kern/135237: sendfile() and SF_NODISKIO blocks on NFS files

[Jordan Newman]

>Number:         135237
>Category:       kern
>Synopsis:       sendfile() and SF_NODISKIO blocks on NFS files
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Jun 04 01:00:06 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Jordan Newman
>Release:        7.2
>Organization:
ISPrime Inc.
>Environment:
FreeBSD XXX 7.2-RELEASE FreeBSD 7.2-RELEASE #8: Wed May 20 01:49:25 EDT 2009     root at XXX:/usr/obj/usr/src/sys/1950-64BITRAID-SMP  amd64


>Description:
Calling sendfile() with the SF_NODISKIO flag, will still block if the descriptor points to a file that is on an NFS mount.  In this situation I feel accessing data over the network should be considered "disk io" and it should return EBUSY.

This seems to happen on every version of FreeBSD, so I do not believe it to be a regression in FreeBSD 7.2 or a new bug.
>How-To-Repeat:
any sendfile call such as:

  sendfile(fd,clientsock,offset,sendsize,&sf,&cnt,SF_NODISKIO);

will still block while the NFS lookup occurs.

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: