[PATCH] kdump: Give crashkernel CMA areas unique names

[Mikhail Zaslonko <zaslonko@linux.ibm.com>]

reserve_crashkernel_cma() names every CMA area it reserves
"crashkernel". If the requested size can't be reserved in one piece,
it falls back to several smaller areas, all with the same name.
With CONFIG_CMA_SYSFS, cma_sysfs_init() then fails to create the second
directory:

  sysfs: cannot create duplicate filename '/kernel/mm/cma/crashkernel'

and the error path removes the sysfs entries of all CMA areas.

With CONFIG_CMA_DEBUGFS, debugfs refuses the duplicate directories as
well:

  debugfs: 'crashkernel' already exists in 'cma'

so only the first area shows up in debugfs.

Keep the name of the first area and add the index to the others:
crashkernel, crashkernel1, crashkernel2, ...

Fixes: ab475510e042 ("kdump: implement reserve_crashkernel_cma")
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
---
Found while adding crashkernel CMA support for s390.

 kernel/crash_reserve.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c
index eee37a11380c..e58318b1e092 100644
--- a/kernel/crash_reserve.c
+++ b/kernel/crash_reserve.c
@@ -483,10 +483,16 @@ void __init reserve_crashkernel_cma(unsigned long long cma_size)
 	while (cma_size > reserved_size &&
 	       crashk_cma_cnt < CRASHKERNEL_CMA_RANGES_MAX) {
 
+		char name[CMA_MAX_NAME];
 		struct cma *res;
 
+		/* CMA area names show up in sysfs and debugfs, keep them unique */
+		if (crashk_cma_cnt)
+			snprintf(name, sizeof(name), "crashkernel%d", crashk_cma_cnt);
+		else
+			strscpy(name, "crashkernel");
 		if (cma_declare_contiguous(0, request_size, 0, 0, 0, false,
-				       "crashkernel", &res)) {
+				       name, &res)) {
 			/* reservation failed, try half-sized blocks */
 			if (request_size <= PAGE_SIZE)
 				break;

base-commit: f66469d9905b39d2c260a15d7d6db450f4db67c1
-- 
2.55.0