[RFC PATCH v2 14/16] mm: Free pages, remove files and clean cache when one alloc fails

[Juan Yescas <jyescas@google.com>]

When one of the requested allocations failed, do

- free the pages that were previously allocated as part of the request.
- remove the files that were created as part of the request.
- clean the kmem cache.
- Erase the struct page_alloc objects from the xarray that were inserted
as part of the request.

Signed-off-by: Juan Yescas <jyescas@google.com>
---

Changes in v2:
	- Remove comment about the future implementation.

 mm/page_alloc_hogger.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc_hogger.c b/mm/page_alloc_hogger.c
index a70c924e4172..ce53a17ac790 100644
--- a/mm/page_alloc_hogger.c
+++ b/mm/page_alloc_hogger.c
@@ -93,6 +93,7 @@
 #include <linux/nodemask.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
+#include <linux/xarray.h>
 
 static struct dentry *mmdir;
 
@@ -252,6 +253,23 @@ static int make_alloc(struct req_alloc *req,
 	return ret;
 }
 
+static int free_alloc_helper(unsigned long alloc_id)
+{
+	struct page_alloc *pa;
+
+	pa = xa_erase(&allocs_xa, alloc_id);
+	if (!pa) {
+		pr_err("The alloc_id %lu was not found!", alloc_id);
+		return -EINVAL;
+	}
+
+	__free_pages(pa->page, pa->req_alloc->order);
+	debugfs_remove(pa->alloc_dentry);
+	kmem_cache_free(page_alloc_cache, pa);
+
+	return 0;
+}
+
 /**
  * req_page_alloc_write() - Allocates the pages on the requested node, zone,
  * order and migrate type. Once the allocation is performed, a file is created
@@ -293,10 +311,15 @@ static ssize_t req_page_alloc_write(struct file *file, const char __user *ubuf,
 	return cnt;
 
 free_allocs:
-	/*
-	 * A proper clean up of the pages and page_alloc allocations will
-	 * be done in a follow up patch of this topic.
-	 */
+	/* Free all the pages and resources previously allocated. */
+	for (int j = 0; j < i; j++) {
+		int ret2 = free_alloc_helper(allocs_ids[j]);
+
+		if (ret2)
+			pr_err("Unable to free pages associated with file %lu",
+			       allocs_ids[j]);
+	}
+
 	kfree(allocs_ids);
 
 	return ret;
-- 
2.55.0.629.g250fe7f194-goog