powerpc/fadump: opt out from freeing pages on cma activation failure

With commit 1033151e9b41 ("powerpc/fadump: Reservationless firmware
assisted dump"), Linux kernel's Contiguous Memory Allocator (CMA) based
reservation was introduced in fadump.  That change was aimed at using CMA
to let applications utilize the memory reserved for fadump while blocking
it from being used for kernel pages.  The assumption was, even if CMA
activation fails for whatever reason, the memory still remains reserved to
avoid it from being used for kernel pages.  But commit 023addc76f0a
("mm/cma: expose all pages to the buddy if activation of an area fails")
breaks this assumption as it started exposing all pages to buddy allocator
on CMA activation failure.  It led to warning messages like below while
running crash-utility on vmcore of a kernel having above two commits:

  crash: seek error: kernel virtual address: <from reserved region>

To fix this problem, opt out from exposing pages to buddy allocator on CMA
activation failure for fadump reserved memory.

Link: https://lkml.kernel.org/r/20220117075246.36072-3-hbathini@linux.ibm.com
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
index 7eb67201ea415ed30ccc42103d8b218e8711b265..4fdb7c77fda1eae17ca9377211820130ef5a5e07 100644 (file)
--- a/arch/powerpc/kernel/fadump.c
+++ b/arch/powerpc/kernel/fadump.c
@@ -112,6 +112,12 @@ static int __init fadump_cma_init(void)
                return 1;
        }
 
+       /*
+        *  If CMA activation fails, keep the pages reserved, instead of
+        *  exposing them to buddy allocator. Same as 'fadump=nocma' case.
+        */
+       cma_reserve_pages_on_error(fadump_cma);
+
        /*
         * So we now have successfully initialized cma area for fadump.
         */