Merge tag 'writeback-proportions' of git://git.kernel.org/pub/scm/lin…

…ux/kernel/git/wfg/linux

Pull writeback updates from Wu Fengguang:
 "Use time based periods to age the writeback proportions, which can
  adapt equally well to fast/slow devices."

Fix up trivial conflict in comment in fs/sync.c

* tag 'writeback-proportions' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
  writeback: Fix some comment errors
  block: Convert BDI proportion calculations to flexible proportions
  lib: Fix possible deadlock in flexible proportion code
  lib: Proportions with flexible period

fs/fs-writeback.c

@@ -628,8 +628,8 @@ static long writeback_sb_inodes(struct super_block *sb,
 		}
 
 		/*
-		 * Don't bother with new inodes or inodes beeing freed, first
-		 * kind does not need peridic writeout yet, and for the latter
+		 * Don't bother with new inodes or inodes being freed, first
+		 * kind does not need periodic writeout yet, and for the latter
 		 * kind writeout is handled by the freer.
 		 */
 		spin_lock(&inode->i_lock);

fs/super.c

@@ -320,7 +320,7 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
 
 /*
  *	grab_super_passive - acquire a passive reference
- *	@s: reference we are trying to grab
+ *	@sb: reference we are trying to grab
  *
  *	Tries to acquire a passive reference. This is used in places where we
  *	cannot take an active reference but we need to ensure that the

include/linux/backing-dev.h

@@ -10,7 +10,7 @@
 
 #include <linux/percpu_counter.h>
 #include <linux/log2.h>
-#include <linux/proportions.h>
+#include <linux/flex_proportions.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
@@ -89,7 +89,7 @@ struct backing_dev_info {
 	unsigned long dirty_ratelimit;
 	unsigned long balanced_dirty_ratelimit;
 
-	struct prop_local_percpu completions;
+	struct fprop_local_percpu completions;
 	int dirty_exceeded;
 
 	unsigned int min_ratio;

include/linux/flex_proportions.h

@@ -0,0 +1,101 @@
+/*
+ * Floating proportions with flexible aging period
+ *
+ *  Copyright (C) 2011, SUSE, Jan Kara <jack@suse.cz>
+ */
+
+#ifndef _LINUX_FLEX_PROPORTIONS_H
+#define _LINUX_FLEX_PROPORTIONS_H
+
+#include <linux/percpu_counter.h>
+#include <linux/spinlock.h>
+#include <linux/seqlock.h>
+
+/*
+ * When maximum proportion of some event type is specified, this is the
+ * precision with which we allow limitting. Note that this creates an upper
+ * bound on the number of events per period like
+ *   ULLONG_MAX >> FPROP_FRAC_SHIFT.
+ */
+#define FPROP_FRAC_SHIFT 10
+#define FPROP_FRAC_BASE (1UL << FPROP_FRAC_SHIFT)
+
+/*
+ * ---- Global proportion definitions ----
+ */
+struct fprop_global {
+	/* Number of events in the current period */
+	struct percpu_counter events;
+	/* Current period */
+	unsigned int period;
+	/* Synchronization with period transitions */
+	seqcount_t sequence;
+};
+
+int fprop_global_init(struct fprop_global *p);
+void fprop_global_destroy(struct fprop_global *p);
+bool fprop_new_period(struct fprop_global *p, int periods);
+
+/*
+ *  ---- SINGLE ----
+ */
+struct fprop_local_single {
+	/* the local events counter */
+	unsigned long events;
+	/* Period in which we last updated events */
+	unsigned int period;
+	raw_spinlock_t lock;	/* Protect period and numerator */
+};
+
+#define INIT_FPROP_LOCAL_SINGLE(name)			\
+{	.lock = __RAW_SPIN_LOCK_UNLOCKED(name.lock),	\
+}
+
+int fprop_local_init_single(struct fprop_local_single *pl);
+void fprop_local_destroy_single(struct fprop_local_single *pl);
+void __fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl);
+void fprop_fraction_single(struct fprop_global *p,
+	struct fprop_local_single *pl, unsigned long *numerator,
+	unsigned long *denominator);
+
+static inline
+void fprop_inc_single(struct fprop_global *p, struct fprop_local_single *pl)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	__fprop_inc_single(p, pl);
+	local_irq_restore(flags);
+}
+
+/*
+ * ---- PERCPU ----
+ */
+struct fprop_local_percpu {
+	/* the local events counter */
+	struct percpu_counter events;
+	/* Period in which we last updated events */
+	unsigned int period;
+	raw_spinlock_t lock;	/* Protect period and numerator */
+};
+
+int fprop_local_init_percpu(struct fprop_local_percpu *pl);
+void fprop_local_destroy_percpu(struct fprop_local_percpu *pl);
+void __fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl);
+void __fprop_inc_percpu_max(struct fprop_global *p, struct fprop_local_percpu *pl,
+			    int max_frac);
+void fprop_fraction_percpu(struct fprop_global *p,
+	struct fprop_local_percpu *pl, unsigned long *numerator,
+	unsigned long *denominator);
+
+static inline
+void fprop_inc_percpu(struct fprop_global *p, struct fprop_local_percpu *pl)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	__fprop_inc_percpu(p, pl);
+	local_irq_restore(flags);
+}
+
+#endif

lib/Makefile

@@ -11,7 +11,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o timerqueue.o\
 	 idr.o int_sqrt.o extable.o prio_tree.o \
 	 sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
-	 proportions.o prio_heap.o ratelimit.o show_mem.o \
+	 proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o
 
 lib-$(CONFIG_MMU) += ioremap.o