New open modes FNODE_DM_NOFLUSH and FMODE_DM_FLUSH_IGN_ERR.

FNODE_DM_NOFLUSH indicates that the device hardware cache doesn't have
to be flushed when processing a barrier (used for mirror log, it is
already flushed explicitly).

FMODE_DM_FLUSH_IGN_ERR indicated that the hardware cache should be
flushed but the error code should be ignored (used for raid1 legs and
multipath, where failing devices are acceptable).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-log.c   |    2 +-
 drivers/md/dm-mpath.c |    3 ++-
 drivers/md/dm-raid1.c |    2 +-
 drivers/md/dm-table.c |   18 ++++++++++++++----
 include/linux/fs.h    |   14 ++++++++++++++
 5 files changed, 32 insertions(+), 7 deletions(-)

Index: linux-2.6.29-rc3-devel/drivers/md/dm-log.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/md/dm-log.c	2009-01-29 05:27:21.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/md/dm-log.c	2009-01-29 05:27:22.000000000 +0100
@@ -564,7 +564,7 @@ static int disk_ctr(struct dm_dirty_log 
 	}
 
 	r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
-			  FMODE_READ | FMODE_WRITE, &dev);
+			  FMODE_READ | FMODE_WRITE | FMODE_DM_NOFLUSH, &dev);
 	if (r)
 		return r;
 
Index: linux-2.6.29-rc3-devel/drivers/md/dm-mpath.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/md/dm-mpath.c	2009-01-29 05:26:28.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/md/dm-mpath.c	2009-01-29 05:27:22.000000000 +0100
@@ -586,7 +586,8 @@ static struct pgpath *parse_path(struct 
 		return ERR_PTR(-ENOMEM);
 
 	r = dm_get_device(ti, shift(as), ti->begin, ti->len,
-			  dm_table_get_mode(ti->table), &p->path.dev);
+			  dm_table_get_mode(ti->table) | FMODE_DM_FLUSH_IGN_ERR,
+			  &p->path.dev);
 	if (r) {
 		ti->error = "error getting device";
 		goto bad;
Index: linux-2.6.29-rc3-devel/include/linux/fs.h
===================================================================
--- linux-2.6.29-rc3-devel.orig/include/linux/fs.h	2009-01-29 05:23:16.000000000 +0100
+++ linux-2.6.29-rc3-devel/include/linux/fs.h	2009-01-29 05:27:22.000000000 +0100
@@ -81,6 +81,20 @@ struct inodes_stat_t {
  */
 #define FMODE_NOCMTIME		((__force fmode_t)2048)
 
+/*
+ * Useable only inside device mapper with dm_get_device().
+ * Inform the dm core that the device cache should not be flushed when
+ * barrier is processed.
+ */
+#define FMODE_DM_NOFLUSH	((__force fmode_t)4096)
+
+/*
+ * Useable only inside device mapper with dm_get_device().
+ * Inform the dm core that flush errors should be ignored when barrier
+ * is processed.
+ */
+#define FMODE_DM_FLUSH_IGN_ERR	((__force fmode_t)8192)
+
 #define RW_MASK		1
 #define RWA_MASK	2
 #define READ 0
Index: linux-2.6.29-rc3-devel/drivers/md/dm-table.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/md/dm-table.c	2009-01-29 05:27:17.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/md/dm-table.c	2009-01-29 05:27:22.000000000 +0100
@@ -994,17 +994,24 @@ struct flush_completion {
 	atomic_t error;
 };
 
-static void bio_end_flush(struct bio *bio, int error)
+static void bio_end_flush_ign_err(struct bio *bio, int error)
 {
 	struct flush_completion *completion = bio->bi_private;
 
 	bio_put(bio);
 
+	if (atomic_dec_and_test(&completion->count))
+		wake_up_process(completion->sleeper);
+}
+
+static void bio_end_flush(struct bio *bio, int error)
+{
+	struct flush_completion *completion = bio->bi_private;
+
 	if (unlikely(error) && unlikely(error != -EOPNOTSUPP))
 		atomic_cmpxchg(&completion->error, 0, error);
 
-	if (atomic_dec_and_test(&completion->count))
-		wake_up_process(completion->sleeper);
+	bio_end_flush_ign_err(bio, error);
 }
 
 static void wait_for_flush_completion(struct flush_completion *completion)
@@ -1040,6 +1047,9 @@ int dm_table_flush_all(struct dm_table *
 	list_for_each_entry(dd, devices, list) {
 		struct bio *bio;
 
+		if (unlikely(dd->dm_dev.mode & FMODE_DM_NOFLUSH))
+			continue;
+
 		atomic_inc(&completion.count);
 
 		bio = bio_kmalloc(GFP_ATOMIC, 0);
@@ -1053,7 +1063,7 @@ int dm_table_flush_all(struct dm_table *
 			bio_init(&reserved_bio);
 			reserved_bio.bi_destructor = bio_null_destructor;
 		}
-		bio->bi_end_io = bio_end_flush;
+		bio->bi_end_io = dd->dm_dev.mode & FMODE_DM_FLUSH_IGN_ERR ? bio_end_flush_ign_err : bio_end_flush;
 		bio->bi_private = &completion;
 		bio->bi_bdev = dd->dm_dev.bdev;
 
Index: linux-2.6.29-rc3-devel/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.29-rc3-devel.orig/drivers/md/dm-raid1.c	2009-01-29 05:38:15.000000000 +0100
+++ linux-2.6.29-rc3-devel/drivers/md/dm-raid1.c	2009-01-29 04:03:00.000000000 +0100
@@ -819,7 +819,7 @@ static int get_mirror(struct mirror_set 
 	}
 
 	if (dm_get_device(ti, argv[0], offset, ti->len,
-			  dm_table_get_mode(ti->table),
+			  dm_table_get_mode(ti->table) | FMODE_DM_FLUSH_IGN_ERR,
 			  &ms->mirror[mirror].dev)) {
 		ti->error = "Device lookup failure";
 		return -ENXIO;