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mm: replace PF_KCOMPACTD flag with kthread_func() check

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PF_KCOMPACTD was introduced by commit ce6d9c1c2b ("NFS: fix
nfs_release_folio() to not deadlock via kcompactd writeback") so
nfs_release_folio() could detect kcompactd context and skip writeback. 
The flag is only consumed by current_is_kcompactd(), whose sole caller is
nfs_release_folio().

Replace the flag-based check with kthread_func(current) == kcompactd,
freeing the 0x00010000 PF flag bit.

Link: https://lore.kernel.org/20260902131653.1338227-5-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Brendan Jackman <brendan.jackman@linux.dev>
Cc: Carlos Maiolino <cem@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
This commit is contained in:
Kefeng Wang 2026-09-02 21:16:53 +08:00 committed by Andrew Morton
parent 27517f701f
commit 44b74ec3ae
4 changed files with 13 additions and 10 deletions
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11
include/linux/compaction.h
View File

@ -81,10 +81,6 @@ static inline unsigned long compact_gap(unsigned int order)
return min(2UL << order, COMPACT_CLUSTER_MAX);
}
static inline int current_is_kcompactd(void)
{
return current->flags & PF_KCOMPACTD;
}
#ifdef CONFIG_COMPACTION
@ -103,7 +99,7 @@ extern void compaction_defer_reset(struct zone *zone, int order,
bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
int alloc_flags, gfp_t gfp_mask);
bool current_is_kcompactd(void);
extern void __meminit kcompactd_run(int nid);
extern void __meminit kcompactd_stop(int nid);
extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
@ -120,6 +116,11 @@ static inline bool compaction_suitable(struct zone *zone, int order,
return false;
}
static inline bool current_is_kcompactd(void)
{
return false;
}
static inline void kcompactd_run(int nid)
{
}

2
include/linux/sched.h
View File

@ -1809,7 +1809,7 @@ extern struct pid __rcu *cad_pid;
#define PF_USED_MATH 0x00002000 /* If unset the fpu must be initialized before use */
#define PF_USER_WORKER 0x00004000 /* Kernel thread cloned from userspace thread */
#define PF_NOFREEZE 0x00008000 /* This thread should not be frozen */
#define PF_KCOMPACTD 0x00010000 /* I am kcompactd */
#define PF__HOLE__00010000 0x00010000
#define PF__HOLE__00020000 0x00020000
#define PF_MEMALLOC_NOFS 0x00040000 /* All allocations inherit GFP_NOFS. See memalloc_nfs_save() */
#define PF_MEMALLOC_NOIO 0x00080000 /* All allocations inherit GFP_NOIO. See memalloc_noio_save() */

9
mm/compaction.c
View File

@ -3197,7 +3197,6 @@ static int kcompactd(void *p)
long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
long timeout = default_timeout;
current->flags |= PF_KCOMPACTD;
set_freezable();
pgdat->kcompactd_max_order = 0;
@ -3254,11 +3253,15 @@ static int kcompactd(void *p)
pgdat->proactive_compact_trigger = false;
}
current->flags &= ~PF_KCOMPACTD;
return 0;
}
bool current_is_kcompactd(void)
{
return kthread_func(current) == kcompactd;
}
EXPORT_SYMBOL_GPL(current_is_kcompactd);
/*
* This kcompactd start function will be called by init and node-hot-add.
* On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added.

1
tools/sched_ext/include/scx/common.bpf.h
View File

@ -31,7 +31,6 @@
#define PF_IDLE 0x00000002 /* I am an IDLE thread */
#define PF_IO_WORKER 0x00000010 /* Task is an IO worker */
#define PF_WQ_WORKER 0x00000020 /* I'm a workqueue worker */
#define PF_KCOMPACTD 0x00010000 /* I am kcompactd */
#define PF_KTHREAD 0x00200000 /* I am a kernel thread */
#define PF_EXITING 0x00000004
#define CLOCK_MONOTONIC 1