Messages in this thread | | | Date | Thu, 15 Nov 2012 12:35:09 +0400 | From | Stanislav Kinsbursky <> | Subject | Re: [PATCH v3] SUNRPC: set desired file system root before connecting local transports |
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15.11.2012 01:01, J. Bruce Fields пишет: > On Mon, Nov 12, 2012 at 12:37:54PM +0400, Stanislav Kinsbursky wrote: >> 07.11.2012 22:33, J. Bruce Fields пишет: >>> On Tue, Nov 06, 2012 at 08:36:05AM -0500, J. Bruce Fields wrote: >>>> On Tue, Nov 06, 2012 at 08:10:18AM -0500, Christoph Hellwig wrote: >>>>> On Tue, Nov 06, 2012 at 08:07:06AM -0500, J. Bruce Fields wrote: >>>>>> So you're worried that a bug in the nfs code could modify the root and >>>>>> then not restore it? >>>>> >>>>> At least the link you pointed to earlier never sets it back. >>>> >>>> This? http://thread.gmane.org/gmane.linux.kernel/1259986/focus=47687 >>>> >>>> + get_fs_root(current->fs, &root); >>>> + set_fs_root(current->fs, &transport->root); >>>> + >>>> status = xs_local_finish_connecting(xprt, sock); >>>> + >>>> + set_fs_root(current->fs, &root); >>>> + path_put(&root); >>>> >>>>> Instead >>>>> of messing with it I'd rather have the sunrpc code use vfs_path_lookup >>>>> and not care about current->fs->root at all. >>>> >>>> The annoyance is that the lookup happens somewhere lower down in the >>>> networking code (net/unix/af_unix.c:unix_find_other, I think). So we'd >>>> need some new (internal) API. We'd likely be the only user of that new >>>> API. >>> >>> So, if the only drawback is really just the risk of introducing a bug >>> that leaves the fs_root changed--the above seems simple enough for that >>> not to be a great risk, right? >>> >> >> If we unshare rpciod fs struct (which is exported already), then we > > I'm not sure what you mean by that. Do workqueues actually have their > own dedicated set of associated tasks? I thought all workqueues shared > a common pool of tasks these days. >
Any kernel thread is cloned in kthreadd context with CLONE_FS flag. I.e. all of them shares same fs struct, and changing fs->root in one of kthreads will affect all others. That's why either fs struct have to be unshared to swap fs->root or fs->cwd, or the whole fs struct have to swapped.
-- Best regards, Stanislav Kinsbursky -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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