Merge tag 'v5.8-rc4' into for-5.9/drivers

Merge in 5.8-rc4 for-5.9/block to setup for-5.9/drivers, to provide
a clean base and making the life for the NVMe changes easier.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

* tag 'v5.8-rc4': (732 commits)
  Linux 5.8-rc4
  x86/ldt: use "pr_info_once()" instead of open-coding it badly
  MIPS: Do not use smp_processor_id() in preemptible code
  MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen
  .gitignore: Do not track `defconfig` from `make savedefconfig`
  io_uring: fix regression with always ignoring signals in io_cqring_wait()
  x86/ldt: Disable 16-bit segments on Xen PV
  x86/entry/32: Fix #MC and #DB wiring on x86_32
  x86/entry/xen: Route #DB correctly on Xen PV
  x86/entry, selftests: Further improve user entry sanity checks
  x86/entry/compat: Clear RAX high bits on Xen PV SYSENTER
  i2c: mlxcpld: check correct size of maximum RECV_LEN packet
  i2c: add Kconfig help text for slave mode
  i2c: slave-eeprom: update documentation
  i2c: eg20t: Load module automatically if ID matches
  i2c: designware: platdrv: Set class based on DMI
  i2c: algo-pca: Add 0x78 as SCL stuck low status for PCA9665
  mm/page_alloc: fix documentation error
  vmalloc: fix the owner argument for the new __vmalloc_node_range callers
  mm/cma.c: use exact_nid true to fix possible per-numa cma leak
  ...

1 files changed, 14 insertions, 3 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index fd988b7e5f2b..86375605faa9 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2316,15 +2316,26 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
 		.page = NULL,
 	};
 
-	current->capture_control = &capc;
+	/*
+	 * Make sure the structs are really initialized before we expose the
+	 * capture control, in case we are interrupted and the interrupt handler
+	 * frees a page.
+	 */
+	barrier();
+	WRITE_ONCE(current->capture_control, &capc);
 
 	ret = compact_zone(&cc, &capc);
 
 	VM_BUG_ON(!list_empty(&cc.freepages));
 	VM_BUG_ON(!list_empty(&cc.migratepages));
 
-	*capture = capc.page;
-	current->capture_control = NULL;
+	/*
+	 * Make sure we hide capture control first before we read the captured
+	 * page pointer, otherwise an interrupt could free and capture a page
+	 * and we would leak it.
+	 */
+	WRITE_ONCE(current->capture_control, NULL);
+	*capture = READ_ONCE(capc.page);
 
 	return ret;
 }