Module Name:	syssrc
Committed By:	chs
Date:		Mon Jan  8 06:21:14 UTC 2001

Modified Files:
	syssrc/sys/uvm: uvm_vnode.c

Log Message:
in uvn_flush(), when PGO_SYNCIO is specified then we should wait for
pending i/os to complete before returning even if PGO_CLEANIT is not
specified.  this fixes two races:

 (1) NFS write rpcs vs. setattr operations which truncate the file.
     if the truncate doesn't wait for pending writes to complete then
     a later write rpc completion can undo the effect of the truncate.
     this problem has been reported by several people.

 (2) write i/os in disk-based filesystem vs. the disk block being
     freed by a truncation, allocated to a new file, and written
     again with different data.  if the disk driver reorders the requests
     and does the second i/o first, the old data will clobber the new,
     corrupting the new file.  I haven't heard of anyone experiencing
     this problem yet, but it's fixed now anyway.


To generate a diff of this commit:
cvs rdiff -r1.40 -r1.41 syssrc/sys/uvm/uvm_vnode.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.