The crashk_low_res should be considered by /sys/kernel/kexec_crash_size
to support two crash kernel regions. Since crashk_res manages the memory
with high address and crashk_low_res manages the memory with low address,
crashk_low_res is shrunken only when all crashk_res is shrunken. And
because when there is only one crash kernel region, crashk_res is always
used. Therefore, if all crashk_res is shrunken and crashk_low_res still
exists, swap them.
Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
kernel/kexec_core.c | 43 ++++++++++++++++++++++++++++++++++++++-----
1 file changed, 38 insertions(+), 5 deletions(-)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index e82bc6d6634136a..c1d50f6566300d9 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1091,6 +1091,11 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs)
}
}
+static inline resource_size_t crash_resource_size(const struct resource *res)
+{
+ return !res->end ? 0 : resource_size(res);
+}
+
ssize_t crash_get_memory_size(void)
{
ssize_t size = 0;
@@ -1098,8 +1103,8 @@ ssize_t crash_get_memory_size(void)
if (!kexec_trylock())
return -EBUSY;
- if (crashk_res.end != crashk_res.start)
- size = resource_size(&crashk_res);
+ size += crash_resource_size(&crashk_res);
+ size += crash_resource_size(&crashk_low_res);
kexec_unlock();
return size;
@@ -1135,7 +1140,7 @@ int __crash_shrink_memory(struct resource *old_res, unsigned long new_size)
int crash_shrink_memory(unsigned long new_size)
{
int ret = 0;
- unsigned long old_size;
+ unsigned long old_size, low_size;
if (!kexec_trylock())
return -EBUSY;
@@ -1144,14 +1149,42 @@ int crash_shrink_memory(unsigned long new_size)
ret = -ENOENT;
goto unlock;
}
- old_size = !crashk_res.end ? 0 : resource_size(&crashk_res);
+
+ low_size = crash_resource_size(&crashk_low_res);
+ old_size = crash_resource_size(&crashk_res) + low_size;
new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
if (new_size >= old_size) {
ret = (new_size == old_size) ? 0 : -EINVAL;
goto unlock;
}
- ret = __crash_shrink_memory(&crashk_res, new_size);
+ /*
+ * (low_size > new_size) implies that low_size is greater than zero.
+ * This also means that if low_size is zero, the else branch is taken.
+ *
+ * If low_size is greater than 0, (low_size > new_size) indicates that
+ * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res
+ * needs to be shrunken.
+ */
+ if (low_size > new_size) {
+ ret = __crash_shrink_memory(&crashk_res, 0);
+ if (ret)
+ goto unlock;
+
+ ret = __crash_shrink_memory(&crashk_low_res, new_size);
+ } else {
+ ret = __crash_shrink_memory(&crashk_res, new_size - low_size);
+ }
+
+ /* Swap crashk_res and crashk_low_res if needed */
+ if (!crashk_res.end && crashk_low_res.end) {
+ crashk_res.start = crashk_low_res.start;
+ crashk_res.end = crashk_low_res.end;
+ release_resource(&crashk_low_res);
+ crashk_low_res.start = 0;
+ crashk_low_res.end = 0;
+ insert_resource(&iomem_resource, &crashk_res);
+ }
unlock:
kexec_unlock();
--
2.25.1
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