The raid5-cache write back mode as 2 states for each stripe: write state
and reclaim state. This patch adds bare state machine for these two
states.
2 flags are added to sh->state for raid5-cache states:
- STRIPE_R5C_FROZEN
- STRIPE_R5C_WRITTEN
STRIPE_R5C_FROZEN is the key flag to differentiate write state
and reclaim state.
STRIPE_R5C_WRITTEN is a helper flag to bring the stripe back from
reclaim state back to write state.
In write through mode, every stripe also goes between write state
and reclaim state (in r5c_handle_stripe_dirtying() and
r5c_handle_stripe_written()).
Please note: this is a "no-op" patch for raid5-cache write through
mode.
The following detailed explanation is copied from the raid5-cache.c:
/*
* raid5 cache state machine
*
* The RAID cache works in two major states for each stripe: write state
* and reclaim state. These states are controlled by flags STRIPE_R5C_FROZEN
* and STRIPE_R5C_WRITTEN
*
* STRIPE_R5C_FROZEN is the key flag to differentiate write state and reclaim
* state. The write state runs w/ STRIPE_R5C_FROZEN == 0. While the reclaim
* state runs w/ STRIPE_R5C_FROZEN == 1.
*
* STRIPE_R5C_WRITTEN is a helper flag to bring the stripe back from reclaim
* state to write state. Specifically, STRIPE_R5C_WRITTEN triggers clean up
* process in r5c_handle_stripe_written. STRIPE_R5C_WRITTEN is set when data
* and parity of a stripe is all in journal device; and cleared when the data
* and parity are all in RAID disks.
*
* The following is another way to show how STRIPE_R5C_FROZEN and
* STRIPE_R5C_WRITTEN work:
*
* write state: STRIPE_R5C_FROZEN = 0 STRIPE_R5C_WRITTEN = 0
* reclaim state: STRIPE_R5C_FROZEN = 1
*
* write => reclaim: set STRIPE_R5C_FROZEN in r5c_freeze_stripe_for_reclaim
* reclaim => write:
* 1. write parity to journal, when finished, set STRIPE_R5C_WRITTEN
* 2. write data/parity to raid disks, when finished, clear both
* STRIPE_R5C_FROZEN and STRIPE_R5C_WRITTEN
*
* In write through mode (journal only) the stripe still goes through these
* state change, except that STRIPE_R5C_FROZEN is set on write in
* r5c_handle_stripe_dirtying().
*/
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
drivers/md/raid5-cache.c | 125 +++++++++++++++++++++++++++++++++++++++++++++--
drivers/md/raid5.c | 20 ++++++--
drivers/md/raid5.h | 10 +++-
3 files changed, 148 insertions(+), 7 deletions(-)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 7557791b..9e05850 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -40,6 +40,47 @@
*/
#define R5L_POOL_SIZE 4
+enum r5c_state {
+ R5C_STATE_NO_CACHE = 0,
+ R5C_STATE_WRITE_THROUGH = 1,
+ R5C_STATE_WRITE_BACK = 2,
+ R5C_STATE_CACHE_BROKEN = 3,
+};
+
+/*
+ * raid5 cache state machine
+ *
+ * The RAID cache works in two major states for each stripe: write state and
+ * reclaim state. These states are controlled by flags STRIPE_R5C_FROZEN and
+ * STRIPE_R5C_WRITTEN
+ *
+ * STRIPE_R5C_FROZEN is the key flag to differentiate write state and reclaim
+ * state. The write state runs w/ STRIPE_R5C_FROZEN == 0. While the reclaim
+ * state runs w/ STRIPE_R5C_FROZEN == 1.
+ *
+ * STRIPE_R5C_WRITTEN is a helper flag to bring the stripe back from reclaim
+ * state to write state. Specifically, STRIPE_R5C_WRITTEN triggers clean up
+ * process in r5c_handle_stripe_written. STRIPE_R5C_WRITTEN is set when data
+ * and parity of a stripe is all in journal device; and cleared when the data
+ * and parity are all in RAID disks.
+ *
+ * The following is another way to show how STRIPE_R5C_FROZEN and
+ * STRIPE_R5C_WRITTEN work:
+ *
+ * write state: STRIPE_R5C_FROZEN = 0 STRIPE_R5C_WRITTEN = 0
+ * reclaim state: STRIPE_R5C_FROZEN = 1
+ *
+ * write => reclaim: set STRIPE_R5C_FROZEN in r5c_freeze_stripe_for_reclaim
+ * reclaim => write:
+ * 1. write parity to journal, when finished, set STRIPE_R5C_WRITTEN
+ * 2. write data/parity to raid disks, when finished, clear both
+ * STRIPE_R5C_FROZEN and STRIPE_R5C_WRITTEN
+ *
+ * In write through mode (journal only) the stripe also goes through these
+ * state change, except that STRIPE_R5C_FROZEN is set on write in
+ * r5c_handle_stripe_dirtying().
+ */
+
struct r5l_log {
struct md_rdev *rdev;
@@ -96,6 +137,9 @@ struct r5l_log {
spinlock_t no_space_stripes_lock;
bool need_cache_flush;
+
+ /* for r5c_cache */
+ enum r5c_state r5c_state;
};
/*
@@ -133,6 +177,11 @@ enum r5l_io_unit_state {
IO_UNIT_STRIPE_END = 3, /* stripes data finished writing to raid */
};
+bool r5c_is_writeback(struct r5l_log *log)
+{
+ return (log != NULL && log->r5c_state == R5C_STATE_WRITE_BACK);
+}
+
static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc)
{
start += inc;
@@ -168,12 +217,44 @@ static void __r5l_set_io_unit_state(struct r5l_io_unit *io,
io->state = state;
}
+/*
+ * Freeze the stripe, thus send the stripe into reclaim path.
+ *
+ * In current implementation, STRIPE_R5C_FROZEN is also set in write through
+ * mode (in r5c_handle_stripe_dirtying). This does not change the behavior of
+ * for write through mode.
+ */
+void r5c_freeze_stripe_for_reclaim(struct stripe_head *sh)
+{
+ struct r5conf *conf = sh->raid_conf;
+ struct r5l_log *log = conf->log;
+
+ if (!log)
+ return;
+ WARN_ON(test_bit(STRIPE_R5C_FROZEN, &sh->state));
+ set_bit(STRIPE_R5C_FROZEN, &sh->state);
+}
+
+static void r5c_finish_cache_stripe(struct stripe_head *sh)
+{
+ struct r5l_log *log = sh->raid_conf->log;
+
+ if (log->r5c_state == R5C_STATE_WRITE_THROUGH) {
+ BUG_ON(!test_bit(STRIPE_R5C_FROZEN, &sh->state));
+ set_bit(STRIPE_R5C_WRITTEN, &sh->state);
+ } else
+ BUG(); /* write back logic in next patch */
+}
+
static void r5l_io_run_stripes(struct r5l_io_unit *io)
{
struct stripe_head *sh, *next;
list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) {
list_del_init(&sh->log_list);
+
+ r5c_finish_cache_stripe(sh);
+
set_bit(STRIPE_HANDLE, &sh->state);
raid5_release_stripe(sh);
}
@@ -412,18 +493,19 @@ static int r5l_log_stripe(struct r5l_log *log, struct stripe_head *sh,
r5l_append_payload_page(log, sh->dev[i].page);
}
- if (sh->qd_idx >= 0) {
+ if (parity_pages == 2) {
r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
sh->sector, sh->dev[sh->pd_idx].log_checksum,
sh->dev[sh->qd_idx].log_checksum, true);
r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
r5l_append_payload_page(log, sh->dev[sh->qd_idx].page);
- } else {
+ } else if (parity_pages == 1) {
r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY,
sh->sector, sh->dev[sh->pd_idx].log_checksum,
0, false);
r5l_append_payload_page(log, sh->dev[sh->pd_idx].page);
- }
+ } else
+ BUG_ON(parity_pages != 0);
list_add_tail(&sh->log_list, &io->stripe_list);
atomic_inc(&io->pending_stripe);
@@ -455,6 +537,8 @@ int r5l_write_stripe(struct r5l_log *log, struct stripe_head *sh)
return -EAGAIN;
}
+ WARN_ON(!test_bit(STRIPE_R5C_FROZEN, &sh->state));
+
for (i = 0; i < sh->disks; i++) {
void *addr;
@@ -1101,6 +1185,39 @@ static void r5l_write_super(struct r5l_log *log, sector_t cp)
set_bit(MD_CHANGE_DEVS, &mddev->flags);
}
+int r5c_handle_stripe_dirtying(struct r5conf *conf,
+ struct stripe_head *sh,
+ struct stripe_head_state *s,
+ int disks)
+{
+ struct r5l_log *log = conf->log;
+
+ if (!log || test_bit(STRIPE_R5C_FROZEN, &sh->state))
+ return -EAGAIN;
+
+ if (conf->log->r5c_state == R5C_STATE_WRITE_THROUGH ||
+ conf->mddev->degraded != 0) {
+ /* write through mode */
+ r5c_freeze_stripe_for_reclaim(sh);
+ return -EAGAIN;
+ }
+ BUG(); /* write back logic in next commit */
+ return 0;
+}
+
+/*
+ * clean up the stripe (clear STRIPE_R5C_FROZEN etc.) after the stripe is
+ * committed to RAID disks
+*/
+void r5c_handle_stripe_written(struct r5conf *conf,
+ struct stripe_head *sh)
+{
+ if (!test_and_clear_bit(STRIPE_R5C_WRITTEN, &sh->state))
+ return;
+ WARN_ON(!test_bit(STRIPE_R5C_FROZEN, &sh->state));
+ clear_bit(STRIPE_R5C_FROZEN, &sh->state);
+}
+
static int r5l_load_log(struct r5l_log *log)
{
struct md_rdev *rdev = log->rdev;
@@ -1236,6 +1353,8 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
INIT_LIST_HEAD(&log->no_space_stripes);
spin_lock_init(&log->no_space_stripes_lock);
+ log->r5c_state = R5C_STATE_WRITE_THROUGH;
+
if (r5l_load_log(log))
goto error;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 67d4f49..2e3e61a 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3506,6 +3506,9 @@ static void handle_stripe_dirtying(struct r5conf *conf,
int rmw = 0, rcw = 0, i;
sector_t recovery_cp = conf->mddev->recovery_cp;
+ if (r5c_handle_stripe_dirtying(conf, sh, s, disks) == 0)
+ return;
+
/* Check whether resync is now happening or should start.
* If yes, then the array is dirty (after unclean shutdown or
* initial creation), so parity in some stripes might be inconsistent.
@@ -4396,13 +4399,23 @@ static void handle_stripe(struct stripe_head *sh)
|| s.expanding)
handle_stripe_fill(sh, &s, disks);
- /* Now to consider new write requests and what else, if anything
- * should be read. We do not handle new writes when:
+ /*
+ * When the stripe finishes full journal write cycle (write to journal
+ * and raid disk), this is the clean up procedure so it is ready for
+ * next operation.
+ */
+ r5c_handle_stripe_written(conf, sh);
+
+ /*
+ * Now to consider new write requests, cache write back and what else,
+ * if anything should be read. We do not handle new writes when:
* 1/ A 'write' operation (copy+xor) is already in flight.
* 2/ A 'check' operation is in flight, as it may clobber the parity
* block.
+ * 3/ A r5c cache log write is in flight.
*/
- if (s.to_write && !sh->reconstruct_state && !sh->check_state)
+ if ((s.to_write || test_bit(STRIPE_R5C_FROZEN, &sh->state)) &&
+ !sh->reconstruct_state && !sh->check_state && !sh->log_io)
handle_stripe_dirtying(conf, sh, &s, disks);
/* maybe we need to check and possibly fix the parity for this stripe
@@ -5122,6 +5135,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi)
* data on failed drives.
*/
if (rw == READ && mddev->degraded == 0 &&
+ !r5c_is_writeback(conf->log) &&
mddev->reshape_position == MaxSector) {
bi = chunk_aligned_read(mddev, bi);
if (!bi)
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 46cfe93..8bae64b 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -345,7 +345,9 @@ enum {
STRIPE_BITMAP_PENDING, /* Being added to bitmap, don't add
* to batch yet.
*/
- STRIPE_LOG_TRAPPED, /* trapped into log */
+ STRIPE_LOG_TRAPPED, /* trapped into log */
+ STRIPE_R5C_FROZEN, /* r5c_cache frozen and being written out */
+ STRIPE_R5C_WRITTEN, /* ready for r5c_handle_stripe_written() */
};
#define STRIPE_EXPAND_SYNC_FLAGS \
@@ -712,4 +714,10 @@ extern void r5l_stripe_write_finished(struct stripe_head *sh);
extern int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
extern void r5l_quiesce(struct r5l_log *log, int state);
extern bool r5l_log_disk_error(struct r5conf *conf);
+extern bool r5c_is_writeback(struct r5l_log *log);
+extern int
+r5c_handle_stripe_dirtying(struct r5conf *conf, struct stripe_head *sh,
+ struct stripe_head_state *s, int disks);
+extern void
+r5c_handle_stripe_written(struct r5conf *conf, struct stripe_head *sh);
#endif
--
2.9.3
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
