forked from luck/tmp_suning_uos_patched
[PATCH] cpuset: memory migration interaction fix
Fix memory migration so that it works regardless of what cpuset the invoking task is in. If a task invoked a memory migration, by doing one of: 1) writing a different nodemask to a cpuset 'mems' file, or 2) writing a tasks pid to a different cpuset's 'tasks' file, where the cpuset had its 'memory_migrate' option turned on, then the allocation of the new pages for the migrated task(s) was constrained by the invoking tasks cpuset. If this task wasn't in a cpuset that allowed the requested memory nodes, the memory migration would happen to some other nodes that were in that invoking tasks cpuset. This was usually surprising and puzzling behaviour: Why didn't the pages move? Why did the pages move -there-? To fix this, temporarilly change the invoking tasks 'mems_allowed' task_struct field to the nodes the migrating tasks is moving to, so that new pages can be allocated there. Signed-off-by: Paul Jackson <pj@sgi.com> Acked-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -833,6 +833,55 @@ static int update_cpumask(struct cpuset *cs, char *buf)
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return 0;
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}
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/*
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* cpuset_migrate_mm
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*
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* Migrate memory region from one set of nodes to another.
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*
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* Temporarilly set tasks mems_allowed to target nodes of migration,
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* so that the migration code can allocate pages on these nodes.
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*
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* Call holding manage_mutex, so our current->cpuset won't change
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* during this call, as manage_mutex holds off any attach_task()
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* calls. Therefore we don't need to take task_lock around the
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* call to guarantee_online_mems(), as we know no one is changing
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* our tasks cpuset.
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*
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* Hold callback_mutex around the two modifications of our tasks
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* mems_allowed to synchronize with cpuset_mems_allowed().
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*
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* While the mm_struct we are migrating is typically from some
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* other task, the task_struct mems_allowed that we are hacking
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* is for our current task, which must allocate new pages for that
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* migrating memory region.
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*
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* We call cpuset_update_task_memory_state() before hacking
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* our tasks mems_allowed, so that we are assured of being in
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* sync with our tasks cpuset, and in particular, callbacks to
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* cpuset_update_task_memory_state() from nested page allocations
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* won't see any mismatch of our cpuset and task mems_generation
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* values, so won't overwrite our hacked tasks mems_allowed
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* nodemask.
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*/
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static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
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const nodemask_t *to)
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{
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struct task_struct *tsk = current;
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cpuset_update_task_memory_state();
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mutex_lock(&callback_mutex);
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tsk->mems_allowed = *to;
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mutex_unlock(&callback_mutex);
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do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
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mutex_lock(&callback_mutex);
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guarantee_online_mems(tsk->cpuset, &tsk->mems_allowed);
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mutex_unlock(&callback_mutex);
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}
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/*
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* Handle user request to change the 'mems' memory placement
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* of a cpuset. Needs to validate the request, update the
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@ -945,10 +994,8 @@ static int update_nodemask(struct cpuset *cs, char *buf)
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struct mm_struct *mm = mmarray[i];
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mpol_rebind_mm(mm, &cs->mems_allowed);
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if (migrate) {
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do_migrate_pages(mm, &oldmem, &cs->mems_allowed,
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MPOL_MF_MOVE_ALL);
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}
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if (migrate)
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cpuset_migrate_mm(mm, &oldmem, &cs->mems_allowed);
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mmput(mm);
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}
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@ -1184,7 +1231,7 @@ static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
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if (mm) {
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mpol_rebind_mm(mm, &to);
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if (is_memory_migrate(cs))
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do_migrate_pages(mm, &from, &to, MPOL_MF_MOVE_ALL);
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cpuset_migrate_mm(mm, &from, &to);
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mmput(mm);
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}
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