[PATCH v2 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users

[PATCH v2 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users

[Marco Crivellari]

Hi!

Below is a summary of a discussion about the Workqueue API and cpu isolation
considerations. Details and more information are available here:

        "workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND."
        https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/

=== Current situation: problems ===

Let's consider a nohz_full system with isolated CPUs: wq_unbound_cpumask is
set to the housekeeping CPUs, for !WQ_UNBOUND the local CPU is selected.

This leads to different scenarios if a work item is scheduled on an isolated
CPU where "delay" value is 0 or greater then 0:
        schedule_delayed_work(, 0);

This will be handled by __queue_work() that will queue the work item on the
current local (isolated) CPU, while:

        schedule_delayed_work(, 1);

Will move the timer on an housekeeping CPU, and schedule the work there.

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

=== Plan and future plans ===

This patchset is the first stone on a refactoring needed in order to
address the points aforementioned; it will have a positive impact also
on the cpu isolation, in the long term, moving away percpu workqueue in
favor to an unbound model.

These are the main steps:
1)  API refactoring (that this patch is introducing)
    -   Make more clear and uniform the system wq names, both per-cpu and
        unbound. This to avoid any possible confusion on what should be
        used.

    -   Introduction of WQ_PERCPU: this flag is the complement of WQ_UNBOUND,
        introduced in this patchset and used on all the callers that are not
        currently using WQ_UNBOUND.

        WQ_UNBOUND will be removed in a future release cycle.

        Most users don't need to be per-cpu, because they don't have
        locality requirements, because of that, a next future step will be
        make "unbound" the default behavior.

2)  Check who really needs to be per-cpu
    -   Remove the WQ_PERCPU flag when is not strictly required.

3)  Add a new API (prefer local cpu)
    -   There are users that don't require a local execution, like mentioned
        above; despite that, local execution yeld to performance gain.

        This new API will prefer the local execution, without requiring it.

=== Introduced Changes by this series ===

1) [P 1-2] Replace use of system_wq and system_unbound_wq

        system_wq is a per-CPU workqueue, but his name is not clear.
        system_unbound_wq is to be used when locality is not required.

        Because of that, system_wq has been renamed in system_percpu_wq, and
        system_unbound_wq has been renamed in system_dfl_wq.

2) [P 3] add WQ_PERCPU to remaining alloc_workqueue() users

        Every alloc_workqueue() caller should use one among WQ_PERCPU or
        WQ_UNBOUND. This is actually enforced warning if both or none of them
        are present at the same time.

        WQ_UNBOUND will be removed in a next release cycle.

Thanks!

---
Changes in v2:
- rebased on 6.17-rc5
- removed the "For maintainers" section from the cover letter: patches are
  already merged, there are no prerequisites.


Marco Crivellari (3):
  fs: replace use of system_unbound_wq with system_dfl_wq
  fs: replace use of system_wq with system_percpu_wq
  fs: WQ_PERCPU added to alloc_workqueue users

 fs/afs/callback.c                |  4 ++--
 fs/afs/main.c                    |  4 ++--
 fs/afs/write.c                   |  2 +-
 fs/aio.c                         |  2 +-
 fs/bcachefs/btree_write_buffer.c |  2 +-
 fs/bcachefs/io_read.c            |  8 ++++----
 fs/bcachefs/journal_io.c         |  2 +-
 fs/bcachefs/super.c              | 10 +++++-----
 fs/btrfs/block-group.c           |  2 +-
 fs/btrfs/disk-io.c               |  2 +-
 fs/btrfs/extent_map.c            |  2 +-
 fs/btrfs/space-info.c            |  4 ++--
 fs/btrfs/zoned.c                 |  2 +-
 fs/ceph/super.c                  |  2 +-
 fs/coredump.c                    |  2 +-
 fs/dlm/lowcomms.c                |  2 +-
 fs/dlm/main.c                    |  2 +-
 fs/ext4/mballoc.c                |  2 +-
 fs/fs-writeback.c                |  4 ++--
 fs/fuse/dev.c                    |  2 +-
 fs/fuse/inode.c                  |  2 +-
 fs/gfs2/main.c                   |  5 +++--
 fs/gfs2/ops_fstype.c             |  6 ++++--
 fs/netfs/misc.c                  |  2 +-
 fs/netfs/objects.c               |  2 +-
 fs/nfs/namespace.c               |  2 +-
 fs/nfs/nfs4renewd.c              |  2 +-
 fs/nfsd/filecache.c              |  2 +-
 fs/notify/mark.c                 |  4 ++--
 fs/ocfs2/dlm/dlmdomain.c         |  3 ++-
 fs/ocfs2/dlmfs/dlmfs.c           |  3 ++-
 fs/quota/dquot.c                 |  2 +-
 fs/smb/client/cifsfs.c           | 16 +++++++++++-----
 fs/smb/server/ksmbd_work.c       |  2 +-
 fs/smb/server/transport_rdma.c   |  3 ++-
 fs/super.c                       |  3 ++-
 fs/verity/verify.c               |  2 +-
 fs/xfs/xfs_log.c                 |  3 +--
 fs/xfs/xfs_mru_cache.c           |  3 ++-
 fs/xfs/xfs_super.c               | 15 ++++++++-------
 40 files changed, 79 insertions(+), 65 deletions(-)

-- 
2.51.0

[PATCH v2 1/3] fs: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

Adding system_dfl_wq to encourage its use when unbound work should be used.

The old system_unbound_wq will be kept for a few release cycles.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 fs/afs/callback.c                | 4 ++--
 fs/afs/write.c                   | 2 +-
 fs/bcachefs/btree_write_buffer.c | 2 +-
 fs/bcachefs/io_read.c            | 8 ++++----
 fs/bcachefs/journal_io.c         | 2 +-
 fs/btrfs/block-group.c           | 2 +-
 fs/btrfs/extent_map.c            | 2 +-
 fs/btrfs/space-info.c            | 4 ++--
 fs/btrfs/zoned.c                 | 2 +-
 fs/coredump.c                    | 2 +-
 fs/ext4/mballoc.c                | 2 +-
 fs/netfs/misc.c                  | 2 +-
 fs/netfs/objects.c               | 2 +-
 fs/nfsd/filecache.c              | 2 +-
 fs/notify/mark.c                 | 4 ++--
 fs/quota/dquot.c                 | 2 +-
 16 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/fs/afs/callback.c b/fs/afs/callback.c
index 69e1dd55b160..894d2bad6b6c 100644
--- a/fs/afs/callback.c
+++ b/fs/afs/callback.c
@@ -42,7 +42,7 @@ static void afs_volume_init_callback(struct afs_volume *volume)
 	list_for_each_entry(vnode, &volume->open_mmaps, cb_mmap_link) {
 		if (vnode->cb_v_check != atomic_read(&volume->cb_v_break)) {
 			afs_clear_cb_promise(vnode, afs_cb_promise_clear_vol_init_cb);
-			queue_work(system_unbound_wq, &vnode->cb_work);
+			queue_work(system_dfl_wq, &vnode->cb_work);
 		}
 	}
 
@@ -90,7 +90,7 @@ void __afs_break_callback(struct afs_vnode *vnode, enum afs_cb_break_reason reas
 		if (reason != afs_cb_break_for_deleted &&
 		    vnode->status.type == AFS_FTYPE_FILE &&
 		    atomic_read(&vnode->cb_nr_mmap))
-			queue_work(system_unbound_wq, &vnode->cb_work);
+			queue_work(system_dfl_wq, &vnode->cb_work);
 
 		trace_afs_cb_break(&vnode->fid, vnode->cb_break, reason, true);
 	} else {
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 2e7526ea883a..93ad86ff3345 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -172,7 +172,7 @@ static void afs_issue_write_worker(struct work_struct *work)
 void afs_issue_write(struct netfs_io_subrequest *subreq)
 {
 	subreq->work.func = afs_issue_write_worker;
-	if (!queue_work(system_unbound_wq, &subreq->work))
+	if (!queue_work(system_dfl_wq, &subreq->work))
 		WARN_ON_ONCE(1);
 }
 
diff --git a/fs/bcachefs/btree_write_buffer.c b/fs/bcachefs/btree_write_buffer.c
index 4b095235a0d2..0afb44ce1a85 100644
--- a/fs/bcachefs/btree_write_buffer.c
+++ b/fs/bcachefs/btree_write_buffer.c
@@ -827,7 +827,7 @@ int bch2_journal_keys_to_write_buffer_end(struct bch_fs *c, struct journal_keys_
 
 	if (bch2_btree_write_buffer_should_flush(c) &&
 	    __enumerated_ref_tryget(&c->writes, BCH_WRITE_REF_btree_write_buffer) &&
-	    !queue_work(system_unbound_wq, &c->btree_write_buffer.flush_work))
+	    !queue_work(system_dfl_wq, &c->btree_write_buffer.flush_work))
 		enumerated_ref_put(&c->writes, BCH_WRITE_REF_btree_write_buffer);
 
 	if (dst->wb == &wb->flushing)
diff --git a/fs/bcachefs/io_read.c b/fs/bcachefs/io_read.c
index e0874ad9a6cf..460e2e6341f1 100644
--- a/fs/bcachefs/io_read.c
+++ b/fs/bcachefs/io_read.c
@@ -684,7 +684,7 @@ static void bch2_rbio_error(struct bch_read_bio *rbio,
 
 	if (bch2_err_matches(ret, BCH_ERR_data_read_retry)) {
 		bch2_rbio_punt(rbio, bch2_rbio_retry,
-			       RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+			       RBIO_CONTEXT_UNBOUND, system_dfl_wq);
 	} else {
 		rbio = bch2_rbio_free(rbio);
 
@@ -921,10 +921,10 @@ static void __bch2_read_endio(struct work_struct *work)
 	bch2_rbio_error(rbio, -BCH_ERR_data_read_retry_csum_err, BLK_STS_IOERR);
 	goto out;
 decompression_err:
-	bch2_rbio_punt(rbio, bch2_read_decompress_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+	bch2_rbio_punt(rbio, bch2_read_decompress_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
 	goto out;
 decrypt_err:
-	bch2_rbio_punt(rbio, bch2_read_decrypt_err, RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+	bch2_rbio_punt(rbio, bch2_read_decrypt_err, RBIO_CONTEXT_UNBOUND, system_dfl_wq);
 	goto out;
 }
 
@@ -963,7 +963,7 @@ static void bch2_read_endio(struct bio *bio)
 	    rbio->promote ||
 	    crc_is_compressed(rbio->pick.crc) ||
 	    bch2_csum_type_is_encryption(rbio->pick.crc.csum_type))
-		context = RBIO_CONTEXT_UNBOUND,	wq = system_unbound_wq;
+		context = RBIO_CONTEXT_UNBOUND,	wq = system_dfl_wq;
 	else if (rbio->pick.crc.csum_type)
 		context = RBIO_CONTEXT_HIGHPRI,	wq = system_highpri_wq;
 
diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index 9e028dbcc3d0..29bea8e0e495 100644
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -1362,7 +1362,7 @@ int bch2_journal_read(struct bch_fs *c,
 					  BCH_DEV_READ_REF_journal_read))
 			closure_call(&ca->journal.read,
 				     bch2_journal_read_device,
-				     system_unbound_wq,
+				     system_dfl_wq,
 				     &jlist.cl);
 		else
 			degraded = true;
diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 9bf282d2453c..9a0af7e4a935 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2031,7 +2031,7 @@ void btrfs_reclaim_bgs(struct btrfs_fs_info *fs_info)
 	btrfs_reclaim_sweep(fs_info);
 	spin_lock(&fs_info->unused_bgs_lock);
 	if (!list_empty(&fs_info->reclaim_bgs))
-		queue_work(system_unbound_wq, &fs_info->reclaim_bgs_work);
+		queue_work(system_dfl_wq, &fs_info->reclaim_bgs_work);
 	spin_unlock(&fs_info->unused_bgs_lock);
 }
 
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 57f52585a6dd..9a5a497edc97 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1372,7 +1372,7 @@ void btrfs_free_extent_maps(struct btrfs_fs_info *fs_info, long nr_to_scan)
 	if (atomic64_cmpxchg(&fs_info->em_shrinker_nr_to_scan, 0, nr_to_scan) != 0)
 		return;
 
-	queue_work(system_unbound_wq, &fs_info->em_shrinker_work);
+	queue_work(system_dfl_wq, &fs_info->em_shrinker_work);
 }
 
 void btrfs_init_extent_map_shrinker_work(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 0481c693ac2e..c573d80550ad 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -1830,7 +1830,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
 							  space_info->flags,
 							  orig_bytes, flush,
 							  "enospc");
-				queue_work(system_unbound_wq, async_work);
+				queue_work(system_dfl_wq, async_work);
 			}
 		} else {
 			list_add_tail(&ticket.list,
@@ -1847,7 +1847,7 @@ static int __reserve_bytes(struct btrfs_fs_info *fs_info,
 		    need_preemptive_reclaim(fs_info, space_info)) {
 			trace_btrfs_trigger_flush(fs_info, space_info->flags,
 						  orig_bytes, flush, "preempt");
-			queue_work(system_unbound_wq,
+			queue_work(system_dfl_wq,
 				   &fs_info->preempt_reclaim_work);
 		}
 	}
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index ea662036f441..3d554ebca08c 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -2515,7 +2515,7 @@ void btrfs_schedule_zone_finish_bg(struct btrfs_block_group *bg,
 	refcount_inc(&eb->refs);
 	bg->last_eb = eb;
 	INIT_WORK(&bg->zone_finish_work, btrfs_zone_finish_endio_workfn);
-	queue_work(system_unbound_wq, &bg->zone_finish_work);
+	queue_work(system_dfl_wq, &bg->zone_finish_work);
 }
 
 void btrfs_clear_data_reloc_bg(struct btrfs_block_group *bg)
diff --git a/fs/coredump.c b/fs/coredump.c
index 5dce257c67fc..f36354785e11 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -635,7 +635,7 @@ static int umh_coredump_setup(struct subprocess_info *info, struct cred *new)
 
 		/*
 		 * Usermode helpers are childen of either
-		 * system_unbound_wq or of kthreadd. So we know that
+		 * system_dfl_wq or of kthreadd. So we know that
 		 * we're starting off with a clean file descriptor
 		 * table. So we should always be able to use
 		 * COREDUMP_PIDFD_NUMBER as our file descriptor value.
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 5898d92ba19f..8b18802e83eb 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3995,7 +3995,7 @@ void ext4_process_freed_data(struct super_block *sb, tid_t commit_tid)
 		list_splice_tail(&freed_data_list, &sbi->s_discard_list);
 		spin_unlock(&sbi->s_md_lock);
 		if (wake)
-			queue_work(system_unbound_wq, &sbi->s_discard_work);
+			queue_work(system_dfl_wq, &sbi->s_discard_work);
 	} else {
 		list_for_each_entry_safe(entry, tmp, &freed_data_list, efd_list)
 			kmem_cache_free(ext4_free_data_cachep, entry);
diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 20748bcfbf59..486166460e17 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -321,7 +321,7 @@ void netfs_wake_collector(struct netfs_io_request *rreq)
 {
 	if (test_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags) &&
 	    !test_bit(NETFS_RREQ_RETRYING, &rreq->flags)) {
-		queue_work(system_unbound_wq, &rreq->work);
+		queue_work(system_dfl_wq, &rreq->work);
 	} else {
 		trace_netfs_rreq(rreq, netfs_rreq_trace_wake_queue);
 		wake_up(&rreq->waitq);
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index e8c99738b5bb..2ebe56b24ddd 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -163,7 +163,7 @@ void netfs_put_request(struct netfs_io_request *rreq, enum netfs_rreq_ref_trace
 		dead = __refcount_dec_and_test(&rreq->ref, &r);
 		trace_netfs_rreq_ref(debug_id, r - 1, what);
 		if (dead)
-			WARN_ON(!queue_work(system_unbound_wq, &rreq->cleanup_work));
+			WARN_ON(!queue_work(system_dfl_wq, &rreq->cleanup_work));
 	}
 }
 
diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 732abf6b92a5..85ca663c052c 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -113,7 +113,7 @@ static void
 nfsd_file_schedule_laundrette(void)
 {
 	if (test_bit(NFSD_FILE_CACHE_UP, &nfsd_file_flags))
-		queue_delayed_work(system_unbound_wq, &nfsd_filecache_laundrette,
+		queue_delayed_work(system_dfl_wq, &nfsd_filecache_laundrette,
 				   NFSD_LAUNDRETTE_DELAY);
 }
 
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 798340db69d7..55a03bb05aa1 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -428,7 +428,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
 		conn->destroy_next = connector_destroy_list;
 		connector_destroy_list = conn;
 		spin_unlock(&destroy_lock);
-		queue_work(system_unbound_wq, &connector_reaper_work);
+		queue_work(system_dfl_wq, &connector_reaper_work);
 	}
 	/*
 	 * Note that we didn't update flags telling whether inode cares about
@@ -439,7 +439,7 @@ void fsnotify_put_mark(struct fsnotify_mark *mark)
 	spin_lock(&destroy_lock);
 	list_add(&mark->g_list, &destroy_list);
 	spin_unlock(&destroy_lock);
-	queue_delayed_work(system_unbound_wq, &reaper_work,
+	queue_delayed_work(system_dfl_wq, &reaper_work,
 			   FSNOTIFY_REAPER_DELAY);
 }
 EXPORT_SYMBOL_GPL(fsnotify_put_mark);
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index df4a9b348769..afa15a214538 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -881,7 +881,7 @@ void dqput(struct dquot *dquot)
 	put_releasing_dquots(dquot);
 	atomic_dec(&dquot->dq_count);
 	spin_unlock(&dq_list_lock);
-	queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
+	queue_delayed_work(system_dfl_wq, &quota_release_work, 1);
 }
 EXPORT_SYMBOL(dqput);
 
-- 
2.51.0

[PATCH v2 2/3] fs: replace use of system_wq with system_percpu_wq

[Marco Crivellari]

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users.
Make it clear by adding a system_percpu_wq to all the fs subsystem.

The old wq will be kept for a few release cylces.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 fs/aio.c            | 2 +-
 fs/fs-writeback.c   | 2 +-
 fs/fuse/dev.c       | 2 +-
 fs/fuse/inode.c     | 2 +-
 fs/nfs/namespace.c  | 2 +-
 fs/nfs/nfs4renewd.c | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 7fc7b6221312..6002617f078c 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -636,7 +636,7 @@ static void free_ioctx_reqs(struct percpu_ref *ref)
 
 	/* Synchronize against RCU protected table->table[] dereferences */
 	INIT_RCU_WORK(&ctx->free_rwork, free_ioctx);
-	queue_rcu_work(system_wq, &ctx->free_rwork);
+	queue_rcu_work(system_percpu_wq, &ctx->free_rwork);
 }
 
 /*
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index a07b8cf73ae2..21aaed728929 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2442,7 +2442,7 @@ static int dirtytime_interval_handler(const struct ctl_table *table, int write,
 
 	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	if (ret == 0 && write)
-		mod_delayed_work(system_wq, &dirtytime_work, 0);
+		mod_delayed_work(system_percpu_wq, &dirtytime_work, 0);
 	return ret;
 }
 
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e80cd8f2c049..8520eb94c527 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -119,7 +119,7 @@ void fuse_check_timeout(struct work_struct *work)
 	    goto abort_conn;
 
 out:
-	queue_delayed_work(system_wq, &fc->timeout.work,
+	queue_delayed_work(system_percpu_wq, &fc->timeout.work,
 			   fuse_timeout_timer_freq);
 	return;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 67c2318bfc42..1e044c4f4a00 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1268,7 +1268,7 @@ static void set_request_timeout(struct fuse_conn *fc, unsigned int timeout)
 {
 	fc->timeout.req_timeout = secs_to_jiffies(timeout);
 	INIT_DELAYED_WORK(&fc->timeout.work, fuse_check_timeout);
-	queue_delayed_work(system_wq, &fc->timeout.work,
+	queue_delayed_work(system_percpu_wq, &fc->timeout.work,
 			   fuse_timeout_timer_freq);
 }
 
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 7f1ec9c67ff2..f9a3a1fbf44c 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -335,7 +335,7 @@ static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
 			num *= HZ;
 		*((int *)kp->arg) = num;
 		if (!list_empty(&nfs_automount_list))
-			mod_delayed_work(system_wq, &nfs_automount_task, num);
+			mod_delayed_work(system_percpu_wq, &nfs_automount_task, num);
 	} else {
 		*((int *)kp->arg) = -1*HZ;
 		cancel_delayed_work(&nfs_automount_task);
diff --git a/fs/nfs/nfs4renewd.c b/fs/nfs/nfs4renewd.c
index db3811af0796..18ae614e5a6c 100644
--- a/fs/nfs/nfs4renewd.c
+++ b/fs/nfs/nfs4renewd.c
@@ -122,7 +122,7 @@ nfs4_schedule_state_renewal(struct nfs_client *clp)
 		timeout = 5 * HZ;
 	dprintk("%s: requeueing work. Lease period = %ld\n",
 			__func__, (timeout + HZ - 1) / HZ);
-	mod_delayed_work(system_wq, &clp->cl_renewd, timeout);
+	mod_delayed_work(system_percpu_wq, &clp->cl_renewd, timeout);
 	set_bit(NFS_CS_RENEWD, &clp->cl_res_state);
 	spin_unlock(&clp->cl_lock);
 }
-- 
2.51.0

[PATCH v2 3/3] fs: WQ_PERCPU added to alloc_workqueue users

[Marco Crivellari]

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.
This lack of consistentcy cannot be addressed without refactoring the API.

alloc_workqueue() treats all queues as per-CPU by default, while unbound
workqueues must opt-in via WQ_UNBOUND.

This default is suboptimal: most workloads benefit from unbound queues,
allowing the scheduler to place worker threads where they’re needed and
reducing noise when CPUs are isolated.

This patch adds a new WQ_PERCPU flag to all the fs subsystem users to
explicitly request the use of the per-CPU behavior. Both flags coexist
for one release cycle to allow callers to transition their calls.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

All existing users have been updated accordingly.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
 fs/afs/main.c                  |  4 ++--
 fs/bcachefs/super.c            | 10 +++++-----
 fs/btrfs/disk-io.c             |  2 +-
 fs/ceph/super.c                |  2 +-
 fs/dlm/lowcomms.c              |  2 +-
 fs/dlm/main.c                  |  2 +-
 fs/fs-writeback.c              |  2 +-
 fs/gfs2/main.c                 |  5 +++--
 fs/gfs2/ops_fstype.c           |  6 ++++--
 fs/ocfs2/dlm/dlmdomain.c       |  3 ++-
 fs/ocfs2/dlmfs/dlmfs.c         |  3 ++-
 fs/smb/client/cifsfs.c         | 16 +++++++++++-----
 fs/smb/server/ksmbd_work.c     |  2 +-
 fs/smb/server/transport_rdma.c |  3 ++-
 fs/super.c                     |  3 ++-
 fs/verity/verify.c             |  2 +-
 fs/xfs/xfs_log.c               |  3 +--
 fs/xfs/xfs_mru_cache.c         |  3 ++-
 fs/xfs/xfs_super.c             | 15 ++++++++-------
 19 files changed, 51 insertions(+), 37 deletions(-)

diff --git a/fs/afs/main.c b/fs/afs/main.c
index 02475d415d88..e6bb8237db98 100644
--- a/fs/afs/main.c
+++ b/fs/afs/main.c
@@ -169,13 +169,13 @@ static int __init afs_init(void)
 
 	printk(KERN_INFO "kAFS: Red Hat AFS client v0.1 registering.\n");
 
-	afs_wq = alloc_workqueue("afs", 0, 0);
+	afs_wq = alloc_workqueue("afs", WQ_PERCPU, 0);
 	if (!afs_wq)
 		goto error_afs_wq;
 	afs_async_calls = alloc_workqueue("kafsd", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
 	if (!afs_async_calls)
 		goto error_async;
-	afs_lock_manager = alloc_workqueue("kafs_lockd", WQ_MEM_RECLAIM, 0);
+	afs_lock_manager = alloc_workqueue("kafs_lockd", WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!afs_lock_manager)
 		goto error_lockmgr;
 
diff --git a/fs/bcachefs/super.c b/fs/bcachefs/super.c
index c46b1053a02c..f2417d298b84 100644
--- a/fs/bcachefs/super.c
+++ b/fs/bcachefs/super.c
@@ -801,13 +801,13 @@ int bch2_fs_init_rw(struct bch_fs *c)
 	if (!(c->btree_update_wq = alloc_workqueue("bcachefs",
 				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_UNBOUND, 512)) ||
 	    !(c->btree_write_complete_wq = alloc_workqueue("bcachefs_btree_write_complete",
-				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
+				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_PERCPU, 1)) ||
 	    !(c->copygc_wq = alloc_workqueue("bcachefs_copygc",
-				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 1)) ||
+				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE|WQ_PERCPU, 1)) ||
 	    !(c->btree_write_submit_wq = alloc_workqueue("bcachefs_btree_write_sumit",
-				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 1)) ||
+				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_PERCPU, 1)) ||
 	    !(c->write_ref_wq = alloc_workqueue("bcachefs_write_ref",
-				WQ_FREEZABLE, 0)))
+				WQ_FREEZABLE|WQ_PERCPU, 0)))
 		return bch_err_throw(c, ENOMEM_fs_other_alloc);
 
 	int ret = bch2_fs_btree_interior_update_init(c) ?:
@@ -975,7 +975,7 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts *opts,
 		sizeof(struct sort_iter_set);
 
 	if (!(c->btree_read_complete_wq = alloc_workqueue("bcachefs_btree_read_complete",
-				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM, 512)) ||
+				WQ_HIGHPRI|WQ_FREEZABLE|WQ_MEM_RECLAIM|WQ_PERCPU, 512)) ||
 	    enumerated_ref_init(&c->writes, BCH_WRITE_REF_NR,
 				bch2_writes_disabled) ||
 	    mempool_init_kmalloc_pool(&c->fill_iter, 1, iter_size) ||
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 70fc4e7cc5a0..aa4393eba997 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1958,7 +1958,7 @@ static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info)
 {
 	u32 max_active = fs_info->thread_pool_size;
 	unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;
-	unsigned int ordered_flags = WQ_MEM_RECLAIM | WQ_FREEZABLE;
+	unsigned int ordered_flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU;
 
 	fs_info->workers =
 		btrfs_alloc_workqueue(fs_info, "worker", flags, max_active, 16);
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index c3eb651862c5..2dc64515f259 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -862,7 +862,7 @@ static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
 	fsc->inode_wq = alloc_workqueue("ceph-inode", WQ_UNBOUND, 0);
 	if (!fsc->inode_wq)
 		goto fail_client;
-	fsc->cap_wq = alloc_workqueue("ceph-cap", 0, 1);
+	fsc->cap_wq = alloc_workqueue("ceph-cap", WQ_PERCPU, 1);
 	if (!fsc->cap_wq)
 		goto fail_inode_wq;
 
diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index e4373bce1bc2..9a0b6c2b6b01 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1703,7 +1703,7 @@ static int work_start(void)
 		return -ENOMEM;
 	}
 
-	process_workqueue = alloc_workqueue("dlm_process", WQ_HIGHPRI | WQ_BH, 0);
+	process_workqueue = alloc_workqueue("dlm_process", WQ_HIGHPRI | WQ_BH | WQ_PERCPU, 0);
 	if (!process_workqueue) {
 		log_print("can't start dlm_process");
 		destroy_workqueue(io_workqueue);
diff --git a/fs/dlm/main.c b/fs/dlm/main.c
index 4887c8a05318..a44d16da7187 100644
--- a/fs/dlm/main.c
+++ b/fs/dlm/main.c
@@ -52,7 +52,7 @@ static int __init init_dlm(void)
 	if (error)
 		goto out_user;
 
-	dlm_wq = alloc_workqueue("dlm_wq", 0, 0);
+	dlm_wq = alloc_workqueue("dlm_wq", WQ_PERCPU, 0);
 	if (!dlm_wq) {
 		error = -ENOMEM;
 		goto out_plock;
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 21aaed728929..4f64971f8c70 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1180,7 +1180,7 @@ void cgroup_writeback_umount(struct super_block *sb)
 
 static int __init cgroup_writeback_init(void)
 {
-	isw_wq = alloc_workqueue("inode_switch_wbs", 0, 0);
+	isw_wq = alloc_workqueue("inode_switch_wbs", WQ_PERCPU, 0);
 	if (!isw_wq)
 		return -ENOMEM;
 	return 0;
diff --git a/fs/gfs2/main.c b/fs/gfs2/main.c
index 0727f60ad028..9d65719353fa 100644
--- a/fs/gfs2/main.c
+++ b/fs/gfs2/main.c
@@ -151,7 +151,8 @@ static int __init init_gfs2_fs(void)
 
 	error = -ENOMEM;
 	gfs2_recovery_wq = alloc_workqueue("gfs2_recovery",
-					  WQ_MEM_RECLAIM | WQ_FREEZABLE, 0);
+					  WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU,
+					  0);
 	if (!gfs2_recovery_wq)
 		goto fail_wq1;
 
@@ -160,7 +161,7 @@ static int __init init_gfs2_fs(void)
 	if (!gfs2_control_wq)
 		goto fail_wq2;
 
-	gfs2_freeze_wq = alloc_workqueue("gfs2_freeze", 0, 0);
+	gfs2_freeze_wq = alloc_workqueue("gfs2_freeze", WQ_PERCPU, 0);
 
 	if (!gfs2_freeze_wq)
 		goto fail_wq3;
diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index efe99b732551..05f936cc5db7 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1193,13 +1193,15 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	error = -ENOMEM;
 	sdp->sd_glock_wq = alloc_workqueue("gfs2-glock/%s",
-			WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_FREEZABLE, 0,
+			WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_FREEZABLE | WQ_PERCPU,
+			0,
 			sdp->sd_fsname);
 	if (!sdp->sd_glock_wq)
 		goto fail_iput;
 
 	sdp->sd_delete_wq = alloc_workqueue("gfs2-delete/%s",
-			WQ_MEM_RECLAIM | WQ_FREEZABLE, 0, sdp->sd_fsname);
+			WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU, 0,
+			sdp->sd_fsname);
 	if (!sdp->sd_delete_wq)
 		goto fail_glock_wq;
 
diff --git a/fs/ocfs2/dlm/dlmdomain.c b/fs/ocfs2/dlm/dlmdomain.c
index 2018501b2249..2347a50f079b 100644
--- a/fs/ocfs2/dlm/dlmdomain.c
+++ b/fs/ocfs2/dlm/dlmdomain.c
@@ -1876,7 +1876,8 @@ static int dlm_join_domain(struct dlm_ctxt *dlm)
 	dlm_debug_init(dlm);
 
 	snprintf(wq_name, O2NM_MAX_NAME_LEN, "dlm_wq-%s", dlm->name);
-	dlm->dlm_worker = alloc_workqueue(wq_name, WQ_MEM_RECLAIM, 0);
+	dlm->dlm_worker = alloc_workqueue(wq_name, WQ_MEM_RECLAIM | WQ_PERCPU,
+					  0);
 	if (!dlm->dlm_worker) {
 		status = -ENOMEM;
 		mlog_errno(status);
diff --git a/fs/ocfs2/dlmfs/dlmfs.c b/fs/ocfs2/dlmfs/dlmfs.c
index 5130ec44e5e1..0b730535b2c8 100644
--- a/fs/ocfs2/dlmfs/dlmfs.c
+++ b/fs/ocfs2/dlmfs/dlmfs.c
@@ -595,7 +595,8 @@ static int __init init_dlmfs_fs(void)
 	}
 	cleanup_inode = 1;
 
-	user_dlm_worker = alloc_workqueue("user_dlm", WQ_MEM_RECLAIM, 0);
+	user_dlm_worker = alloc_workqueue("user_dlm",
+					  WQ_MEM_RECLAIM | WQ_PERCPU, 0);
 	if (!user_dlm_worker) {
 		status = -ENOMEM;
 		goto bail;
diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index e1848276bab4..c99f3916cab2 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1895,7 +1895,9 @@ init_cifs(void)
 		cifs_dbg(VFS, "dir_cache_timeout set to max of 65000 seconds\n");
 	}
 
-	cifsiod_wq = alloc_workqueue("cifsiod", WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+	cifsiod_wq = alloc_workqueue("cifsiod",
+				     WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+				     0);
 	if (!cifsiod_wq) {
 		rc = -ENOMEM;
 		goto out_clean_proc;
@@ -1923,28 +1925,32 @@ init_cifs(void)
 	}
 
 	cifsoplockd_wq = alloc_workqueue("cifsoplockd",
-					 WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+					 WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+					 0);
 	if (!cifsoplockd_wq) {
 		rc = -ENOMEM;
 		goto out_destroy_fileinfo_put_wq;
 	}
 
 	deferredclose_wq = alloc_workqueue("deferredclose",
-					   WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+					   WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+					   0);
 	if (!deferredclose_wq) {
 		rc = -ENOMEM;
 		goto out_destroy_cifsoplockd_wq;
 	}
 
 	serverclose_wq = alloc_workqueue("serverclose",
-					   WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+					   WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+					   0);
 	if (!serverclose_wq) {
 		rc = -ENOMEM;
 		goto out_destroy_deferredclose_wq;
 	}
 
 	cfid_put_wq = alloc_workqueue("cfid_put_wq",
-				      WQ_FREEZABLE|WQ_MEM_RECLAIM, 0);
+				      WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
+				      0);
 	if (!cfid_put_wq) {
 		rc = -ENOMEM;
 		goto out_destroy_serverclose_wq;
diff --git a/fs/smb/server/ksmbd_work.c b/fs/smb/server/ksmbd_work.c
index 72b00ca6e455..4a71f46d7020 100644
--- a/fs/smb/server/ksmbd_work.c
+++ b/fs/smb/server/ksmbd_work.c
@@ -78,7 +78,7 @@ int ksmbd_work_pool_init(void)
 
 int ksmbd_workqueue_init(void)
 {
-	ksmbd_wq = alloc_workqueue("ksmbd-io", 0, 0);
+	ksmbd_wq = alloc_workqueue("ksmbd-io", WQ_PERCPU, 0);
 	if (!ksmbd_wq)
 		return -ENOMEM;
 	return 0;
diff --git a/fs/smb/server/transport_rdma.c b/fs/smb/server/transport_rdma.c
index 5466aa8c39b1..4f89a7a33a26 100644
--- a/fs/smb/server/transport_rdma.c
+++ b/fs/smb/server/transport_rdma.c
@@ -2177,7 +2177,8 @@ int ksmbd_rdma_init(void)
 	 * for lack of credits
 	 */
 	smb_direct_wq = alloc_workqueue("ksmbd-smb_direct-wq",
-					WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
+					WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_PERCPU,
+					0);
 	if (!smb_direct_wq)
 		return -ENOMEM;
 
diff --git a/fs/super.c b/fs/super.c
index 7f876f32343a..5cb3f41e42ca 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -2314,7 +2314,8 @@ int sb_init_dio_done_wq(struct super_block *sb)
 {
 	struct workqueue_struct *old;
 	struct workqueue_struct *wq = alloc_workqueue("dio/%s",
-						      WQ_MEM_RECLAIM, 0,
+						      WQ_MEM_RECLAIM | WQ_PERCPU,
+						      0,
 						      sb->s_id);
 	if (!wq)
 		return -ENOMEM;
diff --git a/fs/verity/verify.c b/fs/verity/verify.c
index a1f00c3fd3b2..628c23710f9f 100644
--- a/fs/verity/verify.c
+++ b/fs/verity/verify.c
@@ -355,7 +355,7 @@ void __init fsverity_init_workqueue(void)
 	 * latency on ARM64.
 	 */
 	fsverity_read_workqueue = alloc_workqueue("fsverity_read_queue",
-						  WQ_HIGHPRI,
+						  WQ_HIGHPRI | WQ_PERCPU,
 						  num_online_cpus());
 	if (!fsverity_read_workqueue)
 		panic("failed to allocate fsverity_read_queue");
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index c8a57e21a1d3..0da19472d603 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1489,8 +1489,7 @@ xlog_alloc_log(
 	log->l_iclog->ic_prev = prev_iclog;	/* re-write 1st prev ptr */
 
 	log->l_ioend_workqueue = alloc_workqueue("xfs-log/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM |
-				    WQ_HIGHPRI),
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_PERCPU),
 			0, mp->m_super->s_id);
 	if (!log->l_ioend_workqueue)
 		goto out_free_iclog;
diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
index 866c71d9fbae..73b7e72944e4 100644
--- a/fs/xfs/xfs_mru_cache.c
+++ b/fs/xfs/xfs_mru_cache.c
@@ -293,7 +293,8 @@ int
 xfs_mru_cache_init(void)
 {
 	xfs_mru_reap_wq = alloc_workqueue("xfs_mru_cache",
-			XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 1);
+			XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU),
+			1);
 	if (!xfs_mru_reap_wq)
 		return -ENOMEM;
 	return 0;
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index bb0a82635a77..43e9aab71610 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -578,19 +578,19 @@ xfs_init_mount_workqueues(
 	struct xfs_mount	*mp)
 {
 	mp->m_buf_workqueue = alloc_workqueue("xfs-buf/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
 			1, mp->m_super->s_id);
 	if (!mp->m_buf_workqueue)
 		goto out;
 
 	mp->m_unwritten_workqueue = alloc_workqueue("xfs-conv/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
 			0, mp->m_super->s_id);
 	if (!mp->m_unwritten_workqueue)
 		goto out_destroy_buf;
 
 	mp->m_reclaim_workqueue = alloc_workqueue("xfs-reclaim/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
 			0, mp->m_super->s_id);
 	if (!mp->m_reclaim_workqueue)
 		goto out_destroy_unwritten;
@@ -602,13 +602,14 @@ xfs_init_mount_workqueues(
 		goto out_destroy_reclaim;
 
 	mp->m_inodegc_wq = alloc_workqueue("xfs-inodegc/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM),
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU),
 			1, mp->m_super->s_id);
 	if (!mp->m_inodegc_wq)
 		goto out_destroy_blockgc;
 
 	mp->m_sync_workqueue = alloc_workqueue("xfs-sync/%s",
-			XFS_WQFLAGS(WQ_FREEZABLE), 0, mp->m_super->s_id);
+			XFS_WQFLAGS(WQ_FREEZABLE | WQ_PERCPU), 0,
+			mp->m_super->s_id);
 	if (!mp->m_sync_workqueue)
 		goto out_destroy_inodegc;
 
@@ -2596,8 +2597,8 @@ xfs_init_workqueues(void)
 	 * AGs in all the filesystems mounted. Hence use the default large
 	 * max_active value for this workqueue.
 	 */
-	xfs_alloc_wq = alloc_workqueue("xfsalloc",
-			XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE), 0);
+	xfs_alloc_wq = alloc_workqueue("xfsalloc", XFS_WQFLAGS(WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_PERCPU),
+			0);
 	if (!xfs_alloc_wq)
 		return -ENOMEM;
 
-- 
2.51.0

Re: [PATCH v2 0/3] fs: replace wq users and add WQ_PERCPU to alloc_workqueue() users

[Christian Brauner]

On Tue, 16 Sep 2025 10:29:03 +0200, Marco Crivellari wrote:
> Below is a summary of a discussion about the Workqueue API and cpu isolation
> considerations. Details and more information are available here:
> 
>         "workqueue: Always use wq_select_unbound_cpu() for WORK_CPU_UNBOUND."
>         https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
> 
> === Current situation: problems ===
> 
> [...]

Applied to the vfs-6.18.workqueue branch of the vfs/vfs.git tree.
Patches in the vfs-6.18.workqueue branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.18.workqueue

[1/3] fs: replace use of system_unbound_wq with system_dfl_wq
      https://git.kernel.org/vfs/vfs/c/08621f25a268
[2/3] fs: replace use of system_wq with system_percpu_wq
      https://git.kernel.org/vfs/vfs/c/d33fa88429c5
[3/3] fs: WQ_PERCPU added to alloc_workqueue users
      https://git.kernel.org/vfs/vfs/c/13549bd48bbf