[PATCH 15/20] ufs: remove the BKL

[Arnd Bergmann <arnd@arndb.de>]

This introduces a new per-superblock mutex in UFS to replace
the big kernel lock. I have been careful to avoid nested
calls to lock_ufs and to get the lock order right with
respect to other mutexes, in particular lock_super.

I did not make any attempt to prove that the big kernel
lock is not needed in a particular place in the code,
which is very possible.

The code is still only compile-tested, but it should
at least be harmless on non-SMP systems, since the
new mutex is not taken on those.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
---
 fs/ufs/Kconfig    |    1 -
 fs/ufs/inode.c    |   78 ++++++++++++++--------------------------------------
 fs/ufs/namei.c    |   35 +++++++++++------------
 fs/ufs/super.c    |   55 +++++++++++++++++++++---------------
 fs/ufs/truncate.c |    5 +--
 fs/ufs/ufs.h      |    6 +++-
 6 files changed, 77 insertions(+), 103 deletions(-)

diff --git a/fs/ufs/Kconfig b/fs/ufs/Kconfig
index 30c8f22..e4f10a4 100644
--- a/fs/ufs/Kconfig
+++ b/fs/ufs/Kconfig
@@ -1,7 +1,6 @@
 config UFS_FS
 	tristate "UFS file system support (read only)"
 	depends on BLOCK
-	depends on BKL # probably fixable
 	help
 	  BSD and derivate versions of Unix (such as SunOS, FreeBSD, NetBSD,
 	  OpenBSD and NeXTstep) use a file system called UFS. Some System V
diff --git a/fs/ufs/inode.c b/fs/ufs/inode.c
index 2b251f2..03c255f 100644
--- a/fs/ufs/inode.c
+++ b/fs/ufs/inode.c
@@ -34,7 +34,6 @@
 #include <linux/stat.h>
 #include <linux/string.h>
 #include <linux/mm.h>
-#include <linux/smp_lock.h>
 #include <linux/buffer_head.h>
 #include <linux/writeback.h>
 
@@ -43,7 +42,7 @@
 #include "swab.h"
 #include "util.h"
 
-static u64 ufs_frag_map(struct inode *inode, sector_t frag);
+static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock);
 
 static int ufs_block_to_path(struct inode *inode, sector_t i_block, sector_t offsets[4])
 {
@@ -82,7 +81,7 @@ static int ufs_block_to_path(struct inode *inode, sector_t i_block, sector_t off
  * the begining of the filesystem.
  */
 
-static u64 ufs_frag_map(struct inode *inode, sector_t frag)
+static u64 ufs_frag_map(struct inode *inode, sector_t frag, bool needs_lock)
 {
 	struct ufs_inode_info *ufsi = UFS_I(inode);
 	struct super_block *sb = inode->i_sb;
@@ -107,7 +106,8 @@ static u64 ufs_frag_map(struct inode *inode, sector_t frag)
 
 	p = offsets;
 
-	lock_kernel();
+	if (needs_lock)
+		lock_ufs(sb);
 	if ((flags & UFS_TYPE_MASK) == UFS_TYPE_UFS2)
 		goto ufs2;
 
@@ -152,7 +152,8 @@ ufs2:
 	ret = temp + (u64) (frag & uspi->s_fpbmask);
 
 out:
-	unlock_kernel();
+	if (needs_lock)
+		unlock_ufs(sb);
 	return ret;
 }
 
@@ -415,14 +416,16 @@ out:
 int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head *bh_result, int create)
 {
 	struct super_block * sb = inode->i_sb;
-	struct ufs_sb_private_info * uspi = UFS_SB(sb)->s_uspi;
+	struct ufs_sb_info * sbi = UFS_SB(sb);
+	struct ufs_sb_private_info * uspi = sbi->s_uspi;
 	struct buffer_head * bh;
 	int ret, err, new;
 	unsigned long ptr,phys;
 	u64 phys64 = 0;
+	bool needs_lock = (sbi->mutex_owner != current);
 	
 	if (!create) {
-		phys64 = ufs_frag_map(inode, fragment);
+		phys64 = ufs_frag_map(inode, fragment, needs_lock);
 		UFSD("phys64 = %llu\n", (unsigned long long)phys64);
 		if (phys64)
 			map_bh(bh_result, sb, phys64);
@@ -436,7 +439,8 @@ int ufs_getfrag_block(struct inode *inode, sector_t fragment, struct buffer_head
 	ret = 0;
 	bh = NULL;
 
-	lock_kernel();
+	if (needs_lock)
+		lock_ufs(sb);
 
 	UFSD("ENTER, ino %lu, fragment %llu\n", inode->i_ino, (unsigned long long)fragment);
 	if (fragment >
@@ -498,7 +502,9 @@ out:
 		set_buffer_new(bh_result);
 	map_bh(bh_result, sb, phys);
 abort:
-	unlock_kernel();
+	if (needs_lock)
+		unlock_ufs(sb);
+
 	return err;
 
 abort_too_big:
@@ -506,48 +512,6 @@ abort_too_big:
 	goto abort;
 }
 
-static struct buffer_head *ufs_getfrag(struct inode *inode,
-				       unsigned int fragment,
-				       int create, int *err)
-{
-	struct buffer_head dummy;
-	int error;
-
-	dummy.b_state = 0;
-	dummy.b_blocknr = -1000;
-	error = ufs_getfrag_block(inode, fragment, &dummy, create);
-	*err = error;
-	if (!error && buffer_mapped(&dummy)) {
-		struct buffer_head *bh;
-		bh = sb_getblk(inode->i_sb, dummy.b_blocknr);
-		if (buffer_new(&dummy)) {
-			memset(bh->b_data, 0, inode->i_sb->s_blocksize);
-			set_buffer_uptodate(bh);
-			mark_buffer_dirty(bh);
-		}
-		return bh;
-	}
-	return NULL;
-}
-
-struct buffer_head * ufs_bread (struct inode * inode, unsigned fragment,
-	int create, int * err)
-{
-	struct buffer_head * bh;
-
-	UFSD("ENTER, ino %lu, fragment %u\n", inode->i_ino, fragment);
-	bh = ufs_getfrag (inode, fragment, create, err);
-	if (!bh || buffer_uptodate(bh)) 		
-		return bh;
-	ll_rw_block (READ, 1, &bh);
-	wait_on_buffer (bh);
-	if (buffer_uptodate(bh))
-		return bh;
-	brelse (bh);
-	*err = -EIO;
-	return NULL;
-}
-
 static int ufs_writepage(struct page *page, struct writeback_control *wbc)
 {
 	return block_write_full_page(page,ufs_getfrag_block,wbc);
@@ -900,9 +864,9 @@ static int ufs_update_inode(struct inode * inode, int do_sync)
 int ufs_write_inode(struct inode *inode, struct writeback_control *wbc)
 {
 	int ret;
-	lock_kernel();
+	lock_ufs(inode->i_sb);
 	ret = ufs_update_inode(inode, wbc->sync_mode == WB_SYNC_ALL);
-	unlock_kernel();
+	unlock_ufs(inode->i_sb);
 	return ret;
 }
 
@@ -922,22 +886,22 @@ void ufs_evict_inode(struct inode * inode)
 	if (want_delete) {
 		loff_t old_i_size;
 		/*UFS_I(inode)->i_dtime = CURRENT_TIME;*/
-		lock_kernel();
+		lock_ufs(inode->i_sb);
 		mark_inode_dirty(inode);
 		ufs_update_inode(inode, IS_SYNC(inode));
 		old_i_size = inode->i_size;
 		inode->i_size = 0;
 		if (inode->i_blocks && ufs_truncate(inode, old_i_size))
 			ufs_warning(inode->i_sb, __func__, "ufs_truncate failed\n");
-		unlock_kernel();
+		unlock_ufs(inode->i_sb);
 	}
 
 	invalidate_inode_buffers(inode);
 	end_writeback(inode);
 
 	if (want_delete) {
-		lock_kernel();
+		lock_ufs(inode->i_sb);
 		ufs_free_inode (inode);
-		unlock_kernel();
+		unlock_ufs(inode->i_sb);
 	}
 }
diff --git a/fs/ufs/namei.c b/fs/ufs/namei.c
index 12f39b9..205030a 100644
--- a/fs/ufs/namei.c
+++ b/fs/ufs/namei.c
@@ -29,7 +29,6 @@
 
 #include <linux/time.h>
 #include <linux/fs.h>
-#include <linux/smp_lock.h>
 
 #include "ufs_fs.h"
 #include "ufs.h"
@@ -55,16 +54,16 @@ static struct dentry *ufs_lookup(struct inode * dir, struct dentry *dentry, stru
 	if (dentry->d_name.len > UFS_MAXNAMLEN)
 		return ERR_PTR(-ENAMETOOLONG);
 
-	lock_kernel();
+	lock_ufs(dir->i_sb);
 	ino = ufs_inode_by_name(dir, &dentry->d_name);
 	if (ino) {
 		inode = ufs_iget(dir->i_sb, ino);
 		if (IS_ERR(inode)) {
-			unlock_kernel();
+			unlock_ufs(dir->i_sb);
 			return ERR_CAST(inode);
 		}
 	}
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 	d_add(dentry, inode);
 	return NULL;
 }
@@ -93,9 +92,9 @@ static int ufs_create (struct inode * dir, struct dentry * dentry, int mode,
 		inode->i_fop = &ufs_file_operations;
 		inode->i_mapping->a_ops = &ufs_aops;
 		mark_inode_dirty(inode);
-		lock_kernel();
+		lock_ufs(dir->i_sb);
 		err = ufs_add_nondir(dentry, inode);
-		unlock_kernel();
+		unlock_ufs(dir->i_sb);
 	}
 	UFSD("END: err=%d\n", err);
 	return err;
@@ -115,9 +114,9 @@ static int ufs_mknod (struct inode * dir, struct dentry *dentry, int mode, dev_t
 		init_special_inode(inode, mode, rdev);
 		ufs_set_inode_dev(inode->i_sb, UFS_I(inode), rdev);
 		mark_inode_dirty(inode);
-		lock_kernel();
+		lock_ufs(dir->i_sb);
 		err = ufs_add_nondir(dentry, inode);
-		unlock_kernel();
+		unlock_ufs(dir->i_sb);
 	}
 	return err;
 }
@@ -133,7 +132,7 @@ static int ufs_symlink (struct inode * dir, struct dentry * dentry,
 	if (l > sb->s_blocksize)
 		goto out_notlocked;
 
-	lock_kernel();
+	lock_ufs(dir->i_sb);
 	inode = ufs_new_inode(dir, S_IFLNK | S_IRWXUGO);
 	err = PTR_ERR(inode);
 	if (IS_ERR(inode))
@@ -156,7 +155,7 @@ static int ufs_symlink (struct inode * dir, struct dentry * dentry,
 
 	err = ufs_add_nondir(dentry, inode);
 out:
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 out_notlocked:
 	return err;
 
@@ -172,9 +171,9 @@ static int ufs_link (struct dentry * old_dentry, struct inode * dir,
 	struct inode *inode = old_dentry->d_inode;
 	int error;
 
-	lock_kernel();
+	lock_ufs(dir->i_sb);
 	if (inode->i_nlink >= UFS_LINK_MAX) {
-		unlock_kernel();
+		unlock_ufs(dir->i_sb);
 		return -EMLINK;
 	}
 
@@ -183,7 +182,7 @@ static int ufs_link (struct dentry * old_dentry, struct inode * dir,
 	ihold(inode);
 
 	error = ufs_add_nondir(dentry, inode);
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 	return error;
 }
 
@@ -195,7 +194,7 @@ static int ufs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 	if (dir->i_nlink >= UFS_LINK_MAX)
 		goto out;
 
-	lock_kernel();
+	lock_ufs(dir->i_sb);
 	inode_inc_link_count(dir);
 
 	inode = ufs_new_inode(dir, S_IFDIR|mode);
@@ -216,7 +215,7 @@ static int ufs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
 	err = ufs_add_link(dentry, inode);
 	if (err)
 		goto out_fail;
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 
 	d_instantiate(dentry, inode);
 out:
@@ -228,7 +227,7 @@ out_fail:
 	iput (inode);
 out_dir:
 	inode_dec_link_count(dir);
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 	goto out;
 }
 
@@ -259,7 +258,7 @@ static int ufs_rmdir (struct inode * dir, struct dentry *dentry)
 	struct inode * inode = dentry->d_inode;
 	int err= -ENOTEMPTY;
 
-	lock_kernel();
+	lock_ufs(dir->i_sb);
 	if (ufs_empty_dir (inode)) {
 		err = ufs_unlink(dir, dentry);
 		if (!err) {
@@ -268,7 +267,7 @@ static int ufs_rmdir (struct inode * dir, struct dentry *dentry)
 			inode_dec_link_count(dir);
 		}
 	}
-	unlock_kernel();
+	unlock_ufs(dir->i_sb);
 	return err;
 }
 
diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index 2c61ac5..f4612f2 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -84,7 +84,6 @@
 #include <linux/blkdev.h>
 #include <linux/init.h>
 #include <linux/parser.h>
-#include <linux/smp_lock.h>
 #include <linux/buffer_head.h>
 #include <linux/vfs.h>
 #include <linux/log2.h>
@@ -96,6 +95,26 @@
 #include "swab.h"
 #include "util.h"
 
+void lock_ufs(struct super_block *sb)
+{
+#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
+	struct ufs_sb_info *sbi = UFS_SB(sb);
+
+	mutex_lock(&sbi->mutex);
+	sbi->mutex_owner = current;
+#endif
+}
+
+void unlock_ufs(struct super_block *sb)
+{
+#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
+	struct ufs_sb_info *sbi = UFS_SB(sb);
+
+	sbi->mutex_owner = NULL;
+	mutex_unlock(&sbi->mutex);
+#endif
+}
+
 static struct inode *ufs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)
 {
 	struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
@@ -313,7 +332,6 @@ void ufs_panic (struct super_block * sb, const char * function,
 	struct ufs_super_block_first * usb1;
 	va_list args;
 	
-	lock_kernel();
 	uspi = UFS_SB(sb)->s_uspi;
 	usb1 = ubh_get_usb_first(uspi);
 	
@@ -646,8 +664,6 @@ static void ufs_put_super_internal(struct super_block *sb)
 	
 	UFSD("ENTER\n");
 
-	lock_kernel();
-
 	ufs_put_cstotal(sb);
 	size = uspi->s_cssize;
 	blks = (size + uspi->s_fsize - 1) >> uspi->s_fshift;
@@ -676,8 +692,6 @@ static void ufs_put_super_internal(struct super_block *sb)
 	kfree (sbi->s_ucg);
 	kfree (base);
 
-	unlock_kernel();
-
 	UFSD("EXIT\n");
 }
 
@@ -696,8 +710,6 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
 	unsigned maxsymlen;
 	int ret = -EINVAL;
 
-	lock_kernel();
-
 	uspi = NULL;
 	ubh = NULL;
 	flags = 0;
@@ -1165,7 +1177,6 @@ magic_found:
 			goto failed;
 
 	UFSD("EXIT\n");
-	unlock_kernel();
 	return 0;
 
 dalloc_failed:
@@ -1177,12 +1188,10 @@ failed:
 	kfree(sbi);
 	sb->s_fs_info = NULL;
 	UFSD("EXIT (FAILED)\n");
-	unlock_kernel();
 	return ret;
 
 failed_nomem:
 	UFSD("EXIT (NOMEM)\n");
-	unlock_kernel();
 	return -ENOMEM;
 }
 
@@ -1193,8 +1202,8 @@ static int ufs_sync_fs(struct super_block *sb, int wait)
 	struct ufs_super_block_third * usb3;
 	unsigned flags;
 
+	lock_ufs(sb);
 	lock_super(sb);
-	lock_kernel();
 
 	UFSD("ENTER\n");
 
@@ -1213,8 +1222,8 @@ static int ufs_sync_fs(struct super_block *sb, int wait)
 	sb->s_dirt = 0;
 
 	UFSD("EXIT\n");
-	unlock_kernel();
 	unlock_super(sb);
+	unlock_ufs(sb);
 
 	return 0;
 }
@@ -1256,7 +1265,7 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 	unsigned new_mount_opt, ufstype;
 	unsigned flags;
 
-	lock_kernel();
+	lock_ufs(sb);
 	lock_super(sb);
 	uspi = UFS_SB(sb)->s_uspi;
 	flags = UFS_SB(sb)->s_flags;
@@ -1272,7 +1281,7 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 	ufs_set_opt (new_mount_opt, ONERROR_LOCK);
 	if (!ufs_parse_options (data, &new_mount_opt)) {
 		unlock_super(sb);
-		unlock_kernel();
+		unlock_ufs(sb);
 		return -EINVAL;
 	}
 	if (!(new_mount_opt & UFS_MOUNT_UFSTYPE)) {
@@ -1280,14 +1289,14 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 	} else if ((new_mount_opt & UFS_MOUNT_UFSTYPE) != ufstype) {
 		printk("ufstype can't be changed during remount\n");
 		unlock_super(sb);
-		unlock_kernel();
+		unlock_ufs(sb);
 		return -EINVAL;
 	}
 
 	if ((*mount_flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY)) {
 		UFS_SB(sb)->s_mount_opt = new_mount_opt;
 		unlock_super(sb);
-		unlock_kernel();
+		unlock_ufs(sb);
 		return 0;
 	}
 	
@@ -1313,7 +1322,7 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 		printk("ufs was compiled with read-only support, "
 		"can't be mounted as read-write\n");
 		unlock_super(sb);
-		unlock_kernel();
+		unlock_ufs(sb);
 		return -EINVAL;
 #else
 		if (ufstype != UFS_MOUNT_UFSTYPE_SUN && 
@@ -1323,13 +1332,13 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 		    ufstype != UFS_MOUNT_UFSTYPE_UFS2) {
 			printk("this ufstype is read-only supported\n");
 			unlock_super(sb);
-			unlock_kernel();
+			unlock_ufs(sb);
 			return -EINVAL;
 		}
 		if (!ufs_read_cylinder_structures(sb)) {
 			printk("failed during remounting\n");
 			unlock_super(sb);
-			unlock_kernel();
+			unlock_ufs(sb);
 			return -EPERM;
 		}
 		sb->s_flags &= ~MS_RDONLY;
@@ -1337,7 +1346,7 @@ static int ufs_remount (struct super_block *sb, int *mount_flags, char *data)
 	}
 	UFS_SB(sb)->s_mount_opt = new_mount_opt;
 	unlock_super(sb);
-	unlock_kernel();
+	unlock_ufs(sb);
 	return 0;
 }
 
@@ -1371,7 +1380,7 @@ static int ufs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	struct ufs_super_block_third *usb3;
 	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 
-	lock_kernel();
+	lock_ufs(sb);
 
 	usb1 = ubh_get_usb_first(uspi);
 	usb2 = ubh_get_usb_second(uspi);
@@ -1395,7 +1404,7 @@ static int ufs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_fsid.val[0] = (u32)id;
 	buf->f_fsid.val[1] = (u32)(id >> 32);
 
-	unlock_kernel();
+	unlock_ufs(sb);
 
 	return 0;
 }
diff --git a/fs/ufs/truncate.c b/fs/ufs/truncate.c
index a58f915..e56a4f5 100644
--- a/fs/ufs/truncate.c
+++ b/fs/ufs/truncate.c
@@ -40,7 +40,6 @@
 #include <linux/time.h>
 #include <linux/stat.h>
 #include <linux/string.h>
-#include <linux/smp_lock.h>
 #include <linux/buffer_head.h>
 #include <linux/blkdev.h>
 #include <linux/sched.h>
@@ -467,7 +466,6 @@ int ufs_truncate(struct inode *inode, loff_t old_i_size)
 
 	block_truncate_page(inode->i_mapping, inode->i_size, ufs_getfrag_block);
 
-	lock_kernel();
 	while (1) {
 		retry = ufs_trunc_direct(inode);
 		retry |= ufs_trunc_indirect(inode, UFS_IND_BLOCK,
@@ -487,7 +485,6 @@ int ufs_truncate(struct inode *inode, loff_t old_i_size)
 
 	inode->i_mtime = inode->i_ctime = CURRENT_TIME_SEC;
 	ufsi->i_lastfrag = DIRECT_FRAGMENT;
-	unlock_kernel();
 	mark_inode_dirty(inode);
 out:
 	UFSD("EXIT: err %d\n", err);
@@ -510,7 +507,9 @@ int ufs_setattr(struct dentry *dentry, struct iattr *attr)
 		/* XXX(truncate): truncate_setsize should be called last */
 		truncate_setsize(inode, attr->ia_size);
 
+		lock_ufs(inode->i_sb);
 		error = ufs_truncate(inode, old_i_size);
+		unlock_ufs(inode->i_sb);
 		if (error)
 			return error;
 	}
diff --git a/fs/ufs/ufs.h b/fs/ufs/ufs.h
index c08782e..5be2755 100644
--- a/fs/ufs/ufs.h
+++ b/fs/ufs/ufs.h
@@ -18,6 +18,8 @@ struct ufs_sb_info {
 	unsigned s_cgno[UFS_MAX_GROUP_LOADED];
 	unsigned short s_cg_loaded;
 	unsigned s_mount_opt;
+	struct mutex mutex;
+	struct task_struct *mutex_owner;
 };
 
 struct ufs_inode_info {
@@ -109,7 +111,6 @@ extern struct inode *ufs_iget(struct super_block *, unsigned long);
 extern int ufs_write_inode (struct inode *, struct writeback_control *);
 extern int ufs_sync_inode (struct inode *);
 extern void ufs_evict_inode (struct inode *);
-extern struct buffer_head * ufs_bread (struct inode *, unsigned, int, int *);
 extern int ufs_getfrag_block (struct inode *inode, sector_t fragment, struct buffer_head *bh_result, int create);
 
 /* namei.c */
@@ -154,4 +155,7 @@ static inline u32 ufs_dtogd(struct ufs_sb_private_info * uspi, u64 b)
 	return do_div(b, uspi->s_fpg);
 }
 
+extern void lock_ufs(struct super_block *sb);
+extern void unlock_ufs(struct super_block *sb);
+
 #endif /* _UFS_UFS_H */
-- 
1.7.1