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md/r5cache: flush data only stripes in r5l_recovery_log() 

For safer operation, all arrays start in write-through mode, which has been
better tested and is more mature. And actually the write-through/write-mode
isn't persistent after array restarted, so we always start array in
write-through mode. However, if recovery found data-only stripes before the
shutdown (from previous write-back mode), it is not safe to start the array in
write-through mode, as write-through mode can not handle stripes with data in
write-back cache. To solve this problem, we flush all data-only stripes in
r5l_recovery_log(). When r5l_recovery_log() returns, the array starts with
empty cache in write-through mode.

This logic is implemented in r5c_recovery_flush_data_only_stripes():

1. enable write back cache
2. flush all stripes
3. wake up conf->mddev->thread
4. wait for all stripes get flushed (reuse wait_for_quiescent)
5. disable write back cache

The wait in 4 will be waked up in release_inactive_stripe_list()
when conf->active_stripes reaches 0.

It is safe to wake up mddev->thread here because all the resource
required for the thread has been initialized.

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
This commit is contained in:
Song Liu 2017-01-23 17:12:57 -08:00 committed by Shaohua Li
parent ba02684daf
commit a85dd7b8df
2 changed files with 45 additions and 16 deletions
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5
drivers/md/md.c
View File

@ -5291,6 +5291,11 @@ int md_run(struct mddev *mddev)
if (start_readonly && mddev->ro == 0)
mddev->ro = 2; /* read-only, but switch on first write */
/*
* NOTE: some pers->run(), for example r5l_recovery_log(), wakes
* up mddev->thread. It is important to initialize critical
* resources for mddev->thread BEFORE calling pers->run().
*/
err = pers->run(mddev);
if (err)
pr_warn("md: pers->run() failed ...\n");

56
drivers/md/raid5-cache.c
View File

@ -2060,7 +2060,7 @@ static int
r5c_recovery_rewrite_data_only_stripes(struct r5l_log *log,
struct r5l_recovery_ctx *ctx)
{
struct stripe_head *sh, *next;
struct stripe_head *sh;
struct mddev *mddev = log->rdev->mddev;
struct page *page;
sector_t next_checkpoint = MaxSector;
@ -2074,7 +2074,7 @@ r5c_recovery_rewrite_data_only_stripes(struct r5l_log *log,
WARN_ON(list_empty(&ctx->cached_list));
list_for_each_entry_safe(sh, next, &ctx->cached_list, lru) {
list_for_each_entry(sh, &ctx->cached_list, lru) {
struct r5l_meta_block *mb;
int i;
int offset;
@ -2124,14 +2124,39 @@ r5c_recovery_rewrite_data_only_stripes(struct r5l_log *log,
ctx->pos = write_pos;
ctx->seq += 1;
next_checkpoint = sh->log_start;
list_del_init(&sh->lru);
raid5_release_stripe(sh);
}
log->next_checkpoint = next_checkpoint;
__free_page(page);
return 0;
}
static void r5c_recovery_flush_data_only_stripes(struct r5l_log *log,
struct r5l_recovery_ctx *ctx)
{
struct mddev *mddev = log->rdev->mddev;
struct r5conf *conf = mddev->private;
struct stripe_head *sh, *next;
if (ctx->data_only_stripes == 0)
return;
log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_BACK;
list_for_each_entry_safe(sh, next, &ctx->cached_list, lru) {
r5c_make_stripe_write_out(sh);
set_bit(STRIPE_HANDLE, &sh->state);
list_del_init(&sh->lru);
raid5_release_stripe(sh);
}
md_wakeup_thread(conf->mddev->thread);
/* reuse conf->wait_for_quiescent in recovery */
wait_event(conf->wait_for_quiescent,
atomic_read(&conf->active_stripes) == 0);
log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH;
}
static int r5l_recovery_log(struct r5l_log *log)
{
struct mddev *mddev = log->rdev->mddev;
@ -2158,32 +2183,31 @@ static int r5l_recovery_log(struct r5l_log *log)
pos = ctx.pos;
ctx.seq += 10000;
if (ctx.data_only_stripes == 0) {
log->next_checkpoint = ctx.pos;
r5l_log_write_empty_meta_block(log, ctx.pos, ctx.seq++);
ctx.pos = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
}
if ((ctx.data_only_stripes == 0) && (ctx.data_parity_stripes == 0))
pr_debug("md/raid:%s: starting from clean shutdown\n",
mdname(mddev));
else {
else
pr_debug("md/raid:%s: recovering %d data-only stripes and %d data-parity stripes\n",
mdname(mddev), ctx.data_only_stripes,
ctx.data_parity_stripes);
if (ctx.data_only_stripes > 0)
if (r5c_recovery_rewrite_data_only_stripes(log, &ctx)) {
pr_err("md/raid:%s: failed to rewrite stripes to journal\n",
mdname(mddev));
return -EIO;
}
if (ctx.data_only_stripes == 0) {
log->next_checkpoint = ctx.pos;
r5l_log_write_empty_meta_block(log, ctx.pos, ctx.seq++);
ctx.pos = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
} else if (r5c_recovery_rewrite_data_only_stripes(log, &ctx)) {
pr_err("md/raid:%s: failed to rewrite stripes to journal\n",
mdname(mddev));
return -EIO;
}
log->log_start = ctx.pos;
log->seq = ctx.seq;
log->last_checkpoint = pos;
r5l_write_super(log, pos);
r5c_recovery_flush_data_only_stripes(log, &ctx);
return 0;
}