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author | Ben Blum <bblum@andrew.cmu.edu> | 2011-05-26 16:25:21 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-05-26 17:12:34 -0700 |
commit | d846687d7f84e45f23ecf3846dbb43312a1206dd (patch) | |
tree | 5c19cf2e0e2faf288bb536f6878cddf11498ef3e | |
parent | 74a1166dfe1135dcc168d35fa5261aa7e087011b (diff) | |
download | linux-d846687d7f84e45f23ecf3846dbb43312a1206dd.tar.bz2 |
cgroups: use flex_array in attach_proc
Convert cgroup_attach_proc to use flex_array.
The cgroup_attach_proc implementation requires a pre-allocated array to
store task pointers to atomically move a thread-group, but asking for a
monolithic array with kmalloc() may be unreliable for very large groups.
Using flex_array provides the same functionality with less risk of
failure.
This is a post-patch for cgroup-procs-write.patch.
Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | kernel/cgroup.c | 33 |
1 files changed, 24 insertions, 9 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 5e6a9745f0e7..00a884342d3d 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -57,6 +57,7 @@ #include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */ #include <linux/eventfd.h> #include <linux/poll.h> +#include <linux/flex_array.h> /* used in cgroup_attach_proc */ #include <asm/atomic.h> @@ -1995,7 +1996,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) struct cgroupfs_root *root = cgrp->root; /* threadgroup list cursor and array */ struct task_struct *tsk; - struct task_struct **group; + struct flex_array *group; /* * we need to make sure we have css_sets for all the tasks we're * going to move -before- we actually start moving them, so that in @@ -2012,9 +2013,15 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) * and if threads exit, this will just be an over-estimate. */ group_size = get_nr_threads(leader); - group = kmalloc(group_size * sizeof(*group), GFP_KERNEL); + /* flex_array supports very large thread-groups better than kmalloc. */ + group = flex_array_alloc(sizeof(struct task_struct *), group_size, + GFP_KERNEL); if (!group) return -ENOMEM; + /* pre-allocate to guarantee space while iterating in rcu read-side. */ + retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL); + if (retval) + goto out_free_group_list; /* prevent changes to the threadgroup list while we take a snapshot. */ rcu_read_lock(); @@ -2037,7 +2044,12 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) /* as per above, nr_threads may decrease, but not increase. */ BUG_ON(i >= group_size); get_task_struct(tsk); - group[i] = tsk; + /* + * saying GFP_ATOMIC has no effect here because we did prealloc + * earlier, but it's good form to communicate our expectations. + */ + retval = flex_array_put_ptr(group, i, tsk, GFP_ATOMIC); + BUG_ON(retval != 0); i++; } while_each_thread(leader, tsk); /* remember the number of threads in the array for later. */ @@ -2059,7 +2071,8 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) if (ss->can_attach_task) { /* run on each task in the threadgroup. */ for (i = 0; i < group_size; i++) { - retval = ss->can_attach_task(cgrp, group[i]); + tsk = flex_array_get_ptr(group, i); + retval = ss->can_attach_task(cgrp, tsk); if (retval) { failed_ss = ss; cancel_failed_ss = true; @@ -2075,7 +2088,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) */ INIT_LIST_HEAD(&newcg_list); for (i = 0; i < group_size; i++) { - tsk = group[i]; + tsk = flex_array_get_ptr(group, i); /* nothing to do if this task is already in the cgroup */ oldcgrp = task_cgroup_from_root(tsk, root); if (cgrp == oldcgrp) @@ -2114,7 +2127,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) ss->pre_attach(cgrp); } for (i = 0; i < group_size; i++) { - tsk = group[i]; + tsk = flex_array_get_ptr(group, i); /* leave current thread as it is if it's already there */ oldcgrp = task_cgroup_from_root(tsk, root); if (cgrp == oldcgrp) @@ -2167,10 +2180,12 @@ out_cancel_attach: } } /* clean up the array of referenced threads in the group. */ - for (i = 0; i < group_size; i++) - put_task_struct(group[i]); + for (i = 0; i < group_size; i++) { + tsk = flex_array_get_ptr(group, i); + put_task_struct(tsk); + } out_free_group_list: - kfree(group); + flex_array_free(group); return retval; } |