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/*
* linux/fs/ext2/dir.c
*
* Copyright (C) 1992, 1993, 1994, 1995
* Remy Card (card@masi.ibp.fr)
* Laboratoire MASI - Institut Blaise Pascal
* Universite Pierre et Marie Curie (Paris VI)
*
* from
*
* linux/fs/minix/dir.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* ext2 directory handling functions
*
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller (davem@caip.rutgers.edu), 1995
*/
#include <linux/fs.h>
static int ext2_readdir(struct file *, void *, filldir_t);
struct file_operations ext2_dir_operations = {
read: generic_read_dir,
readdir: ext2_readdir,
ioctl: ext2_ioctl,
fsync: ext2_sync_file,
};
int ext2_check_dir_entry (const char * function, struct inode * dir,
struct ext2_dir_entry_2 * de,
struct buffer_head * bh,
unsigned long offset)
{
const char * error_msg = NULL;
if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(1))
error_msg = "rec_len is smaller than minimal";
else if (le16_to_cpu(de->rec_len) % 4 != 0)
error_msg = "rec_len % 4 != 0";
else if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(de->name_len))
error_msg = "rec_len is too small for name_len";
else if (dir && ((char *) de - bh->b_data) + le16_to_cpu(de->rec_len) >
dir->i_sb->s_blocksize)
error_msg = "directory entry across blocks";
else if (dir && le32_to_cpu(de->inode) > le32_to_cpu(dir->i_sb->u.ext2_sb.s_es->s_inodes_count))
error_msg = "inode out of bounds";
if (error_msg != NULL)
ext2_error (dir->i_sb, function, "bad entry in directory #%lu: %s - "
"offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
dir->i_ino, error_msg, offset,
(unsigned long) le32_to_cpu(de->inode),
le16_to_cpu(de->rec_len), de->name_len);
return error_msg == NULL ? 1 : 0;
}
static int ext2_readdir(struct file * filp,
void * dirent, filldir_t filldir)
{
int error = 0;
unsigned long offset, blk;
int i, num, stored;
struct buffer_head * bh, * tmp, * bha[16];
struct ext2_dir_entry_2 * de;
struct super_block * sb;
int err;
struct inode *inode = filp->f_dentry->d_inode;
sb = inode->i_sb;
stored = 0;
bh = NULL;
offset = filp->f_pos & (sb->s_blocksize - 1);
while (!error && !stored && filp->f_pos < inode->i_size) {
blk = (filp->f_pos) >> EXT2_BLOCK_SIZE_BITS(sb);
bh = ext2_bread (inode, blk, 0, &err);
if (!bh) {
ext2_error (sb, "ext2_readdir",
"directory #%lu contains a hole at offset %lu",
inode->i_ino, (unsigned long)filp->f_pos);
filp->f_pos += sb->s_blocksize - offset;
continue;
}
/*
* Do the readahead
*/
if (!offset) {
for (i = 16 >> (EXT2_BLOCK_SIZE_BITS(sb) - 9), num = 0;
i > 0; i--) {
tmp = ext2_getblk (inode, ++blk, 0, &err);
if (tmp && !buffer_uptodate(tmp) && !buffer_locked(tmp))
bha[num++] = tmp;
else
brelse (tmp);
}
if (num) {
ll_rw_block (READA, num, bha);
for (i = 0; i < num; i++)
brelse (bha[i]);
}
}
revalidate:
/* If the dir block has changed since the last call to
* readdir(2), then we might be pointing to an invalid
* dirent right now. Scan from the start of the block
* to make sure. */
if (filp->f_version != inode->i_version) {
for (i = 0; i < sb->s_blocksize && i < offset; ) {
de = (struct ext2_dir_entry_2 *)
(bh->b_data + i);
/* It's too expensive to do a full
* dirent test each time round this
* loop, but we do have to test at
* least that it is non-zero. A
* failure will be detected in the
* dirent test below. */
if (le16_to_cpu(de->rec_len) < EXT2_DIR_REC_LEN(1))
break;
i += le16_to_cpu(de->rec_len);
}
offset = i;
filp->f_pos = (filp->f_pos & ~(sb->s_blocksize - 1))
| offset;
filp->f_version = inode->i_version;
}
while (!error && filp->f_pos < inode->i_size
&& offset < sb->s_blocksize) {
de = (struct ext2_dir_entry_2 *) (bh->b_data + offset);
if (!ext2_check_dir_entry ("ext2_readdir", inode, de,
bh, offset)) {
/* On error, skip the f_pos to the
next block. */
filp->f_pos = (filp->f_pos | (sb->s_blocksize - 1))
+ 1;
brelse (bh);
return stored;
}
offset += le16_to_cpu(de->rec_len);
if (le32_to_cpu(de->inode)) {
/* We might block in the next section
* if the data destination is
* currently swapped out. So, use a
* version stamp to detect whether or
* not the directory has been modified
* during the copy operation.
*/
unsigned long version = filp->f_version;
error = filldir(dirent, de->name,
de->name_len,
filp->f_pos, le32_to_cpu(de->inode));
if (error)
break;
if (version != filp->f_version)
goto revalidate;
stored ++;
}
filp->f_pos += le16_to_cpu(de->rec_len);
}
offset = 0;
brelse (bh);
}
UPDATE_ATIME(inode);
return 0;
}
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