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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 e086b55381
commit 99504ff826
3 changed files with 14 additions and 11 deletions
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6
src/backend/utils/mmgr/freepage.c
View File

@ -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);
}
}

4
src/include/utils/freepage.h
View File

@ -78,11 +78,11 @@ struct FreePageManager
#define fpm_pointer_is_page_aligned(base, ptr) \
(((Size) (((char *) (ptr)) - (base))) % FPM_PAGE_SIZE == 0)
#define fpm_relptr_is_page_aligned(base, relptr) \
((relptr).relptr_off % FPM_PAGE_SIZE == 0)
(relptr_offset(relptr) % FPM_PAGE_SIZE == 0)
/* Macro to find base address of the segment containing a FreePageManager. */
#define fpm_segment_base(fpm) \
(((char *) fpm) - fpm->self.relptr_off)
(((char *) fpm) - relptr_offset(fpm->self))
/* Macro to access a FreePageManager's largest consecutive run of pages. */
#define fpm_largest(fpm) \

15
src/include/utils/relptr.h
View File

@ -42,7 +42,7 @@
#define relptr_access(base, rp) \
(AssertVariableIsOfTypeMacro(base, char *), \
(__typeof__((rp).relptr_type)) ((rp).relptr_off == 0 ? NULL : \
(base + (rp).relptr_off)))
(base) + (rp).relptr_off - 1))
#else
/*
* If we don't have __builtin_types_compatible_p, assume we might not have
@ -50,12 +50,15 @@
*/
#define relptr_access(base, rp) \
(AssertVariableIsOfTypeMacro(base, char *), \
(void *) ((rp).relptr_off == 0 ? NULL : (base + (rp).relptr_off)))
(void *) ((rp).relptr_off == 0 ? NULL : (base) + (rp).relptr_off - 1))
#endif
#define relptr_is_null(rp) \
((rp).relptr_off == 0)
#define relptr_offset(rp) \
((rp).relptr_off - 1)
/* We use this inline to avoid double eval of "val" in relptr_store */
static inline Size
relptr_store_eval(char *base, char *val)
@ -64,8 +67,8 @@ relptr_store_eval(char *base, char *val)
return 0;
else
{
Assert(val > base);
return val - base;
Assert(val >= base);
return val - base + 1;
}
}
@ -73,7 +76,7 @@ relptr_store_eval(char *base, char *val)
#define relptr_store(base, rp, val) \
(AssertVariableIsOfTypeMacro(base, char *), \
AssertVariableIsOfTypeMacro(val, __typeof__((rp).relptr_type)), \
(rp).relptr_off = relptr_store_eval(base, (char *) (val)))
(rp).relptr_off = relptr_store_eval((base), (char *) (val)))
#else
/*
* If we don't have __builtin_types_compatible_p, assume we might not have
@ -81,7 +84,7 @@ relptr_store_eval(char *base, char *val)
*/
#define relptr_store(base, rp, val) \
(AssertVariableIsOfTypeMacro(base, char *), \
(rp).relptr_off = relptr_store_eval(base, (char *) (val)))
(rp).relptr_off = relptr_store_eval((base), (char *) (val)))
#endif
#define relptr_copy(rp1, rp2) \