FAILED: patch "[PATCH] cifs/smb3: Fix data inconsistent when punch hole" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From acc91c2d8de4ef46ed751c5f9df99ed9a109b100 Mon Sep 17 00:00:00 2001
From: Zhang Xiaoxu <[email protected]>
Date: Tue, 23 Jun 2020 07:31:53 -0400
Subject: [PATCH] cifs/smb3: Fix data inconsistent when punch hole

When punch hole success, we also can read old data from file:

  # strace -e trace=pread64,fallocate xfs_io -f -c "pread 20 40" \
           -c "fpunch 20 40" -c"pread 20 40" file
  pread64(3, " version 5.8.0-rc1+"..., 40, 20) = 40
  fallocate(3, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE, 20, 40) = 0
  pread64(3, " version 5.8.0-rc1+"..., 40, 20) = 40

CIFS implements the fallocate(FALLOCATE_FL_PUNCH_HOLE) with send SMB ioctl(FSCTL_SET_ZERO_DATA) to server. It just set the range of the remote file to zero, but local page caches not updated, then the local page caches inconsistent with server.

Also can be found by xfstests generic/316.

So, we need to remove the page caches before send the SMB ioctl(FSCTL_SET_ZERO_DATA) to server.

index 876a0d9e3d46..d9fdafa5eb60 100644
@@ -3259,6 +3259,12 @@ static long smb3_punch_hole(struct file *file, struct cifs_tcon *tcon,
 		return rc;
 	}
 
+	/*
+	 * We implement the punch hole through ioctl, so we need remove the page
+	 * caches first, otherwise the data may be inconsistent with the server.
+	 */
+	truncate_pagecache_range(inode, offset, offset + len - 1);
+
 	cifs_dbg(FYI, "Offset %lld len %lld\n", offset, len);
 
 	fsctl_buf.FileOffset = cpu_to_le64(offset);