From 46307fd6e27a3f678a1678b02e667678c22aa8cc Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Michal=20Koutn=C3=BD?= Date: Mon, 10 Oct 2022 10:29:18 +0200 Subject: [PATCH 1/7] cgroup: Reorganize css_set_lock and kernfs path processing MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The commit 74e4b956eb1c incorrectly wrapped kernfs_walk_and_get (might_sleep) under css_set_lock (spinlock). css_set_lock is needed by __cset_cgroup_from_root to ensure stable cset->cgrp_links but not for kernfs_walk_and_get. We only need to make sure that the returned root_cgrp won't be freed under us. This is given in the case of global root because it is static (cgrp_dfl_root.cgrp). When the root_cgrp is lower in the hierarchy, it is pinned by cgroup_ns->root_cset (and `current` task cannot switch namespace asynchronously so ns_proxy pins cgroup_ns). Note this reasoning won't hold for root cgroups in v1 hierarchies, therefore create a special-cased helper function just for the default hierarchy. Fixes: 74e4b956eb1c ("cgroup: Honor caller's cgroup NS when resolving path") Reported-by: Dan Carpenter Signed-off-by: Michal Koutný Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 40 +++++++++++++++++++++++++++------------- 1 file changed, 27 insertions(+), 13 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 764bdd5fd8d1..ecf409e3c3a7 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1392,6 +1392,9 @@ static void cgroup_destroy_root(struct cgroup_root *root) cgroup_free_root(root); } +/* + * Returned cgroup is without refcount but it's valid as long as cset pins it. + */ static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset, struct cgroup_root *root) { @@ -1403,6 +1406,7 @@ static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset, res_cgroup = cset->dfl_cgrp; } else { struct cgrp_cset_link *link; + lockdep_assert_held(&css_set_lock); list_for_each_entry(link, &cset->cgrp_links, cgrp_link) { struct cgroup *c = link->cgrp; @@ -1414,6 +1418,7 @@ static inline struct cgroup *__cset_cgroup_from_root(struct css_set *cset, } } + BUG_ON(!res_cgroup); return res_cgroup; } @@ -1436,23 +1441,36 @@ current_cgns_cgroup_from_root(struct cgroup_root *root) rcu_read_unlock(); - BUG_ON(!res); return res; } +/* + * Look up cgroup associated with current task's cgroup namespace on the default + * hierarchy. + * + * Unlike current_cgns_cgroup_from_root(), this doesn't need locks: + * - Internal rcu_read_lock is unnecessary because we don't dereference any rcu + * pointers. + * - css_set_lock is not needed because we just read cset->dfl_cgrp. + * - As a bonus returned cgrp is pinned with the current because it cannot + * switch cgroup_ns asynchronously. + */ +static struct cgroup *current_cgns_cgroup_dfl(void) +{ + struct css_set *cset; + + cset = current->nsproxy->cgroup_ns->root_cset; + return __cset_cgroup_from_root(cset, &cgrp_dfl_root); +} + /* look up cgroup associated with given css_set on the specified hierarchy */ static struct cgroup *cset_cgroup_from_root(struct css_set *cset, struct cgroup_root *root) { - struct cgroup *res = NULL; - lockdep_assert_held(&cgroup_mutex); lockdep_assert_held(&css_set_lock); - res = __cset_cgroup_from_root(cset, root); - - BUG_ON(!res); - return res; + return __cset_cgroup_from_root(cset, root); } /* @@ -6105,9 +6123,7 @@ struct cgroup *cgroup_get_from_id(u64 id) if (!cgrp) return ERR_PTR(-ENOENT); - spin_lock_irq(&css_set_lock); - root_cgrp = current_cgns_cgroup_from_root(&cgrp_dfl_root); - spin_unlock_irq(&css_set_lock); + root_cgrp = current_cgns_cgroup_dfl(); if (!cgroup_is_descendant(cgrp, root_cgrp)) { cgroup_put(cgrp); return ERR_PTR(-ENOENT); @@ -6686,10 +6702,8 @@ struct cgroup *cgroup_get_from_path(const char *path) struct cgroup *cgrp = ERR_PTR(-ENOENT); struct cgroup *root_cgrp; - spin_lock_irq(&css_set_lock); - root_cgrp = current_cgns_cgroup_from_root(&cgrp_dfl_root); + root_cgrp = current_cgns_cgroup_dfl(); kn = kernfs_walk_and_get(root_cgrp->kn, path); - spin_unlock_irq(&css_set_lock); if (!kn) goto out; From 03db7716159477b595e9af01be8003b7e994cc79 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 10 Oct 2022 11:08:17 -1000 Subject: [PATCH 2/7] Revert "cgroup: enable cgroup_get_from_file() on cgroup1" This reverts commit f3a2aebdd6fb90e444d595e46de64e822af419da. The commit enabled looking up v1 cgroups via cgroup_get_from_file(). However, there are multiple users, including CLONE_INTO_CGROUP, which have been assuming that it would only look up v2 cgroups. Returning v1 cgroups breaks them. Let's revert the commit and retry later with a separate lookup interface which allows both v1 and v2. Signed-off-by: Tejun Heo Link: http://lkml.kernel.org/r/000000000000385cbf05ea3f1862@google.com Cc: Yosry Ahmed --- kernel/cgroup/cgroup.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index ecf409e3c3a7..6d8a5a40c24d 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6234,6 +6234,11 @@ static struct cgroup *cgroup_get_from_file(struct file *f) return ERR_CAST(css); cgrp = css->cgroup; + if (!cgroup_on_dfl(cgrp)) { + cgroup_put(cgrp); + return ERR_PTR(-EBADF); + } + return cgrp; } From a6d1ce5951185ee91bbe6909fe2758f3625561b0 Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Tue, 11 Oct 2022 00:33:58 +0000 Subject: [PATCH 3/7] cgroup: add cgroup_v1v2_get_from_[fd/file]() Add cgroup_v1v2_get_from_fd() and cgroup_v1v2_get_from_file() that support both cgroup1 and cgroup2. Signed-off-by: Yosry Ahmed Signed-off-by: Tejun Heo --- include/linux/cgroup.h | 1 + kernel/cgroup/cgroup.c | 50 +++++++++++++++++++++++++++++++++++++----- 2 files changed, 45 insertions(+), 6 deletions(-) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 398f0bce7c21..a88de5bdeaa9 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -106,6 +106,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, struct cgroup *cgroup_get_from_path(const char *path); struct cgroup *cgroup_get_from_fd(int fd); +struct cgroup *cgroup_v1v2_get_from_fd(int fd); int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 6d8a5a40c24d..6349a9fe9ec1 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6224,16 +6224,36 @@ void cgroup_fork(struct task_struct *child) INIT_LIST_HEAD(&child->cg_list); } -static struct cgroup *cgroup_get_from_file(struct file *f) +/** + * cgroup_v1v2_get_from_file - get a cgroup pointer from a file pointer + * @f: file corresponding to cgroup_dir + * + * Find the cgroup from a file pointer associated with a cgroup directory. + * Returns a pointer to the cgroup on success. ERR_PTR is returned if the + * cgroup cannot be found. + */ +static struct cgroup *cgroup_v1v2_get_from_file(struct file *f) { struct cgroup_subsys_state *css; - struct cgroup *cgrp; css = css_tryget_online_from_dir(f->f_path.dentry, NULL); if (IS_ERR(css)) return ERR_CAST(css); - cgrp = css->cgroup; + return css->cgroup; +} + +/** + * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports + * cgroup2. + */ +static struct cgroup *cgroup_get_from_file(struct file *f) +{ + struct cgroup *cgrp = cgroup_v1v2_get_from_file(f); + + if (IS_ERR(cgrp)) + return ERR_CAST(cgrp); + if (!cgroup_on_dfl(cgrp)) { cgroup_put(cgrp); return ERR_PTR(-EBADF); @@ -6734,14 +6754,14 @@ EXPORT_SYMBOL_GPL(cgroup_get_from_path); /** * cgroup_get_from_fd - get a cgroup pointer from a fd - * @fd: fd obtained by open(cgroup2_dir) + * @fd: fd obtained by open(cgroup_dir) * * Find the cgroup from a fd which should be obtained * by opening a cgroup directory. Returns a pointer to the * cgroup on success. ERR_PTR is returned if the cgroup * cannot be found. */ -struct cgroup *cgroup_get_from_fd(int fd) +struct cgroup *cgroup_v1v2_get_from_fd(int fd) { struct cgroup *cgrp; struct file *f; @@ -6750,10 +6770,28 @@ struct cgroup *cgroup_get_from_fd(int fd) if (!f) return ERR_PTR(-EBADF); - cgrp = cgroup_get_from_file(f); + cgrp = cgroup_v1v2_get_from_file(f); fput(f); return cgrp; } + +/** + * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports + * cgroup2. + */ +struct cgroup *cgroup_get_from_fd(int fd) +{ + struct cgroup *cgrp = cgroup_v1v2_get_from_fd(fd); + + if (IS_ERR(cgrp)) + return ERR_CAST(cgrp); + + if (!cgroup_on_dfl(cgrp)) { + cgroup_put(cgrp); + return ERR_PTR(-EBADF); + } + return cgrp; +} EXPORT_SYMBOL_GPL(cgroup_get_from_fd); static u64 power_of_ten(int power) From 35256d673a9cf723d9e2edb5d51e1b1b6b197ba3 Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Tue, 11 Oct 2022 00:33:59 +0000 Subject: [PATCH 4/7] bpf: cgroup_iter: support cgroup1 using cgroup fd Use cgroup_v1v2_get_from_fd() in cgroup_iter to support attaching to both cgroup v1 and v2 using fds. Signed-off-by: Yosry Ahmed Acked-by: Martin KaFai Lau Signed-off-by: Tejun Heo --- kernel/bpf/cgroup_iter.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c index 0d200a993489..9fcf09f2ef00 100644 --- a/kernel/bpf/cgroup_iter.c +++ b/kernel/bpf/cgroup_iter.c @@ -196,7 +196,7 @@ static int bpf_iter_attach_cgroup(struct bpf_prog *prog, return -EINVAL; if (fd) - cgrp = cgroup_get_from_fd(fd); + cgrp = cgroup_v1v2_get_from_fd(fd); else if (id) cgrp = cgroup_get_from_id(id); else /* walk the entire hierarchy by default. */ From 8248fe413216732f98563e8882b6c6ae617c327b Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Mon, 10 Oct 2022 22:28:08 -0700 Subject: [PATCH 5/7] perf stat: Support old kernels for bperf cgroup counting The recent change in the cgroup will break the backward compatiblity in the BPF program. It should support both old and new kernels using BPF CO-RE technique. Like the task_struct->__state handling in the offcpu analysis, we can check the field name in the cgroup struct. Acked-by: Jiri Olsa Acked-by: Andrii Nakryiko Signed-off-by: Namhyung Kim Signed-off-by: Tejun Heo --- tools/perf/util/bpf_skel/bperf_cgroup.bpf.c | 29 ++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c index 435a87556688..6a438e0102c5 100644 --- a/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c +++ b/tools/perf/util/bpf_skel/bperf_cgroup.bpf.c @@ -43,6 +43,18 @@ struct { __uint(value_size, sizeof(struct bpf_perf_event_value)); } cgrp_readings SEC(".maps"); +/* new kernel cgroup definition */ +struct cgroup___new { + int level; + struct cgroup *ancestors[]; +} __attribute__((preserve_access_index)); + +/* old kernel cgroup definition */ +struct cgroup___old { + int level; + u64 ancestor_ids[]; +} __attribute__((preserve_access_index)); + const volatile __u32 num_events = 1; const volatile __u32 num_cpus = 1; @@ -50,6 +62,21 @@ int enabled = 0; int use_cgroup_v2 = 0; int perf_subsys_id = -1; +static inline __u64 get_cgroup_v1_ancestor_id(struct cgroup *cgrp, int level) +{ + /* recast pointer to capture new type for compiler */ + struct cgroup___new *cgrp_new = (void *)cgrp; + + if (bpf_core_field_exists(cgrp_new->ancestors)) { + return BPF_CORE_READ(cgrp_new, ancestors[level], kn, id); + } else { + /* recast pointer to capture old type for compiler */ + struct cgroup___old *cgrp_old = (void *)cgrp; + + return BPF_CORE_READ(cgrp_old, ancestor_ids[level]); + } +} + static inline int get_cgroup_v1_idx(__u32 *cgrps, int size) { struct task_struct *p = (void *)bpf_get_current_task(); @@ -77,7 +104,7 @@ static inline int get_cgroup_v1_idx(__u32 *cgrps, int size) break; // convert cgroup-id to a map index - cgrp_id = BPF_CORE_READ(cgrp, ancestors[i], kn, id); + cgrp_id = get_cgroup_v1_ancestor_id(cgrp, i); elem = bpf_map_lookup_elem(&cgrp_idx, &cgrp_id); if (!elem) continue; From b675d4bdfefac2fd46838383ecb3c06ad0f4c94d Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Tue, 11 Oct 2022 22:51:55 +0000 Subject: [PATCH 6/7] mm: cgroup: fix comments for get from fd/file helpers Fix the documentation comments for cgroup_[v1v2_]get_from_[fd/file](). Reported-by: kernel test robot Signed-off-by: Yosry Ahmed Signed-off-by: Tejun Heo --- kernel/cgroup/cgroup.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 6349a9fe9ec1..d922773fa90b 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6246,6 +6246,7 @@ static struct cgroup *cgroup_v1v2_get_from_file(struct file *f) /** * cgroup_get_from_file - same as cgroup_v1v2_get_from_file, but only supports * cgroup2. + * @f: file corresponding to cgroup2_dir */ static struct cgroup *cgroup_get_from_file(struct file *f) { @@ -6753,7 +6754,7 @@ struct cgroup *cgroup_get_from_path(const char *path) EXPORT_SYMBOL_GPL(cgroup_get_from_path); /** - * cgroup_get_from_fd - get a cgroup pointer from a fd + * cgroup_v1v2_get_from_fd - get a cgroup pointer from a fd * @fd: fd obtained by open(cgroup_dir) * * Find the cgroup from a fd which should be obtained @@ -6778,6 +6779,7 @@ struct cgroup *cgroup_v1v2_get_from_fd(int fd) /** * cgroup_get_from_fd - same as cgroup_v1v2_get_from_fd, but only supports * cgroup2. + * @fd: fd obtained by open(cgroup2_dir) */ struct cgroup *cgroup_get_from_fd(int fd) { From 79a818b5087393d5a4cb356d4545d02f55bf1a2f Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 17 Oct 2022 08:08:05 -1000 Subject: [PATCH 7/7] blkcg: Update MAINTAINERS entry Josef wrote iolatency and iocost is missing from the files list. Let's add Josef as a maintainer and add blk-iocost.c to the files list. Signed-off-by: Tejun Heo Acked-by: Jens Axboe --- MAINTAINERS | 2 ++ 1 file changed, 2 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index 0dc4a769216b..4a5ce3863deb 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5256,6 +5256,7 @@ F: tools/testing/selftests/cgroup/ CONTROL GROUP - BLOCK IO CONTROLLER (BLKIO) M: Tejun Heo +M: Josef Bacik M: Jens Axboe L: cgroups@vger.kernel.org L: linux-block@vger.kernel.org @@ -5263,6 +5264,7 @@ T: git git://git.kernel.dk/linux-block F: Documentation/admin-guide/cgroup-v1/blkio-controller.rst F: block/bfq-cgroup.c F: block/blk-cgroup.c +F: block/blk-iocost.c F: block/blk-iolatency.c F: block/blk-throttle.c F: include/linux/blk-cgroup.h