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SubjectRe: [PATCH V2 1/3] dcache: add a new enum type for 'dentry_d_lock_class'
From
Date
On 08.12.19 20:11, Al Viro wrote:
> On Sat, Nov 30, 2019 at 11:36:15AM -0800, Matthew Wilcox wrote:
>> On Sat, Nov 30, 2019 at 03:53:10PM +0800, yukuai (C) wrote:
>>> On 2019/11/30 11:43, Matthew Wilcox wrote:
>>>> On Sat, Nov 30, 2019 at 10:02:23AM +0800, yu kuai wrote:
>>>>> However, a single 'DENTRY_D_LOCK_NESTED' may not be enough if more than
>>>>> two dentry are involed. So, add in 'DENTRY_D_LOCK_NESTED_TWICE'.
>>>>
>>>> No. These need meaningful names. Indeed, I think D_LOCK_NESTED is
>>>> a terrible name.
>>>>
>>>> The exception is __d_move() where I think we should actually name the
>>>> different lock classes instead of using a bare '2' and '3'. Something
>>>> like this, perhaps:
>>>
>>> Thanks for looking into this, do you mind if I replace your patch with the
>>> first two patches in the patchset?
>>
>> That's fine by me, but I think we should wait for Al to give his approval
>> before submitting a new version.
>
> IMO this is a wrong approach. It's papering over a confused code in
> debugfs recursive removal and it would be better to get rid of _that_,
> rather than try and slap bandaids on it.
>
> I suspect that the following would be a better way to deal with it; it adds
> a new primitive and converts debugfs and tracefs to that. There are
> followups converting other such places, still not finished.
>
> commit 7e9c8a08889bf42bbe64e80e456d2eca824e5db2
> Author: Al Viro <viro@zeniv.linux.org.uk>
> Date: Mon Nov 18 09:43:10 2019 -0500
>
> simple_recursive_removal(): kernel-side rm -rf for ramfs-style filesystems
>
> two requirements: no file creations in IS_DEADDIR and no cross-directory
> renames whatsoever.
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
>
> diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> index 042b688ed124..da936c54d879 100644
> --- a/fs/debugfs/inode.c
> +++ b/fs/debugfs/inode.c
> @@ -309,7 +309,10 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
> parent = debugfs_mount->mnt_root;
>
> inode_lock(d_inode(parent));
> - dentry = lookup_one_len(name, parent, strlen(name));
> + if (unlikely(IS_DEADDIR(d_inode(parent))))
> + dentry = ERR_PTR(-ENOENT);
> + else
> + dentry = lookup_one_len(name, parent, strlen(name));
> if (!IS_ERR(dentry) && d_really_is_positive(dentry)) {
> if (d_is_dir(dentry))
> pr_err("Directory '%s' with parent '%s' already present!\n",
> @@ -657,62 +660,15 @@ static void __debugfs_file_removed(struct dentry *dentry)
> wait_for_completion(&fsd->active_users_drained);
> }
>
> -static int __debugfs_remove(struct dentry *dentry, struct dentry *parent)
> -{
> - int ret = 0;
> -
> - if (simple_positive(dentry)) {
> - dget(dentry);
> - if (d_is_dir(dentry)) {
> - ret = simple_rmdir(d_inode(parent), dentry);
> - if (!ret)
> - fsnotify_rmdir(d_inode(parent), dentry);
> - } else {
> - simple_unlink(d_inode(parent), dentry);
> - fsnotify_unlink(d_inode(parent), dentry);
> - }
> - if (!ret)
> - d_delete(dentry);
> - if (d_is_reg(dentry))
> - __debugfs_file_removed(dentry);
> - dput(dentry);
> - }
> - return ret;
> -}
> -
> -/**
> - * debugfs_remove - removes a file or directory from the debugfs filesystem
> - * @dentry: a pointer to a the dentry of the file or directory to be
> - * removed. If this parameter is NULL or an error value, nothing
> - * will be done.
> - *
> - * This function removes a file or directory in debugfs that was previously
> - * created with a call to another debugfs function (like
> - * debugfs_create_file() or variants thereof.)
> - *
> - * This function is required to be called in order for the file to be
> - * removed, no automatic cleanup of files will happen when a module is
> - * removed, you are responsible here.
> - */
> -void debugfs_remove(struct dentry *dentry)
> +static void remove_one(struct dentry *victim)
> {
> - struct dentry *parent;
> - int ret;
> -
> - if (IS_ERR_OR_NULL(dentry))
> - return;
> -
> - parent = dentry->d_parent;
> - inode_lock(d_inode(parent));
> - ret = __debugfs_remove(dentry, parent);
> - inode_unlock(d_inode(parent));
> - if (!ret)
> - simple_release_fs(&debugfs_mount, &debugfs_mount_count);
> + if (d_is_reg(victim))
> + __debugfs_file_removed(victim);
> + simple_release_fs(&debugfs_mount, &debugfs_mount_count);
> }
> -EXPORT_SYMBOL_GPL(debugfs_remove);
>
> /**
> - * debugfs_remove_recursive - recursively removes a directory
> + * debugfs_remove - recursively removes a directory
> * @dentry: a pointer to a the dentry of the directory to be removed. If this
> * parameter is NULL or an error value, nothing will be done.
> *
> @@ -724,65 +680,16 @@ EXPORT_SYMBOL_GPL(debugfs_remove);
> * removed, no automatic cleanup of files will happen when a module is
> * removed, you are responsible here.
> */
> -void debugfs_remove_recursive(struct dentry *dentry)
> +void debugfs_remove(struct dentry *dentry)
> {
> - struct dentry *child, *parent;
> -
> if (IS_ERR_OR_NULL(dentry))
> return;
>
> - parent = dentry;
> - down:
> - inode_lock(d_inode(parent));
> - loop:
> - /*
> - * The parent->d_subdirs is protected by the d_lock. Outside that
> - * lock, the child can be unlinked and set to be freed which can
> - * use the d_u.d_child as the rcu head and corrupt this list.
> - */
> - spin_lock(&parent->d_lock);
> - list_for_each_entry(child, &parent->d_subdirs, d_child) {
> - if (!simple_positive(child))
> - continue;
> -
> - /* perhaps simple_empty(child) makes more sense */
> - if (!list_empty(&child->d_subdirs)) {
> - spin_unlock(&parent->d_lock);
> - inode_unlock(d_inode(parent));
> - parent = child;
> - goto down;
> - }
> -
> - spin_unlock(&parent->d_lock);
> -
> - if (!__debugfs_remove(child, parent))
> - simple_release_fs(&debugfs_mount, &debugfs_mount_count);
> -
> - /*
> - * The parent->d_lock protects agaist child from unlinking
> - * from d_subdirs. When releasing the parent->d_lock we can
> - * no longer trust that the next pointer is valid.
> - * Restart the loop. We'll skip this one with the
> - * simple_positive() check.
> - */
> - goto loop;
> - }
> - spin_unlock(&parent->d_lock);
> -
> - inode_unlock(d_inode(parent));
> - child = parent;
> - parent = parent->d_parent;
> - inode_lock(d_inode(parent));
> -
> - if (child != dentry)
> - /* go up */
> - goto loop;
> -
> - if (!__debugfs_remove(child, parent))
> - simple_release_fs(&debugfs_mount, &debugfs_mount_count);
> - inode_unlock(d_inode(parent));
> + simple_pin_fs(&debug_fs_type, &debugfs_mount, &debugfs_mount_count);
> + simple_recursive_removal(dentry, remove_one);
> + simple_release_fs(&debugfs_mount, &debugfs_mount_count);
> }
> -EXPORT_SYMBOL_GPL(debugfs_remove_recursive);
> +EXPORT_SYMBOL_GPL(debugfs_remove);
>
> /**
> * debugfs_rename - rename a file/directory in the debugfs filesystem
> diff --git a/fs/libfs.c b/fs/libfs.c
> index 540611b99b9a..b67003a948ed 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -19,6 +19,7 @@
> #include <linux/buffer_head.h> /* sync_mapping_buffers */
> #include <linux/fs_context.h>
> #include <linux/pseudo_fs.h>
> +#include <linux/fsnotify.h>
>
> #include <linux/uaccess.h>
>
> @@ -239,6 +240,75 @@ const struct inode_operations simple_dir_inode_operations = {
> };
> EXPORT_SYMBOL(simple_dir_inode_operations);
>
> +static struct dentry *find_next_child(struct dentry *parent, struct dentry *prev)
> +{
> + struct dentry *child = NULL;
> + struct list_head *p = prev ? &prev->d_child : &parent->d_subdirs;
> +
> + spin_lock(&parent->d_lock);
> + while ((p = p->next) != &parent->d_subdirs) {
> + struct dentry *d = container_of(p, struct dentry, d_child);
> + if (simple_positive(d)) {
> + spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
> + if (simple_positive(d))
> + child = dget_dlock(d);
> + spin_unlock(&d->d_lock);
> + if (likely(child))
> + break;
> + }
> + }
> + spin_unlock(&parent->d_lock);
> + dput(prev);
> + return child;
> +}
> +
> +void simple_recursive_removal(struct dentry *dentry,
> + void (*callback)(struct dentry *))
> +{
> + struct dentry *this = dentry;
> + while (true) {
> + struct dentry *victim = NULL, *child;
> + struct inode *inode = this->d_inode;
> +
> + inode_lock(inode);
> + if (d_is_dir(this))
> + inode->i_flags |= S_DEAD;
> + while ((child = find_next_child(this, victim)) == NULL) {
> + // kill and ascend
> + // update metadata while it's still locked
> + inode->i_ctime = current_time(inode);
> + clear_nlink(inode);
> + inode_unlock(inode);
> + victim = this;
> + this = this->d_parent;
> + inode = this->d_inode;
> + inode_lock(inode);
> + if (simple_positive(victim)) {
> + d_invalidate(victim); // avoid lost mounts
> + if (d_is_dir(victim))
> + fsnotify_rmdir(inode, victim);
> + else
> + fsnotify_unlink(inode, victim);
> + if (callback)
> + callback(victim);
> + dput(victim); // unpin it
> + }
> + if (victim == dentry) {
> + inode->i_ctime = inode->i_mtime =
> + current_time(inode);
> + if (d_is_dir(dentry))
> + drop_nlink(inode);
> + inode_unlock(inode);
> + dput(dentry);
> + return;
> + }
> + }
> + inode_unlock(inode);
> + this = child;
> + }
> +}
> +EXPORT_SYMBOL(simple_recursive_removal);
> +
> static const struct super_operations simple_super_operations = {
> .statfs = simple_statfs,
> };
> diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> index eeeae0475da9..2a16c0eb97e4 100644
> --- a/fs/tracefs/inode.c
> +++ b/fs/tracefs/inode.c
> @@ -329,7 +329,10 @@ static struct dentry *start_creating(const char *name, struct dentry *parent)
> parent = tracefs_mount->mnt_root;
>
> inode_lock(parent->d_inode);
> - dentry = lookup_one_len(name, parent, strlen(name));
> + if (unlikely(IS_DEADDIR(parent->d_inode)))
> + dentry = ERR_PTR(-ENOENT);
> + else
> + dentry = lookup_one_len(name, parent, strlen(name));
> if (!IS_ERR(dentry) && dentry->d_inode) {
> dput(dentry);
> dentry = ERR_PTR(-EEXIST);
> @@ -495,122 +498,27 @@ __init struct dentry *tracefs_create_instance_dir(const char *name,
> return dentry;
> }
>
> -static int __tracefs_remove(struct dentry *dentry, struct dentry *parent)
> +static void remove_one(struct dentry *victim)
> {
> - int ret = 0;
> -
> - if (simple_positive(dentry)) {
> - if (dentry->d_inode) {
> - dget(dentry);
> - switch (dentry->d_inode->i_mode & S_IFMT) {
> - case S_IFDIR:
> - ret = simple_rmdir(parent->d_inode, dentry);
> - if (!ret)
> - fsnotify_rmdir(parent->d_inode, dentry);
> - break;
> - default:
> - simple_unlink(parent->d_inode, dentry);
> - fsnotify_unlink(parent->d_inode, dentry);
> - break;
> - }
> - if (!ret)
> - d_delete(dentry);
> - dput(dentry);
> - }
> - }
> - return ret;
> -}
> -
> -/**
> - * tracefs_remove - removes a file or directory from the tracefs filesystem
> - * @dentry: a pointer to a the dentry of the file or directory to be
> - * removed.
> - *
> - * This function removes a file or directory in tracefs that was previously
> - * created with a call to another tracefs function (like
> - * tracefs_create_file() or variants thereof.)
> - */
> -void tracefs_remove(struct dentry *dentry)
> -{
> - struct dentry *parent;
> - int ret;
> -
> - if (IS_ERR_OR_NULL(dentry))
> - return;
> -
> - parent = dentry->d_parent;
> - inode_lock(parent->d_inode);
> - ret = __tracefs_remove(dentry, parent);
> - inode_unlock(parent->d_inode);
> - if (!ret)
> - simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> + simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> }
>
> /**
> - * tracefs_remove_recursive - recursively removes a directory
> + * tracefs_remove - recursively removes a directory
> * @dentry: a pointer to a the dentry of the directory to be removed.
> *
> * This function recursively removes a directory tree in tracefs that
> * was previously created with a call to another tracefs function
> * (like tracefs_create_file() or variants thereof.)
> */
> -void tracefs_remove_recursive(struct dentry *dentry)
> +void tracefs_remove(struct dentry *dentry)
> {
> - struct dentry *child, *parent;
> -
> if (IS_ERR_OR_NULL(dentry))
> return;
>
> - parent = dentry;
> - down:
> - inode_lock(parent->d_inode);
> - loop:
> - /*
> - * The parent->d_subdirs is protected by the d_lock. Outside that
> - * lock, the child can be unlinked and set to be freed which can
> - * use the d_u.d_child as the rcu head and corrupt this list.
> - */
> - spin_lock(&parent->d_lock);
> - list_for_each_entry(child, &parent->d_subdirs, d_child) {
> - if (!simple_positive(child))
> - continue;
> -
> - /* perhaps simple_empty(child) makes more sense */
> - if (!list_empty(&child->d_subdirs)) {
> - spin_unlock(&parent->d_lock);
> - inode_unlock(parent->d_inode);
> - parent = child;
> - goto down;
> - }
> -
> - spin_unlock(&parent->d_lock);
> -
> - if (!__tracefs_remove(child, parent))
> - simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> -
> - /*
> - * The parent->d_lock protects agaist child from unlinking
> - * from d_subdirs. When releasing the parent->d_lock we can
> - * no longer trust that the next pointer is valid.
> - * Restart the loop. We'll skip this one with the
> - * simple_positive() check.
> - */
> - goto loop;
> - }
> - spin_unlock(&parent->d_lock);
> -
> - inode_unlock(parent->d_inode);
> - child = parent;
> - parent = parent->d_parent;
> - inode_lock(parent->d_inode);
> -
> - if (child != dentry)
> - /* go up */
> - goto loop;
> -
> - if (!__tracefs_remove(child, parent))
> - simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> - inode_unlock(parent->d_inode);
> + simple_pin_fs(&trace_fs_type, &tracefs_mount, &tracefs_mount_count);
> + simple_recursive_removal(dentry, remove_one);
> + simple_release_fs(&tracefs_mount, &tracefs_mount_count);
> }
>
> /**
> diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
> index 58424eb3b329..0a817d763f0f 100644
> --- a/include/linux/debugfs.h
> +++ b/include/linux/debugfs.h
> @@ -82,7 +82,7 @@ struct dentry *debugfs_create_automount(const char *name,
> void *data);
>
> void debugfs_remove(struct dentry *dentry);
> -void debugfs_remove_recursive(struct dentry *dentry);
> +#define debugfs_remove_recursive debugfs_remove
>
> const struct file_operations *debugfs_real_fops(const struct file *filp);
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 997a530ff4e9..73ffc8654987 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3242,6 +3242,8 @@ extern int simple_unlink(struct inode *, struct dentry *);
> extern int simple_rmdir(struct inode *, struct dentry *);
> extern int simple_rename(struct inode *, struct dentry *,
> struct inode *, struct dentry *, unsigned int);
> +extern void simple_recursive_removal(struct dentry *,
> + void (*callback)(struct dentry *));
> extern int noop_fsync(struct file *, loff_t, loff_t, int);
> extern int noop_set_page_dirty(struct page *page);
> extern void noop_invalidatepage(struct page *page, unsigned int offset,
> diff --git a/include/linux/tracefs.h b/include/linux/tracefs.h
> index 88d279c1b863..99912445974c 100644
> --- a/include/linux/tracefs.h
> +++ b/include/linux/tracefs.h
> @@ -28,7 +28,6 @@ struct dentry *tracefs_create_file(const char *name, umode_t mode,
> struct dentry *tracefs_create_dir(const char *name, struct dentry *parent);
>
> void tracefs_remove(struct dentry *dentry);
> -void tracefs_remove_recursive(struct dentry *dentry);
>
> struct dentry *tracefs_create_instance_dir(const char *name, struct dentry *parent,
> int (*mkdir)(const char *name),
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 563e80f9006a..88d94dc3ed37 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -8366,7 +8366,7 @@ struct trace_array *trace_array_create(const char *name)
>
> ret = event_trace_add_tracer(tr->dir, tr);
> if (ret) {
> - tracefs_remove_recursive(tr->dir);
> + tracefs_remove(tr->dir);
> goto out_free_tr;
> }
>
> @@ -8422,7 +8422,7 @@ static int __remove_instance(struct trace_array *tr)
> event_trace_del_tracer(tr);
> ftrace_clear_pids(tr);
> ftrace_destroy_function_files(tr);
> - tracefs_remove_recursive(tr->dir);
> + tracefs_remove(tr->dir);
> free_trace_buffers(tr);
>
> for (i = 0; i < tr->nr_topts; i++) {
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 648930823b57..25bb3e8fb170 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -696,7 +696,7 @@ static void remove_subsystem(struct trace_subsystem_dir *dir)
> return;
>
> if (!--dir->nr_events) {
> - tracefs_remove_recursive(dir->entry);
> + tracefs_remove(dir->entry);
> list_del(&dir->list);
> __put_system_dir(dir);
> }
> @@ -715,7 +715,7 @@ static void remove_event_file_dir(struct trace_event_file *file)
> }
> spin_unlock(&dir->d_lock);
>
> - tracefs_remove_recursive(dir);
> + tracefs_remove(dir);
> }
>
> list_del(&file->list);
> @@ -3032,7 +3032,7 @@ int event_trace_del_tracer(struct trace_array *tr)
>
> down_write(&trace_event_sem);
> __trace_remove_event_dirs(tr);
> - tracefs_remove_recursive(tr->event_dir);
> + tracefs_remove(tr->event_dir);
> up_write(&trace_event_sem);
>
> tr->event_dir = NULL;
> diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
> index fa95139445b2..fa45a031848c 100644
> --- a/kernel/trace/trace_hwlat.c
> +++ b/kernel/trace/trace_hwlat.c
> @@ -551,7 +551,7 @@ static int init_tracefs(void)
> return 0;
>
> err:
> - tracefs_remove_recursive(top_dir);
> + tracefs_remove(top_dir);
> return -ENOMEM;
> }
>
>

The patch in linux-next

commit 653f0d05be0948e7610bb786e6570bb6c48a4e75 (HEAD, refs/bisect/bad)
Author: Al Viro <viro@zeniv.linux.org.uk>
Date: Mon Nov 18 09:43:10 2019 -0500

simple_recursive_removal(): kernel-side rm -rf for ramfs-style
filesystems

two requirements: no file creations in IS_DEADDIR and no cross-directory
renames whatsoever.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>


Makes my simple QEMU setup crash when booting


[ 4.571181] list_del corruption. prev->next should be
ffff8b75df3408d0, but was ffff8b75df340d50
[ 4.572064] ------------[ cut here ]------------
[ 4.572448] kernel BUG at lib/list_debug.c:51!
[ 4.572838] invalid opcode: 0000 [#1] SMP NOPTI
[ 4.573235] CPU: 0 PID: 479 Comm: systemd-udevd Not tainted
5.5.0-rc1+ #14
[ 4.573827] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4
[ 4.574782] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55
[ 4.575252] Code: 0d 3d a8 e8 14 dd bd ff 0f 0b 48 c7 c7 00 0e 3d a8
e8 06 dd bd ff 0f 0b 48 89 f2 48 89 fe 48 c7b
[ 4.576829] RSP: 0018:ffffaef9401ebd30 EFLAGS: 00010246
[ 4.577283] RAX: 0000000000000054 RBX: ffff8b75df3416c0 RCX:
0000000000000000
[ 4.577879] RDX: 0000000000000000 RSI: ffff8b757fa1a248 RDI:
ffff8b757fa1a248
[ 4.578479] RBP: ffff8b75df3407e0 R08: 0000000000000000 R09:
0000000000000000
[ 4.579055] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff8b75df340860
[ 4.579660] R13: 0000000000000000 R14: ffff8b75df3416c0 R15:
ffff8b75d6bda620
[ 4.580257] FS: 00007f3016d08940(0000) GS:ffff8b757fa00000(0000)
knlGS:0000000000000000
[ 4.580941] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4.581425] CR2: 00005555eedf9cf3 CR3: 0000000197fa2000 CR4:
00000000000006f0
[ 4.582034] Call Trace:
[ 4.582256] __dentry_kill+0x86/0x190
[ 4.582577] ? dput+0x20/0x460
[ 4.582839] dput+0x2a6/0x460
[ 4.583100] debugfs_remove+0x40/0x60
[ 4.583403] blk_mq_debugfs_unregister_sched+0x15/0x30
[ 4.583825] blk_mq_exit_sched+0x6b/0xa0
[ 4.584154] __elevator_exit+0x32/0x50
[ 4.584460] elevator_switch_mq+0x63/0x170
[ 4.584801] elevator_switch+0x33/0x70
[ 4.585114] elv_iosched_store+0x135/0x1b0
[ 4.585450] queue_attr_store+0x47/0x70
[ 4.585779] kernfs_fop_write+0xdc/0x1c0
[ 4.586128] vfs_write+0xdb/0x1d0
[ 4.586423] ksys_write+0x65/0xe0
[ 4.586716] do_syscall_64+0x5c/0xa0
[ 4.587029] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 4.587472] RIP: 0033:0x7f3017d4a467
[ 4.587782] Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00
00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 854
[ 4.589353] RSP: 002b:00007ffc7fa4f518 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[ 4.589994] RAX: ffffffffffffffda RBX: 0000000000000004 RCX:
00007f3017d4a467
[ 4.590605] RDX: 0000000000000004 RSI: 00007ffc7fa4f600 RDI:
000000000000000f
[ 4.591212] RBP: 00007ffc7fa4f600 R08: fefefefefefefeff R09:
ffffffff00000000
[ 4.591820] R10: 0000000000000000 R11: 0000000000000246 R12:
0000000000000004
[ 4.592423] R13: 000055cdeaffe190 R14: 0000000000000004 R15:
00007f3017e1b700
[ 4.593032] Modules linked in:
[ 4.593307] ---[ end trace 42f66ce1e6e1c1fe ]---
[ 4.593694] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55
[ 4.594173] Code: 0d 3d a8 e8 14 dd bd ff 0f 0b 48 c7 c7 00 0e 3d a8
e8 06 dd bd ff 0f 0b 48 89 f2 48 89 fe 48 c7b
[ 4.595756] RSP: 0018:ffffaef9401ebd30 EFLAGS: 00010246
[ 4.596205] RAX: 0000000000000054 RBX: ffff8b75df3416c0 RCX:
0000000000000000
[ 4.596818] RDX: 0000000000000000 RSI: ffff8b757fa1a248 RDI:
ffff8b757fa1a248
[ 4.597423] RBP: ffff8b75df3407e0 R08: 0000000000000000 R09:
0000000000000000
[ 4.598038] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff8b75df340860
[ 4.598640] R13: 0000000000000000 R14: ffff8b75df3416c0 R15:
ffff8b75d6bda620
[ 4.599241] FS: 00007f3016d08940(0000) GS:ffff8b757fa00000(0000)
knlGS:0000000000000000
[ 4.599936] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4.600415] CR2: 00005555eedf9cf3 CR3: 0000000197fa2000 CR4:
00000000000006f0
[ 4.601034] BUG: sleeping function called from invalid context at
include/linux/percpu-rwsem.h:38
[ 4.601789] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid:
479, name: systemd-udevd
[ 4.602505] INFO: lockdep is turned off.
[ 4.602837] CPU: 0 PID: 479 Comm: systemd-udevd Tainted: G D
5.5.0-rc1+ #14
[ 4.603549] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4
[ 4.604520] Call Trace:
[ 4.604736] dump_stack+0x8f/0xd0
[ 4.605020] ___might_sleep.cold+0xb3/0xc3
[ 4.605374] exit_signals+0x30/0x2d0
[ 4.605689] do_exit+0xb4/0xc40
[ 4.605961] ? ksys_write+0x65/0xe0
[ 4.606256] rewind_stack_do_exit+0x17/0x20
[ 4.606624] note: systemd-udevd[479] exited with preempt_count 2
[ 4.611186] list_del corruption. prev->next should be
ffff8b75df3489f0, but was ffff8b75df3480f0
[ 4.611972] ------------[ cut here ]------------
[ 4.612371] kernel BUG at lib/list_debug.c:51!
[ 4.612783] invalid opcode: 0000 [#2] SMP NOPTI
[ 4.613161] CPU: 0 PID: 511 Comm: systemd-udevd Tainted: G D W
5.5.0-rc1+ #14
[ 4.613875] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu4
[ 4.614842] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55
[ 4.615309] Code: 0d 3d a8 e8 14 dd bd ff 0f 0b 48 c7 c7 00 0e 3d a8
e8 06 dd bd ff 0f 0b 48 89 f2 48 89 fe 48 c7b
[ 4.616880] RSP: 0018:ffffaef9402a3d30 EFLAGS: 00010246
[ 4.617327] RAX: 0000000000000054 RBX: ffff8b75df347240 RCX:
0000000000000000
[ 4.617930] RDX: 0000000000000000 RSI: ffff8b757fa1a248 RDI:
ffff8b757fa1a248
[ 4.618541] RBP: ffff8b75df348900 R08: 0000000000000000 R09:
0000000000000001
[ 4.619140] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff8b75df348980
[ 4.619743] R13: 0000000000000000 R14: ffff8b75df347240 R15:
ffff8b75d6a25020
[ 4.620349] FS: 00007f3016d08940(0000) GS:ffff8b757fa00000(0000)
knlGS:0000000000000000
[ 4.621030] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4.621508] CR2: 000055cdeb042e48 CR3: 000000019e202000 CR4:
00000000000006f0
[ 4.622099] Call Trace:
[ 4.622322] __dentry_kill+0x86/0x190
[ 4.622645] ? dput+0x20/0x460
[ 4.622911] dput+0x2a6/0x460
[ 4.623170] debugfs_remove+0x40/0x60
[ 4.623495] blk_mq_debugfs_unregister_sched+0x15/0x30
[ 4.623929] blk_mq_exit_sched+0x6b/0xa0
[ 4.624264] __elevator_exit+0x32/0x50
[ 4.624593] elevator_switch_mq+0x63/0x170
[ 4.624945] elevator_switch+0x33/0x70
[ 4.625268] elv_iosched_store+0x135/0x1b0
[ 4.625619] queue_attr_store+0x47/0x70
[ 4.625951] kernfs_fop_write+0xdc/0x1c0
[ 4.626289] vfs_write+0xdb/0x1d0
[ 4.626583] ksys_write+0x65/0xe0
[ 4.626870] do_syscall_64+0x5c/0xa0
[ 4.627180] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 4.627616] RIP: 0033:0x7f3017d4a467
[ 4.627925] Code: 64 89 02 48 c7 c0 ff ff ff ff eb bb 0f 1f 80 00 00
00 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 854
[ 4.629499] RSP: 002b:00007ffc7fa4f578 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[ 4.630136] RAX: ffffffffffffffda RBX: 0000000000000004 RCX:
00007f3017d4a467
[ 4.630735] RDX: 0000000000000004 RSI: 00007ffc7fa4f660 RDI:
000000000000000f
[ 4.631334] RBP: 00007ffc7fa4f660 R08: fefefefefefefeff R09:
ffffffff00000000
[ 4.631940] R10: 0000000000000000 R11: 0000000000000246 R12:
0000000000000004
[ 4.632540] R13: 000055cdeaffe190 R14: 0000000000000004 R15:
00007f3017e1b700
[ 4.633141] Modules linked in:
[ 4.633414] ---[ end trace 42f66ce1e6e1c1ff ]---
[ 4.633814] RIP: 0010:__list_del_entry_valid.cold+0x31/0x55
[ 4.634289] Code: 0d 3d a8 e8 14 dd bd ff 0f 0b 48 c7 c7 00 0e 3d a8
e8 06 dd bd ff 0f 0b 48 89 f2 48 89 fe 48 c7b
[ 4.635881] RSP: 0018:ffffaef9401ebd30 EFLAGS: 00010246
[ 4.636329] RAX: 0000000000000054 RBX: ffff8b75df3416c0 RCX:
0000000000000000
[ 4.636940] RDX: 0000000000000000 RSI: ffff8b757fa1a248 RDI:
ffff8b757fa1a248
[ 4.637544] RBP: ffff8b75df3407e0 R08: 0000000000000000 R09:
0000000000000000
[ 4.638149] R10: 0000000000000000 R11: 0000000000000000 R12:
ffff8b75df340860
[ 4.638750] R13: 0000000000000000 R14: ffff8b75df3416c0 R15:
ffff8b75d6bda620
[ 4.639360] FS: 00007f3016d08940(0000) GS:ffff8b757fa00000(0000)
knlGS:0000000000000000
[ 4.640047] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4.640537] CR2: 000055cdeb042e48 CR3: 000000019e202000 CR4:
00000000000006f0
[ 4.641128] note: systemd-udevd[511] exited with preempt_count 2


Reverting that commit makes it work again. How does that untested and
unreviewed patch end up in linux-next? Took me 30min to bisect.

--
Thanks,

David / dhildenb

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