cvs commit: src/sys/nfsclient nfs_vnops.c
mcdouga9 at egr.msu.edu
Sat Dec 29 06:33:25 UTC 2007
Can this be merged to 6 as well? I've been running the patch
ported to 6-stable for a while with no problems. Thanks.
On Tue, Nov 27, 2007 at 12:20:59PM +0000, Robert Watson wrote:
rwatson 2007-11-27 12:20:59 UTC
FreeBSD src repository
Modified files: (Branch: RELENG_7)
Merge nfs_vnops.c:1.277 from HEAD to RELENG_7:
Remove hacks from the NFSv2/3 client intended to handle a lack of a
server-side RPC retranmission cache for non-idempotent operations: these
hacks substituted 0 (success) for the expected EEXIST in the event that
a target name already existed for LINK, SYMLINK, and MKDIR operations,
under the assumption that EEXIST represented a second application of the
original RPC rather than a true failure.
Background: certain NFS operations (in this case, LINK, SYMLINK, and
MKDIR) are not idempotent, as they leave behind persisting state on the
server that prevents them from being replayed without an error;if an UDP
RPC reply is lost leading to a retransmission by theclient, the second
reply will return EEXIST rather than success, asthe new object has
already been created. The NFS client previouslysilently mapped the
EEXIST return into success to paper over thisproblem.
However, in all modern NFS server implementations, a reply cache is kept
in order to retransmit the original reply to a retransmitted request,
rather than performing the operation a second time, allowing this hack
to be avoided. This allows link()-based filelocking over NFS to operate
correctly, as an application requestingthe creation of a new link for a
file to tell if it succeededatomically or not.
Other NFS clients, including Solaris and Linux, generally follow this
behavior for the same reasons. Most clients also now default to TCP,
which also helps avoid the issue of retransmitted but non-idempotent
requests in most cases.
Reported by: Adam McDougall <mcdouga9 at egr dot msu dot edu>,
Timo Sirainen <tss at iki dot fi>
Reviewed by: mohans
Approved by: re (kensmith)
Revision Changes Path
1.276.2.1 +4 -25 src/sys/nfsclient/nfs_vnops.c
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