diff mbox

ceph: fix slab error when removing ceph module

Message ID 1518180059-171011-1-git-send-email-cgxu519@icloud.com (mailing list archive)
State New, archived
Headers show

Commit Message

Chengguang Xu Feb. 9, 2018, 12:40 p.m. UTC 
When failing from ceph_fs_debugfs_init() in ceph_real_mount(),
there is lack of dput of root_dentry and it causes slab errors,
so change the calling order of ceph_fs_debugfs_init() and
open_root_dentry() and do some cleanups to avoid this issue.

Detail error messages:

Comments

Yan, Zheng Feb. 9, 2018, 2:28 p.m. UTC | #1 
I’m curious how did you make ceph_fs_debugfs_init fail

Yan, Zheng

> On 9 Feb 2018, at 20:40, Chengguang Xu <cgxu519@icloud.com> wrote:
> 
> When failing from ceph_fs_debugfs_init() in ceph_real_mount(),
> there is lack of dput of root_dentry and it causes slab errors,
> so change the calling order of ceph_fs_debugfs_init() and
> open_root_dentry() and do some cleanups to avoid this issue.
> 
> Detail error messages:
> =============================================================================
> BUG  ceph_inode_info  (Not  tainted):  Objects  remaining  in  ceph_inode_info  on  __kmem_cache_shutdown()
> -----------------------------------------------------------------------------
> Disabling  lock  debugging  due  to  kernel  taint
> INFO:  Slab  0x000000001037cfd2  objects=23  used=1  fp=0x000000006c0dc265  flags=0x2fffff80008100
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> slab_err+0xb4/0xe0
> ?  on_each_cpu_mask+0x24/0x60
> ?  on_each_cpu_cond+0xad/0x140
> ?  __kmalloc+0x1be/0x1f0
> ?  __kmem_cache_shutdown+0x175/0x3c0
> __kmem_cache_shutdown+0x196/0x3c0
> shutdown_cache+0x13/0x1a0
> kmem_cache_destroy+0x1e4/0x220
> destroy_caches+0x16/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> INFO:  Object  0x00000000568b3053  @offset=0
> kmem_cache_destroy  ceph_inode_info:  Slab  cache  still  has  objects
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> kmem_cache_destroy+0x203/0x220
> destroy_caches+0x16/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> =============================================================================
> BUG  ceph_dentry_info  (Tainted:  G  B  ):  Objects  remaining  in  ceph_dentry_info  on  __kmem_cache_shutdown()
> -----------------------------------------------------------------------------
> INFO:  Slab  0x00000000aabb3f88  objects=51  used=1  fp=0x000000002436421a  flags=0x2fffff80000100
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> slab_err+0xb4/0xe0
> ?  on_each_cpu_cond+0xad/0x140
> ?  __kmalloc+0x1be/0x1f0
> ?  __kmem_cache_shutdown+0x175/0x3c0
> __kmem_cache_shutdown+0x196/0x3c0
> shutdown_cache+0x13/0x1a0
> kmem_cache_destroy+0x1e4/0x220
> destroy_caches+0x3a/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> INFO:  Object  0x0000000034be48a6  @offset=0
> kmem_cache_destroy  ceph_dentry_info:  Slab  cache  still  has  objects
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> kmem_cache_destroy+0x203/0x220
> destroy_caches+0x3a/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> 
> Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
> ---
> fs/ceph/super.c | 16 +++++-----------
> 1 file changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index a62d2a9..26526601 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -836,7 +836,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
> 	int err;
> 	unsigned long started = jiffies;  /* note the start time */
> 	struct dentry *root;
> -	int first = 0;   /* first vfsmount for this super_block */
> 
> 	dout("mount start %p\n", fsc);
> 	mutex_lock(&fsc->client->mount_mutex);
> @@ -861,17 +860,17 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
> 			path = fsc->mount_options->server_path + 1;
> 			dout("mount opening path %s\n", path);
> 		}
> +
> +		err = ceph_fs_debugfs_init(fsc);
> +		if (err < 0)
> +			goto out;
> +
> 		root = open_root_dentry(fsc, path, started);
> 		if (IS_ERR(root)) {
> 			err = PTR_ERR(root);
> 			goto out;
> 		}
> 		fsc->sb->s_root = dget(root);
> -		first = 1;
> -
> -		err = ceph_fs_debugfs_init(fsc);
> -		if (err < 0)
> -			goto fail;
> 	} else {
> 		root = dget(fsc->sb->s_root);
> 	}
> @@ -881,11 +880,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
> 	mutex_unlock(&fsc->client->mount_mutex);
> 	return root;
> 
> -fail:
> -	if (first) {
> -		dput(fsc->sb->s_root);
> -		fsc->sb->s_root = NULL;
> -	}
> out:
> 	mutex_unlock(&fsc->client->mount_mutex);
> 	return ERR_PTR(err);
> -- 
> 1.8.3.1
> 

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Chengguang Xu Feb. 9, 2018, 2:53 p.m. UTC | #2 
> 在 2018年2月9日，下午10:28，Yan, Zheng <zyan@redhat.com> 写道：
> 
> I’m curious how did you make ceph_fs_debugfs_init fail

Hi Yan,

Actually I got some error messages during my hacking work 
in mount process, I did some diagnostics for the reason and
found this issue. Let ceph_fs_debugfs_init fail in a natural
way may be difficult, so I explicitly let it fail in the code
to see what will happen in this context.


> 
> Yan, Zheng
> 
>> On 9 Feb 2018, at 20:40, Chengguang Xu <cgxu519@icloud.com> wrote:
>> 
>> When failing from ceph_fs_debugfs_init() in ceph_real_mount(),
>> there is lack of dput of root_dentry and it causes slab errors,
>> so change the calling order of ceph_fs_debugfs_init() and
>> open_root_dentry() and do some cleanups to avoid this issue.
>> 
>> Detail error messages:
>> =============================================================================
>> BUG  ceph_inode_info  (Not  tainted):  Objects  remaining  in  ceph_inode_info  on  __kmem_cache_shutdown()
>> -----------------------------------------------------------------------------
>> Disabling  lock  debugging  due  to  kernel  taint
>> INFO:  Slab  0x000000001037cfd2  objects=23  used=1  fp=0x000000006c0dc265  flags=0x2fffff80008100
>> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
>> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
>> Call  Trace:
>> dump_stack+0x5c/0x7c
>> slab_err+0xb4/0xe0
>> ?  on_each_cpu_mask+0x24/0x60
>> ?  on_each_cpu_cond+0xad/0x140
>> ?  __kmalloc+0x1be/0x1f0
>> ?  __kmem_cache_shutdown+0x175/0x3c0
>> __kmem_cache_shutdown+0x196/0x3c0
>> shutdown_cache+0x13/0x1a0
>> kmem_cache_destroy+0x1e4/0x220
>> destroy_caches+0x16/0x46  [ceph]
>> SyS_delete_module+0x168/0x240
>> ?  exit_to_usermode_loop+0x6e/0x93
>> entry_SYSCALL_64_fastpath+0x20/0x83
>> RIP:  0033:0x7f8650f87c27
>> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
>> INFO:  Object  0x00000000568b3053  @offset=0
>> kmem_cache_destroy  ceph_inode_info:  Slab  cache  still  has  objects
>> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
>> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
>> Call  Trace:
>> dump_stack+0x5c/0x7c
>> kmem_cache_destroy+0x203/0x220
>> destroy_caches+0x16/0x46  [ceph]
>> SyS_delete_module+0x168/0x240
>> ?  exit_to_usermode_loop+0x6e/0x93
>> entry_SYSCALL_64_fastpath+0x20/0x83
>> RIP:  0033:0x7f8650f87c27
>> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
>> =============================================================================
>> BUG  ceph_dentry_info  (Tainted:  G  B  ):  Objects  remaining  in  ceph_dentry_info  on  __kmem_cache_shutdown()
>> -----------------------------------------------------------------------------
>> INFO:  Slab  0x00000000aabb3f88  objects=51  used=1  fp=0x000000002436421a  flags=0x2fffff80000100
>> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
>> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
>> Call  Trace:
>> dump_stack+0x5c/0x7c
>> slab_err+0xb4/0xe0
>> ?  on_each_cpu_cond+0xad/0x140
>> ?  __kmalloc+0x1be/0x1f0
>> ?  __kmem_cache_shutdown+0x175/0x3c0
>> __kmem_cache_shutdown+0x196/0x3c0
>> shutdown_cache+0x13/0x1a0
>> kmem_cache_destroy+0x1e4/0x220
>> destroy_caches+0x3a/0x46  [ceph]
>> SyS_delete_module+0x168/0x240
>> ?  exit_to_usermode_loop+0x6e/0x93
>> entry_SYSCALL_64_fastpath+0x20/0x83
>> RIP:  0033:0x7f8650f87c27
>> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
>> INFO:  Object  0x0000000034be48a6  @offset=0
>> kmem_cache_destroy  ceph_dentry_info:  Slab  cache  still  has  objects
>> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
>> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
>> Call  Trace:
>> dump_stack+0x5c/0x7c
>> kmem_cache_destroy+0x203/0x220
>> destroy_caches+0x3a/0x46  [ceph]
>> SyS_delete_module+0x168/0x240
>> ?  exit_to_usermode_loop+0x6e/0x93
>> entry_SYSCALL_64_fastpath+0x20/0x83
>> RIP:  0033:0x7f8650f87c27
>> 
>> Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
>> ---
>> fs/ceph/super.c | 16 +++++-----------
>> 1 file changed, 5 insertions(+), 11 deletions(-)
>> 
>> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
>> index a62d2a9..26526601 100644
>> --- a/fs/ceph/super.c
>> +++ b/fs/ceph/super.c
>> @@ -836,7 +836,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>> 	int err;
>> 	unsigned long started = jiffies;  /* note the start time */
>> 	struct dentry *root;
>> -	int first = 0;   /* first vfsmount for this super_block */
>> 
>> 	dout("mount start %p\n", fsc);
>> 	mutex_lock(&fsc->client->mount_mutex);
>> @@ -861,17 +860,17 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>> 			path = fsc->mount_options->server_path + 1;
>> 			dout("mount opening path %s\n", path);
>> 		}
>> +
>> +		err = ceph_fs_debugfs_init(fsc);
>> +		if (err < 0)
>> +			goto out;
>> +
>> 		root = open_root_dentry(fsc, path, started);
>> 		if (IS_ERR(root)) {
>> 			err = PTR_ERR(root);
>> 			goto out;
>> 		}
>> 		fsc->sb->s_root = dget(root);
>> -		first = 1;
>> -
>> -		err = ceph_fs_debugfs_init(fsc);
>> -		if (err < 0)
>> -			goto fail;
>> 	} else {
>> 		root = dget(fsc->sb->s_root);
>> 	}
>> @@ -881,11 +880,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>> 	mutex_unlock(&fsc->client->mount_mutex);
>> 	return root;
>> 
>> -fail:
>> -	if (first) {
>> -		dput(fsc->sb->s_root);
>> -		fsc->sb->s_root = NULL;
>> -	}
>> out:
>> 	mutex_unlock(&fsc->client->mount_mutex);
>> 	return ERR_PTR(err);
>> -- 
>> 1.8.3.1
>> 
> 
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Yan, Zheng Feb. 12, 2018, 2:53 a.m. UTC | #3 
On Fri, Feb 9, 2018 at 8:40 PM, Chengguang Xu <cgxu519@icloud.com> wrote:
> When failing from ceph_fs_debugfs_init() in ceph_real_mount(),
> there is lack of dput of root_dentry and it causes slab errors,
> so change the calling order of ceph_fs_debugfs_init() and
> open_root_dentry() and do some cleanups to avoid this issue.
>
> Detail error messages:
> =============================================================================
> BUG  ceph_inode_info  (Not  tainted):  Objects  remaining  in  ceph_inode_info  on  __kmem_cache_shutdown()
> -----------------------------------------------------------------------------
> Disabling  lock  debugging  due  to  kernel  taint
> INFO:  Slab  0x000000001037cfd2  objects=23  used=1  fp=0x000000006c0dc265  flags=0x2fffff80008100
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> slab_err+0xb4/0xe0
> ?  on_each_cpu_mask+0x24/0x60
> ?  on_each_cpu_cond+0xad/0x140
> ?  __kmalloc+0x1be/0x1f0
> ?  __kmem_cache_shutdown+0x175/0x3c0
> __kmem_cache_shutdown+0x196/0x3c0
> shutdown_cache+0x13/0x1a0
> kmem_cache_destroy+0x1e4/0x220
> destroy_caches+0x16/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> INFO:  Object  0x00000000568b3053  @offset=0
> kmem_cache_destroy  ceph_inode_info:  Slab  cache  still  has  objects
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> kmem_cache_destroy+0x203/0x220
> destroy_caches+0x16/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> =============================================================================
> BUG  ceph_dentry_info  (Tainted:  G  B  ):  Objects  remaining  in  ceph_dentry_info  on  __kmem_cache_shutdown()
> -----------------------------------------------------------------------------
> INFO:  Slab  0x00000000aabb3f88  objects=51  used=1  fp=0x000000002436421a  flags=0x2fffff80000100
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> slab_err+0xb4/0xe0
> ?  on_each_cpu_cond+0xad/0x140
> ?  __kmalloc+0x1be/0x1f0
> ?  __kmem_cache_shutdown+0x175/0x3c0
> __kmem_cache_shutdown+0x196/0x3c0
> shutdown_cache+0x13/0x1a0
> kmem_cache_destroy+0x1e4/0x220
> destroy_caches+0x3a/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
> RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
> INFO:  Object  0x0000000034be48a6  @offset=0
> kmem_cache_destroy  ceph_dentry_info:  Slab  cache  still  has  objects
> CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
> Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
> Call  Trace:
> dump_stack+0x5c/0x7c
> kmem_cache_destroy+0x203/0x220
> destroy_caches+0x3a/0x46  [ceph]
> SyS_delete_module+0x168/0x240
> ?  exit_to_usermode_loop+0x6e/0x93
> entry_SYSCALL_64_fastpath+0x20/0x83
> RIP:  0033:0x7f8650f87c27
>
> Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
> ---
>  fs/ceph/super.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index a62d2a9..26526601 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -836,7 +836,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>         int err;
>         unsigned long started = jiffies;  /* note the start time */
>         struct dentry *root;
> -       int first = 0;   /* first vfsmount for this super_block */
>
>         dout("mount start %p\n", fsc);
>         mutex_lock(&fsc->client->mount_mutex);
> @@ -861,17 +860,17 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>                         path = fsc->mount_options->server_path + 1;
>                         dout("mount opening path %s\n", path);
>                 }
> +
> +               err = ceph_fs_debugfs_init(fsc);
> +               if (err < 0)
> +                       goto out;
> +
>                 root = open_root_dentry(fsc, path, started);
>                 if (IS_ERR(root)) {
>                         err = PTR_ERR(root);
>                         goto out;
>                 }
>                 fsc->sb->s_root = dget(root);
> -               first = 1;
> -
> -               err = ceph_fs_debugfs_init(fsc);
> -               if (err < 0)
> -                       goto fail;
>         } else {
>                 root = dget(fsc->sb->s_root);
>         }
> @@ -881,11 +880,6 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
>         mutex_unlock(&fsc->client->mount_mutex);
>         return root;
>
> -fail:
> -       if (first) {
> -               dput(fsc->sb->s_root);
> -               fsc->sb->s_root = NULL;
> -       }
>  out:
>         mutex_unlock(&fsc->client->mount_mutex);
>         return ERR_PTR(err);
> --
> 1.8.3.1
>

Applied, thanks

Yan, Zheng

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diff mbox

Patch

=============================================================================
BUG  ceph_inode_info  (Not  tainted):  Objects  remaining  in  ceph_inode_info  on  __kmem_cache_shutdown()
-----------------------------------------------------------------------------
Disabling  lock  debugging  due  to  kernel  taint
INFO:  Slab  0x000000001037cfd2  objects=23  used=1  fp=0x000000006c0dc265  flags=0x2fffff80008100
CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
Call  Trace:
dump_stack+0x5c/0x7c
slab_err+0xb4/0xe0
?  on_each_cpu_mask+0x24/0x60
?  on_each_cpu_cond+0xad/0x140
?  __kmalloc+0x1be/0x1f0
?  __kmem_cache_shutdown+0x175/0x3c0
__kmem_cache_shutdown+0x196/0x3c0
shutdown_cache+0x13/0x1a0
kmem_cache_destroy+0x1e4/0x220
destroy_caches+0x16/0x46  [ceph]
SyS_delete_module+0x168/0x240
?  exit_to_usermode_loop+0x6e/0x93
entry_SYSCALL_64_fastpath+0x20/0x83
RIP:  0033:0x7f8650f87c27
RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
INFO:  Object  0x00000000568b3053  @offset=0
kmem_cache_destroy  ceph_inode_info:  Slab  cache  still  has  objects
CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
Call  Trace:
dump_stack+0x5c/0x7c
kmem_cache_destroy+0x203/0x220
destroy_caches+0x16/0x46  [ceph]
SyS_delete_module+0x168/0x240
?  exit_to_usermode_loop+0x6e/0x93
entry_SYSCALL_64_fastpath+0x20/0x83
RIP:  0033:0x7f8650f87c27
RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
=============================================================================
BUG  ceph_dentry_info  (Tainted:  G  B  ):  Objects  remaining  in  ceph_dentry_info  on  __kmem_cache_shutdown()
-----------------------------------------------------------------------------
INFO:  Slab  0x00000000aabb3f88  objects=51  used=1  fp=0x000000002436421a  flags=0x2fffff80000100
CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
Call  Trace:
dump_stack+0x5c/0x7c
slab_err+0xb4/0xe0
?  on_each_cpu_cond+0xad/0x140
?  __kmalloc+0x1be/0x1f0
?  __kmem_cache_shutdown+0x175/0x3c0
__kmem_cache_shutdown+0x196/0x3c0
shutdown_cache+0x13/0x1a0
kmem_cache_destroy+0x1e4/0x220
destroy_caches+0x3a/0x46  [ceph]
SyS_delete_module+0x168/0x240
?  exit_to_usermode_loop+0x6e/0x93
entry_SYSCALL_64_fastpath+0x20/0x83
RIP:  0033:0x7f8650f87c27
RSP:  002b:00007ffda546ff88  EFLAGS:  00000206
INFO:  Object  0x0000000034be48a6  @offset=0
kmem_cache_destroy  ceph_dentry_info:  Slab  cache  still  has  objects
CPU:  0  PID:  27086  Comm:  rmmod  Tainted:  G  B  4.15.0-rc8+  #7
Hardware  name:  Fedora  Project  OpenStack  Nova,  BIOS  seabios-1.7.5-11.el7  04/01/2014
Call  Trace:
dump_stack+0x5c/0x7c
kmem_cache_destroy+0x203/0x220
destroy_caches+0x3a/0x46  [ceph]
SyS_delete_module+0x168/0x240
?  exit_to_usermode_loop+0x6e/0x93
entry_SYSCALL_64_fastpath+0x20/0x83
RIP:  0033:0x7f8650f87c27

Signed-off-by: Chengguang Xu <cgxu519@icloud.com>
---
 fs/ceph/super.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index a62d2a9..26526601 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -836,7 +836,6 @@  static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 	int err;
 	unsigned long started = jiffies;  /* note the start time */
 	struct dentry *root;
-	int first = 0;   /* first vfsmount for this super_block */
 
 	dout("mount start %p\n", fsc);
 	mutex_lock(&fsc->client->mount_mutex);
@@ -861,17 +860,17 @@  static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 			path = fsc->mount_options->server_path + 1;
 			dout("mount opening path %s\n", path);
 		}
+
+		err = ceph_fs_debugfs_init(fsc);
+		if (err < 0)
+			goto out;
+
 		root = open_root_dentry(fsc, path, started);
 		if (IS_ERR(root)) {
 			err = PTR_ERR(root);
 			goto out;
 		}
 		fsc->sb->s_root = dget(root);
-		first = 1;
-
-		err = ceph_fs_debugfs_init(fsc);
-		if (err < 0)
-			goto fail;
 	} else {
 		root = dget(fsc->sb->s_root);
 	}
@@ -881,11 +880,6 @@  static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc)
 	mutex_unlock(&fsc->client->mount_mutex);
 	return root;
 
-fail:
-	if (first) {
-		dput(fsc->sb->s_root);
-		fsc->sb->s_root = NULL;
-	}
 out:
 	mutex_unlock(&fsc->client->mount_mutex);
 	return ERR_PTR(err);