SPL-14059 mm: cma: sync everything after EBUSY

Since file-backed memory on CMA area could take long-term pinning.

By Minchan Kim's debug commit 151e084af494 ("mm: page_alloc:
dump migrate-failed pages only at -EBUSY")
We know the pinned page comes from buffer_head, ext4 journal, FS metadata.

Sync everything after EBUSY that can unpin most file-system pages.
And raise the success rate at next time try.

Link: https://lkml.kernel.org/r/20220615021504.23358-1-edwardwu@realtek.com
Signed-off-by: Edward Wu <edwardwu@realtek.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/mm/cma.c b/mm/cma.c
index 30b6ca30009b..3ebf66d6d597 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -31,6 +31,7 @@
 #include <linux/highmem.h>
 #include <linux/io.h>
 #include <linux/kmemleak.h>
+#include <linux/syscalls.h>
 #include <trace/events/cma.h>
 
 #include "cma.h"
@@ -411,6 +412,24 @@ static void cma_debug_show_areas(struct cma *cma)
 static inline void cma_debug_show_areas(struct cma *cma) { }
 #endif
 
+static void cma_sync_work(struct work_struct *work)
+{
+	ksys_sync();
+	kfree(work);
+	pr_debug("%s(): EBUSY Sync complete\n", __func__);
+}
+
+static void cma_ebusy_sync_pinned_pages(void)
+{
+	struct work_struct *work;
+
+	work = kmalloc(sizeof(*work), GFP_ATOMIC);
+	if (work) {
+		INIT_WORK(work, cma_sync_work);
+		schedule_work(work);
+	}
+}
+
 /**
  * cma_alloc() - allocate pages from contiguous area
  * @cma:   Contiguous memory region for which the allocation is performed.
@@ -431,6 +450,7 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
 	unsigned long i;
 	struct page *page = NULL;
 	int ret = -ENOMEM;
+	bool sys_synchronized = false;
 
 	if (!cma || !cma->count || !cma->bitmap)
 		goto out;
@@ -482,6 +502,11 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
 		if (ret != -EBUSY)
 			break;
 
+		if (!sys_synchronized) {
+			sys_synchronized = true;
+			cma_ebusy_sync_pinned_pages();
+		}
+
 		pr_debug("%s(): memory range at %p is busy, retrying\n",
 			 __func__, pfn_to_page(pfn));