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* [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
@ 2018-04-09 12:25 Geert Uytterhoeven
  2018-04-09 21:59 ` Marek Vasut
  0 siblings, 1 reply; 9+ messages in thread
From: Geert Uytterhoeven @ 2018-04-09 12:25 UTC (permalink / raw)
  To: David Woodhouse, Brian Norris, Boris Brezillon, Marek Vasut,
	Richard Weinberger
  Cc: linux-mtd, linux-renesas-soc, linux-kernel, Geert Uytterhoeven

Currently add_mtd_device() failures are plainly ignored, which may lead
to kernel crashes later.

E.g. after flipping SW17 on r8a7791/koelsch, to switch from the large to
the small QSPI FLASH, without updating the partition description in DT,
the following happens:

    m25p80 spi0.0: found s25sl032p, expected s25fl512s
    3 fixed-partitions partitions found on MTD device spi0.0
    Creating 3 MTD partitions on "spi0.0":
    0x000000000000-0x000000080000 : "loader"
    0x000000080000-0x000000600000 : "user"
    mtd: partition "user" extends beyond the end of device "spi0.0" -- size truncated to 0x380000

The second partition is truncated correctly.

    0x000000600000-0x000004000000 : "flash"
    mtd: partition "flash" is out of reach -- disabled

The third partition is disabled by allocate_partition(), which means
fields like erasesize are not filled in.  Hence add_mtd_device() fails
and screams, rightfully:

    ------------[ cut here ]------------
    WARNING: CPU: 1 PID: 1 at drivers/mtd/mtdcore.c:508 add_mtd_device+0x2a0/0x2e0
    Modules linked in:
    CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-koelsch-08649-g58e35e77b00c075d #4029
    Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
    [<c020f660>] (unwind_backtrace) from [<c020b2f4>] (show_stack+0x10/0x14)
    [<c020b2f4>] (show_stack) from [<c076d088>] (dump_stack+0x7c/0x9c)
    [<c076d088>] (dump_stack) from [<c02210d8>] (__warn+0xd4/0x104)
    [<c02210d8>] (__warn) from [<c0221218>] (warn_slowpath_null+0x38/0x44)
    [<c0221218>] (warn_slowpath_null) from [<c0553db4>] (add_mtd_device+0x2a0/0x2e0)
    [<c0553db4>] (add_mtd_device) from [<c0556a70>] (add_mtd_partitions+0xd0/0x16c)
    [<c0556a70>] (add_mtd_partitions) from [<c0553f88>] (mtd_device_parse_register+0xc4/0x1b4)
    [<c0553f88>] (mtd_device_parse_register) from [<c055a97c>] (m25p_probe+0x148/0x188)
    [<c055a97c>] (m25p_probe) from [<c055e278>] (spi_drv_probe+0x84/0xa0)

    [...]

    ---[ end trace d43ce221bca7ab5c ]---

However, that failure is ignored by add_mtd_partitions(), leading to a
crash later:

    ------------[ cut here ]------------
    kernel BUG at fs/sysfs/file.c:330!
    Internal error: Oops - BUG: 0 [#1] SMP ARM
    Modules linked in:
    CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W        4.16.0-koelsch-08649-g58e35e77b00c075d #4029
    Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
    PC is at sysfs_create_file_ns+0x24/0x40
    LR is at 0x1
    pc : [<c03604cc>]    lr : [<00000001>]    psr: 60000013
    sp : eb447c00  ip : 00000000  fp : c0e20174
    r10: 00000003  r9 : c0e20150  r8 : eb7e3818
    r7 : ea8b20f8  r6 : c0e2017c  r5 : 00000000  r4 : 00000000
    r3 : 00000200  r2 : 00000000  r1 : c0e2019c  r0 : 00000000
    Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
    Control: 30c5387d  Table: 40003000  DAC: 55555555
    Process swapper/0 (pid: 1, stack limit = 0x7eba272f)
    Stack: (0xeb447c00 to 0xeb448000)

    [...]

    [<c03604cc>] (sysfs_create_file_ns) from [<c036051c>] (sysfs_create_files+0x34/0x70)
    [<c036051c>] (sysfs_create_files) from [<c0556288>] (mtd_add_partition_attrs+0x10/0x34)
    [<c0556288>] (mtd_add_partition_attrs) from [<c0556a78>] (add_mtd_partitions+0xd8/0x16c)
    [<c0556a78>] (add_mtd_partitions) from [<c0553f88>] (mtd_device_parse_register+0xc4/0x1b4)
    [<c0553f88>] (mtd_device_parse_register) from [<c055a97c>] (m25p_probe+0x148/0x188)
    [<c055a97c>] (m25p_probe) from [<c055e278>] (spi_drv_probe+0x84/0xa0)

Fix this by ignoring and freeing partitions that failed to add in
add_mtd_partitions().  The same issue is present in mtd_add_partition(),
so fix that as well.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
I don't know if it is worthwhile factoring out the common handling.

Should allocate_partition() fail instead?  There's a comment saying
"let's register it anyway to preserve ordering".
---
 drivers/mtd/mtdpart.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index 023516a632766c42..d41adc1397dcf95e 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -637,7 +637,14 @@ int mtd_add_partition(struct mtd_info *parent, const char *name,
 	list_add(&new->list, &mtd_partitions);
 	mutex_unlock(&mtd_partitions_mutex);
 
-	add_mtd_device(&new->mtd);
+	ret = add_mtd_device(&new->mtd);
+	if (ret) {
+		mutex_lock(&mtd_partitions_mutex);
+		list_del(&new->list);
+		mutex_unlock(&mtd_partitions_mutex);
+		free_partition(new);
+		return ret;
+	}
 
 	mtd_add_partition_attrs(new);
 
@@ -731,7 +738,7 @@ int add_mtd_partitions(struct mtd_info *master,
 {
 	struct mtd_part *slave;
 	uint64_t cur_offset = 0;
-	int i;
+	int i, ret;
 
 	printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);
 
@@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
 		list_add(&slave->list, &mtd_partitions);
 		mutex_unlock(&mtd_partitions_mutex);
 
-		add_mtd_device(&slave->mtd);
+		ret = add_mtd_device(&slave->mtd);
+		if (ret) {
+			mutex_lock(&mtd_partitions_mutex);
+			list_del(&slave->list);
+			mutex_unlock(&mtd_partitions_mutex);
+			free_partition(slave);
+			continue;
+		}
+
 		mtd_add_partition_attrs(slave);
 		if (parts[i].types)
 			mtd_parse_part(slave, parts[i].types);
-- 
2.7.4

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-09 12:25 [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully Geert Uytterhoeven
@ 2018-04-09 21:59 ` Marek Vasut
  2018-04-10 13:26   ` Geert Uytterhoeven
  0 siblings, 1 reply; 9+ messages in thread
From: Marek Vasut @ 2018-04-09 21:59 UTC (permalink / raw)
  To: Geert Uytterhoeven, David Woodhouse, Brian Norris,
	Boris Brezillon, Richard Weinberger
  Cc: linux-mtd, linux-renesas-soc, linux-kernel

On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
> Currently add_mtd_device() failures are plainly ignored, which may lead
> to kernel crashes later.
> 
> E.g. after flipping SW17 on r8a7791/koelsch, to switch from the large to
> the small QSPI FLASH, without updating the partition description in DT,
> the following happens:
> 
>     m25p80 spi0.0: found s25sl032p, expected s25fl512s
>     3 fixed-partitions partitions found on MTD device spi0.0
>     Creating 3 MTD partitions on "spi0.0":
>     0x000000000000-0x000000080000 : "loader"
>     0x000000080000-0x000000600000 : "user"
>     mtd: partition "user" extends beyond the end of device "spi0.0" -- size truncated to 0x380000
> 
> The second partition is truncated correctly.
> 
>     0x000000600000-0x000004000000 : "flash"
>     mtd: partition "flash" is out of reach -- disabled
> 
> The third partition is disabled by allocate_partition(), which means
> fields like erasesize are not filled in.  Hence add_mtd_device() fails
> and screams, rightfully:
> 
>     ------------[ cut here ]------------
>     WARNING: CPU: 1 PID: 1 at drivers/mtd/mtdcore.c:508 add_mtd_device+0x2a0/0x2e0
>     Modules linked in:
>     CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.16.0-koelsch-08649-g58e35e77b00c075d #4029
>     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>     [<c020f660>] (unwind_backtrace) from [<c020b2f4>] (show_stack+0x10/0x14)
>     [<c020b2f4>] (show_stack) from [<c076d088>] (dump_stack+0x7c/0x9c)
>     [<c076d088>] (dump_stack) from [<c02210d8>] (__warn+0xd4/0x104)
>     [<c02210d8>] (__warn) from [<c0221218>] (warn_slowpath_null+0x38/0x44)
>     [<c0221218>] (warn_slowpath_null) from [<c0553db4>] (add_mtd_device+0x2a0/0x2e0)
>     [<c0553db4>] (add_mtd_device) from [<c0556a70>] (add_mtd_partitions+0xd0/0x16c)
>     [<c0556a70>] (add_mtd_partitions) from [<c0553f88>] (mtd_device_parse_register+0xc4/0x1b4)
>     [<c0553f88>] (mtd_device_parse_register) from [<c055a97c>] (m25p_probe+0x148/0x188)
>     [<c055a97c>] (m25p_probe) from [<c055e278>] (spi_drv_probe+0x84/0xa0)
> 
>     [...]
> 
>     ---[ end trace d43ce221bca7ab5c ]---
> 
> However, that failure is ignored by add_mtd_partitions(), leading to a
> crash later:
> 
>     ------------[ cut here ]------------
>     kernel BUG at fs/sysfs/file.c:330!
>     Internal error: Oops - BUG: 0 [#1] SMP ARM
>     Modules linked in:
>     CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W        4.16.0-koelsch-08649-g58e35e77b00c075d #4029
>     Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
>     PC is at sysfs_create_file_ns+0x24/0x40
>     LR is at 0x1
>     pc : [<c03604cc>]    lr : [<00000001>]    psr: 60000013
>     sp : eb447c00  ip : 00000000  fp : c0e20174
>     r10: 00000003  r9 : c0e20150  r8 : eb7e3818
>     r7 : ea8b20f8  r6 : c0e2017c  r5 : 00000000  r4 : 00000000
>     r3 : 00000200  r2 : 00000000  r1 : c0e2019c  r0 : 00000000
>     Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
>     Control: 30c5387d  Table: 40003000  DAC: 55555555
>     Process swapper/0 (pid: 1, stack limit = 0x7eba272f)
>     Stack: (0xeb447c00 to 0xeb448000)
> 
>     [...]
> 
>     [<c03604cc>] (sysfs_create_file_ns) from [<c036051c>] (sysfs_create_files+0x34/0x70)
>     [<c036051c>] (sysfs_create_files) from [<c0556288>] (mtd_add_partition_attrs+0x10/0x34)
>     [<c0556288>] (mtd_add_partition_attrs) from [<c0556a78>] (add_mtd_partitions+0xd8/0x16c)
>     [<c0556a78>] (add_mtd_partitions) from [<c0553f88>] (mtd_device_parse_register+0xc4/0x1b4)
>     [<c0553f88>] (mtd_device_parse_register) from [<c055a97c>] (m25p_probe+0x148/0x188)
>     [<c055a97c>] (m25p_probe) from [<c055e278>] (spi_drv_probe+0x84/0xa0)
> 
> Fix this by ignoring and freeing partitions that failed to add in
> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
> so fix that as well.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> I don't know if it is worthwhile factoring out the common handling.
> 
> Should allocate_partition() fail instead?  There's a comment saying
> "let's register it anyway to preserve ordering".
> ---
>  drivers/mtd/mtdpart.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index 023516a632766c42..d41adc1397dcf95e 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -637,7 +637,14 @@ int mtd_add_partition(struct mtd_info *parent, const char *name,
>  	list_add(&new->list, &mtd_partitions);
>  	mutex_unlock(&mtd_partitions_mutex);
>  
> -	add_mtd_device(&new->mtd);
> +	ret = add_mtd_device(&new->mtd);
> +	if (ret) {
> +		mutex_lock(&mtd_partitions_mutex);
> +		list_del(&new->list);
> +		mutex_unlock(&mtd_partitions_mutex);
> +		free_partition(new);
> +		return ret;
> +	}
>  
>  	mtd_add_partition_attrs(new);
>  
> @@ -731,7 +738,7 @@ int add_mtd_partitions(struct mtd_info *master,
>  {
>  	struct mtd_part *slave;
>  	uint64_t cur_offset = 0;
> -	int i;
> +	int i, ret;
>  
>  	printk(KERN_NOTICE "Creating %d MTD partitions on \"%s\":\n", nbparts, master->name);
>  
> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>  		list_add(&slave->list, &mtd_partitions);
>  		mutex_unlock(&mtd_partitions_mutex);
>  
> -		add_mtd_device(&slave->mtd);
> +		ret = add_mtd_device(&slave->mtd);
> +		if (ret) {
> +			mutex_lock(&mtd_partitions_mutex);
> +			list_del(&slave->list);
> +			mutex_unlock(&mtd_partitions_mutex);
> +			free_partition(slave);
> +			continue;
> +		}

Why is the partition even in the list in the first place ? Can we avoid
adding it rather than adding and removing it ?

>  		mtd_add_partition_attrs(slave);
>  		if (parts[i].types)
>  			mtd_parse_part(slave, parts[i].types);
> 


-- 
Best regards,
Marek Vasut

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-09 21:59 ` Marek Vasut
@ 2018-04-10 13:26   ` Geert Uytterhoeven
  2018-04-10 14:37     ` Marek Vasut
  2018-04-26 17:53     ` Boris Brezillon
  0 siblings, 2 replies; 9+ messages in thread
From: Geert Uytterhoeven @ 2018-04-10 13:26 UTC (permalink / raw)
  To: Marek Vasut
  Cc: Geert Uytterhoeven, David Woodhouse, Brian Norris,
	Boris Brezillon, Richard Weinberger, MTD Maling List,
	Linux-Renesas, Linux Kernel Mailing List

Hi Marek,

On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
> On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>> Currently add_mtd_device() failures are plainly ignored, which may lead
>> to kernel crashes later.

>> Fix this by ignoring and freeing partitions that failed to add in
>> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>> so fix that as well.
>>
>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> ---
>> I don't know if it is worthwhile factoring out the common handling.
>>
>> Should allocate_partition() fail instead?  There's a comment saying
>> "let's register it anyway to preserve ordering".

>> --- a/drivers/mtd/mtdpart.c
>> +++ b/drivers/mtd/mtdpart.c

>> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>>               list_add(&slave->list, &mtd_partitions);
>>               mutex_unlock(&mtd_partitions_mutex);
>>
>> -             add_mtd_device(&slave->mtd);
>> +             ret = add_mtd_device(&slave->mtd);
>> +             if (ret) {
>> +                     mutex_lock(&mtd_partitions_mutex);
>> +                     list_del(&slave->list);
>> +                     mutex_unlock(&mtd_partitions_mutex);
>> +                     free_partition(slave);
>> +                     continue;
>> +             }
>
> Why is the partition even in the list in the first place ? Can we avoid
> adding it rather than adding and removing it ?

Hence my question "Should allocate_partition() fail instead?".
Note that if we go that route, it should be a "soft" failure, as we
probably don't
want to drop all other partitions on the device.

>>               mtd_add_partition_attrs(slave);
>>               if (parts[i].types)
>>                       mtd_parse_part(slave, parts[i].types);
>>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-10 13:26   ` Geert Uytterhoeven
@ 2018-04-10 14:37     ` Marek Vasut
  2018-04-10 14:47       ` Geert Uytterhoeven
  2018-04-26 17:53     ` Boris Brezillon
  1 sibling, 1 reply; 9+ messages in thread
From: Marek Vasut @ 2018-04-10 14:37 UTC (permalink / raw)
  To: Geert Uytterhoeven
  Cc: Geert Uytterhoeven, David Woodhouse, Brian Norris,
	Boris Brezillon, Richard Weinberger, MTD Maling List,
	Linux-Renesas, Linux Kernel Mailing List

On 04/10/2018 03:26 PM, Geert Uytterhoeven wrote:
> Hi Marek,
> 
> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>> On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>>> Currently add_mtd_device() failures are plainly ignored, which may lead
>>> to kernel crashes later.
> 
>>> Fix this by ignoring and freeing partitions that failed to add in
>>> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>>> so fix that as well.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>> ---
>>> I don't know if it is worthwhile factoring out the common handling.
>>>
>>> Should allocate_partition() fail instead?  There's a comment saying
>>> "let's register it anyway to preserve ordering".
> 
>>> --- a/drivers/mtd/mtdpart.c
>>> +++ b/drivers/mtd/mtdpart.c
> 
>>> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>>>               list_add(&slave->list, &mtd_partitions);
>>>               mutex_unlock(&mtd_partitions_mutex);
>>>
>>> -             add_mtd_device(&slave->mtd);
>>> +             ret = add_mtd_device(&slave->mtd);
>>> +             if (ret) {
>>> +                     mutex_lock(&mtd_partitions_mutex);
>>> +                     list_del(&slave->list);
>>> +                     mutex_unlock(&mtd_partitions_mutex);
>>> +                     free_partition(slave);
>>> +                     continue;
>>> +             }
>>
>> Why is the partition even in the list in the first place ? Can we avoid
>> adding it rather than adding and removing it ?
> 
> Hence my question "Should allocate_partition() fail instead?".
> Note that if we go that route, it should be a "soft" failure, as we
> probably don't
> want to drop all other partitions on the device.
Is the number of partitions ie. in /proc/mtdparts an ABI ?

-- 
Best regards,
Marek Vasut

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-10 14:37     ` Marek Vasut
@ 2018-04-10 14:47       ` Geert Uytterhoeven
  2018-04-10 16:34         ` Steve deRosier
  0 siblings, 1 reply; 9+ messages in thread
From: Geert Uytterhoeven @ 2018-04-10 14:47 UTC (permalink / raw)
  To: Marek Vasut
  Cc: Geert Uytterhoeven, David Woodhouse, Brian Norris,
	Boris Brezillon, Richard Weinberger, MTD Maling List,
	Linux-Renesas, Linux Kernel Mailing List

Hi Marek,

On Tue, Apr 10, 2018 at 4:37 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
> On 04/10/2018 03:26 PM, Geert Uytterhoeven wrote:
>> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>> On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>>>> Currently add_mtd_device() failures are plainly ignored, which may lead
>>>> to kernel crashes later.
>>
>>>> Fix this by ignoring and freeing partitions that failed to add in
>>>> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>>>> so fix that as well.
>>>>
>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>>> ---
>>>> I don't know if it is worthwhile factoring out the common handling.
>>>>
>>>> Should allocate_partition() fail instead?  There's a comment saying
>>>> "let's register it anyway to preserve ordering".
>>
>>>> --- a/drivers/mtd/mtdpart.c
>>>> +++ b/drivers/mtd/mtdpart.c
>>
>>>> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>>>>               list_add(&slave->list, &mtd_partitions);
>>>>               mutex_unlock(&mtd_partitions_mutex);
>>>>
>>>> -             add_mtd_device(&slave->mtd);
>>>> +             ret = add_mtd_device(&slave->mtd);
>>>> +             if (ret) {
>>>> +                     mutex_lock(&mtd_partitions_mutex);
>>>> +                     list_del(&slave->list);
>>>> +                     mutex_unlock(&mtd_partitions_mutex);
>>>> +                     free_partition(slave);
>>>> +                     continue;
>>>> +             }
>>>
>>> Why is the partition even in the list in the first place ? Can we avoid
>>> adding it rather than adding and removing it ?
>>
>> Hence my question "Should allocate_partition() fail instead?".
>> Note that if we go that route, it should be a "soft" failure, as we
>> probably don't
>> want to drop all other partitions on the device.
> Is the number of partitions ie. in /proc/mtdparts an ABI ?

I don't know.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-10 14:47       ` Geert Uytterhoeven
@ 2018-04-10 16:34         ` Steve deRosier
  0 siblings, 0 replies; 9+ messages in thread
From: Steve deRosier @ 2018-04-10 16:34 UTC (permalink / raw)
  To: Geert Uytterhoeven
  Cc: Marek Vasut, Boris Brezillon, Geert Uytterhoeven,
	Richard Weinberger, Linux Kernel Mailing List, Linux-Renesas,
	MTD Maling List, Brian Norris, David Woodhouse

On Tue, Apr 10, 2018 at 7:47 AM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> Hi Marek,
>
> On Tue, Apr 10, 2018 at 4:37 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>> On 04/10/2018 03:26 PM, Geert Uytterhoeven wrote:
>>> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>>>> On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>>>>> Currently add_mtd_device() failures are plainly ignored, which may lead
>>>>> to kernel crashes later.
>>>
>>>>> Fix this by ignoring and freeing partitions that failed to add in
>>>>> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>>>>> so fix that as well.
>>>>>
>>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>>>> ---
>>>>> I don't know if it is worthwhile factoring out the common handling.
>>>>>
>>>>> Should allocate_partition() fail instead?  There's a comment saying
>>>>> "let's register it anyway to preserve ordering".
>>>
>>>>> --- a/drivers/mtd/mtdpart.c
>>>>> +++ b/drivers/mtd/mtdpart.c
>>>
>>>>> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>>>>>               list_add(&slave->list, &mtd_partitions);
>>>>>               mutex_unlock(&mtd_partitions_mutex);
>>>>>
>>>>> -             add_mtd_device(&slave->mtd);
>>>>> +             ret = add_mtd_device(&slave->mtd);
>>>>> +             if (ret) {
>>>>> +                     mutex_lock(&mtd_partitions_mutex);
>>>>> +                     list_del(&slave->list);
>>>>> +                     mutex_unlock(&mtd_partitions_mutex);
>>>>> +                     free_partition(slave);
>>>>> +                     continue;
>>>>> +             }
>>>>
>>>> Why is the partition even in the list in the first place ? Can we avoid
>>>> adding it rather than adding and removing it ?
>>>
>>> Hence my question "Should allocate_partition() fail instead?".
>>> Note that if we go that route, it should be a "soft" failure, as we
>>> probably don't
>>> want to drop all other partitions on the device.
>> Is the number of partitions ie. in /proc/mtdparts an ABI ?
>
> I don't know.
>

I don't know if it's an ABI, but having consistent /dev/mtdX numbering
is important, even in the case of a failed partition.  Many scripts on
embedded systems are hard-coded to /dev/mtdX identifies with the
expectation that they can access a particular address region of flash.
I'm sure that's what the "let's register it anyway to preserve
ordering" comment was trying to get across. I've even seen weird
things in dts files where later entries specify earlier addresses in
order to leave the old /dev/mtdX numbering alone.

Obviously, a better user solution is to construct the mtdX number from
/proc/mtd based on filtering for the name field, but not everyone
does.

I'd be wary about doing any fix that disturbs the numbering as you'll
be disturbing users.  At a minum, a loud warning in the log.

That said - obviously fixing the kernel crash must happen.

- Steve

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-10 13:26   ` Geert Uytterhoeven
  2018-04-10 14:37     ` Marek Vasut
@ 2018-04-26 17:53     ` Boris Brezillon
  2018-04-26 17:56       ` Geert Uytterhoeven
  1 sibling, 1 reply; 9+ messages in thread
From: Boris Brezillon @ 2018-04-26 17:53 UTC (permalink / raw)
  To: Geert Uytterhoeven
  Cc: Marek Vasut, Boris Brezillon, Geert Uytterhoeven,
	Richard Weinberger, Linux Kernel Mailing List, Linux-Renesas,
	MTD Maling List, Brian Norris, David Woodhouse

Hi Geert,

Sorry for the late reply.

On Tue, 10 Apr 2018 15:26:20 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> Hi Marek,
> 
> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
> > On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:  
> >> Currently add_mtd_device() failures are plainly ignored, which may lead
> >> to kernel crashes later.  
> 
> >> Fix this by ignoring and freeing partitions that failed to add in
> >> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
> >> so fix that as well.
> >>
> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> >> ---
> >> I don't know if it is worthwhile factoring out the common handling.
> >>
> >> Should allocate_partition() fail instead?  There's a comment saying
> >> "let's register it anyway to preserve ordering".  
> 
> >> --- a/drivers/mtd/mtdpart.c
> >> +++ b/drivers/mtd/mtdpart.c  
> 
> >> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
> >>               list_add(&slave->list, &mtd_partitions);
> >>               mutex_unlock(&mtd_partitions_mutex);
> >>
> >> -             add_mtd_device(&slave->mtd);
> >> +             ret = add_mtd_device(&slave->mtd);
> >> +             if (ret) {
> >> +                     mutex_lock(&mtd_partitions_mutex);
> >> +                     list_del(&slave->list);
> >> +                     mutex_unlock(&mtd_partitions_mutex);
> >> +                     free_partition(slave);
> >> +                     continue;
> >> +             }  
> >
> > Why is the partition even in the list in the first place ? Can we avoid
> > adding it rather than adding and removing it ?  
> 
> Hence my question "Should allocate_partition() fail instead?".

I'd prefer this option too. Can you prepare a new version doing that?

Thanks,

Boris

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-26 17:53     ` Boris Brezillon
@ 2018-04-26 17:56       ` Geert Uytterhoeven
  2018-04-26 18:09         ` Boris Brezillon
  0 siblings, 1 reply; 9+ messages in thread
From: Geert Uytterhoeven @ 2018-04-26 17:56 UTC (permalink / raw)
  To: Boris Brezillon
  Cc: Marek Vasut, Boris Brezillon, Geert Uytterhoeven,
	Richard Weinberger, Linux Kernel Mailing List, Linux-Renesas,
	MTD Maling List, Brian Norris, David Woodhouse

Hi Boris,

On Thu, Apr 26, 2018 at 7:53 PM, Boris Brezillon
<boris.brezillon@bootlin.com> wrote:
> On Tue, 10 Apr 2018 15:26:20 +0200
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:
>> > On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:
>> >> Currently add_mtd_device() failures are plainly ignored, which may lead
>> >> to kernel crashes later.
>>
>> >> Fix this by ignoring and freeing partitions that failed to add in
>> >> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
>> >> so fix that as well.
>> >>
>> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>> >> ---
>> >> I don't know if it is worthwhile factoring out the common handling.
>> >>
>> >> Should allocate_partition() fail instead?  There's a comment saying
>> >> "let's register it anyway to preserve ordering".
>>
>> >> --- a/drivers/mtd/mtdpart.c
>> >> +++ b/drivers/mtd/mtdpart.c
>>
>> >> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
>> >>               list_add(&slave->list, &mtd_partitions);
>> >>               mutex_unlock(&mtd_partitions_mutex);
>> >>
>> >> -             add_mtd_device(&slave->mtd);
>> >> +             ret = add_mtd_device(&slave->mtd);
>> >> +             if (ret) {
>> >> +                     mutex_lock(&mtd_partitions_mutex);
>> >> +                     list_del(&slave->list);
>> >> +                     mutex_unlock(&mtd_partitions_mutex);
>> >> +                     free_partition(slave);
>> >> +                     continue;
>> >> +             }
>> >
>> > Why is the partition even in the list in the first place ? Can we avoid
>> > adding it rather than adding and removing it ?
>>
>> Hence my question "Should allocate_partition() fail instead?".
>
> I'd prefer this option too. Can you prepare a new version doing that?

OK, then I have another question ;-)

Should this be a special failure, so all other valid partitions on the
same FLASH
are still added, or should it be fatal, so no partitions are added at all?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully
  2018-04-26 17:56       ` Geert Uytterhoeven
@ 2018-04-26 18:09         ` Boris Brezillon
  0 siblings, 0 replies; 9+ messages in thread
From: Boris Brezillon @ 2018-04-26 18:09 UTC (permalink / raw)
  To: Geert Uytterhoeven
  Cc: Marek Vasut, Boris Brezillon, Geert Uytterhoeven,
	Richard Weinberger, Linux Kernel Mailing List, Linux-Renesas,
	MTD Maling List, Brian Norris, David Woodhouse

On Thu, 26 Apr 2018 19:56:58 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> Hi Boris,
> 
> On Thu, Apr 26, 2018 at 7:53 PM, Boris Brezillon
> <boris.brezillon@bootlin.com> wrote:
> > On Tue, 10 Apr 2018 15:26:20 +0200
> > Geert Uytterhoeven <geert@linux-m68k.org> wrote:  
> >> On Mon, Apr 9, 2018 at 11:59 PM, Marek Vasut <marek.vasut@gmail.com> wrote:  
> >> > On 04/09/2018 02:25 PM, Geert Uytterhoeven wrote:  
> >> >> Currently add_mtd_device() failures are plainly ignored, which may lead
> >> >> to kernel crashes later.  
> >>  
> >> >> Fix this by ignoring and freeing partitions that failed to add in
> >> >> add_mtd_partitions().  The same issue is present in mtd_add_partition(),
> >> >> so fix that as well.
> >> >>
> >> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> >> >> ---
> >> >> I don't know if it is worthwhile factoring out the common handling.
> >> >>
> >> >> Should allocate_partition() fail instead?  There's a comment saying
> >> >> "let's register it anyway to preserve ordering".  
> >>  
> >> >> --- a/drivers/mtd/mtdpart.c
> >> >> +++ b/drivers/mtd/mtdpart.c  
> >>  
> >> >> @@ -746,7 +753,15 @@ int add_mtd_partitions(struct mtd_info *master,
> >> >>               list_add(&slave->list, &mtd_partitions);
> >> >>               mutex_unlock(&mtd_partitions_mutex);
> >> >>
> >> >> -             add_mtd_device(&slave->mtd);
> >> >> +             ret = add_mtd_device(&slave->mtd);
> >> >> +             if (ret) {
> >> >> +                     mutex_lock(&mtd_partitions_mutex);
> >> >> +                     list_del(&slave->list);
> >> >> +                     mutex_unlock(&mtd_partitions_mutex);
> >> >> +                     free_partition(slave);
> >> >> +                     continue;
> >> >> +             }  
> >> >
> >> > Why is the partition even in the list in the first place ? Can we avoid
> >> > adding it rather than adding and removing it ?  
> >>
> >> Hence my question "Should allocate_partition() fail instead?".  
> >
> > I'd prefer this option too. Can you prepare a new version doing that?  
> 
> OK, then I have another question ;-)
> 
> Should this be a special failure, so all other valid partitions on the
> same FLASH
> are still added, or should it be fatal, so no partitions are added at all?

I guess we can go for the "drop the invalid partitions and print a
warning" approach. Anyway, I'm sure people will notice really quickly
when one of their partition is missing, so it's not a big deal IMO.

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2018-04-26 18:09 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-04-09 12:25 [PATCH] mtd: partitions: Handle add_mtd_device() failures gracefully Geert Uytterhoeven
2018-04-09 21:59 ` Marek Vasut
2018-04-10 13:26   ` Geert Uytterhoeven
2018-04-10 14:37     ` Marek Vasut
2018-04-10 14:47       ` Geert Uytterhoeven
2018-04-10 16:34         ` Steve deRosier
2018-04-26 17:53     ` Boris Brezillon
2018-04-26 17:56       ` Geert Uytterhoeven
2018-04-26 18:09         ` Boris Brezillon

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