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| author |   Alexander Gordeev <agordeev@linux.ibm.com> | 2022-07-19 07:16:35 +0200 |
|---|---|---|
| committer | Alexander Gordeev <agordeev@linux.ibm.com> | 2022-07-20 17:21:41 +0200 |
| commit | 6d2e5a4a13da2e91a46a37cd00d23dba8613ad7b (patch) | |
| tree | edbdcca483dc5378818aa1a20582fa7a1b4c9927 /arch/s390 | |
| parent | s390/crash: move copy_to_user_real() to crash_dump.c (diff) | |
| download | linux-dev-6d2e5a4a13da2e91a46a37cd00d23dba8613ad7b.tar.xz linux-dev-6d2e5a4a13da2e91a46a37cd00d23dba8613ad7b.zip | |
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.c | 26 |
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; } /* |