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NFS: clean up short packet handling for NFSv4 readdir

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Currently, the NFS readdir decoders have a workaround for buggy servers
that send an empty readdir response with the EOF bit unset. If the
server sends a malformed response in some cases, this workaround kicks
in and just returns an empty response rather than returning a proper
error to the caller.

This patch does 3 things:

1) have malformed responses with no entries return error (-EIO)

2) preserve existing workaround for servers that send empty
   responses with the EOF marker unset.

3) Add some comments to clarify the logic in decode_readdir().

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Jeff Layton 2008-02-22 14:50:01 -05:00 committed by Trond Myklebust
parent 643f81115b
commit 7bda2cdf48
1 changed files with 27 additions and 10 deletions
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37
fs/nfs/nfs4xdr.c
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@ -3481,7 +3481,7 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
size_t hdrlen;
u32 recvd, pglen = rcvbuf->page_len;
__be32 *end, *entry, *p, *kaddr;
unsigned int nr;
unsigned int nr = 0;
int status;
status = decode_op_hdr(xdr, OP_READDIR);
@ -3505,7 +3505,12 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
kaddr = p = kmap_atomic(page, KM_USER0);
end = p + ((pglen + readdir->pgbase) >> 2);
entry = p;
for (nr = 0; *p++; nr++) {
/* Make sure the packet actually has a value_follows and EOF entry */
if ((entry + 1) > end)
goto short_pkt;
for (; *p++; nr++) {
u32 len, attrlen, xlen;
if (end - p < 3)
goto short_pkt;
@ -3532,20 +3537,32 @@ static int decode_readdir(struct xdr_stream *xdr, struct rpc_rqst *req, struct n
p += attrlen; /* attributes */
entry = p;
}
if (!nr && (entry[0] != 0 || entry[1] == 0))
goto short_pkt;
/*
* Apparently some server sends responses that are a valid size, but
* contain no entries, and have value_follows==0 and EOF==0. For
* those, just set the EOF marker.
*/
if (!nr && entry[1] == 0) {
dprintk("NFS: readdir reply truncated!\n");
entry[1] = 1;
}
out:
kunmap_atomic(kaddr, KM_USER0);
return 0;
short_pkt:
/*
* When we get a short packet there are 2 possibilities. We can
* return an error, or fix up the response to look like a valid
* response and return what we have so far. If there are no
* entries and the packet was short, then return -EIO. If there
* are valid entries in the response, return them and pretend that
* the call was successful, but incomplete. The caller can retry the
* readdir starting at the last cookie.
*/
dprintk("%s: short packet at entry %d\n", __FUNCTION__, nr);
entry[0] = entry[1] = 0;
/* truncate listing ? */
if (!nr) {
dprintk("NFS: readdir reply truncated!\n");
entry[1] = 1;
}
goto out;
if (nr)
goto out;
err_unmap:
kunmap_atomic(kaddr, KM_USER0);
return -errno_NFSERR_IO;