From: Namjae Jeon <[email protected]>
linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
(block: add plug for blkdev_issue_discard )
For example,
1) DISCARD rq-1 with size size 4GB
2) DISCARD rq-2 with size size 1GB
If these 2 discard requests get merged, final request size will be 5GB.
In this case, request's __data_len field may overflow as it can store
max 4GB(unsigned int).
This issue was observed while doing mkfs.f2fs on 5GB SD card:
https://lkml.org/lkml/2013/4/1/292
# mkfs.f2fs /dev/mmcblk0p3
Info: sector size = 512
Info: total sectors = 11370496 (in 512bytes)
Info: zone aligned segment0 blkaddr: 512
[ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
mkfs process gets stuck in D state and I see the following in the dmesg:
[ 257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081
[ 257.789764] sector 4194304, nr/cnr 2981888/4294959104
[ 257.789764] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
[ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
[ 257.794921] request botched: dev mmcblk0: type=1, flags=122c8081
[ 257.794921] sector 4194304, nr/cnr 2981888/4294959104
[ 257.794921] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
Few drivers(e.g. mmc, mtd..) set q->limits.max_discard_sectors
more than UINT_MAX >> 9 sectors which is incorrect and it may lead to overflow
of request's __data_len field if merged discard request's size exceeds 4GB.
This patchset fixes this issue by updating helper function
blk_queue_max_discard_sectors which is used to set max_discard_sectors limit.
This patchset also replaces "q->limits.max_discard_sector = max_discard_sectors"
with blk_queue_max_discard_sectors call in other drivers like mmc, mtd etc.
Namjae Jeon (9):
block: fix max discard sectors limit
mmc: fix max_discard_sectors
sd: use generic helper to set max_discard_sectors
mtd: use generic helper to set max_discard_sectors
loop: use generic helper to set max_discard_sectors
nbd: use generic helper to set max_discard_sectors
brd: use generic helper to set max_discard_sectors
dm thin: use generic helper to set max_discard_sectors
bcache: use generic helper to set max_discard_sectors
--
1.7.9.5
On Sat, 2013-04-20 at 01:40 +0900, Namjae Jeon wrote:
> From: Namjae Jeon <[email protected]>
>
> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
> (block: add plug for blkdev_issue_discard )
>
> For example,
> 1) DISCARD rq-1 with size size 4GB
> 2) DISCARD rq-2 with size size 1GB
>
> If these 2 discard requests get merged, final request size will be 5GB.
>
> In this case, request's __data_len field may overflow as it can store
> max 4GB(unsigned int).
>
> This issue was observed while doing mkfs.f2fs on 5GB SD card:
> https://lkml.org/lkml/2013/4/1/292
>
> # mkfs.f2fs /dev/mmcblk0p3
> Info: sector size = 512
> Info: total sectors = 11370496 (in 512bytes)
> Info: zone aligned segment0 blkaddr: 512
> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
>
> mkfs process gets stuck in D state and I see the following in the dmesg:
>
> [ 257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081
> [ 257.789764] sector 4194304, nr/cnr 2981888/4294959104
> [ 257.789764] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
> [ 257.794921] request botched: dev mmcblk0: type=1, flags=122c8081
> [ 257.794921] sector 4194304, nr/cnr 2981888/4294959104
> [ 257.794921] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
>
> Few drivers(e.g. mmc, mtd..) set q->limits.max_discard_sectors
> more than UINT_MAX >> 9 sectors which is incorrect and it may lead to overflow
> of request's __data_len field if merged discard request's size exceeds 4GB.
>
> This patchset fixes this issue by updating helper function
> blk_queue_max_discard_sectors which is used to set max_discard_sectors limit.
>
> This patchset also replaces "q->limits.max_discard_sector = max_discard_sectors"
> with blk_queue_max_discard_sectors call in other drivers like mmc, mtd etc.
I really don't understand this explanation. How can you be affected by
the incorrect setting of q->limits.max_discard sectors when n the
blkdev_issue_discard() code you see:
max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >>
9);
?
The problem is not that we issue discards bigger than __data_len can
allow, the problem is that we merge them larger than __data_len will
allow. That means the merge code needs fixing to pay attention to
max_discard_sectors, so isn't this the correct fix:
James
---
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 78feda9..33f358f 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -838,7 +838,7 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
unsigned int cmd_flags)
{
if (unlikely(cmd_flags & REQ_DISCARD))
- return q->limits.max_discard_sectors;
+ return min(q->limits.max_discard_sectors, UINT_MAX >> 9);
if (unlikely(cmd_flags & REQ_WRITE_SAME))
return q->limits.max_write_same_sectors;
2013/4/21 James Bottomley <[email protected]>:
> On Sat, 2013-04-20 at 01:40 +0900, Namjae Jeon wrote:
>> From: Namjae Jeon <[email protected]>
>>
>> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
>> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
>> (block: add plug for blkdev_issue_discard )
>>
>> For example,
>> 1) DISCARD rq-1 with size size 4GB
>> 2) DISCARD rq-2 with size size 1GB
>>
>> If these 2 discard requests get merged, final request size will be 5GB.
>>
>> In this case, request's __data_len field may overflow as it can store
>> max 4GB(unsigned int).
>>
>> This issue was observed while doing mkfs.f2fs on 5GB SD card:
>> https://lkml.org/lkml/2013/4/1/292
>>
>> # mkfs.f2fs /dev/mmcblk0p3
>> Info: sector size = 512
>> Info: total sectors = 11370496 (in 512bytes)
>> Info: zone aligned segment0 blkaddr: 512
>> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
>>
>> mkfs process gets stuck in D state and I see the following in the dmesg:
>>
>> [ 257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081
>> [ 257.789764] sector 4194304, nr/cnr 2981888/4294959104
>> [ 257.789764] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
>> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
>> [ 257.794921] request botched: dev mmcblk0: type=1, flags=122c8081
>> [ 257.794921] sector 4194304, nr/cnr 2981888/4294959104
>> [ 257.794921] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
>>
>> Few drivers(e.g. mmc, mtd..) set q->limits.max_discard_sectors
>> more than UINT_MAX >> 9 sectors which is incorrect and it may lead to overflow
>> of request's __data_len field if merged discard request's size exceeds 4GB.
>>
>> This patchset fixes this issue by updating helper function
>> blk_queue_max_discard_sectors which is used to set max_discard_sectors limit.
>>
>> This patchset also replaces "q->limits.max_discard_sector = max_discard_sectors"
>> with blk_queue_max_discard_sectors call in other drivers like mmc, mtd etc.
>
Hi. James.
> I really don't understand this explanation. How can you be affected by
> the incorrect setting of q->limits.max_discard sectors when n the
> blkdev_issue_discard() code you see:
>
> max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >>
> 9);
>
> ?
>
> The problem is not that we issue discards bigger than __data_len can
> allow, the problem is that we merge them larger than __data_len will
> allow. That means the merge code needs fixing to pay attention to
> max_discard_sectors, so isn't this the correct fix:
Yes, I agree. And the below patch looks good to fix this issue.
Thanks for your comment.
>
> James
>
> ---
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 78feda9..33f358f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -838,7 +838,7 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
> unsigned int cmd_flags)
> {
> if (unlikely(cmd_flags & REQ_DISCARD))
> - return q->limits.max_discard_sectors;
> + return min(q->limits.max_discard_sectors, UINT_MAX >> 9);
>
> if (unlikely(cmd_flags & REQ_WRITE_SAME))
> return q->limits.max_write_same_sectors;
>
>
On Sat, Apr 20, 2013 at 01:40:02AM +0900, Namjae Jeon wrote:
> From: Namjae Jeon <[email protected]>
>
> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
> (block: add plug for blkdev_issue_discard )
>
> For example,
> 1) DISCARD rq-1 with size size 4GB
> 2) DISCARD rq-2 with size size 1GB
>
> If these 2 discard requests get merged, final request size will be 5GB.
>
> In this case, request's __data_len field may overflow as it can store
> max 4GB(unsigned int).
Complete NACK - like James said, this fix is nonsensical. This should be
fixed by just checking for overflow before merging requests, not with
weird hacks in the drivers.
2013/4/23, Kent Overstreet <[email protected]>:
> On Sat, Apr 20, 2013 at 01:40:02AM +0900, Namjae Jeon wrote:
>> From: Namjae Jeon <[email protected]>
>>
>> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
>> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
>> (block: add plug for blkdev_issue_discard )
>>
>> For example,
>> 1) DISCARD rq-1 with size size 4GB
>> 2) DISCARD rq-2 with size size 1GB
>>
>> If these 2 discard requests get merged, final request size will be 5GB.
>>
>> In this case, request's __data_len field may overflow as it can store
>> max 4GB(unsigned int).
>
> Complete NACK - like James said, this fix is nonsensical. This should be
> fixed by just checking for overflow before merging requests, not with
> weird hacks in the drivers.
that agree to your opinion, and will change at only appropriate
place(James'change) and will send the updated patch soon.
Thanks.
>
On 04/20/2013 09:50 PM, James Bottomley wrote:
> On Sat, 2013-04-20 at 01:40 +0900, Namjae Jeon wrote:
>> From: Namjae Jeon <[email protected]>
>>
>> linux-v3.8-rc1 and later support for plug for blkdev_issue_discard with
>> commit 0cfbcafcae8b7364b5fa96c2b26ccde7a3a296a9
>> (block: add plug for blkdev_issue_discard )
>>
>> For example,
>> 1) DISCARD rq-1 with size size 4GB
>> 2) DISCARD rq-2 with size size 1GB
>>
>> If these 2 discard requests get merged, final request size will be 5GB.
>>
>> In this case, request's __data_len field may overflow as it can store
>> max 4GB(unsigned int).
>>
>> This issue was observed while doing mkfs.f2fs on 5GB SD card:
>> https://lkml.org/lkml/2013/4/1/292
>>
>> # mkfs.f2fs /dev/mmcblk0p3
>> Info: sector size = 512
>> Info: total sectors = 11370496 (in 512bytes)
>> Info: zone aligned segment0 blkaddr: 512
>> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
>>
>> mkfs process gets stuck in D state and I see the following in the dmesg:
>>
>> [ 257.789733] __end_that: dev mmcblk0: type=1, flags=122c8081
>> [ 257.789764] sector 4194304, nr/cnr 2981888/4294959104
>> [ 257.789764] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
>> [ 257.789764] blk_update_request: bio idx 0 >= vcnt 0
>> [ 257.794921] request botched: dev mmcblk0: type=1, flags=122c8081
>> [ 257.794921] sector 4194304, nr/cnr 2981888/4294959104
>> [ 257.794921] bio df3840c0, biotail df3848c0, buffer (null), len 1526726656
>>
>> Few drivers(e.g. mmc, mtd..) set q->limits.max_discard_sectors
>> more than UINT_MAX >> 9 sectors which is incorrect and it may lead to overflow
>> of request's __data_len field if merged discard request's size exceeds 4GB.
>>
>> This patchset fixes this issue by updating helper function
>> blk_queue_max_discard_sectors which is used to set max_discard_sectors limit.
>>
>> This patchset also replaces "q->limits.max_discard_sector = max_discard_sectors"
>> with blk_queue_max_discard_sectors call in other drivers like mmc, mtd etc.
>
> I really don't understand this explanation. How can you be affected by
> the incorrect setting of q->limits.max_discard sectors when n the
> blkdev_issue_discard() code you see:
>
> max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >>
> 9);
>
> ?
>
> The problem is not that we issue discards bigger than __data_len can
> allow, the problem is that we merge them larger than __data_len will
> allow. That means the merge code needs fixing to pay attention to
> max_discard_sectors, so isn't this the correct fix:
>
> James
>
> ---
>
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 78feda9..33f358f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -838,7 +838,7 @@ static inline unsigned int blk_queue_get_max_sectors(struct request_queue *q,
> unsigned int cmd_flags)
> {
> if (unlikely(cmd_flags & REQ_DISCARD))
> - return q->limits.max_discard_sectors;
> + return min(q->limits.max_discard_sectors, UINT_MAX >> 9);
>
> if (unlikely(cmd_flags & REQ_WRITE_SAME))
> return q->limits.max_write_same_sectors;
>
>
Patch works, and fixes the discard failing issue I've been pestering
mkp with at LSF. Please apply.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
[email protected] +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: J. Hawn, J. Guild, F. Imend?rffer, HRB 16746 (AG N?rnberg)