[PATCH 09/10] xfs: xfs_fs_write_inode() can fail to write inodes synchronously V2

[Christoph Hellwig]

FYI I did some benchmarking on this, and the syncmodes 2 and 5 of
fs_mark, which use sys_sync regress almost 10% on my test setup
with this patch.  The barriers are only a small part of it,
from instrumentation it seems like the constant log forces don't
really help.  Now given that we only get data integrity writes
from sync_filesystem do we really need to bother with catching
all that pending I/O here?  It would be much easier to rely
on ->sync_fs to do that for us once, which is does anyway.