cgroup: Avoid -Wstringop-overflow warnings

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler warnings with no subsystems").

Signed-off-by Gustavo A. R. Silva <[email protected]>

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler warnings with no subsystems").

Signed-off-by Gustavo A. R. Silva <[email protected]>

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler warnings with no subsystems").

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
 kernel/cgroup/cgroup.c | 6 ++++++
 1 file changed, 6 insertions(+)

kernel/cgroup/cgroup.c +3 -0

index cd497b90e11a..1ee76e62eb98 100644
@@ -1200,6 +1200,9 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	unsigned long key;
 	int ssid;
 
+	if (!CGROUP_HAS_SUBSYS_CONFIG)
+		return NULL;
+
 	lockdep_assert_held(&cgroup_mutex);
 
 	/* First see if we already have a cgroup group that matches

Quoted 31 lines · Gustavo A. R. Silva

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler warnings with no subsystems").

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
  kernel/cgroup/cgroup.c | 6 ++++++
  1 file changed, 6 insertions(+)

kernel/cgroup/cgroup.c +3 -0

index cd497b90e11a..1ee76e62eb98 100644
@@ -1200,6 +1200,9 @@ static struct css_set *find_css_set(struct css_set *old_cset,
  	unsigned long key;
  	int ssid;
 
+	if (!CGROUP_HAS_SUBSYS_CONFIG)
+		return NULL;
+
  	lockdep_assert_held(&cgroup_mutex);
 
  	/* First see if we already have a cgroup group that matches

kernel/cgroup/cgroup.c int __init cgroup_init(void) · line 6056

Quoted 9 lines

kernel/cgroup/cgroup.c +3 -0

@@ -6045,6 +6048,9 @@ int __init cgroup_init(void)
  	struct cgroup_subsys *ss;
  	int ssid;
 
+	if (!CGROUP_HAS_SUBSYS_CONFIG)
+		return -EINVAL;
+
  	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
  	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
  	BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));

This change (which landed in linux-next) causes a boot failure on my (arm32) board because the cgroup filesystem isn't created which upsets systemd:

[   11.474767] systemd[1]: Failed to mount tmpfs at /sys/fs/cgroup: No such file or directory
[   11.489933] systemd[1]: Failed to mount cgroup at /sys/fs/cgroup/systemd: No such file or directory

[!!!!!!] Failed to mount API filesystems.

Reverting this commit on the head of linux-next gets the board working again.

Quoted 2 lines

Reverting this commit on the head of linux-next gets the board working again.

Thanks for reporting this issue. I'll take a look.

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

Quoted 8 lines · Gustavo A. R. Silva

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

Hi,

This patch landed in next but causes boot failures on Exynos ARMv7 board (32 bit) with systemd (exynos_defconfig):

NFS-Mount: 192.168.1.10:/srv/nfs/odroidhc1
Waiting 10 seconds for device /dev/nfs ...
ERROR: device '/dev/nfs' not found. Skipping fsck.
Mount cmd:
mount.nfs4 -o vers=4,nolock 192.168.1.10:/srv/nfs/odroidhc1 /new_root :: running cleanup hook [udev]

[   23.752917] systemd[1]: System time before build time, advancing clock.
[   23.851828] systemd[1]: Failed to mount tmpfs at /sys/fs/cgroup: No such file or directory
[   23.868459] systemd[1]: Failed to mount cgroup at /sys/fs/cgroup/systemd: No such file or directory
[!!!!!!] Failed to mount API filesystems.
[   23.914562] systemd[1]: Freezing execution.

Full log:
https://krzk.eu/#/builders/21/builds/4110/steps/15/logs/serial0

Address the following -Wstringop-overflow warnings seen when
built with ARM architecture and aspeed_g4_defconfig configuration
(notice that under this configuration CGROUP_SUBSYS_COUNT == 0):
kernel/cgroup/cgroup.c:1208:16: warning: 'find_existing_css_set' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:1258:15: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6089:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=] kernel/cgroup/cgroup.c:6153:18: warning: 'css_set_hash' accessing 4 bytes in a region of size 0 [-Wstringop-overflow=]

These changes are based on commit d20d30ebb199 ("cgroup: Avoid compiler warnings with no subsystems").

Signed-off-by Gustavo A. R. Silva <[email protected]>

---
  kernel/cgroup/cgroup.c | 6 ++++++
  1 file changed, 6 insertions(+)

kernel/cgroup/cgroup.c +6 -0

index cd497b90e11a..1ee76e62eb98 100644
@@ -1200,6 +1200,9 @@ static struct css_set *find_css_set(struct css_set *old_cset,
  	unsigned long key;
  	int ssid;
 
+	if (!CGROUP_HAS_SUBSYS_CONFIG)
+		return NULL;
+
  	lockdep_assert_held(&cgroup_mutex);
 
  	/* First see if we already have a cgroup group that matches

@@ -6045,6 +6048,9 @@ int __init cgroup_init(void)
  	struct cgroup_subsys *ss;
  	int ssid;
 
+	if (!CGROUP_HAS_SUBSYS_CONFIG)
+		return -EINVAL;
+
  	BUILD_BUG_ON(CGROUP_SUBSYS_COUNT > 16);
  	BUG_ON(cgroup_init_cftypes(NULL, cgroup_base_files));
  	BUG_ON(cgroup_init_cftypes(NULL, cgroup_psi_files));

Hi all,

I wonder if you have any suggestions on how to address this issue. As it seems that my last attempt caused some boot failures[1][2].

At first, I thought that the right way to fix this was through a similar fix as this one[3]. But it seems I'm missing something else that I cannot determine yet.

These -Wstringop-overflow warnings are mostly the last ones remaining before we can finally enable this compiler option, globally.

Any help or advice on how to properly address this is greatly appreciated. :)