[PATCH v8 01/15] xfs: don't skip the flush before shifting extents

[Chris Mason <mason@kernel.org>]

On an XFS file larger than 4 EiB, collapse range and insert range can
drop dirty data without writing it back, and then fail with
EFSCORRUPTED.

xfs_prepare_shift() flushes the page cache from its offset to EOF, but
passes i_size as the length. Above 4 EiB the end of that range can
overflow and turn negative. filemap_write_and_wait_range() then writes
nothing, but truncate_pagecache_range() takes the end as unsigned and
drops every folio from the start of the range onward.

A delalloc extent under a dropped folio stays in the data fork, and the
shift returns -EFSCORRUPTED for it.

The fix used here is to pass i_size - offset as the length.

Fixes: 7f9f71be84bc ("xfs: extent shifting doesn't fully invalidate page cache")
Fixes: feeb9b269523 ("filemap: skip write and wait if end offset precedes start")
Signed-off-by: Chris Mason <mason@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---

Notes:
    v7->v8:
    - No change.
    
    v6->v7:
    - No change.

 fs/xfs/xfs_bmap_util.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 865aec3ae5ab..537c6b29417c 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -980,7 +980,7 @@ xfs_prepare_shift(
 	 * Writeback and invalidate cache for the remainder of the file as we're
 	 * about to shift down every extent from offset to EOF.
 	 */
-	error = xfs_flush_unmap_range(ip, offset, XFS_ISIZE(ip));
+	error = xfs_flush_unmap_range(ip, offset, XFS_ISIZE(ip) - offset);
 	if (error)
 		return error;
 
-- 
2.55.0