*/
#define R5L_POOL_SIZE 4
+/*
+ * r5c journal modes of the array: write-back or write-through.
+ * write-through mode has identical behavior as existing log only
+ * implementation.
+ */
+enum r5c_journal_mode {
+ R5C_JOURNAL_MODE_WRITE_THROUGH = 0,
+ R5C_JOURNAL_MODE_WRITE_BACK = 1,
+};
+
+/*
+ * raid5 cache state machine
+ *
+ * With rhe RAID cache, each stripe works in two phases:
+ * - caching phase
+ * - writing-out phase
+ *
+ * These two phases are controlled by bit STRIPE_R5C_CACHING:
+ * if STRIPE_R5C_CACHING == 0, the stripe is in writing-out phase
+ * if STRIPE_R5C_CACHING == 1, the stripe is in caching phase
+ *
+ * When there is no journal, or the journal is in write-through mode,
+ * the stripe is always in writing-out phase.
+ *
+ * For write-back journal, the stripe is sent to caching phase on write
+ * (r5c_try_caching_write). r5c_make_stripe_write_out() kicks off
+ * the write-out phase by clearing STRIPE_R5C_CACHING.
+ *
+ * Stripes in caching phase do not write the raid disks. Instead, all
+ * writes are committed from the log device. Therefore, a stripe in
+ * caching phase handles writes as:
+ * - write to log device
+ * - return IO
+ *
+ * Stripes in writing-out phase handle writes as:
+ * - calculate parity
+ * - write pending data and parity to journal
+ * - write data and parity to raid disks
+ * - return IO for pending writes
+ */
+
struct r5l_log {
struct md_rdev *rdev;
spinlock_t no_space_stripes_lock;
bool need_cache_flush;
+
+ /* for r5c_cache */
+ enum r5c_journal_mode r5c_journal_mode;
};
/*
IO_UNIT_STRIPE_END = 3, /* stripes data finished writing to raid */
};
+bool r5c_is_writeback(struct r5l_log *log)
+{
+ return (log != NULL &&
+ log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK);
+}
+
static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc)
{
start += inc;
io->state = state;
}
+/*
+ * Put the stripe into writing-out phase by clearing STRIPE_R5C_CACHING.
+ * This function should only be called in write-back mode.
+ */
+static void r5c_make_stripe_write_out(struct stripe_head *sh)
+{
+ struct r5conf *conf = sh->raid_conf;
+ struct r5l_log *log = conf->log;
+
+ BUG_ON(!r5c_is_writeback(log));
+
+ WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
+ clear_bit(STRIPE_R5C_CACHING, &sh->state);
+}
+
+/*
+ * Setting proper flags after writing (or flushing) data and/or parity to the
+ * log device. This is called from r5l_log_endio() or r5l_log_flush_endio().
+ */
+static void r5c_finish_cache_stripe(struct stripe_head *sh)
+{
+ struct r5l_log *log = sh->raid_conf->log;
+
+ if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) {
+ BUG_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
+ /*
+ * Set R5_InJournal for parity dev[pd_idx]. This means
+ * all data AND parity in the journal. For RAID 6, it is
+ * NOT necessary to set the flag for dev[qd_idx], as the
+ * two parities are written out together.
+ */
+ set_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags);
+ } 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);
}
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 /* Just writing data, not parity, in caching phase */
+ BUG_ON(parity_pages != 0);
list_add_tail(&sh->log_list, &io->stripe_list);
atomic_inc(&io->pending_stripe);
return -EAGAIN;
}
+ WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
+
for (i = 0; i < sh->disks; i++) {
void *addr;
set_bit(MD_CHANGE_DEVS, &mddev->flags);
}
+/*
+ * Try handle write operation in caching phase. This function should only
+ * be called in write-back mode.
+ *
+ * If all outstanding writes can be handled in caching phase, returns 0
+ * If writes requires write-out phase, call r5c_make_stripe_write_out()
+ * and returns -EAGAIN
+ */
+int r5c_try_caching_write(struct r5conf *conf,
+ struct stripe_head *sh,
+ struct stripe_head_state *s,
+ int disks)
+{
+ struct r5l_log *log = conf->log;
+
+ BUG_ON(!r5c_is_writeback(log));
+
+ /* more write-back logic in next patches */
+ r5c_make_stripe_write_out(sh);
+ return -EAGAIN;
+}
+
+/*
+ * clean up the stripe (clear R5_InJournal for dev[pd_idx] etc.) after the
+ * stripe is committed to RAID disks.
+ */
+void r5c_finish_stripe_write_out(struct r5conf *conf,
+ struct stripe_head *sh,
+ struct stripe_head_state *s)
+{
+ if (!conf->log ||
+ !test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags))
+ return;
+
+ WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
+ clear_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags);
+
+ if (conf->log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH)
+ return;
+ BUG(); /* write-back logic in following patches */
+}
+
+
static int r5l_load_log(struct r5l_log *log)
{
struct md_rdev *rdev = log->rdev;
INIT_LIST_HEAD(&log->no_space_stripes);
spin_lock_init(&log->no_space_stripes_lock);
+ log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;
+
if (r5l_load_log(log))
goto error;
if (rdev && !test_bit(Faulty, &rdev->flags))
do_recovery = 1;
}
+
+ if (test_bit(R5_InJournal, &dev->flags))
+ s->injournal++;
}
if (test_bit(STRIPE_SYNCING, &sh->state)) {
/* If there is a failed device being replaced,
|| 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_finish_stripe_write_out(conf, sh, &s);
+
+ /*
+ * 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)
- handle_stripe_dirtying(conf, sh, &s, disks);
+
+ if (!sh->reconstruct_state && !sh->check_state && !sh->log_io) {
+ if (!r5c_is_writeback(conf->log)) {
+ if (s.to_write)
+ handle_stripe_dirtying(conf, sh, &s, disks);
+ } else { /* write back cache */
+ int ret = 0;
+
+ /* First, try handle writes in caching phase */
+ if (s.to_write)
+ ret = r5c_try_caching_write(conf, sh, &s,
+ disks);
+ /*
+ * If caching phase failed: ret == -EAGAIN
+ * OR
+ * stripe under reclaim: !caching && injournal
+ *
+ * fall back to handle_stripe_dirtying()
+ */
+ if (ret == -EAGAIN ||
+ /* stripe under reclaim: !caching && injournal */
+ (!test_bit(STRIPE_R5C_CACHING, &sh->state) &&
+ s.injournal > 0))
+ handle_stripe_dirtying(conf, sh, &s, disks);
+ }
+ }
/* maybe we need to check and possibly fix the parity for this stripe
* Any reads will already have been scheduled, so we just see if enough
* 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)
int syncing, expanding, expanded, replacing;
int locked, uptodate, to_read, to_write, failed, written;
int to_fill, compute, req_compute, non_overwrite;
+ int injournal;
int failed_num[2];
int p_failed, q_failed;
int dec_preread_active;
*/
R5_Discard, /* Discard the stripe */
R5_SkipCopy, /* Don't copy data from bio to stripe cache */
+ R5_InJournal, /* data being written is in the journal device.
+ * if R5_InJournal is set for parity pd_idx, all the
+ * data and parity being written are in the journal
+ * device
+ */
};
/*
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 (see raid5-cache.c)
+ * this bit is used in two scenarios:
+ *
+ * 1. write-out phase
+ * set in first entry of r5l_write_stripe
+ * clear in second entry of r5l_write_stripe
+ * used to bypass logic in handle_stripe
+ *
+ * 2. caching phase
+ * set in r5c_try_caching_write()
+ * clear when journal write is done
+ * used to initiate r5c_cache_data()
+ * also used to bypass logic in handle_stripe
+ */
+ STRIPE_R5C_CACHING, /* the stripe is in caching phase
+ * see more detail in the raid5-cache.c
+ */
};
#define STRIPE_EXPAND_SYNC_FLAGS \
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_try_caching_write(struct r5conf *conf, struct stripe_head *sh,
+ struct stripe_head_state *s, int disks);
+extern void
+r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh,
+ struct stripe_head_state *s);
#endif
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