question again about ext2 fs/ext2/namei.c

afei@jhu.edu
Sun, 12 Dec 1999 06:51:58 -0500 (EST)

I did not see any implementation in ext2_find_entry of forward
compatibility hooks for B-tree directories in fs/ext2/namei.c
>From what I read, it simply scans the the block and the read ahead blocks
to find the directory entry. There is no B-tree involved
So what I am missing here, or B-tree directory is used somewhere else?
Thank you.

Fei
/*
* linux/fs/ext2/namei.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/namei.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* Big-endian to little-endian byte-swapping/bitmaps by
* David S. Miller (davem@caip.rutgers.edu), 1995
* Directory entry file type support and forward compatibility hooks
* for B-tree directories by Theodore Ts'o (tytso@mit.edu), 1998
*/

static struct buffer_head * ext2_find_entry (struct inode * dir,
const char * const name, int namelen,
struct ext2_dir_entry_2 ** res_dir)
{
struct super_block * sb;
struct buffer_head * bh_use[NAMEI_RA_SIZE];
struct buffer_head * bh_read[NAMEI_RA_SIZE];
unsigned long offset;
int block, toread, i, err;

*res_dir = NULL;
sb = dir->i_sb;

if (namelen > EXT2_NAME_LEN)
return NULL;

memset (bh_use, 0, sizeof (bh_use));
toread = 0;
for (block = 0; block < NAMEI_RA_SIZE; ++block) {
struct buffer_head * bh;

if ((block << EXT2_BLOCK_SIZE_BITS (sb)) >= dir->i_size)
break;
bh = ext2_getblk (dir, block, 0, &err);
bh_use[block] = bh;
if (bh && !buffer_uptodate(bh))
bh_read[toread++] = bh;
}

for (block = 0, offset = 0; offset < dir->i_size; block++) {
struct buffer_head * bh;
struct ext2_dir_entry_2 * de;
char * dlimit;

if ((block % NAMEI_RA_BLOCKS) == 0 && toread) {
ll_rw_block (READ, toread, bh_read);
toread = 0;
}
bh = bh_use[block % NAMEI_RA_SIZE];
if (!bh) {
#if 0
ext2_error (sb, "ext2_find_entry",
"directory #%lu contains a hole at offset %lu",
dir->i_ino, offset);
#endif
offset += sb->s_blocksize;
continue;
}
wait_on_buffer (bh);
if (!buffer_uptodate(bh)) {
/*
* read error: all bets are off
*/
break;
}

de = (struct ext2_dir_entry_2 *) bh->b_data;
dlimit = bh->b_data + sb->s_blocksize;
while ((char * ) de < dlimit) {
/* this code is executed quadratically often */
/* do minimal checking `by hand' */
int de_len;

if ((char * ) de + namelen <= dlimit &&
ext2_match (namelen, name, de)) {
/* found a match -
just to be sure, do a full check */
if (!ext2_check_dir_entry("ext2_find_entry",
dir, de, bh, offset))
goto failure;
for (i = 0; i < NAMEI_RA_SIZE; ++i) {
if (bh_use[i] != bh)
brelse (bh_use[i]);
}
*res_dir = de;
return bh;
}
/* prevent looping on a bad block */
de_len = le16_to_cpu(de->rec_len);
if (de_len <= 0)
goto failure;
offset += de_len;
de = (struct ext2_dir_entry_2 *)
((char * ) de + de_len);
}

brelse (bh);
if (((block + NAMEI_RA_SIZE) << EXT2_BLOCK_SIZE_BITS (sb)) >=
dir->i_size)
bh = NULL;
else
bh = ext2_getblk (dir, block + NAMEI_RA_SIZE, 0, &err);
bh_use[block % NAMEI_RA_SIZE] = bh;
if (bh && !buffer_uptodate(bh))
bh_read[toread++] = bh;
}

failure:
for (i = 0; i < NAMEI_RA_SIZE; ++i)
brelse (bh_use[i]);
return NULL;
}

*~~~~~~~~~~~~~~~~~~~~~+_____________________+~~~~~~~~~~~~~~~~~~~*
* Email:afei@jhu.edu | WWW: http://aa.eps.jhu.edu/~feiliu *
* (410)889-9876(H) | Johns Hopkins Univ. | (410)516-7047(O) *
*-------------------+_____________________+-----------------*

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/