Re: [PATCH] cgroups: fix API thinko
On Wed, Aug 25, 2010 at 02:35:20PM -0700, Andrew Morton wrote: > On Fri, 06 Aug 2010 10:38:24 -0600 > Alex Williamson wrote: > > > On Fri, 2010-08-06 at 09:34 -0700, Sridhar Samudrala wrote: > > > On 8/5/2010 3:59 PM, Michael S. Tsirkin wrote: > > > > cgroup_attach_task_current_cg API that have upstream is backwards: we > > > > really need an API to attach to the cgroups from another process A to > > > > the current one. > > > > > > > > In our case (vhost), a priveledged user wants to attach it's task to > > > > cgroups > > > > from a less priveledged one, the API makes us run it in the other > > > > task's context, and this fails. > > > > > > > > So let's make the API generic and just pass in 'from' and 'to' tasks. > > > > Add an inline wrapper for cgroup_attach_task_current_cg to avoid > > > > breaking bisect. > > > > > > > > Signed-off-by: Michael S. Tsirkin > > > > --- > > > > > > > > Paul, Li, Sridhar, could you please review the following > > > > patch? > > > > > > > > I only compile-tested it due to travel, but looks > > > > straight-forward to me. > > > > Alex Williamson volunteered to test and report the results. > > > > Sending out now for review as I might be offline for a bit. > > > > Will only try to merge when done, obviously. > > > > > > > > If OK, I would like to merge this through -net tree, > > > > together with the patch fixing vhost-net. > > > > Let me know if that sounds ok. > > > > > > > > Thanks! > > > > > > > > This patch is on top of net-next, it is needed for fix > > > > vhost-net regression in net-next, where a non-priveledged > > > > process can't enable the device anymore: > > > > > > > > when qemu uses vhost, inside the ioctl call it > > > > creates a thread, and tries to add > > > > this thread to the groups of current, and it fails. > > > > But we control the thread, so to solve the problem, > > > > we really should tell it 'connect to out cgroups'. > > So am I correct to assume that this change is now needed in 2.6.36, and > unneeded in 2.6.35? Yes, I think so. Unless there are objections, I intend to merge this (with the review fixes) through net-2.6 together with a vhost-net patch that depends on this fix. > Can it affect the userspace<->kernel API in amy manner? If so, it > should be backported into earlier kernels to reduce the number of > incompatible kernels out there. I think it doesn't affect anything except 2.6.36-rcX, earlier kernels didn't use this API. > Paul, did you have any comments? > > I didn't see any update in response to the minor review comments, so... > > > include/linux/cgroup.h |1 + > kernel/cgroup.c|6 +++--- > 2 files changed, 4 insertions(+), 3 deletions(-) > > diff -puN include/linux/cgroup.h~cgroups-fix-api-thinko-fix > include/linux/cgroup.h > --- a/include/linux/cgroup.h~cgroups-fix-api-thinko-fix > +++ a/include/linux/cgroup.h > @@ -579,6 +579,7 @@ void cgroup_iter_end(struct cgroup *cgrp > int cgroup_scan_tasks(struct cgroup_scanner *scan); > int cgroup_attach_task(struct cgroup *, struct task_struct *); > int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); > + > static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) > { > return cgroup_attach_task_all(current, tsk); > diff -puN kernel/cgroup.c~cgroups-fix-api-thinko-fix kernel/cgroup.c > --- a/kernel/cgroup.c~cgroups-fix-api-thinko-fix > +++ a/kernel/cgroup.c > @@ -1798,13 +1798,13 @@ out: > int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) > { > struct cgroupfs_root *root; > - struct cgroup *cur_cg; > int retval = 0; > > cgroup_lock(); > for_each_active_root(root) { > - cur_cg = task_cgroup_from_root(from, root); > - retval = cgroup_attach_task(cur_cg, tsk); > + struct cgroup *from_cg = task_cgroup_from_root(from, root); > + > + retval = cgroup_attach_task(from_cg, tsk); > if (retval) > break; > } > _ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] cgroups: fix API thinko
On Wed, Aug 25, 2010 at 2:35 PM, Andrew Morton wrote: > > So am I correct to assume that this change is now needed in 2.6.36, and > unneeded in 2.6.35? > > Can it affect the userspace<->kernel API in amy manner? If so, it > should be backported into earlier kernels to reduce the number of > incompatible kernels out there. AFAICS it shouldn't affect any existing APIs, either in-kernel or to userspace - it just makes the existing function cgroup_attach_task_current_cg() a specialization of a more generic new function. > > Paul, did you have any comments? Other than the language being a bit confusing, it seems fine. I'd probably word the patch description as: Add cgroup_attach_task_all() The existing cgroup_attach_task_current_cg() API is called by a thread to attach another thread to all of its cgroups; this is unsuitable for cases where a privileged task wants to attach itself to the cgroups of a less privileged one, since the call must be made from the context of the target task. This patch adds a more generic cgroup_attach_task_all() API that allows both the source task and to-be-moved task to be specified. cgroup_attach_task_current_cg() becomes a specialization of the more generic new function. Acked-by: Paul Menage -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] cgroups: fix API thinko
On Fri, 06 Aug 2010 10:38:24 -0600 Alex Williamson wrote: > On Fri, 2010-08-06 at 09:34 -0700, Sridhar Samudrala wrote: > > On 8/5/2010 3:59 PM, Michael S. Tsirkin wrote: > > > cgroup_attach_task_current_cg API that have upstream is backwards: we > > > really need an API to attach to the cgroups from another process A to > > > the current one. > > > > > > In our case (vhost), a priveledged user wants to attach it's task to > > > cgroups > > > from a less priveledged one, the API makes us run it in the other > > > task's context, and this fails. > > > > > > So let's make the API generic and just pass in 'from' and 'to' tasks. > > > Add an inline wrapper for cgroup_attach_task_current_cg to avoid > > > breaking bisect. > > > > > > Signed-off-by: Michael S. Tsirkin > > > --- > > > > > > Paul, Li, Sridhar, could you please review the following > > > patch? > > > > > > I only compile-tested it due to travel, but looks > > > straight-forward to me. > > > Alex Williamson volunteered to test and report the results. > > > Sending out now for review as I might be offline for a bit. > > > Will only try to merge when done, obviously. > > > > > > If OK, I would like to merge this through -net tree, > > > together with the patch fixing vhost-net. > > > Let me know if that sounds ok. > > > > > > Thanks! > > > > > > This patch is on top of net-next, it is needed for fix > > > vhost-net regression in net-next, where a non-priveledged > > > process can't enable the device anymore: > > > > > > when qemu uses vhost, inside the ioctl call it > > > creates a thread, and tries to add > > > this thread to the groups of current, and it fails. > > > But we control the thread, so to solve the problem, > > > we really should tell it 'connect to out cgroups'. So am I correct to assume that this change is now needed in 2.6.36, and unneeded in 2.6.35? Can it affect the userspace<->kernel API in amy manner? If so, it should be backported into earlier kernels to reduce the number of incompatible kernels out there. Paul, did you have any comments? I didn't see any update in response to the minor review comments, so... include/linux/cgroup.h |1 + kernel/cgroup.c|6 +++--- 2 files changed, 4 insertions(+), 3 deletions(-) diff -puN include/linux/cgroup.h~cgroups-fix-api-thinko-fix include/linux/cgroup.h --- a/include/linux/cgroup.h~cgroups-fix-api-thinko-fix +++ a/include/linux/cgroup.h @@ -579,6 +579,7 @@ void cgroup_iter_end(struct cgroup *cgrp int cgroup_scan_tasks(struct cgroup_scanner *scan); int cgroup_attach_task(struct cgroup *, struct task_struct *); int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); + static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) { return cgroup_attach_task_all(current, tsk); diff -puN kernel/cgroup.c~cgroups-fix-api-thinko-fix kernel/cgroup.c --- a/kernel/cgroup.c~cgroups-fix-api-thinko-fix +++ a/kernel/cgroup.c @@ -1798,13 +1798,13 @@ out: int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) { struct cgroupfs_root *root; - struct cgroup *cur_cg; int retval = 0; cgroup_lock(); for_each_active_root(root) { - cur_cg = task_cgroup_from_root(from, root); - retval = cgroup_attach_task(cur_cg, tsk); + struct cgroup *from_cg = task_cgroup_from_root(from, root); + + retval = cgroup_attach_task(from_cg, tsk); if (retval) break; } _ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] cgroups: fix API thinko
(Just came back from vacation) Michael S. Tsirkin wrote: > cgroup_attach_task_current_cg API that have upstream is backwards: we > really need an API to attach to the cgroups from another process A to > the current one. > > In our case (vhost), a priveledged user wants to attach it's task to cgroups > from a less priveledged one, the API makes us run it in the other > task's context, and this fails. > > So let's make the API generic and just pass in 'from' and 'to' tasks. > Add an inline wrapper for cgroup_attach_task_current_cg to avoid > breaking bisect. > > Signed-off-by: Michael S. Tsirkin Acked-by: Li Zefan I also don't like the name, but I'm not good at English or naming. ;) > --- > > Paul, Li, Sridhar, could you please review the following > patch? > > I only compile-tested it due to travel, but looks > straight-forward to me. > Alex Williamson volunteered to test and report the results. > Sending out now for review as I might be offline for a bit. > Will only try to merge when done, obviously. > > If OK, I would like to merge this through -net tree, > together with the patch fixing vhost-net. > Let me know if that sounds ok. > That's Ok. ... > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 43b2072..b38ec60 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, > void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it); > int cgroup_scan_tasks(struct cgroup_scanner *scan); > int cgroup_attach_task(struct cgroup *, struct task_struct *); > -int cgroup_attach_task_current_cg(struct task_struct *); > +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); a nitpick: better add a blank line here. > +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) > +{ > + return cgroup_attach_task_all(current, tsk); > +} -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] cgroups: fix API thinko
On Fri, 2010-08-06 at 09:34 -0700, Sridhar Samudrala wrote: > On 8/5/2010 3:59 PM, Michael S. Tsirkin wrote: > > cgroup_attach_task_current_cg API that have upstream is backwards: we > > really need an API to attach to the cgroups from another process A to > > the current one. > > > > In our case (vhost), a priveledged user wants to attach it's task to cgroups > > from a less priveledged one, the API makes us run it in the other > > task's context, and this fails. > > > > So let's make the API generic and just pass in 'from' and 'to' tasks. > > Add an inline wrapper for cgroup_attach_task_current_cg to avoid > > breaking bisect. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > > > Paul, Li, Sridhar, could you please review the following > > patch? > > > > I only compile-tested it due to travel, but looks > > straight-forward to me. > > Alex Williamson volunteered to test and report the results. > > Sending out now for review as I might be offline for a bit. > > Will only try to merge when done, obviously. > > > > If OK, I would like to merge this through -net tree, > > together with the patch fixing vhost-net. > > Let me know if that sounds ok. > > > > Thanks! > > > > This patch is on top of net-next, it is needed for fix > > vhost-net regression in net-next, where a non-priveledged > > process can't enable the device anymore: > > > > when qemu uses vhost, inside the ioctl call it > > creates a thread, and tries to add > > this thread to the groups of current, and it fails. > > But we control the thread, so to solve the problem, > > we really should tell it 'connect to out cgroups'. > > > So an unprivileged qemu cannot attach vhost thread to its own cgroups. > I guess you are planning to make the cgroup_attach_task_all() call in > vhost_worker() > to attach itself to the cgroups of qemu. Yes, exactly. Alex > The new API looks fine, but the > name is little confusing. How about >task_inherit_cgroups(struct task_struct *from, struct task_struct *to) > > > What this patch does is add an API for that. > > > > include/linux/cgroup.h | 11 ++- > > kernel/cgroup.c|9 + > > 2 files changed, 15 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > > index 43b2072..b38ec60 100644 > > --- a/include/linux/cgroup.h > > +++ b/include/linux/cgroup.h > > @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup > > *cgrp, > > void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it); > > int cgroup_scan_tasks(struct cgroup_scanner *scan); > > int cgroup_attach_task(struct cgroup *, struct task_struct *); > > -int cgroup_attach_task_current_cg(struct task_struct *); > > +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); > > +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) > > +{ > > + return cgroup_attach_task_all(current, tsk); > > +} > > > > /* > >* CSS ID is ID for cgroup_subsys_state structs under subsys. This only > > works > > @@ -583,6 +587,11 @@ static inline int cgroupstats_build(struct cgroupstats > > *stats, > > } > > > > /* No cgroups - nothing to do */ > > +static inline int cgroup_attach_task_all(struct task_struct *from, > > +struct task_struct *t) > > +{ > > + return 0; > > +} > > static inline int cgroup_attach_task_current_cg(struct task_struct *t) > > { > > return 0; > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > > index dce8ebc..e6293b8 100644 > > --- a/kernel/cgroup.c > > +++ b/kernel/cgroup.c > > @@ -1606,10 +1606,11 @@ int cgroup_attach_task(struct cgroup *cgrp, struct > > task_struct *tsk) > > } > > > > /** > > - * cgroup_attach_task_current_cg - attach task 'tsk' to current task's > > cgroup > > + * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from' > > + * @from: attach to all cgroups of a given task > >* @tsk: the task to be attached > >*/ > > -int cgroup_attach_task_current_cg(struct task_struct *tsk) > > +int cgroup_attach_task_all(struct task_struct *from, struct task_struct > > *tsk) > > { > > struct cgroupfs_root *root; > > struct cgroup *cur_cg; > > @@ -1617,7 +1618,7 @@ int cgroup_attach_task_current_cg(struct task_struct > > *tsk) > > > > cgroup_lock(); > > for_each_active_root(root) { > > - cur_cg = task_cgroup_from_root(current, root); > > + cur_cg = task_cgroup_from_root(from, root); > > > Now that we are not operating on current, cur_cg should be renamed as > from_cg > > retval = cgroup_attach_task(cur_cg, tsk); > > if (retval) > > break; > > @@ -1626,7 +1627,7 @@ int cgroup_attach_task_current_cg(struct task_struct > > *tsk) > > > > return retval; > > } > > -EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg); > > +EXPORT_SYMBOL_GPL(cgroup_attach_task_all); > > > > /* > >* Attach task with pid 'pid' to cgroup '
Re: [PATCH] cgroups: fix API thinko
On 8/5/2010 3:59 PM, Michael S. Tsirkin wrote: cgroup_attach_task_current_cg API that have upstream is backwards: we really need an API to attach to the cgroups from another process A to the current one. In our case (vhost), a priveledged user wants to attach it's task to cgroups from a less priveledged one, the API makes us run it in the other task's context, and this fails. So let's make the API generic and just pass in 'from' and 'to' tasks. Add an inline wrapper for cgroup_attach_task_current_cg to avoid breaking bisect. Signed-off-by: Michael S. Tsirkin --- Paul, Li, Sridhar, could you please review the following patch? I only compile-tested it due to travel, but looks straight-forward to me. Alex Williamson volunteered to test and report the results. Sending out now for review as I might be offline for a bit. Will only try to merge when done, obviously. If OK, I would like to merge this through -net tree, together with the patch fixing vhost-net. Let me know if that sounds ok. Thanks! This patch is on top of net-next, it is needed for fix vhost-net regression in net-next, where a non-priveledged process can't enable the device anymore: when qemu uses vhost, inside the ioctl call it creates a thread, and tries to add this thread to the groups of current, and it fails. But we control the thread, so to solve the problem, we really should tell it 'connect to out cgroups'. So an unprivileged qemu cannot attach vhost thread to its own cgroups. I guess you are planning to make the cgroup_attach_task_all() call in vhost_worker() to attach itself to the cgroups of qemu. The new API looks fine, but the name is little confusing. How about task_inherit_cgroups(struct task_struct *from, struct task_struct *to) What this patch does is add an API for that. include/linux/cgroup.h | 11 ++- kernel/cgroup.c|9 + 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 43b2072..b38ec60 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it); int cgroup_scan_tasks(struct cgroup_scanner *scan); int cgroup_attach_task(struct cgroup *, struct task_struct *); -int cgroup_attach_task_current_cg(struct task_struct *); +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) +{ + return cgroup_attach_task_all(current, tsk); +} /* * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works @@ -583,6 +587,11 @@ static inline int cgroupstats_build(struct cgroupstats *stats, } /* No cgroups - nothing to do */ +static inline int cgroup_attach_task_all(struct task_struct *from, +struct task_struct *t) +{ + return 0; +} static inline int cgroup_attach_task_current_cg(struct task_struct *t) { return 0; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index dce8ebc..e6293b8 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1606,10 +1606,11 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) } /** - * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup + * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from' + * @from: attach to all cgroups of a given task * @tsk: the task to be attached */ -int cgroup_attach_task_current_cg(struct task_struct *tsk) +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) { struct cgroupfs_root *root; struct cgroup *cur_cg; @@ -1617,7 +1618,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk) cgroup_lock(); for_each_active_root(root) { - cur_cg = task_cgroup_from_root(current, root); + cur_cg = task_cgroup_from_root(from, root); Now that we are not operating on current, cur_cg should be renamed as from_cg retval = cgroup_attach_task(cur_cg, tsk); if (retval) break; @@ -1626,7 +1627,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk) return retval; } -EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg); +EXPORT_SYMBOL_GPL(cgroup_attach_task_all); /* * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] cgroups: fix API thinko
On Fri, 2010-08-06 at 01:59 +0300, Michael S. Tsirkin wrote: > cgroup_attach_task_current_cg API that have upstream is backwards: we > really need an API to attach to the cgroups from another process A to > the current one. > > In our case (vhost), a priveledged user wants to attach it's task to cgroups > from a less priveledged one, the API makes us run it in the other > task's context, and this fails. > > So let's make the API generic and just pass in 'from' and 'to' tasks. > Add an inline wrapper for cgroup_attach_task_current_cg to avoid > breaking bisect. > > Signed-off-by: Michael S. Tsirkin > --- > > Paul, Li, Sridhar, could you please review the following > patch? > > I only compile-tested it due to travel, but looks > straight-forward to me. > Alex Williamson volunteered to test and report the results. > Sending out now for review as I might be offline for a bit. > Will only try to merge when done, obviously. This does seem to be working here, so please review and let us know if this looks like a suitable interface. Thanks, Alex > If OK, I would like to merge this through -net tree, > together with the patch fixing vhost-net. > Let me know if that sounds ok. > > Thanks! > > This patch is on top of net-next, it is needed for fix > vhost-net regression in net-next, where a non-priveledged > process can't enable the device anymore: > > when qemu uses vhost, inside the ioctl call it > creates a thread, and tries to add > this thread to the groups of current, and it fails. > But we control the thread, so to solve the problem, > we really should tell it 'connect to out cgroups'. > > What this patch does is add an API for that. > > include/linux/cgroup.h | 11 ++- > kernel/cgroup.c|9 + > 2 files changed, 15 insertions(+), 5 deletions(-) > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 43b2072..b38ec60 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, > void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it); > int cgroup_scan_tasks(struct cgroup_scanner *scan); > int cgroup_attach_task(struct cgroup *, struct task_struct *); > -int cgroup_attach_task_current_cg(struct task_struct *); > +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); > +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) > +{ > + return cgroup_attach_task_all(current, tsk); > +} > > /* > * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works > @@ -583,6 +587,11 @@ static inline int cgroupstats_build(struct cgroupstats > *stats, > } > > /* No cgroups - nothing to do */ > +static inline int cgroup_attach_task_all(struct task_struct *from, > + struct task_struct *t) > +{ > + return 0; > +} > static inline int cgroup_attach_task_current_cg(struct task_struct *t) > { > return 0; > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index dce8ebc..e6293b8 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -1606,10 +1606,11 @@ int cgroup_attach_task(struct cgroup *cgrp, struct > task_struct *tsk) > } > > /** > - * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup > + * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from' > + * @from: attach to all cgroups of a given task > * @tsk: the task to be attached > */ > -int cgroup_attach_task_current_cg(struct task_struct *tsk) > +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) > { > struct cgroupfs_root *root; > struct cgroup *cur_cg; > @@ -1617,7 +1618,7 @@ int cgroup_attach_task_current_cg(struct task_struct > *tsk) > > cgroup_lock(); > for_each_active_root(root) { > - cur_cg = task_cgroup_from_root(current, root); > + cur_cg = task_cgroup_from_root(from, root); > retval = cgroup_attach_task(cur_cg, tsk); > if (retval) > break; > @@ -1626,7 +1627,7 @@ int cgroup_attach_task_current_cg(struct task_struct > *tsk) > > return retval; > } > -EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg); > +EXPORT_SYMBOL_GPL(cgroup_attach_task_all); > > /* > * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] cgroups: fix API thinko
cgroup_attach_task_current_cg API that have upstream is backwards: we really need an API to attach to the cgroups from another process A to the current one. In our case (vhost), a priveledged user wants to attach it's task to cgroups from a less priveledged one, the API makes us run it in the other task's context, and this fails. So let's make the API generic and just pass in 'from' and 'to' tasks. Add an inline wrapper for cgroup_attach_task_current_cg to avoid breaking bisect. Signed-off-by: Michael S. Tsirkin --- Paul, Li, Sridhar, could you please review the following patch? I only compile-tested it due to travel, but looks straight-forward to me. Alex Williamson volunteered to test and report the results. Sending out now for review as I might be offline for a bit. Will only try to merge when done, obviously. If OK, I would like to merge this through -net tree, together with the patch fixing vhost-net. Let me know if that sounds ok. Thanks! This patch is on top of net-next, it is needed for fix vhost-net regression in net-next, where a non-priveledged process can't enable the device anymore: when qemu uses vhost, inside the ioctl call it creates a thread, and tries to add this thread to the groups of current, and it fails. But we control the thread, so to solve the problem, we really should tell it 'connect to out cgroups'. What this patch does is add an API for that. include/linux/cgroup.h | 11 ++- kernel/cgroup.c|9 + 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 43b2072..b38ec60 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -525,7 +525,11 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it); int cgroup_scan_tasks(struct cgroup_scanner *scan); int cgroup_attach_task(struct cgroup *, struct task_struct *); -int cgroup_attach_task_current_cg(struct task_struct *); +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); +static inline int cgroup_attach_task_current_cg(struct task_struct *tsk) +{ + return cgroup_attach_task_all(current, tsk); +} /* * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works @@ -583,6 +587,11 @@ static inline int cgroupstats_build(struct cgroupstats *stats, } /* No cgroups - nothing to do */ +static inline int cgroup_attach_task_all(struct task_struct *from, +struct task_struct *t) +{ + return 0; +} static inline int cgroup_attach_task_current_cg(struct task_struct *t) { return 0; diff --git a/kernel/cgroup.c b/kernel/cgroup.c index dce8ebc..e6293b8 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1606,10 +1606,11 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) } /** - * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup + * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from' + * @from: attach to all cgroups of a given task * @tsk: the task to be attached */ -int cgroup_attach_task_current_cg(struct task_struct *tsk) +int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) { struct cgroupfs_root *root; struct cgroup *cur_cg; @@ -1617,7 +1618,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk) cgroup_lock(); for_each_active_root(root) { - cur_cg = task_cgroup_from_root(current, root); + cur_cg = task_cgroup_from_root(from, root); retval = cgroup_attach_task(cur_cg, tsk); if (retval) break; @@ -1626,7 +1627,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk) return retval; } -EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg); +EXPORT_SYMBOL_GPL(cgroup_attach_task_all); /* * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex -- 1.7.2.rc0.14.g41c1c -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html