linux-kernel - Re: [PATCH 1/1] mm: vmalloc: Bail out early in find_vmap

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Date: Sun, 24 Mar 2024 16:32:00 -0700
From: Christoph Hellwig <hch@...radead.org>
To: "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Baoquan He <bhe@...hat.com>,
	Lorenzo Stoakes <lstoakes@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Matthew Wilcox <willy@...radead.org>,
	Dave Chinner <david@...morbit.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org
Subject: Re: [PATCH 1/1] mm: vmalloc: Bail out early in find_vmap_area() if
 vmap is not init

I guess this is ok as an urgend bandaid to get s390 booting again,
but calling find_vmap_area before the vmap area is initialized
seems an actual issue in the s390 mm init code.

Adding the s390 maintainers to see if they have and idea how this could
get fixed in a better way.


On Sat, Mar 23, 2024 at 03:15:44PM +0100, Uladzislau Rezki (Sony) wrote:
> During the boot the s390 system triggers "spinlock bad magic" messages
> if the spinlock debugging is enabled:
> 
> [    0.465445] BUG: spinlock bad magic on CPU#0, swapper/0
> [    0.465490]  lock: single+0x1860/0x1958, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> [    0.466067] CPU: 0 PID: 0 Comm: swapper Not tainted 6.8.0-12955-g8e938e398669 #1
> [    0.466188] Hardware name: QEMU 8561 QEMU (KVM/Linux)
> [    0.466270] Call Trace:
> [    0.466470]  [<00000000011f26c8>] dump_stack_lvl+0x98/0xd8
> [    0.466516]  [<00000000001dcc6a>] do_raw_spin_lock+0x8a/0x108
> [    0.466545]  [<000000000042146c>] find_vmap_area+0x6c/0x108
> [    0.466572]  [<000000000042175a>] find_vm_area+0x22/0x40
> [    0.466597]  [<000000000012f152>] __set_memory+0x132/0x150
> [    0.466624]  [<0000000001cc0398>] vmem_map_init+0x40/0x118
> [    0.466651]  [<0000000001cc0092>] paging_init+0x22/0x68
> [    0.466677]  [<0000000001cbbed2>] setup_arch+0x52a/0x708
> [    0.466702]  [<0000000001cb6140>] start_kernel+0x80/0x5c8
> [    0.466727]  [<0000000000100036>] startup_continue+0x36/0x40
> 
> it happens because such system tries to access some vmap areas
> whereas the vmalloc initialization is not even yet done:
> 
> [    0.465490] lock: single+0x1860/0x1958, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
> [    0.466067] CPU: 0 PID: 0 Comm: swapper Not tainted 6.8.0-12955-g8e938e398669 #1
> [    0.466188] Hardware name: QEMU 8561 QEMU (KVM/Linux)
> [    0.466270] Call Trace:
> [    0.466470] dump_stack_lvl (lib/dump_stack.c:117)
> [    0.466516] do_raw_spin_lock (kernel/locking/spinlock_debug.c:87 kernel/locking/spinlock_debug.c:115)
> [    0.466545] find_vmap_area (mm/vmalloc.c:1059 mm/vmalloc.c:2364)
> [    0.466572] find_vm_area (mm/vmalloc.c:3150)
> [    0.466597] __set_memory (arch/s390/mm/pageattr.c:360 arch/s390/mm/pageattr.c:393)
> [    0.466624] vmem_map_init (./arch/s390/include/asm/set_memory.h:55 arch/s390/mm/vmem.c:660)
> [    0.466651] paging_init (arch/s390/mm/init.c:97)
> [    0.466677] setup_arch (arch/s390/kernel/setup.c:972)
> [    0.466702] start_kernel (init/main.c:899)
> [    0.466727] startup_continue (arch/s390/kernel/head64.S:35)
> [    0.466811] INFO: lockdep is turned off.
> ...
> [    0.718250] vmalloc init - busy lock init 0000000002871860
> [    0.718328] vmalloc init - busy lock init 00000000028731b8
> 
> Some background. It worked before because the lock that is in question
> was statically defined and initialized. As of now, the locks and data
> structures are initialized in the vmalloc_init() function.
> 
> To address that issue add the check whether the "vmap_initialized"
> variable is set, if not find_vmap_area() bails out on entry returning NULL.
> 
> Fixes: 72210662c5a2 ("mm: vmalloc: offload free_vmap_area_lock lock")
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  mm/vmalloc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 22aa63f4ef63..0d77d171b5d9 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2343,6 +2343,9 @@ struct vmap_area *find_vmap_area(unsigned long addr)
>  	struct vmap_area *va;
>  	int i, j;
>  
> +	if (unlikely(!vmap_initialized))
> +		return NULL;
> +
>  	/*
>  	 * An addr_to_node_id(addr) converts an address to a node index
>  	 * where a VA is located. If VA spans several zones and passed
> -- 
> 2.39.2
> 
---end quoted text---