[PATCH 03/13] s390/chsc_sch: Use kzalloc() for CHSC requests
From: Mike Rapoport (Microsoft)
Date: Mon Sep 07 2026 - 06:25:24 EST
The CHSC ioctl handlers allocate request and response areas for
CHSC commands issued on behalf of userspace.
This memory can be allocated with kmalloc() as there's nothing special
about it to go directly to the page allocator.
kmalloc() provides a better API that does not require ugly casts and
kfree() does not need to know the size of the freed object.
Performance difference between kmalloc() and __get_free_pages() is not
measurable as both allocators take an object/page from a per-CPU list for
fast path allocations.
For the slow path the performance is anyway determined by the amount of
reclaim involved rather than by what allocator is used.
Replace use of get_zeroed_page() with kzalloc() and free_page() with
kfree().
Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@xxxxxxxxxx
Assisted-by: copilot:claude-opus
Signed-off-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
---
drivers/s390/cio/chsc_sch.c | 44 ++++++++++++++++++++++----------------------
1 file changed, 22 insertions(+), 22 deletions(-)
diff --git a/drivers/s390/cio/chsc_sch.c b/drivers/s390/cio/chsc_sch.c
index b6cb8bb8bcc4b..c8d6871d1841e 100644
--- a/drivers/s390/cio/chsc_sch.c
+++ b/drivers/s390/cio/chsc_sch.c
@@ -292,7 +292,7 @@ static int chsc_ioctl_start(void __user *user_area)
if (!css_general_characteristics.dynio)
/* It makes no sense to try. */
return -EOPNOTSUPP;
- chsc_area = (void *)get_zeroed_page(GFP_DMA | GFP_KERNEL);
+ chsc_area = kzalloc(PAGE_SIZE, GFP_DMA | GFP_KERNEL);
if (!chsc_area)
return -ENOMEM;
request = kzalloc_obj(*request);
@@ -321,7 +321,7 @@ static int chsc_ioctl_start(void __user *user_area)
snprintf(dbf, sizeof(dbf), "ret:%d", ret);
CHSC_LOG(0, dbf);
kfree(request);
- free_page((unsigned long)chsc_area);
+ kfree(chsc_area);
return ret;
}
@@ -340,7 +340,7 @@ static int chsc_ioctl_on_close_set(void __user *user_area)
ret = -ENOMEM;
goto out_unlock;
}
- on_close_chsc_area = (void *)get_zeroed_page(GFP_DMA | GFP_KERNEL);
+ on_close_chsc_area = kzalloc(PAGE_SIZE, GFP_DMA | GFP_KERNEL);
if (!on_close_chsc_area) {
ret = -ENOMEM;
goto out_free_request;
@@ -353,7 +353,7 @@ static int chsc_ioctl_on_close_set(void __user *user_area)
goto out_unlock;
out_free_chsc:
- free_page((unsigned long)on_close_chsc_area);
+ kfree(on_close_chsc_area);
on_close_chsc_area = NULL;
out_free_request:
kfree(on_close_request);
@@ -375,7 +375,7 @@ static int chsc_ioctl_on_close_remove(void)
ret = -ENOENT;
goto out_unlock;
}
- free_page((unsigned long)on_close_chsc_area);
+ kfree(on_close_chsc_area);
on_close_chsc_area = NULL;
kfree(on_close_request);
on_close_request = NULL;
@@ -392,7 +392,7 @@ static int chsc_ioctl_start_sync(void __user *user_area)
struct chsc_sync_area *chsc_area;
int ret, ccode;
- chsc_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ chsc_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!chsc_area)
return -ENOMEM;
if (copy_from_user(chsc_area, user_area, PAGE_SIZE)) {
@@ -414,7 +414,7 @@ static int chsc_ioctl_start_sync(void __user *user_area)
else
ret = 0;
out_free:
- free_page((unsigned long)chsc_area);
+ kfree(chsc_area);
return ret;
}
@@ -438,7 +438,7 @@ static int chsc_ioctl_info_channel_path(void __user *user_cd)
u8 data[PAGE_SIZE - 20];
} __attribute__ ((packed)) *scpcd_area;
- scpcd_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ scpcd_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!scpcd_area)
return -ENOMEM;
cd = kzalloc_obj(*cd);
@@ -476,7 +476,7 @@ static int chsc_ioctl_info_channel_path(void __user *user_cd)
ret = 0;
out_free:
kfree(cd);
- free_page((unsigned long)scpcd_area);
+ kfree(scpcd_area);
return ret;
}
@@ -500,7 +500,7 @@ static int chsc_ioctl_info_cu(void __user *user_cd)
u8 data[PAGE_SIZE - 20];
} __attribute__ ((packed)) *scucd_area;
- scucd_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ scucd_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!scucd_area)
return -ENOMEM;
cd = kzalloc_obj(*cd);
@@ -538,7 +538,7 @@ static int chsc_ioctl_info_cu(void __user *user_cd)
ret = 0;
out_free:
kfree(cd);
- free_page((unsigned long)scucd_area);
+ kfree(scucd_area);
return ret;
}
@@ -563,7 +563,7 @@ static int chsc_ioctl_info_sch_cu(void __user *user_cud)
u8 data[PAGE_SIZE - 20];
} __attribute__ ((packed)) *sscud_area;
- sscud_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ sscud_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!sscud_area)
return -ENOMEM;
cud = kzalloc_obj(*cud);
@@ -602,7 +602,7 @@ static int chsc_ioctl_info_sch_cu(void __user *user_cud)
ret = 0;
out_free:
kfree(cud);
- free_page((unsigned long)sscud_area);
+ kfree(sscud_area);
return ret;
}
@@ -625,7 +625,7 @@ static int chsc_ioctl_conf_info(void __user *user_ci)
u8 data[PAGE_SIZE - 20];
} __attribute__ ((packed)) *sci_area;
- sci_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ sci_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!sci_area)
return -ENOMEM;
ci = kzalloc_obj(*ci);
@@ -662,7 +662,7 @@ static int chsc_ioctl_conf_info(void __user *user_ci)
ret = 0;
out_free:
kfree(ci);
- free_page((unsigned long)sci_area);
+ kfree(sci_area);
return ret;
}
@@ -696,7 +696,7 @@ static int chsc_ioctl_conf_comp_list(void __user *user_ccl)
u32 res;
} __attribute__ ((packed)) *cssids_parm;
- sccl_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ sccl_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!sccl_area)
return -ENOMEM;
ccl = kzalloc_obj(*ccl);
@@ -745,7 +745,7 @@ static int chsc_ioctl_conf_comp_list(void __user *user_ccl)
ret = 0;
out_free:
kfree(ccl);
- free_page((unsigned long)sccl_area);
+ kfree(sccl_area);
return ret;
}
@@ -756,7 +756,7 @@ static int chsc_ioctl_chpd(void __user *user_chpd)
int ret;
chpd = kzalloc_obj(*chpd);
- scpd_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ scpd_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!scpd_area || !chpd) {
ret = -ENOMEM;
goto out_free;
@@ -775,7 +775,7 @@ static int chsc_ioctl_chpd(void __user *user_chpd)
ret = -EFAULT;
out_free:
kfree(chpd);
- free_page((unsigned long)scpd_area);
+ kfree(scpd_area);
return ret;
}
@@ -796,7 +796,7 @@ static int chsc_ioctl_dcal(void __user *user_dcal)
u8 data[PAGE_SIZE - 36];
} __attribute__ ((packed)) *sdcal_area;
- sdcal_area = (void *)get_zeroed_page(GFP_KERNEL | GFP_DMA);
+ sdcal_area = kzalloc(PAGE_SIZE, GFP_KERNEL | GFP_DMA);
if (!sdcal_area)
return -ENOMEM;
dcal = kzalloc_obj(*dcal);
@@ -834,7 +834,7 @@ static int chsc_ioctl_dcal(void __user *user_dcal)
ret = 0;
out_free:
kfree(dcal);
- free_page((unsigned long)sdcal_area);
+ kfree(sdcal_area);
return ret;
}
@@ -904,7 +904,7 @@ static int chsc_release(struct inode *inode, struct file *filp)
}
snprintf(dbf, sizeof(dbf), "relret:%d", ret);
CHSC_LOG(0, dbf);
- free_page((unsigned long)on_close_chsc_area);
+ kfree(on_close_chsc_area);
on_close_chsc_area = NULL;
kfree(on_close_request);
on_close_request = NULL;
--
2.53.0