[dm-devel] [PATCH RFC 2/3] make priority groups modular and rm ps's HW knowledge

[Mike Christie <michaelc cs wisc edu>]

02-sep-pg-from-ps.patch - moves the HW stuff out of the selector. Selector's are 
once again notified of path status updates throught the update function.

 dm-path-selector.c |   68 ++++++++++++++---------------------------------------
 dm-path-selector.h |   36 +++++++++++-----------------
 2 files changed, 33 insertions(+), 71 deletions(-)

diff -aurp linux-2.6.7-rc2/drivers/md/dm-path-selector.c linux-2.6.7-rc2-pg/drivers/md/dm-path-selector.c
--- linux-2.6.7-rc2/drivers/md/dm-path-selector.c	2004-06-04 03:52:23.334727147 -0700
+++ linux-2.6.7-rc2-pg/drivers/md/dm-path-selector.c	2004-06-04 02:18:57.000000000 -0700
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) 2003 Sistina Software.
+ * Copyright (C) 2004 IBM Corporation
  *
  * Module Author: Heinz Mauelshagen
  *
@@ -142,13 +143,9 @@ EXPORT_SYMBOL(dm_unregister_path_selecto
  * Path handling code, paths are held in lists
  *---------------------------------------------------------------*/
 
-/* FIXME: get rid of this */
-#define RR_FAIL_COUNT	1
-
 struct path_info {
 	struct list_head list;
 	struct path *path;
-	unsigned fail_count;
 };
 
 static struct path_info *path_lookup(struct list_head *head, struct path *p)
@@ -244,35 +241,42 @@ static int rr_add_path(struct path_selec
 		return -ENOMEM;
 	}
 
-	pi->fail_count = 0;
 	pi->path = path;
 
 	spin_lock(&s->lock);
-	list_add(&pi->list, &s->valid_paths);
+	list_add_tail(&pi->list, &s->valid_paths);
 	spin_unlock(&s->lock);
 
 	return 0;
 }
 
-static void rr_end_io(struct path_selector *ps, struct bio *bio, int error,
-		      union map_info *info)
+static void rr_update_path(struct path_selector *ps, struct path *p,
+			   int status)
 {
 	unsigned long flags;
+	struct path_info *pi;
 	struct selector *s = (struct selector *) ps->context;
-	struct path_info *pi = (struct path_info *)info->ptr;
-
-	if (likely(!error))
-		return;
 
 	spin_lock_irqsave(&s->lock, flags);
 
-	if (++pi->fail_count == RR_FAIL_COUNT) {
+	if (status) {
+		pi = path_lookup(&s->valid_paths, p);
+		if (!pi)
+			goto done;
+
 		list_move(&pi->list, &s->invalid_paths);
 
 		if (pi == s->current_path)
 			s->current_path = NULL;
+	} else {
+		pi = path_lookup(&s->invalid_paths, p);
+		if (!pi)
+			goto done;
+
+		list_move(&pi->list, &s->valid_paths);
 	}
 
+ done:
 	spin_unlock_irqrestore(&s->lock, flags);
 }
 
@@ -303,44 +307,9 @@ static struct path *rr_select_path(struc
  done:
 	spin_unlock_irqrestore(&s->lock, flags);
 
-	info->ptr = pi;
 	return pi ? pi->path : NULL;
 }
 
-/* Path status */
-static int rr_status(struct path_selector *ps, struct path *path,
-		     status_type_t type, char *result, unsigned int maxlen)
-{
-	unsigned long flags;
-	struct path_info *pi;
-	int failed = 0;
-	struct selector *s = (struct selector *) ps->context;
-	int sz = 0;
-
-	if (type == STATUSTYPE_TABLE)
-		return 0;
-
-	spin_lock_irqsave(&s->lock, flags);
-
-	/*
-	 * Is status called often for testing or something?
-	 * If so maybe a ps's info should be allocated w/ path
-	 * so a simple container_of can be used.
-	 */
-	pi = path_lookup(&s->valid_paths, path);
-	if (!pi) {
-		failed = 1;
-		pi = path_lookup(&s->invalid_paths, path);
-	}
-
-	sz = scnprintf(result, maxlen, "%s %u ", failed ? "F" : "A",
-		       pi->fail_count);
-
-	spin_unlock_irqrestore(&s->lock, flags);
-
-	return sz;
-}
-
 static struct path_selector_type rr_ps = {
 	.name = "round-robin",
 	.module = THIS_MODULE,
@@ -349,9 +318,8 @@ static struct path_selector_type rr_ps =
 	.ctr = rr_ctr,
 	.dtr = rr_dtr,
 	.add_path = rr_add_path,
-	.end_io = rr_end_io,
+	.update_path = rr_update_path,
 	.select_path = rr_select_path,
-	.status = rr_status,
 };
 
 /*
diff -aurp linux-2.6.7-rc2/drivers/md/dm-path-selector.h linux-2.6.7-rc2-pg/drivers/md/dm-path-selector.h
--- linux-2.6.7-rc2/drivers/md/dm-path-selector.h	2004-06-04 03:52:23.364723227 -0700
+++ linux-2.6.7-rc2-pg/drivers/md/dm-path-selector.h	2004-06-03 22:55:58.000000000 -0700
@@ -16,8 +16,6 @@
 
 struct path;
 
-struct block_device *dm_path_to_bdev(struct path *path);
-
 /*
  * We provide an abstraction for the code that chooses which path
  * to send some io down.
@@ -35,22 +33,6 @@ typedef int (*ps_ctr_fn) (struct path_se
 typedef void (*ps_dtr_fn) (struct path_selector *ps);
 
 /*
- * Allows the ps to initialize itself. It should return one
- * of the following return values. iif DM_PS_INITIALIZING is
- * returned the path-selector must call dm_ps_init_complete
- * when the initializtion has completed.
- */
-enum {
-	DM_PS_SUCCESS,
-	DM_PS_FAILED,
-	DM_PS_INITIALIZING,
-};
-
-void dm_ps_init_complete(struct path_selector *ps);
-
-typedef int (*ps_init_fn) (struct path_selector *ps);
-
-/*
  * Add an opaque path object, along with some selector specific
  * path args (eg, path priority).
  */
@@ -70,16 +52,28 @@ typedef	int (*ps_add_path_fn) (struct pa
 typedef	struct path *(*ps_select_path_fn) (struct path_selector *ps,
 					   struct bio *bio,
 					   union map_info *info);
+/*
+ * The error value here is informative only.
+ * The ps should not offline the path as a result of this value,
+ * this operation is only done through the ps_update_path_fn.
+ */
 typedef void (*ps_end_io) (struct path_selector *ps, struct bio *bio,
 			   int error, union map_info *info);
 
 /*
+ * Notify the selector the path's status has changed.
+ * status != 0 indicates a failure, status == 0 indicates
+ * path reacitvation.
+ */
+typedef void (*ps_update_path_fn) (struct path_selector *ps,
+				   struct path *path, int status);
+
+/*
  * Table content based on parameters added in ps_add_path_fn
  * or path selector status
  */
 typedef	int (*ps_status_fn) (struct path_selector *ps,
-			     struct path *path,
-			     status_type_t type,
+			     struct path *path, status_type_t type,
 			     char *result, unsigned int maxlen);
 
 /* Information about a path selector type */
@@ -91,11 +85,11 @@ struct path_selector_type {
 	unsigned int info_args;
 	ps_ctr_fn ctr;
 	ps_dtr_fn dtr;
-	ps_init_fn init;
 
 	ps_add_path_fn add_path;
 	ps_select_path_fn select_path;
 	ps_end_io end_io;
+	ps_update_path_fn update_path;
 	ps_status_fn status;
 };