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Revert unintentional change in increasing usage count during pin of buffers, 

this makes buffer access strategy have no effect.
Change was a part of commit 48354581a4 during 9.6
release cycle, so backpath to 9.6

Reported-by: Jim Nasby
Author: Alexander Korotkov
Reviewed-by: Jim Nasby, Andres Freund

https://commitfest.postgresql.org/13/1029/
This commit is contained in:
Teodor Sigaev 2017-03-20 18:48:46 +03:00
parent de34123834
commit 9cf6033281
1 changed files with 15 additions and 3 deletions
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18
src/backend/storage/buffer/bufmgr.c
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@ -1595,9 +1595,21 @@ PinBuffer(BufferDesc *buf, BufferAccessStrategy strategy)
/* increase refcount */
buf_state += BUF_REFCOUNT_ONE;
/* increase usagecount unless already max */
if (BUF_STATE_GET_USAGECOUNT(buf_state) != BM_MAX_USAGE_COUNT)
buf_state += BUF_USAGECOUNT_ONE;
if (strategy == NULL)
{
/* Default case: increase usagecount unless already max. */
if (BUF_STATE_GET_USAGECOUNT(buf_state) < BM_MAX_USAGE_COUNT)
buf_state += BUF_USAGECOUNT_ONE;
}
else
{
/*
* Ring buffers shouldn't evict others from pool. Thus we
* don't make usagecount more than 1.
*/
if (BUF_STATE_GET_USAGECOUNT(buf_state) == 0)
buf_state += BUF_USAGECOUNT_ONE;
}
if (pg_atomic_compare_exchange_u32(&buf->state, &old_buf_state,
buf_state))