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mm/damon/sysfs: check DAMOS regions update progress from before_terminate()

PATCH Applied SeongJae Park 1 participant 2 messages Oct 7, 2023

Subsystems (3)
Stable branch Memory management DAMON
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SeongJae Park

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#0 lore raw

PATCH 1/1 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.

Fixes f1d13cacabe1 ("mm/damon/sysfs: implement DAMOS tried regions update command")
Cc <[email protected]> # 6.2.x
Signed-off-by SeongJae Park <[email protected]>
---
 mm/damon/sysfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
mm/damon/sysfs.c +5 -2
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;
Signature · 1 line
2.34.1
author maintainer
#1 lore raw

Hello,

Quoted 10 lines · On Sat, 7 Oct 2023 20:04:32 +0000 SeongJae Park <[email protected]> wrote:

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.

Quoted 2 lines
Fixes f1d13cacabe1 ("mm/damon/sysfs: implement DAMOS tried regions update command")
Cc <[email protected]> # 6.2.x

And this will not cleanly applied to 6.5.y, since this is based on latest mm-unstable tree. I will send a backport once this is merged into the mainline.

Thanks,
SJ

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