Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
A correction,

On (11/22/16 10:09), Sergey Senozhatsky wrote:
[..]
> > > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > > Reported-and-tested-by: David Disseldorp 
> > > Reviewed-by: David Disseldorp 
> > > Cc: 
> > > Signed-off-by: Takashi Iwai 
> 
> 
> > Acked-by: Minchan Kim 
> 
> Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> Cc: [4.5+]
    4.4+


> Acked-by: Sergey Senozhatsky 



but somehow I didn't notice that Takashi Cc'd stable in the original patch.
so mine can be dropped.

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
A correction,

On (11/22/16 10:09), Sergey Senozhatsky wrote:
[..]
> > > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > > Reported-and-tested-by: David Disseldorp 
> > > Reviewed-by: David Disseldorp 
> > > Cc: 
> > > Signed-off-by: Takashi Iwai 
> 
> 
> > Acked-by: Minchan Kim 
> 
> Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> Cc: [4.5+]
    4.4+


> Acked-by: Sergey Senozhatsky 



but somehow I didn't notice that Takashi Cc'd stable in the original patch.
so mine can be dropped.

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
On Tue, 22 Nov 2016 02:39:13 +0100,
Sergey Senozhatsky wrote:
> 
> On (11/22/16 10:33), Minchan Kim wrote:
> > On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> > > On (11/22/16 10:22), Minchan Kim wrote:
> > > [..]
> > > > > > Acked-by: Minchan Kim 
> > > > > 
> > > > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from 
> > > > > zram_remove()")
> > > > > Cc: [4.5+]
> > > > 
> > > > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > > > 4.2+.
> > > 
> > > well, no objections. except that the patch in question was
> > > not picked up -stable
> > > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> > > 
> > > the change appears starting from 4.5
> > > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371
> 
> 
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370
> 
> oh, ok. good find. 4.4+ then? there are no affected stable/longterm
> kernels older than 4.4.x anyway (4.1 lts has no dynamic zram management).

Right, at least, 4.4.x hits the issue (actually the original bug
report was for 4.4.x).


thanks,

Takashi

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
On Tue, 22 Nov 2016 02:39:13 +0100,
Sergey Senozhatsky wrote:
> 
> On (11/22/16 10:33), Minchan Kim wrote:
> > On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> > > On (11/22/16 10:22), Minchan Kim wrote:
> > > [..]
> > > > > > Acked-by: Minchan Kim 
> > > > > 
> > > > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from 
> > > > > zram_remove()")
> > > > > Cc: [4.5+]
> > > > 
> > > > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > > > 4.2+.
> > > 
> > > well, no objections. except that the patch in question was
> > > not picked up -stable
> > > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> > > 
> > > the change appears starting from 4.5
> > > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371
> 
> 
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370
> 
> oh, ok. good find. 4.4+ then? there are no affected stable/longterm
> kernels older than 4.4.x anyway (4.1 lts has no dynamic zram management).

Right, at least, 4.4.x hits the issue (actually the original bug
report was for 4.4.x).


thanks,

Takashi

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
On (11/22/16 10:33), Minchan Kim wrote:
> On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> > On (11/22/16 10:22), Minchan Kim wrote:
> > [..]
> > > > > Acked-by: Minchan Kim 
> > > > 
> > > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > > > Cc: [4.5+]
> > > 
> > > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > > 4.2+.
> > 
> > well, no objections. except that the patch in question was
> > not picked up -stable
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> > 
> > the change appears starting from 4.5
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371


> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370

oh, ok. good find. 4.4+ then? there are no affected stable/longterm
kernels older than 4.4.x anyway (4.1 lts has no dynamic zram management).

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
On (11/22/16 10:33), Minchan Kim wrote:
> On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> > On (11/22/16 10:22), Minchan Kim wrote:
> > [..]
> > > > > Acked-by: Minchan Kim 
> > > > 
> > > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > > > Cc: [4.5+]
> > > 
> > > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > > 4.2+.
> > 
> > well, no objections. except that the patch in question was
> > not picked up -stable
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> > 
> > the change appears starting from 4.5
> > https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371


> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370

oh, ok. good find. 4.4+ then? there are no affected stable/longterm
kernels older than 4.4.x anyway (4.1 lts has no dynamic zram management).

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> On (11/22/16 10:22), Minchan Kim wrote:
> [..]
> > > > Acked-by: Minchan Kim 
> > > 
> > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > > Cc: [4.5+]
> > 
> > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > 4.2+.
> 
> well, no objections. except that the patch in question was
> not picked up -stable
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> 
> the change appears starting from 4.5
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371

https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
On Tue, Nov 22, 2016 at 10:28:12AM +0900, Sergey Senozhatsky wrote:
> On (11/22/16 10:22), Minchan Kim wrote:
> [..]
> > > > Acked-by: Minchan Kim 
> > > 
> > > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > > Cc: [4.5+]
> > 
> > 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> > 4.2+.
> 
> well, no objections. except that the patch in question was
> not picked up -stable
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365
> 
> the change appears starting from 4.5
> https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371

https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.4.34#n1370

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
On (11/22/16 10:22), Minchan Kim wrote:
[..]
> > > Acked-by: Minchan Kim 
> > 
> > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > Cc: [4.5+]
> 
> 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> 4.2+.

well, no objections. except that the patch in question was
not picked up -stable
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365

the change appears starting from 4.5
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
On (11/22/16 10:22), Minchan Kim wrote:
[..]
> > > Acked-by: Minchan Kim 
> > 
> > Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> > Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> > Cc: [4.5+]
> 
> 17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
> 4.2+.

well, no objections. except that the patch in question was
not picked up -stable
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.2#n1365

the change appears starting from 4.5
https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/tree/drivers/block/zram/zram_drv.c?id=refs/tags/v4.5#n1371

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
Hi Sergey,

On Tue, Nov 22, 2016 at 10:09:30AM +0900, Sergey Senozhatsky wrote:
> Cc Andrew
> 
> On (11/22/16 09:11), Minchan Kim wrote:
> [..]
> > > This patch adds the proper error check in hot_remove_store() not to
> > > call idr_remove() unconditionally.
> > > 
> > > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > > Reported-and-tested-by: David Disseldorp 
> > > Reviewed-by: David Disseldorp 
> > > Cc: 
> > > Signed-off-by: Takashi Iwai 
> 
> 
> > Acked-by: Minchan Kim 
> 
> Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> Cc: [4.5+]

17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
4.2+.

Thanks.

> 
> Acked-by: Sergey Senozhatsky 
> 

>   -ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
Hi Sergey,

On Tue, Nov 22, 2016 at 10:09:30AM +0900, Sergey Senozhatsky wrote:
> Cc Andrew
> 
> On (11/22/16 09:11), Minchan Kim wrote:
> [..]
> > > This patch adds the proper error check in hot_remove_store() not to
> > > call idr_remove() unconditionally.
> > > 
> > > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > > Reported-and-tested-by: David Disseldorp 
> > > Reviewed-by: David Disseldorp 
> > > Cc: 
> > > Signed-off-by: Takashi Iwai 
> 
> 
> > Acked-by: Minchan Kim 
> 
> Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
> Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
> Cc: [4.5+]

17ec4cd98578 marked as stable: [4.2+] so we should mark this patch as
4.2+.

Thanks.

> 
> Acked-by: Sergey Senozhatsky 
> 

>   -ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
Cc Andrew

On (11/22/16 09:11), Minchan Kim wrote:
[..]
> > This patch adds the proper error check in hot_remove_store() not to
> > call idr_remove() unconditionally.
> > 
> > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > Reported-and-tested-by: David Disseldorp 
> > Reviewed-by: David Disseldorp 
> > Cc: 
> > Signed-off-by: Takashi Iwai 


> Acked-by: Minchan Kim 

Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
Cc: [4.5+]

Acked-by: Sergey Senozhatsky 

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Sergey Senozhatsky 
Cc Andrew

On (11/22/16 09:11), Minchan Kim wrote:
[..]
> > This patch adds the proper error check in hot_remove_store() not to
> > call idr_remove() unconditionally.
> > 
> > Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> > Reported-and-tested-by: David Disseldorp 
> > Reviewed-by: David Disseldorp 
> > Cc: 
> > Signed-off-by: Takashi Iwai 


> Acked-by: Minchan Kim 

Link: lkml.kernel.org/r/20161121132140.12683-1-ti...@suse.de
Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")
Cc: [4.5+]

Acked-by: Sergey Senozhatsky 

-ss

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
On Mon, Nov 21, 2016 at 02:21:40PM +0100, Takashi Iwai wrote:
> The zram hot removal code calls idr_remove() even when zram_remove()
> returns an error (typically -EBUSY).  This results in a leftover at
> the device release, eventually leading to a crash when the module is
> reloaded.
> 
> As described in the bug report below, the following procedure would
> cause an Oops with zram:
> 
> - provision three zram devices via modprobe zram num_devices=3
> - configure a size for each device
>   + echo "1G" > /sys/block/$zram_name/disksize
> - mkfs and mount zram0 only
> - attempt to hot remove all three devices
>   + echo 2 > /sys/class/zram-control/hot_remove
>   + echo 1 > /sys/class/zram-control/hot_remove
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - zram0 removal fails with EBUSY, as expected
> - unmount zram0
> - try zram0 hot remove again
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - fails with ENODEV (unexpected)
> - unload zram kernel module
>   + completes successfully
> - zram0 device node still exists
> - attempt to mount /dev/zram0
>   + mount command is killed
>   + following BUG is encountered
> 
>  BUG: unable to handle kernel paging request at a0002ba0
>  IP: [] get_disk+0x16/0x50
>  Oops:  [#1] SMP
>  CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
>  task: 88001a9f2800 task.stack: c930
>  RIP: 0010:[]  [] get_disk+0x16/0x50
>  Call Trace:
>   [] exact_lock+0xc/0x20
>   [] kobj_lookup+0xdc/0x160
>   [] ? disk_map_sector_rcu+0x70/0x70
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] get_gendisk+0x2f/0x110
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] __blkdev_get+0x10c/0x3c0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_get+0x19d/0x2e0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_open+0x56/0x70
>   [] do_dentry_open.isra.19+0x1ff/0x310
>   [] vfs_open+0x43/0x60
>   [] path_openat+0x2c9/0xf30
>   [] ? __save_stack_trace+0x40/0xd0
>   [] do_filp_open+0x79/0xd0
>   [] ? kmemleak_alloc+0x49/0xa0
>   [] do_sys_open+0x114/0x1e0
>   [] SyS_open+0x19/0x20
>   [] entry_SYSCALL_64_fastpath+0x13/0x94
> 
> This patch adds the proper error check in hot_remove_store() not to
> call idr_remove() unconditionally.
> 
> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> Reported-and-tested-by: David Disseldorp 
> Reviewed-by: David Disseldorp 
> Cc: 
> Signed-off-by: Takashi Iwai 
Acked-by: Minchan Kim 

Thanks!

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Minchan Kim 
On Mon, Nov 21, 2016 at 02:21:40PM +0100, Takashi Iwai wrote:
> The zram hot removal code calls idr_remove() even when zram_remove()
> returns an error (typically -EBUSY).  This results in a leftover at
> the device release, eventually leading to a crash when the module is
> reloaded.
> 
> As described in the bug report below, the following procedure would
> cause an Oops with zram:
> 
> - provision three zram devices via modprobe zram num_devices=3
> - configure a size for each device
>   + echo "1G" > /sys/block/$zram_name/disksize
> - mkfs and mount zram0 only
> - attempt to hot remove all three devices
>   + echo 2 > /sys/class/zram-control/hot_remove
>   + echo 1 > /sys/class/zram-control/hot_remove
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - zram0 removal fails with EBUSY, as expected
> - unmount zram0
> - try zram0 hot remove again
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - fails with ENODEV (unexpected)
> - unload zram kernel module
>   + completes successfully
> - zram0 device node still exists
> - attempt to mount /dev/zram0
>   + mount command is killed
>   + following BUG is encountered
> 
>  BUG: unable to handle kernel paging request at a0002ba0
>  IP: [] get_disk+0x16/0x50
>  Oops:  [#1] SMP
>  CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
>  task: 88001a9f2800 task.stack: c930
>  RIP: 0010:[]  [] get_disk+0x16/0x50
>  Call Trace:
>   [] exact_lock+0xc/0x20
>   [] kobj_lookup+0xdc/0x160
>   [] ? disk_map_sector_rcu+0x70/0x70
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] get_gendisk+0x2f/0x110
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] __blkdev_get+0x10c/0x3c0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_get+0x19d/0x2e0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_open+0x56/0x70
>   [] do_dentry_open.isra.19+0x1ff/0x310
>   [] vfs_open+0x43/0x60
>   [] path_openat+0x2c9/0xf30
>   [] ? __save_stack_trace+0x40/0xd0
>   [] do_filp_open+0x79/0xd0
>   [] ? kmemleak_alloc+0x49/0xa0
>   [] do_sys_open+0x114/0x1e0
>   [] SyS_open+0x19/0x20
>   [] entry_SYSCALL_64_fastpath+0x13/0x94
> 
> This patch adds the proper error check in hot_remove_store() not to
> call idr_remove() unconditionally.
> 
> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> Reported-and-tested-by: David Disseldorp 
> Reviewed-by: David Disseldorp 
> Cc: 
> Signed-off-by: Takashi Iwai 
Acked-by: Minchan Kim 

Thanks!

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
On Mon, 21 Nov 2016 14:21:40 +0100,
Takashi Iwai wrote:
> 
> The zram hot removal code calls idr_remove() even when zram_remove()
> returns an error (typically -EBUSY).  This results in a leftover at
> the device release, eventually leading to a crash when the module is
> reloaded.
> 
> As described in the bug report below, the following procedure would
> cause an Oops with zram:
> 
> - provision three zram devices via modprobe zram num_devices=3
> - configure a size for each device
>   + echo "1G" > /sys/block/$zram_name/disksize
> - mkfs and mount zram0 only
> - attempt to hot remove all three devices
>   + echo 2 > /sys/class/zram-control/hot_remove
>   + echo 1 > /sys/class/zram-control/hot_remove
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - zram0 removal fails with EBUSY, as expected
> - unmount zram0
> - try zram0 hot remove again
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - fails with ENODEV (unexpected)
> - unload zram kernel module
>   + completes successfully
> - zram0 device node still exists
> - attempt to mount /dev/zram0
>   + mount command is killed
>   + following BUG is encountered
> 
>  BUG: unable to handle kernel paging request at a0002ba0
>  IP: [] get_disk+0x16/0x50
>  Oops:  [#1] SMP
>  CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
>  task: 88001a9f2800 task.stack: c930
>  RIP: 0010:[]  [] get_disk+0x16/0x50
>  Call Trace:
>   [] exact_lock+0xc/0x20
>   [] kobj_lookup+0xdc/0x160
>   [] ? disk_map_sector_rcu+0x70/0x70
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] get_gendisk+0x2f/0x110
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] __blkdev_get+0x10c/0x3c0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_get+0x19d/0x2e0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_open+0x56/0x70
>   [] do_dentry_open.isra.19+0x1ff/0x310
>   [] vfs_open+0x43/0x60
>   [] path_openat+0x2c9/0xf30
>   [] ? __save_stack_trace+0x40/0xd0
>   [] do_filp_open+0x79/0xd0
>   [] ? kmemleak_alloc+0x49/0xa0
>   [] do_sys_open+0x114/0x1e0
>   [] SyS_open+0x19/0x20
>   [] entry_SYSCALL_64_fastpath+0x13/0x94
> 
> This patch adds the proper error check in hot_remove_store() not to
> call idr_remove() unconditionally.
> 
> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> Reported-and-tested-by: David Disseldorp 
> Reviewed-by: David Disseldorp 
> Cc: 
> Signed-off-by: Takashi Iwai 

Forgot to add Fixes tag:

Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")


Takashi


> ---
>  drivers/block/zram/zram_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 04365b17ee67..5163c8f918cb 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1403,7 +1403,8 @@ static ssize_t hot_remove_store(struct class *class,
>   zram = idr_find(_index_idr, dev_id);
>   if (zram) {
>   ret = zram_remove(zram);
> - idr_remove(_index_idr, dev_id);
> + if (!ret)
> + idr_remove(_index_idr, dev_id);
>   } else {
>   ret = -ENODEV;
>   }
> -- 
> 2.10.2
>

Re: [PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
On Mon, 21 Nov 2016 14:21:40 +0100,
Takashi Iwai wrote:
> 
> The zram hot removal code calls idr_remove() even when zram_remove()
> returns an error (typically -EBUSY).  This results in a leftover at
> the device release, eventually leading to a crash when the module is
> reloaded.
> 
> As described in the bug report below, the following procedure would
> cause an Oops with zram:
> 
> - provision three zram devices via modprobe zram num_devices=3
> - configure a size for each device
>   + echo "1G" > /sys/block/$zram_name/disksize
> - mkfs and mount zram0 only
> - attempt to hot remove all three devices
>   + echo 2 > /sys/class/zram-control/hot_remove
>   + echo 1 > /sys/class/zram-control/hot_remove
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - zram0 removal fails with EBUSY, as expected
> - unmount zram0
> - try zram0 hot remove again
>   + echo 0 > /sys/class/zram-control/hot_remove
>  - fails with ENODEV (unexpected)
> - unload zram kernel module
>   + completes successfully
> - zram0 device node still exists
> - attempt to mount /dev/zram0
>   + mount command is killed
>   + following BUG is encountered
> 
>  BUG: unable to handle kernel paging request at a0002ba0
>  IP: [] get_disk+0x16/0x50
>  Oops:  [#1] SMP
>  CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
>  task: 88001a9f2800 task.stack: c930
>  RIP: 0010:[]  [] get_disk+0x16/0x50
>  Call Trace:
>   [] exact_lock+0xc/0x20
>   [] kobj_lookup+0xdc/0x160
>   [] ? disk_map_sector_rcu+0x70/0x70
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] get_gendisk+0x2f/0x110
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] __blkdev_get+0x10c/0x3c0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_get+0x19d/0x2e0
>   [] ? blkdev_get_by_dev+0x50/0x50
>   [] blkdev_open+0x56/0x70
>   [] do_dentry_open.isra.19+0x1ff/0x310
>   [] vfs_open+0x43/0x60
>   [] path_openat+0x2c9/0xf30
>   [] ? __save_stack_trace+0x40/0xd0
>   [] do_filp_open+0x79/0xd0
>   [] ? kmemleak_alloc+0x49/0xa0
>   [] do_sys_open+0x114/0x1e0
>   [] SyS_open+0x19/0x20
>   [] entry_SYSCALL_64_fastpath+0x13/0x94
> 
> This patch adds the proper error check in hot_remove_store() not to
> call idr_remove() unconditionally.
> 
> Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
> Reported-and-tested-by: David Disseldorp 
> Reviewed-by: David Disseldorp 
> Cc: 
> Signed-off-by: Takashi Iwai 

Forgot to add Fixes tag:

Fixes: 17ec4cd98578 ("zram: don't call idr_remove() from zram_remove()")


Takashi


> ---
>  drivers/block/zram/zram_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 04365b17ee67..5163c8f918cb 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1403,7 +1403,8 @@ static ssize_t hot_remove_store(struct class *class,
>   zram = idr_find(_index_idr, dev_id);
>   if (zram) {
>   ret = zram_remove(zram);
> - idr_remove(_index_idr, dev_id);
> + if (!ret)
> + idr_remove(_index_idr, dev_id);
>   } else {
>   ret = -ENODEV;
>   }
> -- 
> 2.10.2
>

[PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
The zram hot removal code calls idr_remove() even when zram_remove()
returns an error (typically -EBUSY).  This results in a leftover at
the device release, eventually leading to a crash when the module is
reloaded.

As described in the bug report below, the following procedure would
cause an Oops with zram:

- provision three zram devices via modprobe zram num_devices=3
- configure a size for each device
  + echo "1G" > /sys/block/$zram_name/disksize
- mkfs and mount zram0 only
- attempt to hot remove all three devices
  + echo 2 > /sys/class/zram-control/hot_remove
  + echo 1 > /sys/class/zram-control/hot_remove
  + echo 0 > /sys/class/zram-control/hot_remove
 - zram0 removal fails with EBUSY, as expected
- unmount zram0
- try zram0 hot remove again
  + echo 0 > /sys/class/zram-control/hot_remove
 - fails with ENODEV (unexpected)
- unload zram kernel module
  + completes successfully
- zram0 device node still exists
- attempt to mount /dev/zram0
  + mount command is killed
  + following BUG is encountered

 BUG: unable to handle kernel paging request at a0002ba0
 IP: [] get_disk+0x16/0x50
 Oops:  [#1] SMP
 CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
 task: 88001a9f2800 task.stack: c930
 RIP: 0010:[]  [] get_disk+0x16/0x50
 Call Trace:
  [] exact_lock+0xc/0x20
  [] kobj_lookup+0xdc/0x160
  [] ? disk_map_sector_rcu+0x70/0x70
  [] ? blkdev_get_by_dev+0x50/0x50
  [] get_gendisk+0x2f/0x110
  [] ? blkdev_get_by_dev+0x50/0x50
  [] __blkdev_get+0x10c/0x3c0
  [] ? blkdev_get_by_dev+0x50/0x50
  [] blkdev_get+0x19d/0x2e0
  [] ? blkdev_get_by_dev+0x50/0x50
  [] blkdev_open+0x56/0x70
  [] do_dentry_open.isra.19+0x1ff/0x310
  [] vfs_open+0x43/0x60
  [] path_openat+0x2c9/0xf30
  [] ? __save_stack_trace+0x40/0xd0
  [] do_filp_open+0x79/0xd0
  [] ? kmemleak_alloc+0x49/0xa0
  [] do_sys_open+0x114/0x1e0
  [] SyS_open+0x19/0x20
  [] entry_SYSCALL_64_fastpath+0x13/0x94

This patch adds the proper error check in hot_remove_store() not to
call idr_remove() unconditionally.

Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
Reported-and-tested-by: David Disseldorp 
Reviewed-by: David Disseldorp 
Cc: 
Signed-off-by: Takashi Iwai 
---
 drivers/block/zram/zram_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 04365b17ee67..5163c8f918cb 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1403,7 +1403,8 @@ static ssize_t hot_remove_store(struct class *class,
zram = idr_find(_index_idr, dev_id);
if (zram) {
ret = zram_remove(zram);
-   idr_remove(_index_idr, dev_id);
+   if (!ret)
+   idr_remove(_index_idr, dev_id);
} else {
ret = -ENODEV;
}
-- 
2.10.2

[PATCH] zram: Fix unbalanced idr management at hot removal

2016-11-21 Thread Takashi Iwai 
The zram hot removal code calls idr_remove() even when zram_remove()
returns an error (typically -EBUSY).  This results in a leftover at
the device release, eventually leading to a crash when the module is
reloaded.

As described in the bug report below, the following procedure would
cause an Oops with zram:

- provision three zram devices via modprobe zram num_devices=3
- configure a size for each device
  + echo "1G" > /sys/block/$zram_name/disksize
- mkfs and mount zram0 only
- attempt to hot remove all three devices
  + echo 2 > /sys/class/zram-control/hot_remove
  + echo 1 > /sys/class/zram-control/hot_remove
  + echo 0 > /sys/class/zram-control/hot_remove
 - zram0 removal fails with EBUSY, as expected
- unmount zram0
- try zram0 hot remove again
  + echo 0 > /sys/class/zram-control/hot_remove
 - fails with ENODEV (unexpected)
- unload zram kernel module
  + completes successfully
- zram0 device node still exists
- attempt to mount /dev/zram0
  + mount command is killed
  + following BUG is encountered

 BUG: unable to handle kernel paging request at a0002ba0
 IP: [] get_disk+0x16/0x50
 Oops:  [#1] SMP
 CPU: 0 PID: 252 Comm: mount Not tainted 4.9.0-rc6 #176
 task: 88001a9f2800 task.stack: c930
 RIP: 0010:[]  [] get_disk+0x16/0x50
 Call Trace:
  [] exact_lock+0xc/0x20
  [] kobj_lookup+0xdc/0x160
  [] ? disk_map_sector_rcu+0x70/0x70
  [] ? blkdev_get_by_dev+0x50/0x50
  [] get_gendisk+0x2f/0x110
  [] ? blkdev_get_by_dev+0x50/0x50
  [] __blkdev_get+0x10c/0x3c0
  [] ? blkdev_get_by_dev+0x50/0x50
  [] blkdev_get+0x19d/0x2e0
  [] ? blkdev_get_by_dev+0x50/0x50
  [] blkdev_open+0x56/0x70
  [] do_dentry_open.isra.19+0x1ff/0x310
  [] vfs_open+0x43/0x60
  [] path_openat+0x2c9/0xf30
  [] ? __save_stack_trace+0x40/0xd0
  [] do_filp_open+0x79/0xd0
  [] ? kmemleak_alloc+0x49/0xa0
  [] do_sys_open+0x114/0x1e0
  [] SyS_open+0x19/0x20
  [] entry_SYSCALL_64_fastpath+0x13/0x94

This patch adds the proper error check in hot_remove_store() not to
call idr_remove() unconditionally.

Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=1010970
Reported-and-tested-by: David Disseldorp 
Reviewed-by: David Disseldorp 
Cc: 
Signed-off-by: Takashi Iwai 
---
 drivers/block/zram/zram_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 04365b17ee67..5163c8f918cb 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1403,7 +1403,8 @@ static ssize_t hot_remove_store(struct class *class,
zram = idr_find(_index_idr, dev_id);
if (zram) {
ret = zram_remove(zram);
-   idr_remove(_index_idr, dev_id);
+   if (!ret)
+   idr_remove(_index_idr, dev_id);
} else {
ret = -ENODEV;
}
-- 
2.10.2