[PATCH V4 11/12] blktrace: add an option to allow displying cgroup path

Shaohua Li
2017-06-28T16:31:29Z

From: Shaohua Li <shli@fb.com>

By default we output cgroup id in blktrace. This adds an option to
display cgroup path. Since get cgroup path is a relativly heavy
operation, we don't enable it by default.

with the option enabled, blktrace will output something like this:
dd-1353 [007] d..2 293.015252: 8,0 /test/level D R 24 + 8 [dd]

Signed-off-by: Shaohua Li <shli@fb.com>
---
fs/kernfs/mount.c | 19 +++++++++++++++++++
include/linux/cgroup.h | 6 ++++++
include/linux/kernfs.h | 2 ++
kernel/cgroup/cgroup.c | 12 ++++++++++++
kernel/trace/blktrace.c | 14 +++++++++++++-
5 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index fa32358..7c452f4 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -65,6 +65,25 @@ const struct super_operations kernfs_sops = {
.show_path = kernfs_sop_show_path,
};

+/*
+ * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
+ * number and generation
+ */
+struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
+ const union kernfs_node_id *id)
+{
+ struct kernfs_node *kn;
+
+ kn = kernfs_find_and_get_node_by_ino(root, id->ino);
+ if (!kn)
+ return NULL;
+ if (kn->id.generation != id->generation) {
+ kernfs_put(kn);
+ return NULL;
+ }
+ return kn;
+}
+
static struct inode *kernfs_fh_get_inode(struct super_block *sb,
u64 ino, u32 generation)
{
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 52ef9a6..6144fe9 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -613,6 +613,9 @@ static inline union kernfs_node_id *cgroup_get_kernfs_id(struct cgroup *cgrp)
{
return &cgrp->kn->id;
}
+
+void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
+ char *buf, size_t buflen);
#else /* !CONFIG_CGROUPS */

struct cgroup_subsys_state;
@@ -645,6 +648,9 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
{
return true;
}
+
+static inline void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
+ char *buf, size_t buflen) {}
#endif /* !CONFIG_CGROUPS */

/*
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index d149361..ab25c8b 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -358,6 +358,8 @@ struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns);

void kernfs_init(void);

+struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
+ const union kernfs_node_id *id);
#else /* CONFIG_KERNFS */

static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4a5cbe9..7fc1eba 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4614,6 +4614,18 @@ static int __init cgroup_wq_init(void)
}
core_initcall(cgroup_wq_init);

+void cgroup_path_from_kernfs_id(const union kernfs_node_id *id,
+ char *buf, size_t buflen)
+{
+ struct kernfs_node *kn;
+
+ kn = kernfs_get_node_by_id(cgrp_dfl_root.kf_root, id);
+ if (!kn)
+ return;
+ kernfs_path(kn, buf, buflen);
+ kernfs_put(kn);
+}
+
/*
* proc_cgroup_show()
* - Print task's cgroup paths into seq_file, one line for each hierarchy
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index f393d7a..e90974e 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -48,12 +48,14 @@ static __cacheline_aligned_in_smp DEFINE_SPINLOCK(running_trace_lock);
/* Select an alternative, minimalistic output than the original one */
#define TRACE_BLK_OPT_CLASSIC 0x1
#define TRACE_BLK_OPT_CGROUP 0x2
+#define TRACE_BLK_OPT_CGNAME 0x4

static struct tracer_opt blk_tracer_opts[] = {
/* Default disable the minimalistic output */
{ TRACER_OPT(blk_classic, TRACE_BLK_OPT_CLASSIC) },
#ifdef CONFIG_BLK_CGROUP
{ TRACER_OPT(blk_cgroup, TRACE_BLK_OPT_CGROUP) },
+ { TRACER_OPT(blk_cgname, TRACE_BLK_OPT_CGNAME) },
#endif
{ }
};
@@ -1213,7 +1215,17 @@ static void blk_log_action(struct trace_iterator *iter, const char *act,
if (has_cg) {
const union kernfs_node_id *id = cgid_start(iter->ent);

- trace_seq_printf(&iter->seq, "%3d,%-3d %x,%-x %2s %3s ",
+ if (blk_tracer_flags.val & TRACE_BLK_OPT_CGNAME) {
+ char blkcg_name_buf[NAME_MAX + 1] = "<...>";
+
+ cgroup_path_from_kernfs_id(id, blkcg_name_buf,
+ sizeof(blkcg_name_buf));
+ trace_seq_printf(&iter->seq, "%3d,%-3d %s %2s %3s ",
+ MAJOR(t->device), MINOR(t->device),
+ blkcg_name_buf, act, rwbs);
+ } else
+ trace_seq_printf(&iter->seq,
+ "%3d,%-3d %x,%-x %2s %3s ",
MAJOR(t->device), MINOR(t->device),
id->ino, id->generation, act, rwbs);
} else
--
2.9.3