Re: [PATCH] stackdepot: respect __GFP_NOLOCKDEP allocation flag

Xiubo Li
2024-04-19T07:22:10Z

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@redhat.com>
> Closes: https://lore.kernel.org/all/a0caa289-ca02-48eb-9bf2-d86fd47b71f4@redhat.com/
> Reported-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
> Closes: https://lore.kernel.org/all/f9ff999a-e170-b66b-7caf-293f2b147ac2@opensource.wdc.com/
> Suggested-by: Dave Chinner <david@fromorbit.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.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