Merge branch 'akpm' (patches from Andrew)

Merge more updates from Andrew Morton:
 "190 patches.

  Subsystems affected by this patch series: mm (hugetlb, userfaultfd,
  vmscan, kconfig, proc, z3fold, zbud, ras, mempolicy, memblock,
  migration, thp, nommu, kconfig, madvise, memory-hotplug, zswap,
  zsmalloc, zram, cleanups, kfence, and hmm), procfs, sysctl, misc,
  core-kernel, lib, lz4, checkpatch, init, kprobes, nilfs2, hfs,
  signals, exec, kcov, selftests, compress/decompress, and ipc"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (190 commits)
  ipc/util.c: use binary search for max_idx
  ipc/sem.c: use READ_ONCE()/WRITE_ONCE() for use_global_lock
  ipc: use kmalloc for msg_queue and shmid_kernel
  ipc sem: use kvmalloc for sem_undo allocation
  lib/decompressors: remove set but not used variabled 'level'
  selftests/vm/pkeys: exercise x86 XSAVE init state
  selftests/vm/pkeys: refill shadow register after implicit kernel write
  selftests/vm/pkeys: handle negative sys_pkey_alloc() return code
  selftests/vm/pkeys: fix alloc_random_pkey() to make it really, really random
  kcov: add __no_sanitize_coverage to fix noinstr for all architectures
  exec: remove checks in __register_bimfmt()
  x86: signal: don't do sas_ss_reset() until we are certain that sigframe won't be abandoned
  hfsplus: report create_date to kstat.btime
  hfsplus: remove unnecessary oom message
  nilfs2: remove redundant continue statement in a while-loop
  kprobes: remove duplicated strong free_insn_page in x86 and s390
  init: print out unknown kernel parameters
  checkpatch: do not complain about positive return values starting with EPOLL
  checkpatch: improve the indented label test
  checkpatch: scripts/spdxcheck.py now requires python3
  ...

1 files changed, 11 insertions, 2 deletions

diff --git a/fs/open.c b/fs/open.c
index 53bc0573c0ec..1a325b3194df 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -852,8 +852,17 @@ static int do_dentry_open(struct file *f,
 	 * XXX: Huge page cache doesn't support writing yet. Drop all page
 	 * cache for this file before processing writes.
 	 */
-	if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))
-		truncate_pagecache(inode, 0);
+	if (f->f_mode & FMODE_WRITE) {
+		/*
+		 * Paired with smp_mb() in collapse_file() to ensure nr_thps
+		 * is up to date and the update to i_writecount by
+		 * get_write_access() is visible. Ensures subsequent insertion
+		 * of THPs into the page cache will fail.
+		 */
+		smp_mb();
+		if (filemap_nr_thps(inode->i_mapping))
+			truncate_pagecache(inode, 0);
+	}
 
 	return 0;