From 4595a298d5563cf76c1d852970f162051fd1a7a6 Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Fri, 25 Sep 2020 11:16:53 -0700
Subject: [PATCH] iomap: Set all uptodate bits for an Uptodate page
Git-commit: 4595a298d5563cf76c1d852970f162051fd1a7a6
Patch-mainline: v5.10-rc1
References: bsc#1179685

For filesystems with block size < page size, we need to set all the
per-block uptodate bits if the page was already uptodate at the time
we create the per-block metadata.  This can happen if the page is
invalidated (eg by a write to drop_caches) but ultimately not removed
from the page cache.

This is a data corruption issue as page writeback skips blocks which
are marked !uptodate.

Fixes: 9dc55f1389f9 ("iomap: add support for sub-pagesize buffered I/O without buffer heads")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reported-by: Qian Cai <cai@redhat.com>
Cc: Brian Foster <bfoster@redhat.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/iomap/buffered-io.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -31,7 +31,10 @@ iomap_page_create(struct inode *inode, s
 	atomic_set(&iop->read_count, 0);
 	atomic_set(&iop->write_count, 0);
 	spin_lock_init(&iop->uptodate_lock);
-	bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
+	if (PageUptodate(page))
+		bitmap_fill(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
+	else
+		bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
 
 	/*
 	 * migrate_page_move_mapping() assumes that pages with private data have