From cd123012d99fde4759500fee611e724e4f3016e3 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 9 May 2007 02:34:50 -0700 Subject: RPC: add wrapper for svc_reserve to account for checksum When the kernel calls svc_reserve to downsize the expected size of an RPC reply, it fails to account for the possibility of a checksum at the end of the packet. If a client mounts a NFSv2/3 with sec=krb5i/p, and does I/O then you'll generally see messages similar to this in the server's ring buffer: RPC request reserved 164 but used 208 While I was never able to verify it, I suspect that this problem is also the root cause of some oopses I've seen under these conditions: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=227726 This is probably also a problem for other sec= types and for NFSv4. The large reserved size for NFSv4 compound packets seems to generally paper over the problem, however. This patch adds a wrapper for svc_reserve that accounts for the possibility of a checksum. It also fixes up the appropriate callers of svc_reserve to call the wrapper. For now, it just uses a hardcoded value that I determined via testing. That value may need to be revised upward as things change, or we may want to eventually add a new auth_op that attempts to calculate this somehow. Unfortunately, there doesn't seem to be a good way to reliably determine the expected checksum length prior to actually calculating it, particularly with schemes like spkm3. Signed-off-by: Jeff Layton Acked-by: Neil Brown Cc: Trond Myklebust Acked-by: J. Bruce Fields Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sunrpc/svc.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'include/linux/sunrpc') diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 35fa4d5aadd0..4a7ae8ab6eb8 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -396,4 +396,23 @@ char * svc_print_addr(struct svc_rqst *, char *, size_t); #define RPC_MAX_ADDRBUFLEN (63U) +/* + * When we want to reduce the size of the reserved space in the response + * buffer, we need to take into account the size of any checksum data that + * may be at the end of the packet. This is difficult to determine exactly + * for all cases without actually generating the checksum, so we just use a + * static value. + */ +static inline void +svc_reserve_auth(struct svc_rqst *rqstp, int space) +{ + int added_space = 0; + + switch(rqstp->rq_authop->flavour) { + case RPC_AUTH_GSS: + added_space = RPC_MAX_AUTH_SIZE; + } + return svc_reserve(rqstp, space + added_space); +} + #endif /* SUNRPC_SVC_H */ -- cgit v1.2.3