linux-kernel - Re: [PATCH] stackdepot: respect __GFP

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Date: Fri, 19 Apr 2024 15:21:59 +0800
From: Xiubo Li <xiubli@...hat.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Potapenko <glider@...gle.com>,
 Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
 Christoph Hellwig <hch@...radead.org>, Dave Chinner <david@...morbit.com>,
 kasan-dev@...glegroups.com, linux-xfs@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] stackdepot: respect __GFP_NOLOCKDEP allocation flag


On 4/18/24 22:11, Andrey Ryabinin wrote:
> If stack_depot_save_flags() allocates memory it always drops
> __GFP_NOLOCKDEP flag. So when KASAN tries to track __GFP_NOLOCKDEP
> allocation we may end up with lockdep splat like bellow:
>
> ======================================================
>   WARNING: possible circular locking dependency detected
>   6.9.0-rc3+ #49 Not tainted
>   ------------------------------------------------------
>   kswapd0/149 is trying to acquire lock:
>   ffff88811346a920
> (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_reclaim_inode+0x3ac/0x590
> [xfs]
>
>   but task is already holding lock:
>   ffffffff8bb33100 (fs_reclaim){+.+.}-{0:0}, at:
> balance_pgdat+0x5d9/0xad0
>
>   which lock already depends on the new lock.
>
>   the existing dependency chain (in reverse order) is:
>   -> #1 (fs_reclaim){+.+.}-{0:0}:
>          __lock_acquire+0x7da/0x1030
>          lock_acquire+0x15d/0x400
>          fs_reclaim_acquire+0xb5/0x100
>   prepare_alloc_pages.constprop.0+0xc5/0x230
>          __alloc_pages+0x12a/0x3f0
>          alloc_pages_mpol+0x175/0x340
>          stack_depot_save_flags+0x4c5/0x510
>          kasan_save_stack+0x30/0x40
>          kasan_save_track+0x10/0x30
>          __kasan_slab_alloc+0x83/0x90
>          kmem_cache_alloc+0x15e/0x4a0
>          __alloc_object+0x35/0x370
>          __create_object+0x22/0x90
>   __kmalloc_node_track_caller+0x477/0x5b0
>          krealloc+0x5f/0x110
>          xfs_iext_insert_raw+0x4b2/0x6e0 [xfs]
>          xfs_iext_insert+0x2e/0x130 [xfs]
>          xfs_iread_bmbt_block+0x1a9/0x4d0 [xfs]
>          xfs_btree_visit_block+0xfb/0x290 [xfs]
>          xfs_btree_visit_blocks+0x215/0x2c0 [xfs]
>          xfs_iread_extents+0x1a2/0x2e0 [xfs]
>   xfs_buffered_write_iomap_begin+0x376/0x10a0 [xfs]
>          iomap_iter+0x1d1/0x2d0
>   iomap_file_buffered_write+0x120/0x1a0
>          xfs_file_buffered_write+0x128/0x4b0 [xfs]
>          vfs_write+0x675/0x890
>          ksys_write+0xc3/0x160
>          do_syscall_64+0x94/0x170
>   entry_SYSCALL_64_after_hwframe+0x71/0x79
>
> Always preserve __GFP_NOLOCKDEP to fix this.
>
> Fixes: cd11016e5f52 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
> Reported-by: Xiubo Li <xiubli@...hat.com>
> Closes: https://lore.kernel.org/all/a0caa289-ca02-48eb-9bf2-d86fd47b71f4@redhat.com/
> Reported-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
> Closes: https://lore.kernel.org/all/f9ff999a-e170-b66b-7caf-293f2b147ac2@opensource.wdc.com/
> Suggested-by: Dave Chinner <david@...morbit.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Signed-off-by: Andrey Ryabinin <ryabinin.a.a@...il.com>
> ---
>   lib/stackdepot.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index 68c97387aa54..cd8f23455285 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -627,10 +627,10 @@ depot_stack_handle_t stack_depot_save_flags(unsigned long *entries,
>   		/*
>   		 * Zero out zone modifiers, as we don't have specific zone
>   		 * requirements. Keep the flags related to allocation in atomic
> -		 * contexts and I/O.
> +		 * contexts, I/O, nolockdep.
>   		 */
>   		alloc_flags &= ~GFP_ZONEMASK;
> -		alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
> +		alloc_flags &= (GFP_ATOMIC | GFP_KERNEL | __GFP_NOLOCKDEP);
>   		alloc_flags |= __GFP_NOWARN;
>   		page = alloc_pages(alloc_flags, DEPOT_POOL_ORDER);
>   		if (page)

Tested it and this patch worked well for me.

Thanks

- Xiubo