On Tue, 16 Jan 2024 10:53:36 -0800
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> Let's at least *try* to move towards a better and simpler world, in other
> words.
OK, but I did just finish the below. I'll save it for another time if the
single inode becomes an issue.
I cropped it to just 31 bits, so I'm not sure how much that would still
expose kernel addresses.
But as you prefer a single inode number, I'll submit that instead, and
store this as one of my many git branches that I hoard.
This patch would give me:
~# ls -i /sys/kernel/tracing/events
2024739183 9p 801480813 iocost 281269778 qdisc
401505785 alarmtimer 641794539 iomap 1206040657 ras
1930290274 avc 1239754069 iommu 275816503 raw_syscalls
1108006611 block 138722947 io_uring 1758073266 rcu
1528091656 bpf_test_run 694421747 ipi 1384703124 regmap
557364529 bpf_trace 2765888 irq 30507018 regulator
1351362737 cfg80211 369905250 irq_matrix 2078862821 resctrl
886445085 cgroup 1115008967 irq_vectors 324090967 rpm
796209754 clk 1448778784 jbd2 1141318882 rseq
478739129 compaction 99410253 kmem 1274783780 rtc
1714397712 cpuhp 2001779594 ksm 1409072807 sched
720701943 csd 51728677 kyber 347239934 scsi
1824588347 dev 1507974437 libata 1768671172 sd
1640041299 devfreq 1421146927 lock 1167562598 signal
121399632 dma_fence 956825721 mac80211 4116590 skb
975908383 drm 738868061 maple_tree 1435501164 smbus
1227060804 e1000e_trace 969175760 mce 1664441095 sock
1770307058 enable 1225375766 mdio 1634697993 spi
1372107864 error_report 744198394 migrate 556841757 swiotlb
1356665351 exceptions 602669807 mmap 400337480 syscalls
[..]
~# ls -i /sys/kernel/tracing/events/sched
1906992193 enable 1210369853 sched_process_wait
592505447 filter 1443020725 sched_stat_blocked
1742488280 sched_kthread_stop 1213185672 sched_stat_iowait
1674576234 sched_kthread_stop_ret 1908510325 sched_stat_runtime
1999376743 sched_kthread_work_execute_end 1570203600 sched_stat_sleep
1041533096 sched_kthread_work_execute_start 608113040 sched_stat_wait
166824308 sched_kthread_work_queue_work 2033295833 sched_stick_numa
492462616 sched_migrate_task 1617500395 sched_swap_numa
1786868196 sched_move_numa 1865216679 sched_switch
691687388 sched_pi_setprio 1465729401 sched_wait_task
1610977146 sched_process_exec 969941227 sched_wake_idle_without_ipi
610128037 sched_process_exit 84398030 sched_wakeup
2139284699 sched_process_fork 750220489 sched_wakeup_new
169172804 sched_process_free 1024064201 sched_waking
-- Steve
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index a0598eb3e26e..57448bf4acb4 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -19,6 +19,7 @@
#include <linux/namei.h>
#include <linux/workqueue.h>
#include <linux/security.h>
+#include <linux/siphash.h>
#include <linux/tracefs.h>
#include <linux/kref.h>
#include <linux/delay.h>
@@ -32,6 +33,9 @@
*/
static DEFINE_MUTEX(eventfs_mutex);
+/* Used for making inode numbers */
+static siphash_key_t inode_key;
+
/*
* The eventfs_inode (ei) itself is protected by SRCU. It is released from
* its parent's list and will have is_freed set (under eventfs_mutex).
@@ -57,6 +61,28 @@ static int eventfs_dir_open(struct inode *inode, struct file *file);
static int eventfs_iterate(struct file *file, struct dir_context *ctx);
static int eventfs_dir_release(struct inode *inode, struct file *file);
+/* Copied from scripts/kconfig/symbol.c */
+static unsigned strhash(const char *s)
+{
+ /* fnv32 hash */
+ unsigned hash = 2166136261U;
+ for (; *s; s++)
+ hash = (hash ^ *s) * 0x01000193;
+ return hash;
+}
+
+/* Just try to make something consistent and unique */
+static int eventfs_inode_ino(struct eventfs_inode *ei, const char *name)
+{
+ unsigned long sip = (unsigned long)ei;
+
+ sip += strhash(name);
+ sip = siphash_1u32((int)sip, &inode_key);
+
+ /* keep it positive */
+ return sip & ((1U << 31) - 1);
+}
+
static void update_attr(struct eventfs_attr *attr, struct iattr *iattr)
{
unsigned int ia_valid = iattr->ia_valid;
@@ -491,6 +517,8 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
mutex_unlock(&eventfs_mutex);
dentry = create_file(name, mode, attr, parent, data, fops);
+ if (!IS_ERR_OR_NULL(dentry))
+ dentry->d_inode->i_ino = eventfs_inode_ino(ei, name);
mutex_lock(&eventfs_mutex);
@@ -585,6 +613,8 @@ create_dir_dentry(struct eventfs_inode *pei, struct eventfs_inode *ei,
mutex_unlock(&eventfs_mutex);
dentry = create_dir(ei, parent);
+ if (!IS_ERR_OR_NULL(dentry))
+ dentry->d_inode->i_ino = eventfs_inode_ino(ei, ei->name);
mutex_lock(&eventfs_mutex);
@@ -721,19 +751,19 @@ struct eventfs_list {
int count;
};
-static int update_entry(struct eventfs_dents *dents, struct dentry *d,
- int type, int cnt)
+static int update_entry(struct eventfs_dents *dents, struct eventfs_inode *ei,
+ const char *name, int type, int cnt)
{
- dents[cnt].name = kstrdup_const(d->d_name.name, GFP_KERNEL);
+ dents[cnt].name = kstrdup_const(name, GFP_KERNEL);
if (!dents[cnt].name)
return -ENOMEM;
- dents[cnt].ino = d->d_inode->i_ino;
+ dents[cnt].ino = eventfs_inode_ino(ei, name);
dents[cnt].type = type;
return 0;
}
-static int add_entry(struct eventfs_dents **edents, struct dentry *d,
- int type, int cnt)
+static int add_entry(struct eventfs_dents **edents, struct eventfs_inode *ei,
+ const char *name, int type, int cnt)
{
struct eventfs_dents *tmp;
@@ -742,7 +772,7 @@ static int add_entry(struct eventfs_dents **edents, struct dentry *d,
return -ENOMEM;
*edents = tmp;
- return update_entry(tmp, d, type, cnt);
+ return update_entry(tmp, ei, name, type, cnt);
}
/*
@@ -758,8 +788,6 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
struct tracefs_inode *ti;
struct eventfs_inode *ei;
struct eventfs_dents *dents;
- struct dentry *ei_dentry = NULL;
- struct dentry *dentry;
const char *name;
umode_t mode;
void *data;
@@ -780,11 +808,11 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
mutex_lock(&eventfs_mutex);
ei = READ_ONCE(ti->private);
- if (ei && !ei->is_freed)
- ei_dentry = READ_ONCE(ei->dentry);
+ if (ei && ei->is_freed)
+ ei = NULL;
mutex_unlock(&eventfs_mutex);
- if (!ei_dentry) {
+ if (!ei) {
srcu_read_unlock(&eventfs_srcu, idx);
return -ENOENT;
}
@@ -810,7 +838,6 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
return -ENOMEM;
}
- inode_lock(ei_dentry->d_inode);
for (i = 0; i < ei->nr_entries; i++) {
void *cdata = data;
entry = &ei->entries[i];
@@ -830,12 +857,7 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
/* callbacks returning zero just means skip this file */
if (r == 0)
continue;
- dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops);
- if (!dentry)
- continue;
-
- ret = update_entry(dents, dentry, DT_REG, cnt);
- dput(dentry);
+ ret = update_entry(dents, ei, name, DT_REG, cnt);
if (ret < 0)
goto fail;
@@ -845,12 +867,7 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
list_for_each_entry_srcu(ei_child, &ei->children, list,
srcu_read_lock_held(&eventfs_srcu)) {
- dentry = create_dir_dentry(ei, ei_child, ei_dentry);
- if (!dentry)
- continue;
-
- ret = add_entry(&dents, dentry, DT_DIR, cnt);
- dput(dentry);
+ ret = add_entry(&dents, ei_child, ei_child->name, DT_DIR, cnt);
if (ret < 0)
goto fail;
cnt++;
@@ -859,12 +876,10 @@ static int eventfs_dir_open(struct inode *inode, struct file *file)
edents->count = cnt;
edents->dents = dents;
- inode_unlock(ei_dentry->d_inode);
srcu_read_unlock(&eventfs_srcu, idx);
file->private_data = edents;
return 0;
fail:
- inode_unlock(ei_dentry->d_inode);
srcu_read_unlock(&eventfs_srcu, idx);
for (; cnt >= 0; cnt--)
kfree_const(dents[cnt].name);
@@ -1029,6 +1044,9 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
if (IS_ERR(dentry))
return ERR_CAST(dentry);
+ if (siphash_key_is_zero(&inode_key))
+ get_random_bytes(&inode_key, sizeof(inode_key));
+
ei = kzalloc(sizeof(*ei), GFP_KERNEL);
if (!ei)
goto fail_ei;
