[PATCH -next v2 10/28] md/raid5-cache: use READ_ONCE/WRITE_ONCE for 'conf->log'

From: Yu Kuai
Date: Sun Aug 27 2023 - 22:06:37 EST

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From: Yu Kuai <yukuai3@xxxxxxxxxx>

'conf->log' is set with 'reconfig_mutex' grabbed, however, readers are
not procted, hence use READ_ONCE/WRITE_ONCE to prevent reading abnormal
value.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/md/raid5-cache.c | 47 +++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 22 deletions(-)

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 518b7cfa78b9..889bba60d6ff 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -327,8 +327,9 @@ void r5l_wake_reclaim(struct r5l_log *log, sector_t space);
void r5c_check_stripe_cache_usage(struct r5conf *conf)
{
int total_cached;
+ struct r5l_log *log = READ_ONCE(conf->log);

- if (!r5c_is_writeback(conf->log))
+ if (!r5c_is_writeback(log))
return;

total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +
@@ -344,7 +345,7 @@ void r5c_check_stripe_cache_usage(struct r5conf *conf)
*/
if (total_cached > conf->min_nr_stripes * 1 / 2 ||
atomic_read(&conf->empty_inactive_list_nr) > 0)
- r5l_wake_reclaim(conf->log, 0);
+ r5l_wake_reclaim(log, 0);
}

/*
@@ -353,7 +354,9 @@ void r5c_check_stripe_cache_usage(struct r5conf *conf)
*/
void r5c_check_cached_full_stripe(struct r5conf *conf)
{
- if (!r5c_is_writeback(conf->log))
+ struct r5l_log *log = READ_ONCE(conf->log);
+
+ if (!r5c_is_writeback(log))
return;

/*
@@ -363,7 +366,7 @@ void r5c_check_cached_full_stripe(struct r5conf *conf)
if (atomic_read(&conf->r5c_cached_full_stripes) >=
min(R5C_FULL_STRIPE_FLUSH_BATCH(conf),
conf->chunk_sectors >> RAID5_STRIPE_SHIFT(conf)))
- r5l_wake_reclaim(conf->log, 0);
+ r5l_wake_reclaim(log, 0);
}

/*
@@ -396,7 +399,7 @@ void r5c_check_cached_full_stripe(struct r5conf *conf)
*/
static sector_t r5c_log_required_to_flush_cache(struct r5conf *conf)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);

if (!r5c_is_writeback(log))
return 0;
@@ -449,7 +452,7 @@ static inline void r5c_update_log_state(struct r5l_log *log)
void r5c_make_stripe_write_out(struct stripe_head *sh)
{
struct r5conf *conf = sh->raid_conf;
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);

BUG_ON(!r5c_is_writeback(log));

@@ -491,7 +494,7 @@ static void r5c_handle_parity_cached(struct stripe_head *sh)
*/
static void r5c_finish_cache_stripe(struct stripe_head *sh)
{
- struct r5l_log *log = sh->raid_conf->log;
+ struct r5l_log *log = READ_ONCE(sh->raid_conf->log);

if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) {
BUG_ON(test_bit(STRIPE_R5C_CACHING, &sh->state));
@@ -692,7 +695,7 @@ static void r5c_disable_writeback_async(struct work_struct *work)

/* wait superblock change before suspend */
wait_event(mddev->sb_wait,
- conf->log == NULL ||
+ !READ_ONCE(conf->log) ||
(!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags) &&
(locked = mddev_trylock(mddev))));
if (locked) {
@@ -1151,7 +1154,7 @@ static void r5l_run_no_space_stripes(struct r5l_log *log)
static sector_t r5c_calculate_new_cp(struct r5conf *conf)
{
struct stripe_head *sh;
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);
sector_t new_cp;
unsigned long flags;

@@ -1159,12 +1162,12 @@ static sector_t r5c_calculate_new_cp(struct r5conf *conf)
return log->next_checkpoint;

spin_lock_irqsave(&log->stripe_in_journal_lock, flags);
- if (list_empty(&conf->log->stripe_in_journal_list)) {
+ if (list_empty(&log->stripe_in_journal_list)) {
/* all stripes flushed */
spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
return log->next_checkpoint;
}
- sh = list_first_entry(&conf->log->stripe_in_journal_list,
+ sh = list_first_entry(&log->stripe_in_journal_list,
struct stripe_head, r5c);
new_cp = sh->log_start;
spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
@@ -1399,7 +1402,7 @@ void r5c_flush_cache(struct r5conf *conf, int num)
struct stripe_head *sh, *next;

lockdep_assert_held(&conf->device_lock);
- if (!conf->log)
+ if (!READ_ONCE(conf->log))
return;

count = 0;
@@ -1420,7 +1423,7 @@ void r5c_flush_cache(struct r5conf *conf, int num)

static void r5c_do_reclaim(struct r5conf *conf)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);
struct stripe_head *sh;
int count = 0;
unsigned long flags;
@@ -1549,7 +1552,7 @@ static void r5l_reclaim_thread(struct md_thread *thread)
{
struct mddev *mddev = thread->mddev;
struct r5conf *conf = mddev->private;
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);

if (!log)
return;
@@ -1591,7 +1594,7 @@ void r5l_quiesce(struct r5l_log *log, int quiesce)

bool r5l_log_disk_error(struct r5conf *conf)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);

/* don't allow write if journal disk is missing */
if (!log)
@@ -2635,7 +2638,7 @@ int r5c_try_caching_write(struct r5conf *conf,
struct stripe_head_state *s,
int disks)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);
int i;
struct r5dev *dev;
int to_cache = 0;
@@ -2802,7 +2805,7 @@ void r5c_finish_stripe_write_out(struct r5conf *conf,
struct stripe_head *sh,
struct stripe_head_state *s)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);
int i;
int do_wakeup = 0;
sector_t tree_index;
@@ -2941,7 +2944,7 @@ int r5c_cache_data(struct r5l_log *log, struct stripe_head *sh)
/* check whether this big stripe is in write back cache. */
bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
{
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);
sector_t tree_index;
void *slot;

@@ -3049,14 +3052,14 @@ int r5l_start(struct r5l_log *log)
void r5c_update_on_rdev_error(struct mddev *mddev, struct md_rdev *rdev)
{
struct r5conf *conf = mddev->private;
- struct r5l_log *log = conf->log;
+ struct r5l_log *log = READ_ONCE(conf->log);

if (!log)
return;

if ((raid5_calc_degraded(conf) > 0 ||
test_bit(Journal, &rdev->flags)) &&
- conf->log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK)
+ log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK)
schedule_work(&log->disable_writeback_work);
}

@@ -3145,7 +3148,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev)
spin_lock_init(&log->stripe_in_journal_lock);
atomic_set(&log->stripe_in_journal_count, 0);

- conf->log = log;
+ WRITE_ONCE(conf->log, log);

set_bit(MD_HAS_JOURNAL, &conf->mddev->flags);
return 0;
@@ -3173,7 +3176,7 @@ void r5l_exit_log(struct r5conf *conf)
* 'reconfig_mutex' is held by caller, set 'confg->log' to NULL to
* ensure disable_writeback_work wakes up and exits.
*/
- conf->log = NULL;
+ WRITE_ONCE(conf->log, NULL);
wake_up(&conf->mddev->sb_wait);
flush_work(&log->disable_writeback_work);

--
2.39.2

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