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

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Message-ID: <90868fbd-8691-4d72-b211-9ecf2f6629f7@roeck-us.net>
Date: Sat, 23 Mar 2024 16:22:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: "Uladzislau Rezki (Sony)" <urezki@...il.com>, linux-mm@...ck.org,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: 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>,
 Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>
Subject: Re: [PATCH 1/1] mm: vmalloc: Bail out early in find_vmap_area() if
 vmap is not init

On 3/23/24 07:15, 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>

Tested-by: Guenter Roeck <linux@...ck-us.net>