linux-kernel - [PATCH v2 14/15] mm/mmap: Use vms accounted pages in mmap

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Date: Tue, 25 Jun 2024 15:11:44 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v2 14/15] mm/mmap: Use vms accounted pages in mmap_region()

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

Change from nr_pages variable to vms.nr_accounted for the charged pages
calculation.  This is necessary for a future patch.

This also avoids checking security_vm_enough_memory_mm() if the amount
of memory won't change.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
Cc: Kees Cook <kees@...nel.org>
---
 mm/mmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index f3edabf83975..adb0bb5ea344 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2970,6 +2970,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	} else {
 		/* Minimal setup of vms */
 		vms.nr_pages = 0;
+		vms.nr_accounted = 0;
 		next = vma_next(&vmi);
 		prev = vma_prev(&vmi);
 		if (prev)
@@ -2981,9 +2982,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	 */
 	if (accountable_mapping(file, vm_flags)) {
 		charged = pglen;
-		charged -= nr_accounted;
-		if (security_vm_enough_memory_mm(mm, charged))
+		charged -= vms.nr_accounted;
+		if (charged && security_vm_enough_memory_mm(mm, charged))
 			goto abort_munmap;
+
 		vms.nr_accounted = 0;
 		vm_flags |= VM_ACCOUNT;
 	}
-- 
2.43.0