linux/net/sunrpc
Chuck Lever 9d11b51ce7 svcrdma: Fix send_reply() scatter/gather set-up
The Linux NFS server returns garbage in the data payload of inline
NFS/RDMA READ replies. These are READs of under 1000 bytes or so
where the client has not provided either a reply chunk or a write
list.

The NFS server delivers the data payload for an NFS READ reply to
the transport in an xdr_buf page list. If the NFS client did not
provide a reply chunk or a write list, send_reply() is supposed to
set up a separate sge for the page containing the READ data, and
another sge for XDR padding if needed, then post all of the sges via
a single SEND Work Request.

The problem is send_reply() does not advance through the xdr_buf
when setting up scatter/gather entries for SEND WR. It always calls
dma_map_xdr with xdr_off set to zero. When there's more than one
sge, dma_map_xdr() sets up the SEND sge's so they all point to the
xdr_buf's head.

The current Linux NFS/RDMA client always provides a reply chunk or
a write list when performing an NFS READ over RDMA. Therefore, it
does not exercise this particular case. The Linux server has never
had to use more than one extra sge for building RPC/RDMA replies
with a Linux client.

However, an NFS/RDMA client _is_ allowed to send small NFS READs
without setting up a write list or reply chunk. The NFS READ reply
fits entirely within the inline reply buffer in this case. This is
perhaps a more efficient way of performing NFS READs that the Linux
NFS/RDMA client may some day adopt.

Fixes: b432e6b3d9 ('svcrdma: Change DMA mapping logic to . . .')
BugLink: https://bugzilla.linux-nfs.org/show_bug.cgi?id=285
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
2015-07-20 14:58:47 -04:00
..
auth_gss sunrpc: use sg_init_one() in krb5_rc4_setup_enc/seq_key() 2015-06-22 14:15:06 -04:00
xprtrdma svcrdma: Fix send_reply() scatter/gather set-up 2015-07-20 14:58:47 -04:00
addr.c replace strict_strto calls 2014-07-12 18:45:49 -04:00
auth_generic.c sunrpc: eliminate RPC_DEBUG 2014-11-24 17:31:46 -05:00
auth_null.c sunrpc: eliminate RPC_DEBUG 2014-11-24 17:31:46 -05:00
auth_unix.c sunrpc: eliminate RPC_DEBUG 2014-11-24 17:31:46 -05:00
auth.c kernel/params: constify struct kernel_param_ops uses 2015-05-28 11:32:10 +09:30
backchannel_rqst.c SUNRPC: Fix a backchannel race 2015-06-05 11:15:43 -04:00
cache.c lib/string_helpers.c: change semantics of string_escape_mem 2015-04-15 16:35:24 -07:00
clnt.c SUNRPC: Handle connection issues correctly on the back channel 2015-06-19 13:04:13 -04:00
debugfs.c SUNRPC: Address kbuild warning in net/sunrpc/debugfs.c 2015-06-11 14:01:06 -04:00
Kconfig rpcrdma: Merge svcrdma and xprtrdma modules into one 2015-06-04 16:56:02 -04:00
Makefile NFS client updates for Linux 4.2 2015-07-02 11:32:23 -07:00
netns.h Merge branch 'for-3.14' of git://linux-nfs.org/~bfields/linux 2014-01-30 10:18:43 -08:00
rpc_pipe.c VFS: net/: d_inode() annotations 2015-04-15 15:06:56 -04:00
rpcb_clnt.c SUNRPC: NULL utsname dereference on NFS umount during namespace cleanup 2015-02-03 16:40:17 -05:00
sched.c SUNRPC: fix build-warning due to format missmatch 2015-03-13 09:05:20 -04:00
socklib.c net: Save software checksum complete 2014-06-11 15:46:13 -07:00
stats.c sunrpc: add rpc_count_iostats_idx 2015-02-03 11:06:38 -08:00
sunrpc_syms.c sunrpc: make debugfs file creation failure non-fatal 2015-04-23 14:42:27 -04:00
sunrpc.h SUNRPC: track whether a request is coming from a loop-back interface. 2014-05-22 15:59:18 -04:00
svc_xprt.c sunrpc/lockd: fix references to the BKL 2015-01-23 10:29:12 -05:00
svc.c NFS client updates for Linux 4.2 2015-07-02 11:32:23 -07:00
svcauth_unix.c
svcauth.c nfsd4: better reservation of head space for krb5 2014-05-30 17:32:17 -04:00
svcsock.c get rid of the size argument of sock_sendmsg() 2015-04-11 15:27:37 -04:00
sysctl.c sunrpc: eliminate RPC_DEBUG 2014-11-24 17:31:46 -05:00
timer.c
xdr.c rpc: fix xdr_truncate_encode to handle buffer ending on page boundary 2015-01-07 14:03:58 -05:00
xprt.c SUNRPC: Ensure we release the TCP socket once it has been closed 2015-06-19 19:20:12 -04:00
xprtsock.c NFS client updates for Linux 4.2 2015-07-02 11:32:23 -07:00