Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 updates from Ted Ts'o:
 "Fix some bugs in converting ext4 to use the new mount API, as well as
  more bug fixes and clean ups in the ext4 fast_commit feature (most
  notably, in the tracepoints).

  In the jbd2 layer, the t_handle_lock spinlock has been removed, with
  the last place where it was actually needed replaced with an atomic
  cmpxchg"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (35 commits)
  ext4: fix kernel doc warnings
  ext4: fix remaining two trace events to use same printk convention
  ext4: add commit tid info in ext4_fc_commit_start/stop trace events
  ext4: add commit_tid info in jbd debug log
  ext4: add transaction tid info in fc_track events
  ext4: add new trace event in ext4_fc_cleanup
  ext4: return early for non-eligible fast_commit track events
  ext4: do not call FC trace event in ext4_fc_commit() if FS does not support FC
  ext4: convert ext4_fc_track_dentry type events to use event class
  ext4: fix ext4_fc_stats trace point
  ext4: remove unused enum EXT4_FC_COMMIT_FAILED
  ext4: warn when dirtying page w/o buffers in data=journal mode
  doc: fixed a typo in ext4 documentation
  ext4: make mb_optimize_scan performance mount option work with extents
  ext4: make mb_optimize_scan option work with set/unset mount cmd
  ext4: don't BUG if someone dirty pages without asking ext4 first
  ext4: remove redundant assignment to variable split_flag1
  ext4: fix underflow in ext4_max_bitmap_size()
  ext4: fix ext4_mb_clear_bb() kernel-doc comment
  ext4: fix fs corruption when tring to remove a non-empty directory with IO error
  ...

1 files changed, 31 insertions, 4 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 4cf55ef54193..3d0ca48d20c8 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1993,6 +1993,15 @@ static int ext4_writepage(struct page *page,
 	else
 		len = PAGE_SIZE;
 
+	/* Should never happen but for bugs in other kernel subsystems */
+	if (!page_has_buffers(page)) {
+		ext4_warning_inode(inode,
+		   "page %lu does not have buffers attached", page->index);
+		ClearPageDirty(page);
+		unlock_page(page);
+		return 0;
+	}
+
 	page_bufs = page_buffers(page);
 	/*
 	 * We cannot do block allocation or other extent handling in this
@@ -2594,6 +2603,22 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
 			wait_on_page_writeback(page);
 			BUG_ON(PageWriteback(page));
 
+			/*
+			 * Should never happen but for buggy code in
+			 * other subsystems that call
+			 * set_page_dirty() without properly warning
+			 * the file system first.  See [1] for more
+			 * information.
+			 *
+			 * [1] https://lore.kernel.org/linux-mm/20180103100430.GE4911@quack2.suse.cz
+			 */
+			if (!page_has_buffers(page)) {
+				ext4_warning_inode(mpd->inode, "page %lu does not have buffers attached", page->index);
+				ClearPageDirty(page);
+				unlock_page(page);
+				continue;
+			}
+
 			if (mpd->map.m_len == 0)
 				mpd->first_page = page->index;
 			mpd->next_page = page->index + 1;
@@ -3548,10 +3573,11 @@ const struct iomap_ops ext4_iomap_report_ops = {
 };
 
 /*
- * Pages can be marked dirty completely asynchronously from ext4's journalling
- * activity.  By filemap_sync_pte(), try_to_unmap_one(), etc.  We cannot do
- * much here because ->set_page_dirty is called under VFS locks.  The page is
- * not necessarily locked.
+ * Whenever the page is being dirtied, corresponding buffers should already be
+ * attached to the transaction (we take care of this in ext4_page_mkwrite() and
+ * ext4_write_begin()). However we cannot move buffers to dirty transaction
+ * lists here because ->set_page_dirty is called under VFS locks and the page
+ * is not necessarily locked.
  *
  * We cannot just dirty the page and leave attached buffers clean, because the
  * buffers' dirty state is "definitive".  We cannot just set the buffers dirty
@@ -3562,6 +3588,7 @@ const struct iomap_ops ext4_iomap_report_ops = {
  */
 static int ext4_journalled_set_page_dirty(struct page *page)
 {
+	WARN_ON_ONCE(!page_has_buffers(page));
 	SetPageChecked(page);
 	return __set_page_dirty_nobuffers(page);
 }