Shaohua Li <shli@xxxxxx> writes:
> Since superblock is updated infrequently, we do a simple trim of log
> disk (a synchronous trim)
>
> Signed-off-by: Shaohua Li <shli@xxxxxx>
> ---
> drivers/md/raid5-cache.c | 38 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 93097a8..6c52168 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -654,6 +654,42 @@ static void r5l_kick_io_unit(struct r5l_log *log)
> }
>
> static void r5l_write_super(struct r5l_log *log, sector_t cp);
> +static void r5l_write_super_and_discard_space(struct r5l_log *log,
> + sector_t end)
> +{
> + struct block_device *bdev = log->rdev->bdev;
> + struct mddev *mddev;
> +
> + r5l_write_super(log, end);
> +
> + if (!blk_queue_discard(bdev_get_queue(bdev)))
> + return;
> +
> + mddev = log->rdev->mddev;
> + if (!mddev_is_locked(mddev)) {
> + set_bit(MD_CHANGE_PENDING, &mddev->flags);
> + md_wakeup_thread(mddev->thread);
> + wait_event(mddev->sb_wait,
> + !test_bit(MD_CHANGE_PENDING, &mddev->flags));
> + } else { /* we are stopping the array, already take reconfig_mutex */
> + md_update_sb(mddev, 1);
> + }
No.
Just because mddev is locked, that doesn't mean that this thread owns
the lock. Some other thread might just happen to have it locked for a
moment, and may unlock it long before we get to md_update_sb().
If you cannot block here, then you need to find a way to schedule the
discard after the md_update_sb() has happened.
Maybe set some flag, and in raid5d(), after md_check_recovery(), see if
the superblock has been written and if the discard is still pending, and
then do the discard. Maybe.
Or pass a flag into r5l_do_reclaim() to say whether this thread holds
the lock or not.
NeilBrown
> +
> + if (log->last_checkpoint < end) {
> + blkdev_issue_discard(bdev,
> + log->last_checkpoint + log->rdev->data_offset,
> + end - log->last_checkpoint, GFP_NOIO, 0);
> + } else {
> + blkdev_issue_discard(bdev,
> + log->last_checkpoint + log->rdev->data_offset,
> + log->device_size - log->last_checkpoint,
> + GFP_NOIO, 0);
> + blkdev_issue_discard(bdev, log->rdev->data_offset, end,
> + GFP_NOIO, 0);
> + }
> +}
> +
> +
> static void r5l_do_reclaim(struct r5l_log *log)
> {
> struct r5l_io_unit *io, *last;
> @@ -709,7 +745,7 @@ static void r5l_do_reclaim(struct r5l_log *log)
> * here, because the log area might be reused soon and we don't want to
> * confuse recovery
> */
> - r5l_write_super(log, last->log_start);
> + r5l_write_super_and_discard_space(log, last->log_start);
>
> mutex_lock(&log->io_mutex);
> log->last_checkpoint = last->log_start;
> --
> 2.4.6
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