[PATCH v2 01/15] ubifs: Set page uptodate in the correct place

[Matthew Wilcox (Oracle)]

Page cache reads are lockless, so setting the freshly allocated page
uptodate before we've overwritten it with the data it's supposed to have
in it will allow a simultaneous reader to see old data.  Move the call
to SetPageUptodate into ubifs_write_end(), which is after we copied the
new data into the page.

Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
Cc: stable at vger.kernel.org
Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org>
---
 fs/ubifs/file.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 5029eb3390a5..d0694b83dd02 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -261,9 +261,6 @@ static int write_begin_slow(struct address_space *mapping,
 				return err;
 			}
 		}
-
-		SetPageUptodate(page);
-		ClearPageError(page);
 	}
 
 	if (PagePrivate(page))
@@ -463,9 +460,6 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
 				return err;
 			}
 		}
-
-		SetPageUptodate(page);
-		ClearPageError(page);
 	}
 
 	err = allocate_budget(c, page, ui, appending);
@@ -475,10 +469,8 @@ static int ubifs_write_begin(struct file *file, struct address_space *mapping,
 		 * If we skipped reading the page because we were going to
 		 * write all of it, then it is not up to date.
 		 */
-		if (skipped_read) {
+		if (skipped_read)
 			ClearPageChecked(page);
-			ClearPageUptodate(page);
-		}
 		/*
 		 * Budgeting failed which means it would have to force
 		 * write-back but didn't, because we set the @fast flag in the
@@ -569,6 +561,9 @@ static int ubifs_write_end(struct file *file, struct address_space *mapping,
 		goto out;
 	}
 
+	if (len == PAGE_SIZE)
+		SetPageUptodate(page);
+
 	if (!PagePrivate(page)) {
 		attach_page_private(page, (void *)1);
 		atomic_long_inc(&c->dirty_pg_cnt);
-- 
2.43.0