The patch titled devcgroup: relax white-list protection down to RCU has been added to the -mm tree. Its filename is devcgroup-relax-white-list-protection-down-to-rcu.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: devcgroup: relax white-list protection down to RCU From: Pavel Emelyanov <xemul@xxxxxxxxxx> Currently this list is protected with a simple spinlock, even for reading from one. This is OK, but can be better. Actually I want it to be better very much, since after replacing the OpenVZ device permissions engine with the cgroup-based one I noticed, that we set 12 default device permissions for each newly created container (for /dev/null, full, terminals, ect devices), and people sometimes have up to 20 perms more, so traversing the ~30-40 elements list under a spinlock doesn't seem very good. Here's the RCU protection for white-list - dev_whitelist_item-s are added and removed under the devcg->lock, but are looked up in permissions checking under the rcu_read_lock. Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxx> Acked-by: Serge Hallyn <serue@xxxxxxxxxx> Cc: Balbir Singh <balbir@xxxxxxxxxx> Cc: Paul Menage <menage@xxxxxxxxxx> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- security/device_cgroup.c | 35 ++++++++++++++++++++++------------- 1 file changed, 22 insertions(+), 13 deletions(-) diff -puN security/device_cgroup.c~devcgroup-relax-white-list-protection-down-to-rcu security/device_cgroup.c --- a/security/device_cgroup.c~devcgroup-relax-white-list-protection-down-to-rcu +++ a/security/device_cgroup.c @@ -41,6 +41,7 @@ struct dev_whitelist_item { short type; short access; struct list_head list; + struct rcu_head rcu; }; struct dev_cgroup { @@ -133,11 +134,19 @@ static int dev_whitelist_add(struct dev_ } if (whcopy != NULL) - list_add_tail(&whcopy->list, &dev_cgroup->whitelist); + list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist); spin_unlock(&dev_cgroup->lock); return 0; } +static void whitelist_item_free(struct rcu_head *rcu) +{ + struct dev_whitelist_item *item; + + item = container_of(rcu, struct dev_whitelist_item, rcu); + kfree(item); +} + /* * called under cgroup_lock() * since the list is visible to other tasks, we need the spinlock also @@ -161,8 +170,8 @@ static void dev_whitelist_rm(struct dev_ remove: walk->access &= ~wh->access; if (!walk->access) { - list_del(&walk->list); - kfree(walk); + list_del_rcu(&walk->list); + call_rcu(&walk->rcu, whitelist_item_free); } } spin_unlock(&dev_cgroup->lock); @@ -269,15 +278,15 @@ static int devcgroup_seq_read(struct cgr struct dev_whitelist_item *wh; char maj[MAJMINLEN], min[MAJMINLEN], acc[ACCLEN]; - spin_lock(&devcgroup->lock); - list_for_each_entry(wh, &devcgroup->whitelist, list) { + rcu_read_lock(); + list_for_each_entry_rcu(wh, &devcgroup->whitelist, list) { set_access(acc, wh->access); set_majmin(maj, wh->major); set_majmin(min, wh->minor); seq_printf(m, "%c %s:%s %s\n", type_to_char(wh->type), maj, min, acc); } - spin_unlock(&devcgroup->lock); + rcu_read_unlock(); return 0; } @@ -510,8 +519,8 @@ int devcgroup_inode_permission(struct in if (!dev_cgroup) return 0; - spin_lock(&dev_cgroup->lock); - list_for_each_entry(wh, &dev_cgroup->whitelist, list) { + rcu_read_lock(); + list_for_each_entry_rcu(wh, &dev_cgroup->whitelist, list) { if (wh->type & DEV_ALL) goto acc_check; if ((wh->type & DEV_BLOCK) && !S_ISBLK(inode->i_mode)) @@ -527,10 +536,10 @@ acc_check: continue; if ((mask & MAY_READ) && !(wh->access & ACC_READ)) continue; - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return 0; } - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return -EPERM; } @@ -545,7 +554,7 @@ int devcgroup_inode_mknod(int mode, dev_ if (!dev_cgroup) return 0; - spin_lock(&dev_cgroup->lock); + rcu_read_lock(); list_for_each_entry(wh, &dev_cgroup->whitelist, list) { if (wh->type & DEV_ALL) goto acc_check; @@ -560,9 +569,9 @@ int devcgroup_inode_mknod(int mode, dev_ acc_check: if (!(wh->access & ACC_MKNOD)) continue; - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return 0; } - spin_unlock(&dev_cgroup->lock); + rcu_read_unlock(); return -EPERM; } _ Patches currently in -mm which might be from xemul@xxxxxxxxxx are origin.patch linux-next.patch mark-res_counter_charge_locked-with-__must_check.patch cgroup-files-clean-up-whitespace-in-struct-cftype.patch cgroup-files-add-write_string-cgroup-control-file-method.patch cgroup-files-move-the-release_agent-file-to-use-typed-handlers.patch cgroups-misc-cleanups-to-write_string-patchset.patch cgroup-files-move-notify_on_release-file-to-separate-write-handler.patch cgroup-files-turn-attach_task_by_pid-directly-into-a-cgroup-write-handler.patch cgroup-files-remove-cpuset_common_file_write.patch cgroup-files-convert-devcgroup_access_write-into-a-cgroup-write_string-handler.patch cgroup-files-convert-res_counter_write-to-be-a-cgroups-write_string-handler.patch devcgroup-relax-white-list-protection-down-to-rcu.patch memcg-make-global-var-read_mostly.patch memcg-avoid-unnecessary-initialization.patch memcg-better-migration-handling.patch memcg-remove-refcnt-from-page_cgroup.patch memcg-remove-refcnt-from-page_cgroup-fix.patch memcg-remove-refcnt-from-page_cgroup-fix-2.patch memcg-remove-refcnt-from-page_cgroup-fix-memcg-fix-mem_cgroup_end_migration-race.patch memcg-remove-refcnt-from-page_cgroup-memcg-fix-shmem_unuse_inode-charging.patch memcg-handle-swap-cache.patch memcg-handle-swap-cache-fix.patch memcg-handle-swap-cache-fix-shmem-page-migration-incorrectness-on-memcgroup.patch memcg-helper-function-for-relcaim-from-shmem.patch memcg-helper-function-for-relcaim-from-shmem-memcg-shmem_getpage-release-page-sooner.patch memcg-helper-function-for-relcaim-from-shmem-memcg-mem_cgroup_shrink_usage-css_put.patch memcg-add-hints-for-branch.patch memcg-remove-a-redundant-check.patch memrlimit-add-memrlimit-controller-documentation.patch memrlimit-setup-the-memrlimit-controller.patch memrlimit-setup-the-memrlimit-controller-memrlimit-correct-mremap-and-move_vma-accounting.patch memrlimit-cgroup-mm-owner-callback-changes-to-add-task-info.patch memrlimit-cgroup-mm-owner-callback-changes-to-add-task-info-memrlimit-fix-mmap_sem-deadlock.patch memrlimit-cgroup-mm-owner-callback-changes-to-add-task-info-memrlimit-fix-sleep-inside-sleeplock-in-mm_update_next_owner.patch memrlimit-add-memrlimit-controller-accounting-and-control.patch memrlimit-add-memrlimit-controller-accounting-and-control-memrlimit-improve-fork-and-error-handling.patch memrlimit-improve-error-handling.patch memrlimit-improve-error-handling-update.patch memrlimit-handle-attach_task-failure-add-can_attach-callback.patch memrlimit-handle-attach_task-failure-add-can_attach-callback-update.patch sysctl-allow-override-of-proc-sys-net-with-cap_net_admin.patch pidns-remove-now-unused-kill_proc-function.patch pidns-remove-now-unused-find_pid-function.patch pidns-remove-find_task_by_pid-unused-for-a-long-time.patch bsdacct-rename-acct_blbls-to-bsd_acct_struct.patch pidns-use-kzalloc-when-allocating-new-pid_namespace-struct.patch pidns-add-the-struct-bsd_acct_struct-pointer-on-pid_namespace-struct.patch bsdacct-truthify-a-comment-near-acct_process.patch bsdacct-make-check-timer-accept-a-bsd_acct_struct-argument.patch bsdacct-turn-the-acct_lock-from-on-the-struct-to-global.patch bsdacct-make-internal-code-work-with-passed-bsd_acct_struct-not-global.patch bsdacct-switch-from-global-bsd_acct_struct-instance-to-per-pidns-one.patch bsdacct-turn-acct-off-for-all-pidns-s-on-umount-time.patch bsdacct-account-dying-tasks-in-all-relevant-namespaces.patch bsdacct-stir-up-comments-around-acct_process.patch reiser4.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html