[Gluster-devel] [PATCH] vfs/glusterfs: in case atime is not passed, set it to the mtime

[Niels de Vos]

Hello,

we were informed that when using Samba+vfs_glusterfs a normal 'write' to 
a file does not correctly set the 'atime'. In fact, the 'atime' is set 
to "2106-02-07 11:58:15.000000000 +0530" according to 'stat'.

Tracing the network and checking the SMB/SET_FILE_INFO shows that the 
Linux CIFS client sends the following date:
- May 28, 60056 07:36:10.955161500 CEST

This date, in fact, shows as 0xffffffff (32-bit -1) in the packet 
capture. The Linux CIFS client sets NO_CHANGE_64 (0xffffffffffffffff, 
64-bit -1) when it intends to not modify the 'atime' (fs/cifs/inode.c).

Debugging the Samba/vfs_glusterfs module with systemtap, showed that the 
'write' that triggers the unexpected 'atime', indeed gets forwarded to 
the GlusterFS volume as -1. Obviously, Samba passes a -1 for the 'atime' 
when it should not get modified. Unfortunately the gfapi library does 
not expose a function to set the 'mtime' only, it is always needed to 
set the 'atime' as well (like 'utimes()').

The attached patch fixes setting the 'atime' to a value way in the 
future. It resolves to setting the 'atime' to the same value as the 
'mtime', whenever the 'atime' is set to -1.

Downstream bug report and detailed results of the debugging:
- https://bugzilla.redhat.com/1051226

Thanks,
Niels

vfs-glusterfs-in-case-atime-is-not-passed-set-it-to-mtime.patch
Description: Text document