linux-kernel - [PATCH 16/19] perf: Further simplify perf

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Message-Id: <20241104135519.354909594@infradead.org>
Date: Mon, 04 Nov 2024 14:39:25 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: mingo@...nel.org,
 lucas.demarchi@...el.com
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 willy@...radead.org,
 acme@...nel.org,
 namhyung@...nel.org,
 mark.rutland@....com,
 alexander.shishkin@...ux.intel.com,
 jolsa@...nel.org,
 irogers@...gle.com,
 adrian.hunter@...el.com,
 kan.liang@...ux.intel.com
Subject: [PATCH 16/19] perf: Further simplify perf_mmap()


Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6644,9 +6644,18 @@ static int perf_mmap(struct file *file,
 		return ret;
 
 	vma_size = vma->vm_end - vma->vm_start;
+	nr_pages = vma_size / PAGE_SIZE;
+
+	if (nr_pages > INT_MAX)
+		return -ENOMEM;
+
+	if (vma_size != PAGE_SIZE * nr_pages)
+		return -EINVAL;
+
+	user_extra = nr_pages;
 
 	if (vma->vm_pgoff == 0) {
-		nr_pages = (vma_size / PAGE_SIZE) - 1;
+		nr_pages -= 1;
 
 		/*
 		 * If we have rb pages ensure they're a power-of-two number, so we
@@ -6655,9 +6664,6 @@ static int perf_mmap(struct file *file,
 		if (nr_pages != 0 && !is_power_of_2(nr_pages))
 			return -EINVAL;
 
-		if (vma_size != PAGE_SIZE * (1 + nr_pages))
-			return -EINVAL;
-
 		WARN_ON_ONCE(event->ctx->parent_ctx);
 again:
 		mutex_lock(&event->mmap_mutex);
@@ -6679,8 +6685,6 @@ static int perf_mmap(struct file *file,
 
 			goto unlock;
 		}
-
-		user_extra = nr_pages + 1;
 	} else {
 		/*
 		 * AUX area mapping: if rb->aux_nr_pages != 0, it's already
@@ -6692,10 +6696,6 @@ static int perf_mmap(struct file *file,
 		if (!event->rb)
 			return -EINVAL;
 
-		nr_pages = vma_size / PAGE_SIZE;
-		if (nr_pages > INT_MAX)
-			return -ENOMEM;
-
 		mutex_lock(&event->mmap_mutex);
 		ret = -EINVAL;
 
@@ -6739,7 +6739,6 @@ static int perf_mmap(struct file *file,
 		}
 
 		atomic_set(&rb->aux_mmap_count, 1);
-		user_extra = nr_pages;
 	}
 
 	user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);