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![Arnd Bergmann](/assets/img/avatar_default.png)
As in other file systems, we can replace the big kernel lock with a private mutex in isofs. This means we can now access multiple file systems concurrently, but it also means that we serialize readdir and lookup across sleeping operations which previously released the big kernel lock. This should not matter though, as these operations are in practice serialized through the hardware access. The isofs_get_blocks functions now does not take any lock any more, it used to recursively get the BKL. After looking at the code for hours, I convinced myself that it was never needed here anyway, because it only reads constant fields of the inode and writes to a buffer head array that is at this time only visible to the caller. The get_sb and fill_super operations do not need the locking at all because they operate on a file system that is either about to be created or to be destroyed but in either case is not visible to other threads. Signed-off-by: Arnd Bergmann <arnd@arndb.de>
288 lines
6.8 KiB
C
288 lines
6.8 KiB
C
/*
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* linux/fs/isofs/dir.c
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*
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* (C) 1992, 1993, 1994 Eric Youngdale Modified for ISO 9660 filesystem.
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*
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* (C) 1991 Linus Torvalds - minix filesystem
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*
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* Steve Beynon : Missing last directory entries fixed
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* (stephen@askone.demon.co.uk) : 21st June 1996
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*
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* isofs directory handling functions
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*/
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#include <linux/gfp.h>
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#include "isofs.h"
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int isofs_name_translate(struct iso_directory_record *de, char *new, struct inode *inode)
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{
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char * old = de->name;
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int len = de->name_len[0];
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int i;
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for (i = 0; i < len; i++) {
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unsigned char c = old[i];
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if (!c)
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break;
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if (c >= 'A' && c <= 'Z')
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c |= 0x20; /* lower case */
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/* Drop trailing '.;1' (ISO 9660:1988 7.5.1 requires period) */
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if (c == '.' && i == len - 3 && old[i + 1] == ';' && old[i + 2] == '1')
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break;
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/* Drop trailing ';1' */
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if (c == ';' && i == len - 2 && old[i + 1] == '1')
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break;
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/* Convert remaining ';' to '.' */
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/* Also '/' to '.' (broken Acorn-generated ISO9660 images) */
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if (c == ';' || c == '/')
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c = '.';
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new[i] = c;
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}
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return i;
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}
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/* Acorn extensions written by Matthew Wilcox <willy@bofh.ai> 1998 */
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int get_acorn_filename(struct iso_directory_record *de,
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char *retname, struct inode *inode)
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{
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int std;
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unsigned char *chr;
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int retnamlen = isofs_name_translate(de, retname, inode);
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if (retnamlen == 0)
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return 0;
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std = sizeof(struct iso_directory_record) + de->name_len[0];
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if (std & 1)
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std++;
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if ((*((unsigned char *) de) - std) != 32)
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return retnamlen;
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chr = ((unsigned char *) de) + std;
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if (strncmp(chr, "ARCHIMEDES", 10))
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return retnamlen;
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if ((*retname == '_') && ((chr[19] & 1) == 1))
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*retname = '!';
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if (((de->flags[0] & 2) == 0) && (chr[13] == 0xff)
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&& ((chr[12] & 0xf0) == 0xf0)) {
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retname[retnamlen] = ',';
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sprintf(retname+retnamlen+1, "%3.3x",
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((chr[12] & 0xf) << 8) | chr[11]);
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retnamlen += 4;
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}
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return retnamlen;
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}
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/*
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* This should _really_ be cleaned up some day..
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*/
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static int do_isofs_readdir(struct inode *inode, struct file *filp,
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void *dirent, filldir_t filldir,
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char *tmpname, struct iso_directory_record *tmpde)
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{
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unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
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unsigned char bufbits = ISOFS_BUFFER_BITS(inode);
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unsigned long block, offset, block_saved, offset_saved;
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unsigned long inode_number = 0; /* Quiet GCC */
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struct buffer_head *bh = NULL;
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int len;
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int map;
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int first_de = 1;
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char *p = NULL; /* Quiet GCC */
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struct iso_directory_record *de;
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struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
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offset = filp->f_pos & (bufsize - 1);
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block = filp->f_pos >> bufbits;
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while (filp->f_pos < inode->i_size) {
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int de_len;
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if (!bh) {
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bh = isofs_bread(inode, block);
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if (!bh)
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return 0;
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}
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de = (struct iso_directory_record *) (bh->b_data + offset);
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de_len = *(unsigned char *) de;
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/*
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* If the length byte is zero, we should move on to the next
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* CDROM sector. If we are at the end of the directory, we
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* kick out of the while loop.
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*/
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if (de_len == 0) {
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brelse(bh);
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bh = NULL;
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filp->f_pos = (filp->f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
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block = filp->f_pos >> bufbits;
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offset = 0;
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continue;
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}
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block_saved = block;
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offset_saved = offset;
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offset += de_len;
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/* Make sure we have a full directory entry */
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if (offset >= bufsize) {
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int slop = bufsize - offset + de_len;
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memcpy(tmpde, de, slop);
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offset &= bufsize - 1;
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block++;
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brelse(bh);
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bh = NULL;
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if (offset) {
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bh = isofs_bread(inode, block);
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if (!bh)
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return 0;
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memcpy((void *) tmpde + slop, bh->b_data, offset);
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}
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de = tmpde;
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}
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/* Basic sanity check, whether name doesn't exceed dir entry */
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if (de_len < de->name_len[0] +
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sizeof(struct iso_directory_record)) {
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printk(KERN_NOTICE "iso9660: Corrupted directory entry"
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" in block %lu of inode %lu\n", block,
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inode->i_ino);
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return -EIO;
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}
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if (first_de) {
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isofs_normalize_block_and_offset(de,
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&block_saved,
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&offset_saved);
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inode_number = isofs_get_ino(block_saved,
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offset_saved, bufbits);
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}
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if (de->flags[-sbi->s_high_sierra] & 0x80) {
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first_de = 0;
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filp->f_pos += de_len;
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continue;
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}
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first_de = 1;
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/* Handle the case of the '.' directory */
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if (de->name_len[0] == 1 && de->name[0] == 0) {
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if (filldir(dirent, ".", 1, filp->f_pos, inode->i_ino, DT_DIR) < 0)
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break;
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filp->f_pos += de_len;
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continue;
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}
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len = 0;
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/* Handle the case of the '..' directory */
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if (de->name_len[0] == 1 && de->name[0] == 1) {
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inode_number = parent_ino(filp->f_path.dentry);
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if (filldir(dirent, "..", 2, filp->f_pos, inode_number, DT_DIR) < 0)
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break;
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filp->f_pos += de_len;
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continue;
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}
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/* Handle everything else. Do name translation if there
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is no Rock Ridge NM field. */
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/*
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* Do not report hidden files if so instructed, or associated
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* files unless instructed to do so
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*/
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if ((sbi->s_hide && (de->flags[-sbi->s_high_sierra] & 1)) ||
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(!sbi->s_showassoc &&
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(de->flags[-sbi->s_high_sierra] & 4))) {
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filp->f_pos += de_len;
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continue;
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}
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map = 1;
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if (sbi->s_rock) {
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len = get_rock_ridge_filename(de, tmpname, inode);
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if (len != 0) { /* may be -1 */
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p = tmpname;
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map = 0;
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}
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}
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if (map) {
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#ifdef CONFIG_JOLIET
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if (sbi->s_joliet_level) {
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len = get_joliet_filename(de, tmpname, inode);
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p = tmpname;
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} else
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#endif
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if (sbi->s_mapping == 'a') {
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len = get_acorn_filename(de, tmpname, inode);
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p = tmpname;
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} else
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if (sbi->s_mapping == 'n') {
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len = isofs_name_translate(de, tmpname, inode);
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p = tmpname;
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} else {
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p = de->name;
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len = de->name_len[0];
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}
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}
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if (len > 0) {
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if (filldir(dirent, p, len, filp->f_pos, inode_number, DT_UNKNOWN) < 0)
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break;
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}
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filp->f_pos += de_len;
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continue;
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}
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if (bh)
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brelse(bh);
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return 0;
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}
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/*
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* Handle allocation of temporary space for name translation and
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* handling split directory entries.. The real work is done by
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* "do_isofs_readdir()".
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*/
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static int isofs_readdir(struct file *filp,
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void *dirent, filldir_t filldir)
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{
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int result;
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char *tmpname;
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struct iso_directory_record *tmpde;
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struct inode *inode = filp->f_path.dentry->d_inode;
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struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
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tmpname = (char *)__get_free_page(GFP_KERNEL);
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if (tmpname == NULL)
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return -ENOMEM;
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mutex_lock(&sbi->s_mutex);
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tmpde = (struct iso_directory_record *) (tmpname+1024);
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result = do_isofs_readdir(inode, filp, dirent, filldir, tmpname, tmpde);
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free_page((unsigned long) tmpname);
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mutex_unlock(&sbi->s_mutex);
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return result;
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}
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const struct file_operations isofs_dir_operations =
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{
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.llseek = generic_file_llseek,
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.read = generic_read_dir,
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.readdir = isofs_readdir,
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};
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/*
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* directories can handle most operations...
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*/
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const struct inode_operations isofs_dir_inode_operations =
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{
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.lookup = isofs_lookup,
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};
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