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Make dsa_allocate interface more like MemoryContextAlloc.

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A new function dsa_allocate_extended now takes flags which indicate
that huge allocations should be permitted, that out-of-memory
conditions should not throw an error, and/or that the returned memory
should be zero-filled, just like MemoryContextAllocateExtended.

Commit 9acb85597f1223ac26a5b19a9345849c43d0ff54, which added
dsa_allocate0, was broken because it failed to account for the
possibility that dsa_allocate() might return InvalidDsaPointer.
This fixes that problem along the way.

Thomas Munro, with some comment changes by me.

Discussion: http://postgr.es/m/CA+Tgmobt7CcF_uQP2UQwWmu4K9qCHehMJP9_9m1urwP8hbOeHQ@mail.gmail.com
This commit is contained in:
Robert Haas
2017-02-19 13:59:53 +05:30
parent 1a16af8b35
commit 16be2fd100
2 changed files with 69 additions and 23 deletions
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16
src/include/utils/dsa.h
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@ -71,12 +71,25 @@ typedef pg_atomic_uint64 dsa_pointer_atomic;
#define DSA_POINTER_FORMAT "%016" INT64_MODIFIER "x"
#endif
/* Flags for dsa_allocate_extended. */
#define DSA_ALLOC_HUGE 0x01 /* allow huge allocation (> 1 GB) */
#define DSA_ALLOC_NO_OOM 0x02 /* no failure if out-of-memory */
#define DSA_ALLOC_ZERO 0x04 /* zero allocated memory */
/* A sentinel value for dsa_pointer used to indicate failure to allocate. */
#define InvalidDsaPointer ((dsa_pointer) 0)
/* Check if a dsa_pointer value is valid. */
#define DsaPointerIsValid(x) ((x) != InvalidDsaPointer)
/* Allocate uninitialized memory with error on out-of-memory. */
#define dsa_allocate(area, size) \
dsa_allocate_extended(area, size, 0)
/* Allocate zero-initialized memory with error on out-of-memory. */
#define dsa_allocate0(area, size) \
dsa_allocate_extended(area, size, DSA_ALLOC_ZERO)
/*
* The type used for dsa_area handles. dsa_handle values can be shared with
* other processes, so that they can attach to them. This provides a way to
@ -105,8 +118,7 @@ extern void dsa_unpin(dsa_area *area);
extern void dsa_set_size_limit(dsa_area *area, Size limit);
extern Size dsa_minimum_size(void);
extern dsa_handle dsa_get_handle(dsa_area *area);
extern dsa_pointer dsa_allocate(dsa_area *area, Size size);
extern dsa_pointer dsa_allocate0(dsa_area *area, Size size);
extern dsa_pointer dsa_allocate_extended(dsa_area *area, Size size, int flags);
extern void dsa_free(dsa_area *area, dsa_pointer dp);
extern void *dsa_get_address(dsa_area *area, dsa_pointer dp);
extern void dsa_trim(dsa_area *area);