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    Subject[PATCH v1 02/15] md/raid5-cache: Refactor r5c_is_writeback() to take a struct r5conf
    Most calls to r5c_is_writeback() have to dereference conf to get the
    log. The log pointer should be protected by RCU, but isn't. Push
    the dereference of conf->log into r5c_is_writeback() to reduce
    the number of sites that dereference conf->log so this can be improved.

    No functional changes intended.

    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    ---
    drivers/md/raid5-cache.c | 25 ++++++++++++++-----------
    drivers/md/raid5-log.h | 2 +-
    drivers/md/raid5.c | 16 ++++++++--------
    3 files changed, 23 insertions(+), 20 deletions(-)

    diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
    index 83c184eddbda..241c271e836d 100644
    --- a/drivers/md/raid5-cache.c
    +++ b/drivers/md/raid5-cache.c
    @@ -247,10 +247,14 @@ enum r5l_io_unit_state {
    IO_UNIT_STRIPE_END = 3, /* stripes data finished writing to raid */
    };

    -bool r5c_is_writeback(struct r5l_log *log)
    +static bool __r5c_is_writeback(struct r5l_log *log)
    {
    - return (log != NULL &&
    - log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK);
    + return log && log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK;
    +}
    +
    +bool r5c_is_writeback(struct r5conf *conf)
    +{
    + return __r5c_is_writeback(conf->log);
    }

    static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc)
    @@ -328,7 +332,7 @@ void r5c_check_stripe_cache_usage(struct r5conf *conf)
    {
    int total_cached;

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

    total_cached = atomic_read(&conf->r5c_cached_partial_stripes) +
    @@ -353,7 +357,7 @@ void r5c_check_stripe_cache_usage(struct r5conf *conf)
    */
    void r5c_check_cached_full_stripe(struct r5conf *conf)
    {
    - if (!r5c_is_writeback(conf->log))
    + if (!r5c_is_writeback(conf))
    return;

    /*
    @@ -398,7 +402,7 @@ static sector_t r5c_log_required_to_flush_cache(struct r5conf *conf)
    {
    struct r5l_log *log = conf->log;

    - if (!r5c_is_writeback(log))
    + if (!r5c_is_writeback(conf))
    return 0;

    return BLOCK_SECTORS *
    @@ -420,7 +424,7 @@ static inline void r5c_update_log_state(struct r5l_log *log)
    sector_t reclaim_space;
    bool wake_reclaim = false;

    - if (!r5c_is_writeback(log))
    + if (!__r5c_is_writeback(log))
    return;

    free_space = r5l_ring_distance(log, log->log_start,
    @@ -449,9 +453,8 @@ 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;

    - BUG_ON(!r5c_is_writeback(log));
    + BUG_ON(!r5c_is_writeback(conf));

    WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state));
    clear_bit(STRIPE_R5C_CACHING, &sh->state);
    @@ -1429,7 +1432,7 @@ static void r5c_do_reclaim(struct r5conf *conf)
    int stripes_to_flush;
    int flushing_partial, flushing_full;

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

    flushing_partial = atomic_read(&conf->r5c_flushing_partial_stripes);
    @@ -2644,7 +2647,7 @@ int r5c_try_caching_write(struct r5conf *conf,
    int ret;
    uintptr_t refcount;

    - BUG_ON(!r5c_is_writeback(log));
    + BUG_ON(!__r5c_is_writeback(log));

    if (!test_bit(STRIPE_R5C_CACHING, &sh->state)) {
    /*
    diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h
    index 270ced4f770f..8a98b5e8c04b 100644
    --- a/drivers/md/raid5-log.h
    +++ b/drivers/md/raid5-log.h
    @@ -11,7 +11,7 @@ void r5l_stripe_write_finished(struct stripe_head *sh);
    int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio);
    void r5l_quiesce(struct r5l_log *log, int quiesce);
    bool r5l_log_disk_error(struct r5conf *conf);
    -bool r5c_is_writeback(struct r5l_log *log);
    +bool r5c_is_writeback(struct r5conf *conf);
    int r5c_try_caching_write(struct r5conf *conf, struct stripe_head *sh,
    struct stripe_head_state *s, int disks);
    void r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh,
    diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
    index 5d09256d7f81..bbc0e1101d0f 100644
    --- a/drivers/md/raid5.c
    +++ b/drivers/md/raid5.c
    @@ -224,7 +224,7 @@ static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
    BUG_ON(!list_empty(&sh->lru));
    BUG_ON(atomic_read(&conf->active_stripes)==0);

    - if (r5c_is_writeback(conf->log))
    + if (r5c_is_writeback(conf))
    for (i = sh->disks; i--; )
    if (test_bit(R5_InJournal, &sh->dev[i].flags))
    injournal++;
    @@ -236,7 +236,7 @@ static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
    * 2. when resync is requested fot the stripe.
    */
    if (test_bit(STRIPE_SYNC_REQUESTED, &sh->state) ||
    - (conf->quiesce && r5c_is_writeback(conf->log) &&
    + (conf->quiesce && r5c_is_writeback(conf) &&
    !test_bit(STRIPE_HANDLE, &sh->state) && injournal != 0)) {
    if (test_bit(STRIPE_R5C_CACHING, &sh->state))
    r5c_make_stripe_write_out(sh);
    @@ -274,7 +274,7 @@ static void do_release_stripe(struct r5conf *conf, struct stripe_head *sh,
    md_wakeup_thread(conf->mddev->thread);
    atomic_dec(&conf->active_stripes);
    if (!test_bit(STRIPE_EXPANDING, &sh->state)) {
    - if (!r5c_is_writeback(conf->log))
    + if (!r5c_is_writeback(conf))
    list_add_tail(&sh->lru, temp_inactive_list);
    else {
    WARN_ON(test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags));
    @@ -1786,7 +1786,7 @@ static void ops_complete_prexor(void *stripe_head_ref)
    pr_debug("%s: stripe %llu\n", __func__,
    (unsigned long long)sh->sector);

    - if (r5c_is_writeback(sh->raid_conf->log))
    + if (r5c_is_writeback(sh->raid_conf))
    /*
    * raid5-cache write back uses orig_page during prexor.
    * After prexor, it is time to free orig_page
    @@ -1905,9 +1905,9 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
    tx = async_copy_data(1, wbi, &dev->page,
    dev->offset,
    dev->sector, tx, sh,
    - r5c_is_writeback(conf->log));
    + r5c_is_writeback(conf));
    if (dev->page != dev->orig_page &&
    - !r5c_is_writeback(conf->log)) {
    + !r5c_is_writeback(conf)) {
    set_bit(R5_SkipCopy, &dev->flags);
    clear_bit(R5_UPTODATE, &dev->flags);
    clear_bit(R5_OVERWRITE, &dev->flags);
    @@ -5085,7 +5085,7 @@ static void handle_stripe(struct stripe_head *sh)
    */

    if (!sh->reconstruct_state && !sh->check_state && !sh->log_io) {
    - if (!r5c_is_writeback(conf->log)) {
    + if (!r5c_is_writeback(conf)) {
    if (s.to_write)
    handle_stripe_dirtying(conf, sh, &s, disks);
    } else { /* write back cache */
    @@ -5533,7 +5533,7 @@ static struct stripe_head *__get_priority_stripe(struct r5conf *conf, int group)
    struct stripe_head *sh, *tmp;
    struct list_head *handle_list = NULL;
    struct r5worker_group *wg;
    - bool second_try = !r5c_is_writeback(conf->log) &&
    + bool second_try = !r5c_is_writeback(conf) &&
    !r5l_log_disk_error(conf);
    bool try_loprio = test_bit(R5C_LOG_TIGHT, &conf->cache_state) ||
    r5l_log_disk_error(conf);
    --
    2.30.2
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