This patch re-adds the ability to optionally run in buffered FILEIO mode
(eg: w/o O_DSYNC) for device backends in order to once again use the
Linux buffered cache as a write-back storage mechanism.
This logic was originally dropped with mainline v3.5-rc commit:
commit a4dff3043c
Author: Nicholas Bellinger <nab@linux-iscsi.org>
Date: Wed May 30 16:25:41 2012 -0700
target/file: Use O_DSYNC by default for FILEIO backends
This difference with this patch is that fd_create_virtdevice() now
forces the explicit setting of emulate_write_cache=1 when buffered FILEIO
operation has been enabled.
(v2: Switch to FDBD_HAS_BUFFERED_IO_WCE + add more detailed
comment as requested by hch)
Reported-by: Ferry <iscsitmp@bananateam.nl>
Cc: Christoph Hellwig <hch@lst.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
b32f4c7ed8