isofs: Remove global fs lock

sbi->s_mutex isn't needed for isofs at all so we can just remove it. Generally,
since isofs is always mounted read-only, filesystem structure cannot change
under us.  So buffer_head contents stays constant after it's filled in. That
leaves us with possible changes of global data structures. Superblock changes
only during filesystem mount (even remount does not change it), inodes are only
filled in during reading from disk. So there are no changes of these structures
to bother about.

Arguments why sbi->s_mutex can be removed at each place:
isofs_readdir: Accesses sb, inode, filp, local variables => s_mutex not needed
isofs_lookup: Protected by directory's i_mutex. Accesses sb, inode, dentry,
  local variables => s_mutex not needed
rock_ridge_symlink_readpage: Protected by page lock. Accesses sb, inode,
  local variables => s_mutex not needed.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/isofs/dir.c

@@ -254,19 +254,16 @@ static int isofs_readdir(struct file *filp,
 	char *tmpname;
 	struct iso_directory_record *tmpde;
 	struct inode *inode = filp->f_path.dentry->d_inode;
-	struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
 
 	tmpname = (char *)__get_free_page(GFP_KERNEL);
 	if (tmpname == NULL)
 		return -ENOMEM;
 
-	mutex_lock(&sbi->s_mutex);
 	tmpde = (struct iso_directory_record *) (tmpname+1024);
 
 	result = do_isofs_readdir(inode, filp, dirent, filldir, tmpname, tmpde);
 
 	free_page((unsigned long) tmpname);
-	mutex_unlock(&sbi->s_mutex);
 	return result;
 }
 

fs/isofs/inode.c

@@ -863,7 +863,6 @@ root_found:
 	sbi->s_utf8 = opt.utf8;
 	sbi->s_nocompress = opt.nocompress;
 	sbi->s_overriderockperm = opt.overriderockperm;
-	mutex_init(&sbi->s_mutex);
 	/*
 	 * It would be incredibly stupid to allow people to mark every file
 	 * on the disk as suid, so we merely allow them to set the default

fs/isofs/isofs.h

@@ -55,7 +55,6 @@ struct isofs_sb_info {
 	gid_t s_gid;
 	uid_t s_uid;
 	struct nls_table *s_nls_iocharset; /* Native language support table */
-	struct mutex s_mutex; /* replaces BKL, please remove if possible */
 };
 
 #define ISOFS_INVALID_MODE ((mode_t) -1)

fs/isofs/namei.c

@@ -168,7 +168,6 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam
 	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;
 
@@ -176,7 +175,6 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 
-	mutex_lock(&sbi->s_mutex);
 	found = isofs_find_entry(dir, dentry,
 				&block, &offset,
 				page_address(page),
@@ -185,7 +183,5 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam
 
 	inode = found ? isofs_iget(dir->i_sb, block, offset) : NULL;
 
-	mutex_unlock(&sbi->s_mutex);
-
 	return d_splice_alias(inode, dentry);
 }

fs/isofs/rock.c

@@ -678,7 +678,6 @@ static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 
 	init_rock_state(&rs, inode);
 	block = ei->i_iget5_block;
-	mutex_lock(&sbi->s_mutex);
 	bh = sb_bread(inode->i_sb, block);
 	if (!bh)
 		goto out_noread;
@@ -748,7 +747,6 @@ repeat:
 		goto fail;
 	brelse(bh);
 	*rpnt = '\0';
-	mutex_unlock(&sbi->s_mutex);
 	SetPageUptodate(page);
 	kunmap(page);
 	unlock_page(page);
@@ -765,7 +763,6 @@ out_bad_span:
 	printk("symlink spans iso9660 blocks\n");
 fail:
 	brelse(bh);
-	mutex_unlock(&sbi->s_mutex);
 error:
 	SetPageError(page);
 	kunmap(page);