stackdepot: respect __GFP_NOLOCKDEP allocation flag

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.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: cd11016 ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Signed-off-by: Andrey Ryabinin <[email protected]>
Reported-by: Xiubo Li <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Reported-by: Damien Le Moal <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Suggested-by: Dave Chinner <[email protected]>
Tested-by: Xiubo Li <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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)