FAILED: patch "[PATCH] mm/damon/sysfs: check DAMOS regions update progress from" failed to apply to 6.5-stable tree

The patch below does not apply to the 6.5-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.5.y
git checkout FETCH_HEAD
git cherry-pick -x 76b7069bcc89dec33f03eb08abee165d0306b754
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023102716-prudishly-reggae-1b29@gregkh' --subject-prefix 'PATCH 6.5.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 76b7069bcc89dec33f03eb08abee165d0306b754 Mon Sep 17 00:00:00 2001
From: SeongJae Park <[email protected]>
Date: Sat, 7 Oct 2023 20:04:32 +0000
Subject: [PATCH] mm/damon/sysfs: check DAMOS regions update progress from
before_terminate()

DAMON_SYSFS can receive DAMOS tried regions update request while kdamond is already out of the main loop and before_terminate callback (damon_sysfs_before_terminate() in this case) is not yet called. And damon_sysfs_handle_cmd() can further be finished before the callback is invoked. Then, damon_sysfs_before_terminate() unlocks damon_sysfs_lock, which is not locked by anyone. This happens because the callback function assumes damon_sysfs_cmd_request_callback() should be called before it. Check if the assumption was true before doing the unlock, to avoid this problem.

index b86ba7b0a921..f60e56150feb 100644
@@ -1208,6 +1208,8 @@ static int damon_sysfs_set_targets(struct damon_ctx *ctx,
 	return 0;
 }
 
+static bool damon_sysfs_schemes_regions_updating;
+
 static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 {
 	struct damon_target *t, *next;

@@ -1219,8 +1221,10 @@ static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 	cmd = damon_sysfs_cmd_request.cmd;
 	if (kdamond && ctx == kdamond->damon_ctx &&
 			(cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS ||
-			 cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES)) {
+			 cmd == DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_BYTES) &&
+			damon_sysfs_schemes_regions_updating) {
 		damon_sysfs_schemes_update_regions_stop(ctx);
+		damon_sysfs_schemes_regions_updating = false;
 		mutex_unlock(&damon_sysfs_lock);
 	}
 

@@ -1340,7 +1344,6 @@ static int damon_sysfs_commit_input(struct damon_sysfs_kdamond *kdamond)
 static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
 {
 	struct damon_sysfs_kdamond *kdamond;
-	static bool damon_sysfs_schemes_regions_updating;
 	bool total_bytes_only = false;
 	int err = 0;
 

DAMON_SYSFS can receive DAMOS tried regions update request while kdamond is already out of the main loop and before_terminate callback (damon_sysfs_before_terminate() in this case) is not yet called. And damon_sysfs_handle_cmd() can further be finished before the callback is invoked. Then, damon_sysfs_before_terminate() unlocks damon_sysfs_lock, which is not locked by anyone. This happens because the callback function assumes damon_sysfs_cmd_request_callback() should be called before it. Check if the assumption was true before doing the unlock, to avoid this problem.

---

I sent this patch yesterday, but seems not archived in lore.kernel.org. Sending again Cc-ing more mailing lists, to ensure it is sent and others can find it, to avoid any duplicated works.

 mm/damon/sysfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

index 33e1d5c9cb54..df165820c605 100644
@@ -1202,6 +1202,8 @@ static int damon_sysfs_set_targets(struct damon_ctx *ctx,
 	return 0;
 }
 
+static bool damon_sysfs_schemes_regions_updating;
+
 static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 {
 	struct damon_target *t, *next;

@@ -1209,10 +1211,12 @@ static void damon_sysfs_before_terminate(struct damon_ctx *ctx)
 
 	/* damon_sysfs_schemes_update_regions_stop() might not yet called */
 	kdamond = damon_sysfs_cmd_request.kdamond;
-	if (kdamond && damon_sysfs_cmd_request.cmd ==
+	if (kdamond && (damon_sysfs_cmd_request.cmd ==
 			DAMON_SYSFS_CMD_UPDATE_SCHEMES_TRIED_REGIONS &&
+			damon_sysfs_schemes_regions_updating) &&
 			ctx == kdamond->damon_ctx) {
 		damon_sysfs_schemes_update_regions_stop(ctx);
+		damon_sysfs_schemes_regions_updating = false;
 		mutex_unlock(&damon_sysfs_lock);
 	}
 

@@ -1331,7 +1335,6 @@ static int damon_sysfs_commit_input(struct damon_sysfs_kdamond *kdamond)
 static int damon_sysfs_cmd_request_callback(struct damon_ctx *c)
 {
 	struct damon_sysfs_kdamond *kdamond;
-	static bool damon_sysfs_schemes_regions_updating;
 	int err = 0;
 
 	/* avoid deadlock due to concurrent state_store('off') */

2.34.1

Now queued up, thanks.

greg k-h