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>

fs/isofs/dir.c

@@ -10,7 +10,6 @@
  *
  *  isofs directory handling functions
  */
-#include <linux/smp_lock.h>
 #include <linux/gfp.h>
 #include "isofs.h"
 
@@ -255,18 +254,19 @@ 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;
 
-	lock_kernel();
+	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);
-	unlock_kernel();
+	mutex_unlock(&sbi->s_mutex);
 	return result;
 }
 

fs/isofs/inode.c

@@ -17,7 +17,6 @@
 #include <linux/slab.h>
 #include <linux/nls.h>
 #include <linux/ctype.h>
-#include <linux/smp_lock.h>
 #include <linux/statfs.h>
 #include <linux/cdrom.h>
 #include <linux/parser.h>
@@ -44,11 +43,7 @@ static void isofs_put_super(struct super_block *sb)
 	struct isofs_sb_info *sbi = ISOFS_SB(sb);
 
 #ifdef CONFIG_JOLIET
-	lock_kernel();
-
 	unload_nls(sbi->s_nls_iocharset);
-
-	unlock_kernel();
 #endif
 
 	kfree(sbi);
@@ -571,15 +566,11 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
 	int table, error = -EINVAL;
 	unsigned int vol_desc_start;
 
-	lock_kernel();
-
 	save_mount_options(s, data);
 
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
-	if (!sbi) {
-		unlock_kernel();
+	if (!sbi)
 		return -ENOMEM;
-	}
 	s->s_fs_info = sbi;
 
 	if (!parse_options((char *)data, &opt))
@@ -827,6 +818,7 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
 	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
@@ -904,7 +896,6 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
 
 	kfree(opt.iocharset);
 
-	unlock_kernel();
 	return 0;
 
 	/*
@@ -944,7 +935,6 @@ static int isofs_fill_super(struct super_block *s, void *data, int silent)
 	kfree(opt.iocharset);
 	kfree(sbi);
 	s->s_fs_info = NULL;
-	unlock_kernel();
 	return error;
 }
 
@@ -983,8 +973,6 @@ int isofs_get_blocks(struct inode *inode, sector_t iblock_s,
 	int section, rv, error;
 	struct iso_inode_info *ei = ISOFS_I(inode);
 
-	lock_kernel();
-
 	error = -EIO;
 	rv = 0;
 	if (iblock < 0 || iblock != iblock_s) {
@@ -1060,7 +1048,6 @@ int isofs_get_blocks(struct inode *inode, sector_t iblock_s,
 
 	error = 0;
 abort:
-	unlock_kernel();
 	return rv != 0 ? rv : error;
 }
 

fs/isofs/isofs.h

@@ -55,6 +55,7 @@ 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

@@ -6,7 +6,6 @@
  *  (C) 1991  Linus Torvalds - minix filesystem
  */
 
-#include <linux/smp_lock.h>
 #include <linux/gfp.h>
 #include "isofs.h"
 
@@ -168,6 +167,7 @@ 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;
 
@@ -177,7 +177,7 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 
-	lock_kernel();
+	mutex_lock(&sbi->s_mutex);
 	found = isofs_find_entry(dir, dentry,
 				&block, &offset,
 				page_address(page),
@@ -188,10 +188,10 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam
 	if (found) {
 		inode = isofs_iget(dir->i_sb, block, offset);
 		if (IS_ERR(inode)) {
-			unlock_kernel();
+			mutex_unlock(&sbi->s_mutex);
 			return ERR_CAST(inode);
 		}
 	}
-	unlock_kernel();
+	mutex_unlock(&sbi->s_mutex);
 	return d_splice_alias(inode, dentry);
 }

fs/isofs/rock.c

@@ -8,7 +8,6 @@
 
 #include <linux/slab.h>
 #include <linux/pagemap.h>
-#include <linux/smp_lock.h>
 
 #include "isofs.h"
 #include "rock.h"
@@ -661,6 +660,7 @@ static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	struct iso_inode_info *ei = ISOFS_I(inode);
+	struct isofs_sb_info *sbi = ISOFS_SB(inode->i_sb);
 	char *link = kmap(page);
 	unsigned long bufsize = ISOFS_BUFFER_SIZE(inode);
 	struct buffer_head *bh;
@@ -673,12 +673,12 @@ static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 	struct rock_state rs;
 	int ret;
 
-	if (!ISOFS_SB(inode->i_sb)->s_rock)
+	if (!sbi->s_rock)
 		goto error;
 
 	init_rock_state(&rs, inode);
 	block = ei->i_iget5_block;
-	lock_kernel();
+	mutex_lock(&sbi->s_mutex);
 	bh = sb_bread(inode->i_sb, block);
 	if (!bh)
 		goto out_noread;
@@ -748,7 +748,7 @@ static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 		goto fail;
 	brelse(bh);
 	*rpnt = '\0';
-	unlock_kernel();
+	mutex_unlock(&sbi->s_mutex);
 	SetPageUptodate(page);
 	kunmap(page);
 	unlock_page(page);
@@ -765,7 +765,7 @@ static int rock_ridge_symlink_readpage(struct file *file, struct page *page)
 	printk("symlink spans iso9660 blocks\n");
 fail:
 	brelse(bh);
-	unlock_kernel();
+	mutex_unlock(&sbi->s_mutex);
 error:
 	SetPageError(page);
 	kunmap(page);