Date: Mon, 19 Oct 2015 18:01:30 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Hans Petter Selasky <hselasky@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r289565 - head/sys/ofed/include/linux Message-ID: <20151019150130.GK2257@kib.kiev.ua> In-Reply-To: <201510191056.t9JAuWhF052021@repo.freebsd.org> References: <201510191056.t9JAuWhF052021@repo.freebsd.org>
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On Mon, Oct 19, 2015 at 10:56:32AM +0000, Hans Petter Selasky wrote: > Author: hselasky > Date: Mon Oct 19 10:56:32 2015 > New Revision: 289565 > URL: https://svnweb.freebsd.org/changeset/base/289565 > > Log: > Merge LinuxKPI changes from DragonflyBSD: > - Implement pagefault_disable() and pagefault_enable(). > > Sponsored by: Mellanox Technologies > > Modified: > head/sys/ofed/include/linux/uaccess.h > > Modified: head/sys/ofed/include/linux/uaccess.h > ============================================================================== > --- head/sys/ofed/include/linux/uaccess.h Mon Oct 19 10:54:24 2015 (r289564) > +++ head/sys/ofed/include/linux/uaccess.h Mon Oct 19 10:56:32 2015 (r289565) > @@ -2,7 +2,8 @@ > * Copyright (c) 2010 Isilon Systems, Inc. > * Copyright (c) 2010 iX Systems, Inc. > * Copyright (c) 2010 Panasas, Inc. > - * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd. > + * Copyright (c) 2013-2015 Mellanox Technologies, Ltd. > + * Copyright (c) 2015 Fran??ois Tigeot > * All rights reserved. > * > * Redistribution and use in source and binary forms, with or without > @@ -32,4 +33,14 @@ > #define get_user(_x, _p) -copyin((_p), &(_x), sizeof(*(_p))) > #define put_user(_x, _p) -copyout(&(_x), (_p), sizeof(*(_p))) > > +static inline void pagefault_disable(void) > +{ > + curthread_pflags_set(TDP_NOFAULTING | TDP_RESETSPUR); > +} > + > +static inline void pagefault_enable(void) > +{ > + curthread_pflags_restore(~(TDP_NOFAULTING | TDP_RESETSPUR)); > +} > + > #endif /* _LINUX_UACCESS_H_ */ This is wrong on many counts. First, we already provide the wrappers to implement the nofaulting behaviour, see vm_fault_disable_pagefaults() and vm_fault_enable_pagefaults(). Second, your implementation ignores possible recursion on the state, unconditionally re-enabling faulting, and more seriously, it unconditionally obliterates the spurious faults tracker. The return value from vm_fault_disable_pagefaults() is there for the reason, and if Linux KPI does not have a place to store the state, some replacement must be implemented instead of silently corrupting the flags on enable.
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