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Date:      Mon, 7 Apr 2014 13:02:05 +0000 (UTC)
From:      Gleb Smirnoff <glebius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-projects@freebsd.org
Subject:   svn commit: r264227 - projects/sendfile/sys/kern
Message-ID:  <201404071302.s37D25lF044161@svn.freebsd.org>
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Author: glebius
Date: Mon Apr  7 13:02:05 2014
New Revision: 264227
URL: http://svnweb.freebsd.org/changeset/base/264227

Log:
  vm_pager_has_page() can hint us that it can read beyond end of file.
  Not sure is this a bug or not, but we need to workaround it when
  doing readahead in sendfile(2).
  
  Sponsored by:	Nginx, Inc.
  Sponsored by:	Netflix

Modified:
  projects/sendfile/sys/kern/uipc_syscalls.c

Modified: projects/sendfile/sys/kern/uipc_syscalls.c
==============================================================================
--- projects/sendfile/sys/kern/uipc_syscalls.c	Mon Apr  7 12:59:30 2014	(r264226)
+++ projects/sendfile/sys/kern/uipc_syscalls.c	Mon Apr  7 13:02:05 2014	(r264227)
@@ -2689,6 +2689,7 @@ fixspace(int old, int new, off_t off, in
 struct sf_io {
 	u_int		nios;
 	int		npages;
+	int		rhpages;
 	struct file	*sock_fp;
 	struct mbuf	*m;
 	vm_page_t	pa[];
@@ -2731,10 +2732,9 @@ sendfile_swapin(vm_object_t obj, struct 
 {
 	vm_page_t *pa = sfio->pa;
 	int npages = sfio->npages;
-	int nios, readahead;
+	int nios;
 
 	nios = 0;
-	readahead = sfreadahead;
 	if (sfpgrabnowait && (flags & SF_NODISKIO))
 		flags = VM_ALLOC_NOWAIT;
 	else
@@ -2746,7 +2746,7 @@ sendfile_swapin(vm_object_t obj, struct 
 		    VM_ALLOC_WIRED | VM_ALLOC_NORMAL | flags);
 		if (pa[i] == NULL) {
 			npages = sfio->npages = i;
-			readahead = 0;
+			sfio->rhpages = 0;
 			break;
 		}
 	}
@@ -2776,7 +2776,7 @@ sendfile_swapin(vm_object_t obj, struct 
 		if (i == j)
 			continue;
 
-		count = min(a + 1, npages + readahead - i);
+		count = min(a + 1, npages + sfio->rhpages - i);
 		for (j = npages; j < i + count; j++) {
 			pa[j] = vm_page_grab(obj, OFF_TO_IDX(vmoff(j, off)),
 			    VM_ALLOC_NORMAL | VM_ALLOC_NOWAIT);
@@ -2985,7 +2985,7 @@ vn_sendfile(struct file *fp, int sockfd,
 		struct sf_io *sfio;
 		vm_page_t *pa;
 		struct mbuf *mtail;
-		int nios, space, npages;
+		int nios, space, npages, rhpages;
 
 		mtail = NULL;
 		/*
@@ -3080,11 +3080,15 @@ retry_space:
 			    (PAGE_SIZE - (off & PAGE_MASK)), PAGE_SIZE);
 		else
 			npages = howmany(space, PAGE_SIZE);
+
+		rhpages = min(howmany(obj_size - (off & ~PAGE_MASK) -
+		    (npages * PAGE_SIZE), PAGE_SIZE), sfreadahead);
+
 		sfio = malloc(sizeof(struct sf_io) +
-		    (sfreadahead + npages) * sizeof(vm_page_t),
-		    M_TEMP, M_WAITOK);
+		    (rhpages + npages) * sizeof(vm_page_t), M_TEMP, M_WAITOK);
 		refcount_init(&sfio->nios, 1);
 		sfio->npages = npages;
+		sfio->rhpages = rhpages;
 
 		nios = sendfile_swapin(obj, sfio, off, space, flags);

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