fs: jbd: replace bh_state lock

I was compiling a kernel in a shell that I set to a priority of 20,
and it locked up on the bit_spin_lock crap of jbd.

This patch adds another spinlock to the buffer head and uses that
instead of the bit_spins.

From: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

--

 fs/buffer.c                 |    3 ++-
 include/linux/buffer_head.h |    1 +
 include/linux/jbd.h         |   12 ++++++------
 3 files changed, 9 insertions(+), 7 deletions(-)

fs/buffer.c

@@ -40,7 +40,6 @@
 #include <linux/cpu.h>
 #include <linux/bitops.h>
 #include <linux/mpage.h>
-#include <linux/bit_spinlock.h>
 
 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
 
@@ -3243,6 +3242,7 @@ struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
 	if (ret) {
 		INIT_LIST_HEAD(&ret->b_assoc_buffers);
 		spin_lock_init(&ret->b_uptodate_lock);
+		spin_lock_init(&ret->b_state_lock);
 		get_cpu_var(bh_accounting).nr++;
 		recalc_bh_state();
 		put_cpu_var(bh_accounting);
@@ -3255,6 +3255,7 @@ void free_buffer_head(struct buffer_head *bh)
 {
 	BUG_ON(!list_empty(&bh->b_assoc_buffers));
 	BUG_ON(spin_is_locked(&bh->b_uptodate_lock));
+	BUG_ON(spin_is_locked(&bh->b_state_lock));
 	kmem_cache_free(bh_cachep, bh);
 	get_cpu_var(bh_accounting).nr--;
 	recalc_bh_state();

include/linux/buffer_head.h

@@ -71,6 +71,7 @@ struct buffer_head {
 						   associated with */
 	atomic_t b_count;		/* users using this buffer_head */
 	spinlock_t b_uptodate_lock;
+	spinlock_t b_state_lock;
 };
 
 /*

include/linux/jbd.h

@@ -315,32 +315,32 @@ static inline struct journal_head *bh2jh(struct buffer_head *bh)
 
 static inline void jbd_lock_bh_state(struct buffer_head *bh)
 {
-	bit_spin_lock(BH_State, &bh->b_state);
+	spin_lock(&bh->b_state_lock);
 }
 
 static inline int jbd_trylock_bh_state(struct buffer_head *bh)
 {
-	return bit_spin_trylock(BH_State, &bh->b_state);
+	return spin_trylock(&bh->b_state_lock);
 }
 
 static inline int jbd_is_locked_bh_state(struct buffer_head *bh)
 {
-	return bit_spin_is_locked(BH_State, &bh->b_state);
+	return spin_is_locked(&bh->b_state_lock);
 }
 
 static inline void jbd_unlock_bh_state(struct buffer_head *bh)
 {
-	bit_spin_unlock(BH_State, &bh->b_state);
+	spin_unlock(&bh->b_state_lock);
 }
 
 static inline void jbd_lock_bh_journal_head(struct buffer_head *bh)
 {
-	bit_spin_lock(BH_JournalHead, &bh->b_state);
+	spin_lock_irq(&bh->b_uptodate_lock);
 }
 
 static inline void jbd_unlock_bh_journal_head(struct buffer_head *bh)
 {
-	bit_spin_unlock(BH_JournalHead, &bh->b_state);
+	spin_unlock_irq(&bh->b_uptodate_lock);
 }
 
 struct jbd_revoke_table_s;