01-ps-failpath.patch - move the path failure decision to the path
selector. Some ps's may want to select paths that have a couple
failures over one that has N failures. If a ps has to track this info
there didn't seem to be a compelling reason to also do it in
dm-mpath.c. Well code duplication and sharing is a good reason to do
it at dm-mpath. It would be nice if I could just add an init function
to any ps and leach off other people's work :) but is that too modular?
Additionally, if a ps fails to activate a path or cannot use it
during initialization it may want to fail it.
diffstat
dm-mpath.c | 71 ++++++++++++-----------------------------------------
dm-path-selector.c | 50 +++++++++++++++++++++++++++++--------
dm-path-selector.h | 8 ++---
3 files changed, 61 insertions(+), 68 deletions(-)
diff -aurp linux-2.6.5-rc1-udm1-orig/drivers/md/dm-mpath.c linux-2.6.5-rc1-udm1-work/drivers/md/dm-mpath.c
--- linux-2.6.5-rc1-udm1-orig/drivers/md/dm-mpath.c 2004-04-02 01:24:18.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/dm-mpath.c 2004-04-03 22:48:45.116161233 -0800
@@ -19,9 +19,6 @@
#include <linux/workqueue.h>
#include <asm/atomic.h>
-/* FIXME: get rid of this */
-#define MPATH_FAIL_COUNT 1
-
/*
* We don't want to call the path selector for every single io
* that comes through, so instead we only consider changing paths
@@ -42,10 +39,6 @@ struct path {
struct dm_dev *dev;
struct priority_group *pg;
-
- spinlock_t failed_lock;
- int has_failed;
- unsigned fail_count;
};
struct priority_group {
@@ -67,7 +60,6 @@ struct multipath {
struct list_head priority_groups;
spinlock_t lock;
- unsigned nr_valid_paths;
struct path *current_path;
unsigned current_count;
@@ -99,11 +91,8 @@ static struct path *alloc_path(void)
{
struct path *path = kmalloc(sizeof(*path), GFP_KERNEL);
- if (path) {
+ if (path)
memset(path, 0, sizeof(*path));
- path->failed_lock = SPIN_LOCK_UNLOCKED;
- path->fail_count = MPATH_FAIL_COUNT;
- }
return path;
}
@@ -204,13 +193,11 @@ static int __choose_path(struct multipat
struct priority_group *pg;
struct path *path = NULL;
- if (m->nr_valid_paths) {
- /* loop through the priority groups until we find a valid path. */
- list_for_each_entry (pg, &m->priority_groups, list) {
- path = pg->ps->type->select_path(pg->ps);
- if (path)
- break;
- }
+ /* loop through the priority groups until we find a valid path. */
+ list_for_each_entry (pg, &m->priority_groups, list) {
+ path = pg->ps->type->select_path(pg->ps);
+ if (path)
+ break;
}
m->current_path = path;
@@ -471,7 +458,6 @@ static int multipath_ctr(struct dm_targe
if (!pg)
goto bad;
- m->nr_valid_paths += pg->nr_paths;
list_add_tail(&pg->list, &m->priority_groups);
}
@@ -512,31 +498,19 @@ static int multipath_map(struct dm_targe
return 1;
}
-static void fail_path(struct path *path)
+static void update_path(struct path *path, int error)
{
unsigned long flags;
- struct multipath *m;
-
- spin_lock_irqsave(&path->failed_lock, flags);
+ struct multipath *m = path->pg->m;
- /* FIXME: path->fail_count is brain dead */
- if (!path->has_failed && !--path->fail_count) {
- m = path->pg->m;
-
- path->has_failed = 1;
- path->pg->ps->type->fail_path(path->pg->ps, path);
- schedule_work(&m->trigger_event);
+ path->pg->ps->type->update_path(path->pg->ps, path, error);
- spin_lock(&m->lock);
- m->nr_valid_paths--;
-
- if (path == m->current_path)
- m->current_path = NULL;
-
- spin_unlock(&m->lock);
- }
+ spin_lock_irqsave(&m->lock, flags);
+ if (path == m->current_path)
+ m->current_path = NULL;
+ spin_unlock_irqrestore(&m->lock, flags);
- spin_unlock_irqrestore(&path->failed_lock, flags);
+ schedule_work(&m->trigger_event);
}
static int do_end_io(struct multipath *m, struct bio *bio,
@@ -545,14 +519,7 @@ static int do_end_io(struct multipath *m
int r;
if (error) {
- spin_lock(&m->lock);
- if (!m->nr_valid_paths) {
- spin_unlock(&m->lock);
- return -EIO;
- }
- spin_unlock(&m->lock);
-
- fail_path(io->path);
+ update_path(io->path, error);
/* remap */
dm_bio_restore(&io->details, bio);
@@ -598,7 +565,6 @@ static int multipath_status(struct dm_ta
char *result, unsigned int maxlen)
{
int sz = 0;
- unsigned long flags;
struct multipath *m = (struct multipath *) ti->private;
struct priority_group *pg;
struct path *p;
@@ -616,12 +582,9 @@ static int multipath_status(struct dm_ta
list_for_each_entry(p, &pg->paths, list) {
format_dev_t(buffer, p->dev->bdev->bd_dev);
- spin_lock_irqsave(&p->failed_lock, flags);
- EMIT("%s %s %u ", buffer,
- p->has_failed ? "F" : "A", p->fail_count);
- pg->ps->type->status(pg->ps, p, type,
+ EMIT("%s ", buffer);
+ sz += pg->ps->type->status(pg->ps, p, type,
result + sz, maxlen - sz);
- spin_unlock_irqrestore(&p->failed_lock, flags);
}
}
break;
diff -aurp linux-2.6.5-rc1-udm1-orig/drivers/md/dm-path-selector.c linux-2.6.5-rc1-udm1-work/drivers/md/dm-path-selector.c
--- linux-2.6.5-rc1-udm1-orig/drivers/md/dm-path-selector.c 2004-04-02 01:24:18.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/dm-path-selector.c 2004-04-03 22:48:53.190046847 -0800
@@ -127,6 +127,8 @@ int dm_unregister_path_selector(struct p
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)
@@ -143,6 +145,10 @@ static struct path_info *path_lookup(str
/*-----------------------------------------------------------------
* Round robin selector
*---------------------------------------------------------------*/
+
+/* FIXME: get rid of this */
+#define MPATH_FAIL_COUNT 1
+
struct selector {
spinlock_t lock;
@@ -215,6 +221,7 @@ static int rr_add_path(struct path_selec
return -ENOMEM;
}
+ pi->fail_count = MPATH_FAIL_COUNT;
pi->path = path;
spin_lock(&s->lock);
@@ -224,7 +231,8 @@ static int rr_add_path(struct path_selec
return 0;
}
-static void rr_fail_path(struct path_selector *ps, struct path *p)
+static void rr_update_path(struct path_selector *ps, struct path *p,
+ int error)
{
unsigned long flags;
struct selector *s = (struct selector *) ps->context;
@@ -235,14 +243,9 @@ static void rr_fail_path(struct path_sel
* mind the expense of these searches.
*/
spin_lock_irqsave(&s->lock, flags);
- pi = path_lookup(&s->valid_paths, p);
- if (!pi)
- pi = path_lookup(&s->invalid_paths, p);
-
- if (!pi)
- DMWARN("asked to change the state of an unknown path");
- else
+ pi = path_lookup(&s->valid_paths, p);
+ if (pi && !--pi->fail_count)
list_move(&pi->list, &s->invalid_paths);
spin_unlock_irqrestore(&s->lock, flags);
@@ -269,7 +272,34 @@ static struct path *rr_select_path(struc
static int rr_status(struct path_selector *ps, struct path *path,
status_type_t type, char *result, unsigned int maxlen)
{
- return 0;
+ 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 = {
@@ -279,7 +309,7 @@ static struct path_selector_type rr_ps =
.ctr = rr_ctr,
.dtr = rr_dtr,
.add_path = rr_add_path,
- .fail_path = rr_fail_path,
+ .update_path = rr_update_path,
.select_path = rr_select_path,
.status = rr_status,
};
diff -aurp linux-2.6.5-rc1-udm1-orig/drivers/md/dm-path-selector.h linux-2.6.5-rc1-udm1-work/drivers/md/dm-path-selector.h
--- linux-2.6.5-rc1-udm1-orig/drivers/md/dm-path-selector.h 2004-04-02 01:24:18.000000000 -0800
+++ linux-2.6.5-rc1-udm1-work/drivers/md/dm-path-selector.h 2004-04-03 22:55:02.669433656 -0800
@@ -52,10 +52,10 @@ typedef int (*ps_add_path_fn) (struct pa
typedef struct path *(*ps_select_path_fn) (struct path_selector *ps);
/*
- * Notify the selector that a path has failed.
+ * Notify the selector that an IO failure has occured.
*/
-typedef void (*ps_fail_path_fn) (struct path_selector *ps,
- struct path *p);
+typedef void (*ps_update_path_fn) (struct path_selector *ps,
+ struct path *p, int error);
/*
* Table content based on parameters added in ps_add_path_fn
@@ -75,7 +75,7 @@ struct path_selector_type {
ps_dtr_fn dtr;
ps_add_path_fn add_path;
- ps_fail_path_fn fail_path;
+ ps_update_path_fn update_path;
ps_select_path_fn select_path;
ps_status_fn status;
};
