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From: Dave Hansen <dave-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
To: Oren Laadan <orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
Cc: linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	Linus Torvalds <torvalds-3NddpPZAyC0@public.gmane.org>,
	Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	"H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Subject: Re: [RFC v10][PATCH 09/13] Restore open file descriprtors
Date: Mon, 01 Dec 2008 13:07:31 -0800	[thread overview]
Message-ID: <1228165651.2971.99.camel@nimitz> (raw)
In-Reply-To: <49345086.4-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>

On Mon, 2008-12-01 at 16:00 -0500, Oren Laadan wrote:
> > Is that sufficient?  It seems like we're depending on the fd's reference
> > to the 'struct file' to keep it valid in the hash.  If something happens
> > to the fd (like the other thread messing with it) the 'struct file' can
> > still go away.
> > 
> > Shouldn't we do another get_file() for the hash's reference?
> 
> When a shared object is inserted to the hash we automatically take another
> reference to it (according to its type) for as long as it remains in the
> hash. See:  'cr_obj_ref_grab()' and 'cr_obj_ref_drop()'.  So by moving that
> call higher up, we protect the struct file.

That's kinda (and by kinda I mean really) disgusting.  Hiding that two
levels deep in what is effectively the hash table code where no one will
ever see it is really bad.  It also makes you lazy thinking that the
hash code will just know how to take references on whatever you give to
it.

I think cr_obj_ref_grab() is hideous obfuscation and needs to die.
Let's just do the get_file() directly, please.

-- Dave

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  parent reply	other threads:[~2008-12-01 21:07 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-11-27  1:04 [RFC v10][PATCH 00/13] Kernel based checkpoint/restart Oren Laadan
     [not found] ` <1227747884-14150-1-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-11-27  1:04   ` [RFC v10][PATCH 01/13] Create syscalls: sys_checkpoint, sys_restart Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 02/13] Checkpoint/restart: initial documentation Oren Laadan
     [not found]     ` <1227747884-14150-3-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-11-28 10:45       ` Al Viro
     [not found]         ` <20081128104554.GP28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-12-01 18:15           ` Dave Hansen
2008-11-27  1:04   ` [RFC v10][PATCH 03/13] General infrastructure for checkpoint restart Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 04/13] x86 support for checkpoint/restart Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 05/13] Dump memory address space Oren Laadan
     [not found]     ` <1227747884-14150-6-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-11-28 10:53       ` Al Viro
     [not found]         ` <20081128105351.GQ28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-12-01 18:00           ` Dave Hansen
2008-12-01 20:57             ` Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 06/13] Restore " Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 07/13] Infrastructure for shared objects Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 08/13] Dump open file descriptors Oren Laadan
     [not found]     ` <1227747884-14150-9-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-11-28 10:19       ` Al Viro
     [not found]         ` <20081128101919.GO28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-12-01 17:47           ` Dave Hansen
2008-12-01 20:23             ` Oren Laadan
     [not found]               ` <493447DD.7010102-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-12-01 20:51                 ` Dave Hansen
2008-12-01 21:02                   ` Linus Torvalds
     [not found]                     ` <alpine.LFD.2.00.0812011258390.3256-nfNrOhbfy2R17+2ddN/4kux8cNe9sq/dYPYVAmT7z5s@public.gmane.org>
2008-12-01 21:25                       ` Dave Hansen
2008-12-01 21:20                   ` Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 09/13] Restore open file descriprtors Oren Laadan
     [not found]     ` <1227747884-14150-10-git-send-email-orenl-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-11-28 11:27       ` Al Viro
     [not found]         ` <20081128112745.GR28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-12-01 19:22           ` Dave Hansen
2008-12-01 20:41             ` Oren Laadan
     [not found]               ` <49344C11.6090204-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-12-01 20:54                 ` Dave Hansen
2008-12-01 21:00                   ` Oren Laadan
     [not found]                     ` <49345086.4-eQaUEPhvms7ENvBUuze7eA@public.gmane.org>
2008-12-01 21:07                       ` Dave Hansen [this message]
2008-12-02  1:31                         ` Dave Hansen
2008-12-02  1:12                       ` Dave Hansen
2008-11-27  1:04   ` [RFC v10][PATCH 10/13] External checkpoint of a task other than ourself Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 11/13] Track in-kernel when we expect checkpoint/restart to work Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 12/13] Checkpoint multiple processes Oren Laadan
2008-11-27  1:04   ` [RFC v10][PATCH 13/13] Restart " Oren Laadan
2008-12-03 23:58   ` [RFC v10][PATCH 00/13] Kernel based checkpoint/restart Serge E. Hallyn

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