Re: Fix condition in shm_toc and remove unused function shm_toc_freespace.

From: Zhang Mingli <zmlpostgres(at)gmail(dot)com>
To: Richard Guo <guofenglinux(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Fix condition in shm_toc and remove unused function shm_toc_freespace.
Date: 2023-01-13 15:09:30
Message-ID: 0c84a55b-9b30-40d1-873a-873ee134c04e@Spark
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Hi,

Regards,
Zhang Mingli
On Jan 12, 2023, 16:54 +0800, Richard Guo <guofenglinux(at)gmail(dot)com>, wrote:
>
> On Thu, Jan 12, 2023 at 2:50 PM Zhang Mingli <zmlpostgres(at)gmail(dot)com> wrote:
> > On Jan 12, 2023, 14:34 +0800, Zhang Mingli <zmlpostgres(at)gmail(dot)com>, wrote:
> > > Some conditions in shm_toc_insert and shm_toc_allocate are bogus, like:
> > > if (toc_bytes + nbytes > total_bytes || toc_bytes + nbytes < toc_bytes)Remove the condition `toc_bytes + nbytes < toc_bytes` and take a sizeof(shm_entry) into account in shm_toc_allocate though
> > > shm_toc_allocate does that too.
> >   shm_toc_insert does that too, and  we can report error earlier.
>
> I don't think we should consider sizeof(shm_toc_entry) in the 'if'
> condition in shm_toc_allocate, as this function is not in charge of
> allocating a new TOC entry.  That's what shm_toc_insert does.
Thanks for review.
Make sense.
Even reserve a sizeof(shm_toc_entry) when shm_toc_allocate, it cloud happen that there is no space  when shm_toc_insert
in case of other processes may take space after that.
Patch updated.

Attachment Content-Type Size
v1-0001-Fix-condition-in-shm_toc-and-remove-unused-functi.patch application/octet-stream 2.7 KB

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