Bug #95030 buf_read_page should be a synchronously operation

• Submitted: 15 Apr 2019 18:23
• Modified: 17 May 2019 12:24
• Reporter: Zongzhi Chen (OCA)
• Status: Verified
• Category: MySQL Server: InnoDB storage engine
• Severity: S3 (Non-critical)
• OS: Any
• CPU Architecture: Any

[15 Apr 2019 18:23] Zongzhi Chen

Description:
In the comment of buf/buf0rea.cc::ibool buf_read_page(const page_id_t &page_id, const page_size_t &page_size). It said that "High-level function which reads a page asynchronously from a file to the buffer buf_pool"

However, after reading the code, even though it will call fil_io=>shard->do_io => os_aio =>pfs_os_aio_func => os_aio_func. There is many function call "aio_", however, it actually call the os_file_read_func, and os_file_read_func will finally call pread, so it should be a synchronously operation, not an asynchronously. 

When I read the code, it actually really confuse me, since there is so much "aio_" functions, but actually it will call pread.

How to repeat:
Read the code

[15 May 2019 14:23] MySQL Verification Team

Hi Zongzhi,

Thank you for your bug report.

If I understand you correctly you would wish that we remove that comment about async operation.

Am I correct ????

[17 May 2019 9:31] Zongzhi Chen

Yes, you are right. Since it actually is a synchronously operation.

[17 May 2019 12:24] MySQL Verification Team

Thank you Mr. Zongzhi,

Verified as reported.