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Implement involuntary preemption check

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Prevent loading the kernel module if the kernel can be involuntarily
preempted

CAS will work if the kernel has been compiled with either
CONFIG_PREEMPT_NONE, CONFIG_PREEMPT_VOLUNTARY, or CONFIG_PREEMPT_DYNAMIC.
If the dynamic configuration is enabled, the kernel must be booted with
preempt=none or preempt=voluntary.

Signed-off-by: Michal Mielewczyk <michal.mielewczyk@huawei.com>
This commit is contained in:
Michal Mielewczyk 2025-03-12 13:14:15 +01:00
parent a135a00627
commit aa660ca0a5
1 changed files with 50 additions and 0 deletions
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50
modules/cas_cache/main.c
View File

@ -1,5 +1,6 @@
/*
* Copyright(c) 2012-2022 Intel Corporation
* Copyright(c) 2025 Huawei Technologies
* SPDX-License-Identifier: BSD-3-Clause
*/
@ -42,10 +43,59 @@ MODULE_PARM_DESC(seq_cut_off_mb,
ocf_ctx_t cas_ctx;
struct cas_module cas_module;
static inline uint32_t involuntary_preemption_enabled(void)
{
bool config_dynamic = IS_ENABLED(CONFIG_PREEMPT_DYNAMIC);
bool config_rt = IS_ENABLED(CONFIG_PREEMPT_RT);
bool config_preempt = IS_ENABLED(CONFIG_PREEMPT);
bool config_lazy = IS_ENABLED(CONFIG_PREEMPT_LAZY);
bool config_none = IS_ENABLED(CONFIG_PREEMPT_NONE);
if (!config_dynamic && !config_rt && !config_preempt && !config_lazy)
return false;
if (config_none)
return false;
if (config_rt || config_preempt || config_lazy) {
printk(KERN_ERR OCF_PREFIX_SHORT
"The kernel has been built with involuntary preemption "
"enabled.\nFailed to load Open CAS kernel module.\n");
return true;
}
#ifdef CONFIG_PREEMPT_DYNAMIC
/* preempt_model_none() or preempt_model_voluntary() are not defined if
* the kernel has been compiled without PREEMPT_DYNAMIC
*/
printk(KERN_WARNING OCF_PREFIX_SHORT
"The kernel has been compiled with preemption configurable\n"
"at boot time (PREEMPT_DYNAMIC=y). Open CAS doesn't support\n"
"kernels with involuntary preemption so make sure to set\n"
"\"preempt=\" to \"none\" or \"voluntary\" in the kernel"
" command line\n");
if (!preempt_model_none() && !preempt_model_voluntary()) {
printk(KERN_ERR OCF_PREFIX_SHORT
"The kernel has been booted with involuntary "
"preemption enabled.\nFailed to load Open CAS kernel "
"module.\n");
return true;
} else {
return false;
}
#endif
return false;
}
static int __init cas_init_module(void)
{
int result = 0;
if (involuntary_preemption_enabled())
return -ENOTSUP;
if (!writeback_queue_unblock_size || !max_writeback_queue_size) {
printk(KERN_ERR OCF_PREFIX_SHORT
"Invalid module parameter.\n");