linux-kernel - [PATCH -mm 3/3] uprobes: turn xol_area->pages[2] into xol

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Message-ID: <20240911131437.GC3448@redhat.com>
Date: Wed, 11 Sep 2024 15:14:37 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Sven Schnelle <svens@...ux.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Michael Ellerman <mpe@...erman.id.au>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrii Nakryiko <andrii@...nel.org>, linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: [PATCH -mm 3/3] uprobes: turn xol_area->pages[2] into xol_area->page

Now that xol_mapping has its own ->fault() method we no longer need
xol_area->pages[1] == NULL, we need a single page.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 kernel/events/uprobes.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index a478e028043f..94a17435cfe6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -99,7 +99,7 @@ struct xol_area {
 	atomic_t 			slot_count;	/* number of in-use slots */
 	unsigned long 			*bitmap;	/* 0 = free slot */
 
-	struct page 			*pages[2];
+	struct page			*page;
 	/*
 	 * We keep the vma's vm_start rather than a pointer to the vma
 	 * itself.  The probed process or a naughty kernel module could make
@@ -1437,7 +1437,7 @@ static vm_fault_t xol_fault(const struct vm_special_mapping *sm,
 {
 	struct xol_area *area = vma->vm_mm->uprobes_state.xol_area;
 
-	vmf->page = area->pages[0];
+	vmf->page = area->page;
 	get_page(vmf->page);
 	return 0;
 }
@@ -1512,10 +1512,9 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
 	if (!area->bitmap)
 		goto free_area;
 
-	area->pages[0] = alloc_page(GFP_HIGHUSER);
-	if (!area->pages[0])
+	area->page = alloc_page(GFP_HIGHUSER);
+	if (!area->page)
 		goto free_bitmap;
-	area->pages[1] = NULL;
 
 	area->vaddr = vaddr;
 	init_waitqueue_head(&area->wq);
@@ -1523,12 +1522,12 @@ static struct xol_area *__create_xol_area(unsigned long vaddr)
 	set_bit(0, area->bitmap);
 	atomic_set(&area->slot_count, 1);
 	insns = arch_uprobe_trampoline(&insns_size);
-	arch_uprobe_copy_ixol(area->pages[0], 0, insns, insns_size);
+	arch_uprobe_copy_ixol(area->page, 0, insns, insns_size);
 
 	if (!xol_add_vma(mm, area))
 		return area;
 
-	__free_page(area->pages[0]);
+	__free_page(area->page);
  free_bitmap:
 	kfree(area->bitmap);
  free_area:
@@ -1570,7 +1569,7 @@ void uprobe_clear_state(struct mm_struct *mm)
 	if (!area)
 		return;
 
-	put_page(area->pages[0]);
+	put_page(area->page);
 	kfree(area->bitmap);
 	kfree(area);
 }
@@ -1637,7 +1636,7 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
 	if (unlikely(!xol_vaddr))
 		return 0;
 
-	arch_uprobe_copy_ixol(area->pages[0], xol_vaddr,
+	arch_uprobe_copy_ixol(area->page, xol_vaddr,
 			      &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
 
 	return xol_vaddr;
-- 
2.25.1.362.g51ebf55