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From: gregkh@linuxfoundation.org
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	Johannes Thumshirn <johannes.thumshirn@wdc.com>,
	David Sterba <dsterba@suse.com>
Subject: [PATCH 4.9 01/11] btrfs: raid56: simplify tracking of Q stripe presence
Date: Wed, 10 Mar 2021 14:25:00 +0100	[thread overview]
Message-ID: <20210310132320.441895184@linuxfoundation.org> (raw)
In-Reply-To: <20210310132320.393957501@linuxfoundation.org>

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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
@@ -1179,22 +1179,19 @@ 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.
@@ -1238,7 +1235,7 @@ 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
@@ -2306,8 +2303,7 @@ 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;
@@ -2317,14 +2313,12 @@ 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;
@@ -2346,7 +2340,7 @@ 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);
@@ -2369,8 +2363,7 @@ 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



  reply	other threads:[~2021-03-10 13:29 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-10 13:24 [PATCH 4.9 00/11] 4.9.261-rc1 review gregkh
2021-03-10 13:25 ` gregkh [this message]
2021-03-10 13:25 ` [PATCH 4.9 02/11] btrfs: fix raid6 qstripe kmap gregkh
2021-03-10 13:25 ` [PATCH 4.9 03/11] usbip: tools: fix build error for multiple definition gregkh
2021-03-10 13:25 ` [PATCH 4.9 04/11] ALSA: ctxfi: cthw20k2: fix mask on conf to allow 4 bits gregkh
2021-03-10 13:25 ` [PATCH 4.9 05/11] rsxx: Return -EFAULT if copy_to_user() fails gregkh
2021-03-10 13:25 ` [PATCH 4.9 06/11] dm table: fix iterate_devices based device capability checks gregkh
2021-03-10 13:25 ` [PATCH 4.9 07/11] dm table: fix DAX " gregkh
2021-03-10 13:25 ` [PATCH 4.9 08/11] iommu/amd: Fix sleeping in atomic in increase_address_space() gregkh
2021-03-10 13:25 ` [PATCH 4.9 09/11] platform/x86: acer-wmi: Add new force_caps module parameter gregkh
2021-03-10 13:25 ` [PATCH 4.9 10/11] PCI: Add function 1 DMA alias quirk for Marvell 9215 SATA controller gregkh
2021-03-10 13:25 ` [PATCH 4.9 11/11] misc: eeprom_93xx46: Add quirk to support Microchip 93LC46B eeprom gregkh
2021-03-10 22:00 ` [PATCH 4.9 00/11] 4.9.261-rc1 review Shuah Khan
2021-03-10 23:50 ` Guenter Roeck
2021-03-11  4:27 ` Florian Fainelli
2021-03-11  8:35 ` Naresh Kamboju

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