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resize_stripes() can be called after mddev_resume() when ppl is no
longer active.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, 2 insertions, 1 deletions

diff --git a/drivers/md/raid5-ppl.c b/drivers/md/raid5-ppl.c
index 355cf3581ef8..71968cf47d7d 100644
--- a/drivers/md/raid5-ppl.c
+++ b/drivers/md/raid5-ppl.c
@@ -328,7 +328,7 @@ int ppl_write_stripe(struct r5conf *conf, struct stripe_head *sh)
 	struct ppl_io_unit *io = sh->ppl_io;
 	struct ppl_log *log;
 
-	if (io || test_bit(STRIPE_SYNCING, &sh->state) ||
+	if (io || test_bit(STRIPE_SYNCING, &sh->state) || !sh->ppl_page ||
 	    !test_bit(R5_Wantwrite, &sh->dev[sh->pd_idx].flags) ||
 	    !test_bit(R5_Insync, &sh->dev[sh->pd_idx].flags)) {
 		clear_bit(STRIPE_LOG_TRAPPED, &sh->state);
@@ -1204,6 +1204,7 @@ int ppl_init_log(struct r5conf *conf)
 	}
 
 	conf->log_private = ppl_conf;
+	set_bit(MD_HAS_PPL, &ppl_conf->mddev->flags);
 
 	return 0;
 err: