[PATCH] remove global_bufferlist_lock

This patch addresses Andrew's FIXME in buffer.c and adds a spinlock that
can be passed to the buffer list manipulation functions to the reiserfs
journal.  This obsoletes the cheks for lock beeing NULL in buffer.c and
the global_bufferlist_lock.

In addition osync_inode_list is changed to use list_for_each_prev as in 2.4
instead of a hand-crafted loop.

A little comment to the reiserfs folks:  your code would be _sooo_ much
easier to understand if you used temporary local variables for often
referenced fields..

fs/buffer.c

@@ -48,15 +48,6 @@ static struct bh_wait_queue_head {
 	wait_queue_head_t wqh;
 } ____cacheline_aligned_in_smp bh_wait_queue_heads[1<<BH_WAIT_TABLE_ORDER];
 
-/*
- * Several of these buffer list functions are exported to filesystems,
- * so we do funny things with the spinlocking to support those
- * filesystems while still using inode->i_bufferlist_lock for
- * most applications.
- * FIXME: put a spinlock in the reiserfs journal and kill this lock.
- */
-static spinlock_t global_bufferlist_lock = SPIN_LOCK_UNLOCKED;
-
 /*
  * Debug/devel support stuff
  */
@@ -448,8 +439,6 @@ __get_hash_table(struct block_device *bdev, sector_t block, int unused)
 void buffer_insert_list(spinlock_t *lock,
 		struct buffer_head *bh, struct list_head *list)
 {
-	if (lock == NULL)
-		lock = &global_bufferlist_lock;
 	spin_lock(lock);
 	list_del(&bh->b_inode_buffers);
 	list_add(&bh->b_inode_buffers, list);
@@ -701,14 +690,10 @@ static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
 	struct list_head *p;
 	int err = 0;
 
-	if (lock == NULL)
-		lock = &global_bufferlist_lock;
-
 	spin_lock(lock);
 repeat:
-	for (p = list->prev; 
-	     bh = BH_ENTRY(p), p != list;
-	     p = bh->b_inode_buffers.prev) {
+	list_for_each_prev(p, list) {
+		bh = BH_ENTRY(p);
 		if (buffer_locked(bh)) {
 			get_bh(bh);
 			spin_unlock(lock);
@@ -749,9 +734,6 @@ int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
 	struct list_head tmp;
 	int err = 0, err2;
 
-	if (lock == NULL)
-		lock = &global_bufferlist_lock;
-	
 	INIT_LIST_HEAD(&tmp);
 
 	spin_lock(lock);

fs/reiserfs/inode.c

@@ -105,9 +105,9 @@ inline void make_le_item_head (struct item_head * ih, const struct cpu_key * key
 }
 
 static void add_to_flushlist(struct inode *inode, struct buffer_head *bh) {
-    struct list_head *list = &(SB_JOURNAL(inode->i_sb)->j_dirty_buffers) ;
+    struct reiserfs_journal *j = &(SB_JOURNAL(inode->i_sb)) ;
 
-    buffer_insert_list(NULL, bh, list) ;
+    buffer_insert_list(j->dirty_buffers_lock, bh, j->j_dirty_buffers) ;
 }
 
 //

fs/reiserfs/journal.c

@@ -2131,6 +2131,7 @@ int journal_init(struct super_block *p_s_sb, const char * j_dev_name, int old_fo
 
   INIT_LIST_HEAD(&SB_JOURNAL(p_s_sb)->j_bitmap_nodes) ;
   INIT_LIST_HEAD(&SB_JOURNAL(p_s_sb)->j_dirty_buffers) ;
+  spin_lock_init(&SB_JOURNAL(p_s_sb)->j_dirty_buffers_lock) ;
   reiserfs_allocate_list_bitmaps(p_s_sb, SB_JOURNAL(p_s_sb)->j_list_bitmap, 
                                  SB_BMAP_NR(p_s_sb)) ;
   allocate_bitmap_nodes(p_s_sb) ;
@@ -3125,7 +3126,8 @@ printk("journal-2020: do_journal_end: BAD desc->j_len is ZERO\n") ;
   SB_JOURNAL_LIST_INDEX(p_s_sb) = jindex ;
 
   /* write any buffers that must hit disk before this commit is done */
-  fsync_buffers_list(NULL, &(SB_JOURNAL(p_s_sb)->j_dirty_buffers)) ;
+  fsync_buffers_list(&(SB_JOURNAL(p_s_sb)->j_dirty_buffers_lock),
+		     &(SB_JOURNAL(p_s_sb)->j_dirty_buffers)) ;
 
   /* honor the flush and async wishes from the caller */
   if (flush) {

include/linux/reiserfs_fs_sb.h

@@ -241,6 +241,7 @@ struct reiserfs_journal {
   int j_used_bitmap_nodes ;
   struct list_head j_bitmap_nodes ;
   struct list_head j_dirty_buffers ;
+  spinlock_t j_dirty_buffers_lock ; /* protects j_dirty_buffers */
   struct reiserfs_list_bitmap j_list_bitmap[JOURNAL_NUM_BITMAPS] ;	/* array of bitmaps to record the deleted blocks */
   struct reiserfs_journal_list j_journal_list[JOURNAL_LIST_COUNT] ;	    /* array of all the journal lists */
   struct reiserfs_journal_cnode *j_hash_table[JOURNAL_HASH_SIZE] ; 	    /* hash table for real buffer heads in current trans */