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Don't block and wait for file server response in case strategy is 

run in pagedaemon context: it gives the file server way more control
over the fate of the entire kernel than what we're comfortable with.
This commit is contained in:
pooka 2007-02-08 04:52:23 +00:00
parent d261ef686a
commit b7a2d4ecbb
1 changed files with 21 additions and 2 deletions
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23
sys/fs/puffs/puffs_vnops.c
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@ -1,4 +1,4 @@
/* $NetBSD: puffs_vnops.c,v 1.44 2007/02/06 01:53:11 pooka Exp $ */
/* $NetBSD: puffs_vnops.c,v 1.45 2007/02/08 04:52:23 pooka Exp $ */
/*
* Copyright (c) 2005, 2006 Antti Kantee. All Rights Reserved.
@ -33,7 +33,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: puffs_vnops.c,v 1.44 2007/02/06 01:53:11 pooka Exp $");
__KERNEL_RCSID(0, "$NetBSD: puffs_vnops.c,v 1.45 2007/02/08 04:52:23 pooka Exp $");
#include <sys/param.h>
#include <sys/fstrans.h>
@ -41,6 +41,7 @@ __KERNEL_RCSID(0, "$NetBSD: puffs_vnops.c,v 1.44 2007/02/06 01:53:11 pooka Exp $
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <uvm/uvm.h>
#include <fs/puffs/puffs_msgif.h>
#include <fs/puffs/puffs_sys.h>
@ -1741,6 +1742,24 @@ puffs_strategy(void *v)
simple_unlock(&vp->v_interlock);
}
/*
* If we're executing as the pagedaemon, do only FAF operations.
* Otherwise the file server has too much power over the fate
* of the entire kernel and things might end up looking like
* in the song (well, almost anyway):
* "sleep", said the pagedaemon
* we are programmed to recv
* you can deadlock any time you like
* and you can never leave
*/
if (curproc == uvm.pagedaemon_proc)
dowritefaf = 1;
#ifdef DIAGNOSTIC
if (dowritefaf)
KASSERT((bp->b_flags & B_READ) == 0);
#endif
if (bp->b_flags & B_READ) {
argsize = sizeof(struct puffs_vnreq_read);
read_argp = malloc(argsize, M_PUFFS, M_NOWAIT | M_ZERO);