From 8c6ae4980e70395cbdfdf605c29673c5a6a89d9a Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 30 Jun 2017 12:03:54 -0400 Subject: [PATCH] sunrpc: Allocate up to RPCSVC_MAXPAGES per svc_rqst svcrdma needs 259 pages allocated to receive 1MB NFSv4.0 WRITE requests: - 1 page for the transport header and head iovec - 256 pages for the data payload - 1 page for the trailing GETATTR request (since NFSD XDR decoding does not look for a tail iovec, the GETATTR is stuck at the end of the rqstp->rq_arg.pages list) - 1 page for building the reply xdr_buf But RPCSVC_MAXPAGES is already 259 (on x86_64). The problem is that svc_alloc_arg never allocates that many pages. To address this: 1. The final element of rq_pages always points to NULL. To accommodate up to 259 pages in rq_pages, add an extra element to rq_pages for the array termination sentinel. 2. Adjust the calculation of "pages" to match how RPCSVC_MAXPAGES is calculated, so it can go up to 259. Bruce noted that the calculation assumes sv_max_mesg is a multiple of PAGE_SIZE, which might not always be true. I didn't change this assumption. 3. Change the loop boundaries to allow 259 pages to be allocated. Additional clean-up: WARN_ON_ONCE adds an extra conditional branch, which is basically never taken. And there's no need to dump the stack here because svc_alloc_arg has only one caller. Keeping that NULL "array termination sentinel"; there doesn't appear to be any code that depends on it, only code in nfsd_splice_actor() which needs the 259th element to be initialized to *something*. So it's possible we could just keep the array at 259 elements and drop that final NULL, but we're being conservative for now. Signed-off-by: Chuck Lever Signed-off-by: J. Bruce Fields --- include/linux/sunrpc/svc.h | 2 +- net/sunrpc/svc_xprt.c | 10 ++++++---- 2 files changed, 7 insertions(+), 5 deletions(-) diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index eec04982a7ea..a3f8af9bd543 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -246,7 +246,7 @@ struct svc_rqst { size_t rq_xprt_hlen; /* xprt header len */ struct xdr_buf rq_arg; struct xdr_buf rq_res; - struct page * rq_pages[RPCSVC_MAXPAGES]; + struct page *rq_pages[RPCSVC_MAXPAGES + 1]; struct page * *rq_respages; /* points into rq_pages */ struct page * *rq_next_page; /* next reply page to use */ struct page * *rq_page_end; /* one past the last page */ diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 7bfe1fb42add..d16a8b423c20 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -659,11 +659,13 @@ static int svc_alloc_arg(struct svc_rqst *rqstp) int i; /* now allocate needed pages. If we get a failure, sleep briefly */ - pages = (serv->sv_max_mesg + PAGE_SIZE) / PAGE_SIZE; - WARN_ON_ONCE(pages >= RPCSVC_MAXPAGES); - if (pages >= RPCSVC_MAXPAGES) + pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT; + if (pages > RPCSVC_MAXPAGES) { + pr_warn_once("svc: warning: pages=%u > RPCSVC_MAXPAGES=%lu\n", + pages, RPCSVC_MAXPAGES); /* use as many pages as possible */ - pages = RPCSVC_MAXPAGES - 1; + pages = RPCSVC_MAXPAGES; + } for (i = 0; i < pages ; i++) while (rqstp->rq_pages[i] == NULL) { struct page *p = alloc_page(GFP_KERNEL);