Re: [PATCH] fuse: defer dentry_tree_work until fuse_dentry_tree_init()

[Luis Henriques <luis@igalia.com>]

On Wed, Nov 11 2026, Sang-Heon Jeon wrote:

> inval_wq_set() schedules dentry_tree_work when inval_wq is enabled.
>
> But inval_wq_set() can be called at boot or module load before
> fuse_dentry_tree_init() initializes the work, so __queue_delayed_work()
> warns and the work never starts.
>
> So defer scheduling the work until fuse_dentry_tree_init() sets it up.
>
> Fixes: ab84ad597386 ("fuse: new work queue to periodically invalidate expired dentries")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
> ---
> QEMU based test result
> - booted with "fuse.inval_wq=5"

Thank you, Sang-Heon.  I've sent a fix for this already[1], but sashiko
still has some race complains which I haven't looked into yet.  But maybe
Miklos is happier with your patch, in which case you can add my

Reviewed-by: Luis Henriques <luis@igalia.com>

[1] https://lore.kernel.org/20261106155512.24801-1-luis%40igalia.com

Cheers,
-- 
Luís

> 1) AS-IS (before fix)
> [    0.011073] Kernel command line: rootwait root=/dev/vda console=tty1 console=ttyS0 nokaslr  fuse.inval_wq=5
> [    0.011114] ------------[ cut here ]------------
> [    0.011115] WARNING: kernel/workqueue.c:2704 at __queue_delayed_work+0x11a/0x140, CPU#0: swapper/0
> [    0.011124] Modules linked in:
> [    0.011128] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.4.0-rc1-00010-gab9787d7e66a #1 PREEMPT(undef) 
> [    0.011130] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1ubuntu1 04/01/2014
> [    0.011131] RIP: 0010:__queue_delayed_work+0x11a/0x140
> [ 0.011133] Code: c4 08 48 89 df 5b e9 85 28 0a 00 90 0f 0b 90 4c 8b 42 08 48 8d
> 42 08 49 39 c0 0f 84 1c ff ff ff 90 0f 0b 90 e9 13 ff ff ff 90 <0f> 0b 90 e9 ec
> fe ff ff bff
> [    0.011134] RSP: 0000:ffffffff82e03e00 EFLAGS: 00010003 ORIG_RAX: 0000000000000000
> [    0.011135] RAX: 0000000000000000 RBX: 0000000000000040 RCX: 0000000000001388
> [    0.011136] RDX: ffffffff83a3f320 RSI: 0000000000000000 RDI: 0000000000000040
> [    0.011136] RBP: 0000000000000000 R08: 0000000000000082 R09: 0000000000000001
> [    0.011136] R10: 000000000000000a R11: 000000000000000a R12: ffffffff82c09fd0
> [    0.011137] R13: ffff88807ffcfb89 R14: 0000000000000000 R15: 0000000000001388
> [    0.011140] FS:  0000000000000000(0000) GS:ffff8880fa26e000(0000) knlGS:0000000000000000
> [    0.011141] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.011141] CR2: ffff888003a67000 CR3: 0000000002e30000 CR4: 00000000000000b0
> [    0.011142] Call Trace:
> [    0.011143]  <TASK>
> [    0.011143]  queue_delayed_work_on+0x6a/0x80
> [    0.011145]  inval_wq_set+0xc4/0xe0
> [    0.011149]  parse_args+0x299/0x3c0
> [    0.011151]  ? __pfx_unknown_bootoption+0x10/0x10
> [    0.011154]  start_kernel+0x3b8/0x7c0
> [    0.011156]  ? __pfx_unknown_bootoption+0x10/0x10
> [    0.011157]  x86_64_start_reservations+0x24/0x30
> [    0.011160]  x86_64_start_kernel+0xd1/0xe0
> [    0.011162]  common_startup_64+0x13e/0x158
> [    0.011165]  </TASK>
> [    0.011166] ---[ end trace 0000000000000000 ]---
> [    0.011173] ------------[ cut here ]------------
>
> 2) TO-BE (after fix)
> - no error while booting, and also fuse_dentry_tree_work works well.
>
> ---
>  fs/fuse/dir.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> index da23ccd8685c..6965a77a871f 100644
> --- a/fs/fuse/dir.c
> +++ b/fs/fuse/dir.c
> @@ -39,6 +39,7 @@ static struct delayed_work dentry_tree_work;
>  /* Minimum invalidation work queue frequency */
>  #define FUSE_DENTRY_INVAL_FREQ_MIN 5
>  
> +static bool inval_wq_ready;
>  unsigned __read_mostly inval_wq;
>  static int inval_wq_set(const char *val, const struct kernel_param *kp)
>  {
> @@ -62,6 +63,10 @@ static int inval_wq_set(const char *val, const struct kernel_param *kp)
>  
>  	*((unsigned int *)kp->arg) = num;
>  
> +	/* Defer the work until fuse_dentry_tree_init() sets it up. */
> +	if (!inval_wq_ready)
> +		return 0;
> +
>  	if (num && !old)
>  		schedule_delayed_work(&dentry_tree_work,
>  				      secs_to_jiffies(num));
> @@ -224,6 +229,11 @@ void fuse_dentry_tree_init(void)
>  		dentry_hash[i].tree = RB_ROOT;
>  	}
>  	INIT_DELAYED_WORK(&dentry_tree_work, fuse_dentry_tree_work);
> +	inval_wq_ready = true;
> +
> +	if (inval_wq)
> +		schedule_delayed_work(&dentry_tree_work,
> +				      secs_to_jiffies(inval_wq));
>  }
>  
>  void fuse_dentry_tree_cleanup(void)
>
> base-commit: ab9787d7e66ac7e6e94fc975b37c5b56fff98ca9
> -- 
> 2.53.0
>