linux/fs/isofs/namei.c
Arnd Bergmann 4f819a7899 BKL: Remove BKL from isofs
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>
2010-10-04 21:10:45 +02:00

198 lines
4.5 KiB
C

/*
* linux/fs/isofs/namei.c
*
* (C) 1992 Eric Youngdale Modified for ISO 9660 filesystem.
*
* (C) 1991 Linus Torvalds - minix filesystem
*/
#include <linux/gfp.h>
#include "isofs.h"
/*
* ok, we cannot use strncmp, as the name is not in our data space.
* Thus we'll have to use isofs_match. No big problem. Match also makes
* some sanity tests.
*/
static int
isofs_cmp(struct dentry *dentry, const char *compare, int dlen)
{
struct qstr qstr;
if (!compare)
return 1;
/* check special "." and ".." files */
if (dlen == 1) {
/* "." */
if (compare[0] == 0) {
if (!dentry->d_name.len)
return 0;
compare = ".";
} else if (compare[0] == 1) {
compare = "..";
dlen = 2;
}
}
qstr.name = compare;
qstr.len = dlen;
return dentry->d_op->d_compare(dentry, &dentry->d_name, &qstr);
}
/*
* isofs_find_entry()
*
* finds an entry in the specified directory with the wanted name. It
* returns the inode number of the found entry, or 0 on error.
*/
static unsigned long
isofs_find_entry(struct inode *dir, struct dentry *dentry,
unsigned long *block_rv, unsigned long *offset_rv,
char *tmpname, struct iso_directory_record *tmpde)
{
unsigned long bufsize = ISOFS_BUFFER_SIZE(dir);
unsigned char bufbits = ISOFS_BUFFER_BITS(dir);
unsigned long block, f_pos, offset, block_saved, offset_saved;
struct buffer_head *bh = NULL;
struct isofs_sb_info *sbi = ISOFS_SB(dir->i_sb);
if (!ISOFS_I(dir)->i_first_extent)
return 0;
f_pos = 0;
offset = 0;
block = 0;
while (f_pos < dir->i_size) {
struct iso_directory_record *de;
int de_len, match, i, dlen;
char *dpnt;
if (!bh) {
bh = isofs_bread(dir, block);
if (!bh)
return 0;
}
de = (struct iso_directory_record *) (bh->b_data + offset);
de_len = *(unsigned char *) de;
if (!de_len) {
brelse(bh);
bh = NULL;
f_pos = (f_pos + ISOFS_BLOCK_SIZE) & ~(ISOFS_BLOCK_SIZE - 1);
block = f_pos >> bufbits;
offset = 0;
continue;
}
block_saved = bh->b_blocknr;
offset_saved = offset;
offset += de_len;
f_pos += de_len;
/* Make sure we have a full directory entry */
if (offset >= bufsize) {
int slop = bufsize - offset + de_len;
memcpy(tmpde, de, slop);
offset &= bufsize - 1;
block++;
brelse(bh);
bh = NULL;
if (offset) {
bh = isofs_bread(dir, block);
if (!bh)
return 0;
memcpy((void *) tmpde + slop, bh->b_data, offset);
}
de = tmpde;
}
dlen = de->name_len[0];
dpnt = de->name;
/* Basic sanity check, whether name doesn't exceed dir entry */
if (de_len < dlen + sizeof(struct iso_directory_record)) {
printk(KERN_NOTICE "iso9660: Corrupted directory entry"
" in block %lu of inode %lu\n", block,
dir->i_ino);
return 0;
}
if (sbi->s_rock &&
((i = get_rock_ridge_filename(de, tmpname, dir)))) {
dlen = i; /* possibly -1 */
dpnt = tmpname;
#ifdef CONFIG_JOLIET
} else if (sbi->s_joliet_level) {
dlen = get_joliet_filename(de, tmpname, dir);
dpnt = tmpname;
#endif
} else if (sbi->s_mapping == 'a') {
dlen = get_acorn_filename(de, tmpname, dir);
dpnt = tmpname;
} else if (sbi->s_mapping == 'n') {
dlen = isofs_name_translate(de, tmpname, dir);
dpnt = tmpname;
}
/*
* Skip hidden or associated files unless hide or showassoc,
* respectively, is set
*/
match = 0;
if (dlen > 0 &&
(!sbi->s_hide ||
(!(de->flags[-sbi->s_high_sierra] & 1))) &&
(sbi->s_showassoc ||
(!(de->flags[-sbi->s_high_sierra] & 4)))) {
match = (isofs_cmp(dentry, dpnt, dlen) == 0);
}
if (match) {
isofs_normalize_block_and_offset(de,
&block_saved,
&offset_saved);
*block_rv = block_saved;
*offset_rv = offset_saved;
brelse(bh);
return 1;
}
}
brelse(bh);
return 0;
}
struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
{
int found;
unsigned long uninitialized_var(block);
unsigned long uninitialized_var(offset);
struct isofs_sb_info *sbi = ISOFS_SB(dir->i_sb);
struct inode *inode;
struct page *page;
dentry->d_op = dir->i_sb->s_root->d_op;
page = alloc_page(GFP_USER);
if (!page)
return ERR_PTR(-ENOMEM);
mutex_lock(&sbi->s_mutex);
found = isofs_find_entry(dir, dentry,
&block, &offset,
page_address(page),
1024 + page_address(page));
__free_page(page);
inode = NULL;
if (found) {
inode = isofs_iget(dir->i_sb, block, offset);
if (IS_ERR(inode)) {
mutex_unlock(&sbi->s_mutex);
return ERR_CAST(inode);
}
}
mutex_unlock(&sbi->s_mutex);
return d_splice_alias(inode, dentry);
}