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Fix relptr's encoding of the base address.

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Previously, we encoded both NULL and the first byte at the base address
as 0.  That confusion led to the assertion in commit e07d4ddc, which
failed when min_dynamic_shared_memory was used.  Give them distinct
encodings, by switching to 1-based offsets for non-NULL pointers.  Also
improve macro hygiene in passing (missing/misplaced parentheses), and
remove open-coded access to the raw offset value from freepage.c/h.

Although e07d4ddc was back-patched to 10, the only code that actually
makes use of relptr at the base address arrived in 84b1c63a, so no need
to back-patch further than 14 for now.

Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Discussion: https://postgr.es/m/20220519193839.GT19626%40telsasoft.com
This commit is contained in:
Thomas Munro
2022-06-27 10:30:15 +12:00
parent ebc584ed49
commit 7201cd1862
3 changed files with 14 additions and 11 deletions
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6
src/backend/utils/mmgr/freepage.c
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@ -434,7 +434,7 @@ FreePageManagerDump(FreePageManager *fpm)
/* Dump general stuff. */
appendStringInfo(&buf, "metadata: self %zu max contiguous pages = %zu\n",
fpm->self.relptr_off, fpm->contiguous_pages);
relptr_offset(fpm->self), fpm->contiguous_pages);
/* Dump btree. */
if (fpm->btree_depth > 0)
@ -1269,7 +1269,7 @@ FreePageManagerDumpBtree(FreePageManager *fpm, FreePageBtree *btp,
if (btp->hdr.magic == FREE_PAGE_INTERNAL_MAGIC)
appendStringInfo(buf, " %zu->%zu",
btp->u.internal_key[index].first_page,
btp->u.internal_key[index].child.relptr_off / FPM_PAGE_SIZE);
relptr_offset(btp->u.internal_key[index].child) / FPM_PAGE_SIZE);
else
appendStringInfo(buf, " %zu(%zu)",
btp->u.leaf_key[index].first_page,
@ -1859,7 +1859,7 @@ FreePagePopSpanLeader(FreePageManager *fpm, Size pageno)
{
Size f = Min(span->npages, FPM_NUM_FREELISTS) - 1;
Assert(fpm->freelist[f].relptr_off == pageno * FPM_PAGE_SIZE);
Assert(relptr_offset(fpm->freelist[f]) == pageno * FPM_PAGE_SIZE);
relptr_copy(fpm->freelist[f], span->next);
}
}