[RFC PATCH 2/3] mm/secretmem: use __GFP_UNMAPPED to allocate pages

From: Mike Rapoport <rppt@kernel.org>
To: linux-mm@kvack.org
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Kees Cook <keescook@chromium.org>,
	Mike Rapoport <rppt@kernel.org>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	linux-kernel@vger.kernel.org, x86@kernel.org
Subject: [RFC PATCH 2/3] mm/secretmem: use __GFP_UNMAPPED to allocate pages
Date: Thu, 27 Jan 2022 10:56:07 +0200	[thread overview]
Message-ID: <20220127085608.306306-3-rppt@kernel.org> (raw)
In-Reply-To: <20220127085608.306306-1-rppt@kernel.org>

From: Mike Rapoport <rppt@linux.ibm.com>

Currently secertmem explicitly removes allocated pages from the direct map.
This fragments direct map because allocated pages may reside in different
pageblocks.

Use __GFP_UNMAPPED to utilize caching of unmapped pages done by the page
allocator.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
 mm/secretmem.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index 22b310adb53d..878ef004d7a7 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -63,16 +63,10 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 retry:
 	page = find_lock_page(mapping, offset);
 	if (!page) {
-		page = alloc_page(gfp | __GFP_ZERO);
+		page = alloc_page(gfp | __GFP_ZERO | __GFP_UNMAPPED);
 		if (!page)
 			return VM_FAULT_OOM;
 
-		err = set_direct_map_invalid_noflush(page);
-		if (err) {
-			put_page(page);
-			return vmf_error(err);
-		}
-
 		__SetPageUptodate(page);
 		err = add_to_page_cache_lru(page, mapping, offset, gfp);
 		if (unlikely(err)) {
-- 
2.34.1

