raid5-ppl: use resize_stripes() when enabling or disabling ppl

Use resize_stripes() instead of raid5_reset_stripe_cache() to allocate
or free sh->ppl_page at runtime for all stripes in the stripe cache.
raid5_reset_stripe_cache() required suspending the mddev and could
deadlock because of GFP_KERNEL allocations.

Move the 'newsize' check to check_reshape() to allow reallocating the
stripes with the same number of disks. Allocate sh->ppl_page in
alloc_stripe() instead of grow_buffers(). Pass 'struct r5conf *conf' as
a parameter to alloc_stripe() because it is needed to check whether to
allocate ppl_page. Add free_stripe() and use it to free stripes rather
than directly call kmem_cache_free(). Also free sh->ppl_page in
free_stripe().

Set MD_HAS_PPL at the end of ppl_init_log() instead of explicitly
setting it in advance and add another parameter to log_init() to allow
calling ppl_init_log() without the bit set. Don't try to calculate
partial parity or add a stripe to log if it does not have ppl_page set.

Enabling ppl can now be performed without suspending the mddev, because
the log won't be used until new stripes are allocated with ppl_page.
Calling mddev_suspend/resume is still necessary when disabling ppl,
because we want all stripes to finish before stopping the log, but
resize_stripes() can be called after mddev_resume() when ppl is no
longer active.

Suggested-by: NeilBrown <neilb@suse.com>
Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/md/raid5-log.h b/drivers/md/raid5-log.h
index 738930ff5d17..27097101ccca 100644
--- a/drivers/md/raid5-log.h
+++ b/drivers/md/raid5-log.h
@@ -93,11 +93,12 @@ static inline void log_exit(struct r5conf *conf)
 		ppl_exit_log(conf);
 }
 
-static inline int log_init(struct r5conf *conf, struct md_rdev *journal_dev)
+static inline int log_init(struct r5conf *conf, struct md_rdev *journal_dev,
+			   bool ppl)
 {
 	if (journal_dev)
 		return r5l_init_log(conf, journal_dev);
-	else if (raid5_has_ppl(conf))
+	else if (ppl)
 		return ppl_init_log(conf);
 
 	return 0;