Re: [PATCH v2 for-akpm for-6.14-rcX] NFS: fix nfs_release_folio() to not deadlock via kcompactd writeback

[Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>]

On Mon, 24 Feb 2025 21:20:02 -0500 Mike Snitzer <snitzer@xxxxxxxxxx> wrote:

> Add PF_KCOMPACTD flag and current_is_kcompactd() helper to check for
> it so nfs_release_folio() can skip calling nfs_wb_folio() from
> kcompactd.
> 

--- a/mm/compaction.c~a
+++ a/mm/compaction.c
@@ -3182,7 +3182,7 @@ static int kcompactd(void *p)
 	long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
 	long timeout = default_timeout;
 
-	tsk->flags |= PF_KCOMPACTD;
+	current->flags |= PF_KCOMPACTD;
 	set_freezable();
 
 	pgdat->kcompactd_max_order = 0;
@@ -3239,7 +3239,7 @@ static int kcompactd(void *p)
 			pgdat->proactive_compact_trigger = false;
 	}
 
-	tsk->flags &= ~PF_KCOMPACTD;
+	current->flags &= ~PF_KCOMPACTD;
 
 	return 0;
 }

I am of course concerned about how well tested this was!