[PATCH 4.14 01/20] btrfs: raid56: simplify tracking of Q stripe presence

gregkh
2021-03-10T13:28:20Z

From: David Sterba <dsterba@suse.com>

commit c17af96554a8a8777cbb0fd53b8497250e548b43 upstream.

There are temporary variables tracking the index of P and Q stripes, but
none of them is really used as such, merely for determining if the Q
stripe is present. This leads to compiler warnings with
-Wunused-but-set-variable and has been reported several times.

fs/btrfs/raid56.c: In function ‘finish_rmw’:
fs/btrfs/raid56.c:1199:6: warning: variable ‘p_stripe’ set but not used [-Wunused-but-set-variable]
1199 | int p_stripe = -1;
| ^~~~~~~~
fs/btrfs/raid56.c: In function ‘finish_parity_scrub’:
fs/btrfs/raid56.c:2356:6: warning: variable ‘p_stripe’ set but not used [-Wunused-but-set-variable]
2356 | int p_stripe = -1;
| ^~~~~~~~

Replace the two variables with one that has a clear meaning and also get
rid of the warnings. The logic that verifies that there are only 2
valid cases is unchanged.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/raid56.c | 37 +++++++++++++++----------------------
1 file changed, 15 insertions(+), 22 deletions(-)

--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1190,22 +1190,19 @@ static noinline void finish_rmw(struct b
int nr_data = rbio->nr_data;
int stripe;
int pagenr;
- int p_stripe = -1;
- int q_stripe = -1;
+ bool has_qstripe;
struct bio_list bio_list;
struct bio *bio;
int ret;

bio_list_init(&bio_list);

- if (rbio->real_stripes - rbio->nr_data == 1) {
- p_stripe = rbio->real_stripes - 1;
- } else if (rbio->real_stripes - rbio->nr_data == 2) {
- p_stripe = rbio->real_stripes - 2;
- q_stripe = rbio->real_stripes - 1;
- } else {
+ if (rbio->real_stripes - rbio->nr_data == 1)
+ has_qstripe = false;
+ else if (rbio->real_stripes - rbio->nr_data == 2)
+ has_qstripe = true;
+ else
BUG();
- }

/* at this point we either have a full stripe,
* or we've read the full stripe from the drive.
@@ -1249,7 +1246,7 @@ static noinline void finish_rmw(struct b
SetPageUptodate(p);
pointers[stripe++] = kmap(p);

- if (q_stripe != -1) {
+ if (has_qstripe) {

/*
* raid6, add the qstripe and call the
@@ -2325,8 +2322,7 @@ static noinline void finish_parity_scrub
int nr_data = rbio->nr_data;
int stripe;
int pagenr;
- int p_stripe = -1;
- int q_stripe = -1;
+ bool has_qstripe;
struct page *p_page = NULL;
struct page *q_page = NULL;
struct bio_list bio_list;
@@ -2336,14 +2332,12 @@ static noinline void finish_parity_scrub

bio_list_init(&bio_list);

- if (rbio->real_stripes - rbio->nr_data == 1) {
- p_stripe = rbio->real_stripes - 1;
- } else if (rbio->real_stripes - rbio->nr_data == 2) {
- p_stripe = rbio->real_stripes - 2;
- q_stripe = rbio->real_stripes - 1;
- } else {
+ if (rbio->real_stripes - rbio->nr_data == 1)
+ has_qstripe = false;
+ else if (rbio->real_stripes - rbio->nr_data == 2)
+ has_qstripe = true;
+ else
BUG();
- }

if (bbio->num_tgtdevs && bbio->tgtdev_map[rbio->scrubp]) {
is_replace = 1;
@@ -2365,7 +2359,7 @@ static noinline void finish_parity_scrub
goto cleanup;
SetPageUptodate(p_page);

- if (q_stripe != -1) {
+ if (has_qstripe) {
q_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (!q_page) {
__free_page(p_page);
@@ -2388,8 +2382,7 @@ static noinline void finish_parity_scrub
/* then add the parity stripe */
pointers[stripe++] = kmap(p_page);

- if (q_stripe != -1) {
-
+ if (has_qstripe) {
/*
* raid6, add the qstripe and call the
* library function to fill in our p/q