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From:   sj@kernel.org
To:     akpm@linux-foundation.org
Cc:     linux-damon@amazon.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, SeongJae Park <sj@kernel.org>
Subject: [PATCH 06/14] mm/damon/sysfs: prohibit multiple physical address space monitoring targets
Date:   Fri, 29 Apr 2022 16:05:58 +0000
Message-Id: <20220429160606.127307-7-sj@kernel.org>
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From: SeongJae Park <sj@kernel.org>

Having multiple targets for physical address space monitoring makes no
sense.  This commit prohibits such a ridiculous DAMON context setup my
making the DAMON context build function to check and return an error for
the case.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 767ab8c33e4d..988247d35862 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -2124,6 +2124,10 @@ static int damon_sysfs_set_targets(struct damon_ctx *ctx,
 {
 	int i, err;
 
+	/* Multiple physical address space monitoring targets makes no sense */
+	if (ctx->ops.id == DAMON_OPS_PADDR && sysfs_targets->nr > 1)
+		return -EINVAL;
+
 	for (i = 0; i < sysfs_targets->nr; i++) {
 		struct damon_sysfs_target *sys_target =
 			sysfs_targets->targets_arr[i];
-- 
2.25.1