linux-kernel - Re: [PATCH] block: Export blk_alloc_discard

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Message-ID: <8f7269b0-e8f1-47cc-9ad7-1f1c2e452b02@gmail.com>
Date: Tue, 3 Sep 2024 18:02:37 +0200
From: Luca Stefani <luca.stefani.ge1@...il.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: Export blk_alloc_discard_bio



On 03/09/24 17:49, Jens Axboe wrote:
> On 9/3/24 1:39 AM, Luca Stefani wrote:
>> The fs trim loops over ranges and sends discard requests, some ranges
>> can be large so it's all transparently handled by blkdev_issue_discard()
>> and processed in smaller chunks.
>>
>> To support cancellation (or suspend) requests we need to insert checks
>> into the the loop, exporting the symbol allows to reimplement
>> such loop with the desired behavior.
>>
>> Signed-off-by: Luca Stefani <luca.stefani.ge1@...il.com>
>> ---
>>   block/blk-lib.c        | 1 +
>>   include/linux/blkdev.h | 2 ++
>>   2 files changed, 3 insertions(+)
>>
>> diff --git a/block/blk-lib.c b/block/blk-lib.c
>> index 4c9f20a689f7..ebaef47d8ce7 100644
>> --- a/block/blk-lib.c
>> +++ b/block/blk-lib.c
>> @@ -59,6 +59,7 @@ struct bio *blk_alloc_discard_bio(struct block_device *bdev,
>>   	cond_resched();
>>   	return bio;
>>   }
>> +EXPORT_SYMBOL_GPL(blk_alloc_discard_bio);
>>   
>>   int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
>>   		sector_t nr_sects, gfp_t gfp_mask, struct bio **biop)
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index b7664d593486..f3631044d905 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -1088,6 +1088,8 @@ static inline long nr_blockdev_pages(void)
>>   
>>   extern void blk_io_schedule(void);
>>   
>> +struct bio *blk_alloc_discard_bio(struct block_device *bdev,
>> +		sector_t *sector, sector_t *nr_sects, gfp_t gfp_mask);
>>   int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
>>   		sector_t nr_sects, gfp_t gfp_mask);
>>   int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
> 
> Since blk_alloc_discard_bio() is already defined in a header (otherwise
> it would've been static and your export symbol above would have failed
> miserably), why add it to another header?
> 

ACK, will remove the header change in v4,

Thanks.