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authorAlexander Gordeev <agordeev@linux.ibm.com>2022-07-19 07:16:35 +0200
committerAlexander Gordeev <agordeev@linux.ibm.com>2022-07-20 17:21:41 +0200
commit6d2e5a4a13da2e91a46a37cd00d23dba8613ad7b (patch)
treeedbdcca483dc5378818aa1a20582fa7a1b4c9927 /arch/s390
parents390/crash: move copy_to_user_real() to crash_dump.c (diff)
downloadlinux-6d2e5a4a13da2e91a46a37cd00d23dba8613ad7b.tar.xz
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s390/crash: use static swap buffer for copy_to_user_real()
Currently a temporary page-size buffer is allocated for copying oldmem to user space. That limits copy_to_user_real() operation only to stages when virtual memory is available and still makes it possible to fail while the system is being dumped. Instead of reallocating single page on each copy_oldmem_page() iteration use a statically allocated buffer. This also paves the way for a further memcpy_real() rework where no swap buffer is needed altogether. Acked-by: Heiko Carstens <hca@linux.ibm.com> Tested-by: Alexander Egorenkov <egorenar@linux.ibm.com> Link: https://lore.kernel.org/r/334ed359680c4d45dd32feb104909f610312ef0f.1658206891.git.agordeev@linux.ibm.com Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/kernel/crash_dump.c26
1 files changed, 12 insertions, 14 deletions
diff --git a/arch/s390/kernel/crash_dump.c b/arch/s390/kernel/crash_dump.c
index 8d7332d4444c..1662f1d81abe 100644
--- a/arch/s390/kernel/crash_dump.c
+++ b/arch/s390/kernel/crash_dump.c
@@ -53,6 +53,8 @@ struct save_area {
};
static LIST_HEAD(dump_save_areas);
+static DEFINE_MUTEX(memcpy_real_mutex);
+static char memcpy_real_buf[PAGE_SIZE];
/*
* Allocate a save area
@@ -178,25 +180,21 @@ int copy_oldmem_kernel(void *dst, unsigned long src, size_t count)
*/
static int copy_to_user_real(void __user *dest, unsigned long src, unsigned long count)
{
- int offs = 0, size, rc;
- char *buf;
+ unsigned long offs = 0, size;
- buf = (char *)__get_free_page(GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
- rc = -EFAULT;
+ mutex_lock(&memcpy_real_mutex);
while (offs < count) {
size = min(PAGE_SIZE, count - offs);
- if (memcpy_real(buf, src + offs, size))
- goto out;
- if (copy_to_user(dest + offs, buf, size))
- goto out;
+ if (memcpy_real(memcpy_real_buf, src + offs, size))
+ break;
+ if (copy_to_user(dest + offs, memcpy_real_buf, size))
+ break;
offs += size;
}
- rc = 0;
-out:
- free_page((unsigned long)buf);
- return rc;
+ mutex_unlock(&memcpy_real_mutex);
+ if (offs < count)
+ return -EFAULT;
+ return 0;
}
/*