78                        offset = ix * QNX4_DIR_ENTRY_SIZE;
  79                        de = (union qnx4_directory_entry *) (bh->b_data + offset);
  80
  81                        if (!de->de_name[0])
  82                                continue;
  83                        if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
  84                                continue;
  85                        if (!(de->de_status & QNX4_FILE_LINK)) {
  86                                size = sizeof(de->inode.di_fname);
  87                                ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
  88                        } else {
  89                                size = sizeof(de->link.dl_fname);
  90                                ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
  91                                        QNX4_INODES_PER_BLOCK +
  92                                        de->link.dl_inode_ndx;
  93                        }
  94                        size = strnlen(de->de_name, size);
  95                        QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
  96                        if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
  97                                brelse(bh);
  98                                return 0;
  99                        }
 100                }
 101                brelse(bh);
 102        }
 103        return 0;
 104}
 105
 106const struct file_operations qnx4_dir_operations =
 107{
 108        .llseek         = generic_file_llseek,
 109        .read           = generic_read_dir,
 110        .iterate_shared = qnx4_readdir,
 111        .fsync          = generic_file_fsync,
 112};
 113
 114const struct inode_operations qnx4_dir_inode_operations =
 115{
 116        .lookup         = qnx4_lookup,
 117};
 118