From b5e8ad92c3ac0b073bbf08ffd1a6a31d3449caae Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Tue, 15 Aug 2017 17:11:59 +0200
Subject: [PATCH] dm integrity: use init_completion instead of
 COMPLETION_INITIALIZER_ONSTACK
Git-commit: b5e8ad92c3ac0b073bbf08ffd1a6a31d3449caae
Patch-mainline: v4.14-rc1
References: bsc#1093023

The new lockdep support for completions causeed the stack usage
in dm-integrity to explode, in case of write_journal from 504 bytes
to 1120 (using arm gcc-7.1.1):

Drivers/md/dm-integrity.c: In function 'write_journal':
drivers/md/dm-integrity.c:827:1: error: the frame size of 1120 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

The problem is that not only the size of 'struct completion' grows
significantly, but we end up having multiple copies of it on the stack
when we assign it from a local variable after the initial declaration.

COMPLETION_INITIALIZER_ONSTACK() is the right thing to use when we
want to declare and initialize a completion on the stack. However,
this driver doesn't do that and instead initializes the completion
just before it is used.

In this case, init_completion() does the same thing more efficiently,
and drops the stack usage for the function above down to 496 bytes.
While the other functions in this file are not bad enough to cause
a warning, they benefit equally from the change, so I do the change
across the entire file. In the one place where we reuse a completion,
I picked the cheaper reinit_completion() over init_completion().

Fixes: cd8084f91c02 ("locking/lockdep: Apply crossrelease to completions")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Acked-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-integrity.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 2b32342da556..ac0d7759594b 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -773,13 +773,13 @@ static void write_journal(struct dm_integrity_c *ic, unsigned commit_start, unsi
 	unsigned i;
 
 	io_comp.ic = ic;
-	io_comp.comp = COMPLETION_INITIALIZER_ONSTACK(io_comp.comp);
+	init_completion(&io_comp.comp);
 
 	if (commit_start + commit_sections <= ic->journal_sections) {
 		io_comp.in_flight = (atomic_t)ATOMIC_INIT(1);
 		if (ic->journal_io) {
 			crypt_comp_1.ic = ic;
-			crypt_comp_1.comp = COMPLETION_INITIALIZER_ONSTACK(crypt_comp_1.comp);
+			init_completion(&crypt_comp_1.comp);
 			crypt_comp_1.in_flight = (atomic_t)ATOMIC_INIT(0);
 			encrypt_journal(ic, true, commit_start, commit_sections, &crypt_comp_1);
 			wait_for_completion_io(&crypt_comp_1.comp);
@@ -795,18 +795,18 @@ static void write_journal(struct dm_integrity_c *ic, unsigned commit_start, unsi
 		to_end = ic->journal_sections - commit_start;
 		if (ic->journal_io) {
 			crypt_comp_1.ic = ic;
-			crypt_comp_1.comp = COMPLETION_INITIALIZER_ONSTACK(crypt_comp_1.comp);
+			init_completion(&crypt_comp_1.comp);
 			crypt_comp_1.in_flight = (atomic_t)ATOMIC_INIT(0);
 			encrypt_journal(ic, true, commit_start, to_end, &crypt_comp_1);
 			if (try_wait_for_completion(&crypt_comp_1.comp)) {
 				rw_journal(ic, REQ_OP_WRITE, REQ_FUA, commit_start, to_end, &io_comp);
-				crypt_comp_1.comp = COMPLETION_INITIALIZER_ONSTACK(crypt_comp_1.comp);
+				reinit_completion(&crypt_comp_1.comp);
 				crypt_comp_1.in_flight = (atomic_t)ATOMIC_INIT(0);
 				encrypt_journal(ic, true, 0, commit_sections - to_end, &crypt_comp_1);
 				wait_for_completion_io(&crypt_comp_1.comp);
 			} else {
 				crypt_comp_2.ic = ic;
-				crypt_comp_2.comp = COMPLETION_INITIALIZER_ONSTACK(crypt_comp_2.comp);
+				init_completion(&crypt_comp_2.comp);
 				crypt_comp_2.in_flight = (atomic_t)ATOMIC_INIT(0);
 				encrypt_journal(ic, true, 0, commit_sections - to_end, &crypt_comp_2);
 				wait_for_completion_io(&crypt_comp_1.comp);
@@ -1679,7 +1679,7 @@ static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map
 	dio->in_flight = (atomic_t)ATOMIC_INIT(2);
 
 	if (need_sync_io) {
-		read_comp = COMPLETION_INITIALIZER_ONSTACK(read_comp);
+		init_completion(&read_comp);
 		dio->completion = &read_comp;
 	} else
 		dio->completion = NULL;
@@ -1840,7 +1840,7 @@ static void do_journal_write(struct dm_integrity_c *ic, unsigned write_start,
 
 	comp.ic = ic;
 	comp.in_flight = (atomic_t)ATOMIC_INIT(1);
-	comp.comp = COMPLETION_INITIALIZER_ONSTACK(comp.comp);
+	init_completion(&comp.comp);
 
 	i = write_start;
 	for (n = 0; n < write_sections; n++, i++, wraparound_section(ic, &i)) {
@@ -2067,7 +2067,7 @@ static void replay_journal(struct dm_integrity_c *ic)
 		if (ic->journal_io) {
 			struct journal_completion crypt_comp;
 			crypt_comp.ic = ic;
-			crypt_comp.comp = COMPLETION_INITIALIZER_ONSTACK(crypt_comp.comp);
+			init_completion(&crypt_comp.comp);
 			crypt_comp.in_flight = (atomic_t)ATOMIC_INIT(0);
 			encrypt_journal(ic, false, 0, ic->journal_sections, &crypt_comp);
 			wait_for_completion(&crypt_comp.comp);
@@ -2640,7 +2640,7 @@ static int create_journal(struct dm_integrity_c *ic, char **error)
 			memset(iv, 0x00, ivsize);
 
 			skcipher_request_set_crypt(req, sg, sg, PAGE_SIZE * ic->journal_pages + sizeof ic->commit_ids, iv);
-			comp.comp = COMPLETION_INITIALIZER_ONSTACK(comp.comp);
+			init_completion(&comp.comp);
 			comp.in_flight = (atomic_t)ATOMIC_INIT(1);
 			if (do_crypt(true, req, &comp))
 				wait_for_completion(&comp.comp);
@@ -2697,7 +2697,7 @@ static int create_journal(struct dm_integrity_c *ic, char **error)
 
 				sg_init_one(&sg, crypt_data, crypt_len);
 				skcipher_request_set_crypt(req, &sg, &sg, crypt_len, iv);
-				comp.comp = COMPLETION_INITIALIZER_ONSTACK(comp.comp);
+				init_completion(&comp.comp);
 				comp.in_flight = (atomic_t)ATOMIC_INIT(1);
 				if (do_crypt(true, req, &comp))
 					wait_for_completion(&comp.comp);
-- 
2.16.3