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simplehash: preserve consistency in case of OOM. 

Compute size first, then allocate, then update the structure.

Previously, an out-of-memory when growing could leave the hashtable in
an inconsistent state.

Discussion: https://postgr.es/m/20231117201334.eyb542qr5yk4gilq@awork3.anarazel.de
Reviewed-by: Andres Freund
Reviewed-by: Gurjeet Singh
This commit is contained in:
Jeff Davis 2023-11-17 13:58:16 -08:00
parent a268a51de6
commit b282fa88df
1 changed files with 31 additions and 11 deletions
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42
src/include/lib/simplehash.h
View File

@ -128,7 +128,8 @@
#define SH_STAT SH_MAKE_NAME(stat)
/* internal helper functions (no externally visible prototypes) */
#define SH_COMPUTE_PARAMETERS SH_MAKE_NAME(compute_parameters)
#define SH_COMPUTE_SIZE SH_MAKE_NAME(compute_size)
#define SH_UPDATE_PARAMETERS SH_MAKE_NAME(update_parameters)
#define SH_NEXT SH_MAKE_NAME(next)
#define SH_PREV SH_MAKE_NAME(prev)
#define SH_DISTANCE_FROM_OPTIMAL SH_MAKE_NAME(distance)
@ -303,11 +304,11 @@ SH_SCOPE void SH_STAT(SH_TYPE * tb);
#endif
/*
* Compute sizing parameters for hashtable. Called when creating and growing
* the hashtable.
* Compute allocation size for hashtable. Result can be passed to
* SH_UPDATE_PARAMETERS.
*/
static inline void
SH_COMPUTE_PARAMETERS(SH_TYPE * tb, uint64 newsize)
static inline uint64
SH_COMPUTE_SIZE(uint64 newsize)
{
uint64 size;
@ -325,6 +326,18 @@ SH_COMPUTE_PARAMETERS(SH_TYPE * tb, uint64 newsize)
if (unlikely((((uint64) sizeof(SH_ELEMENT_TYPE)) * size) >= SIZE_MAX / 2))
sh_error("hash table too large");
return size;
}
/*
* Update sizing parameters for hashtable. Called when creating and growing
* the hashtable.
*/
static inline void
SH_UPDATE_PARAMETERS(SH_TYPE * tb, uint64 newsize)
{
uint64 size = SH_COMPUTE_SIZE(newsize);
/* now set size */
tb->size = size;
tb->sizemask = (uint32) (size - 1);
@ -446,10 +459,11 @@ SH_CREATE(MemoryContext ctx, uint32 nelements, void *private_data)
/* increase nelements by fillfactor, want to store nelements elements */
size = Min((double) SH_MAX_SIZE, ((double) nelements) / SH_FILLFACTOR);
SH_COMPUTE_PARAMETERS(tb, size);
size = SH_COMPUTE_SIZE(size);
tb->data = (SH_ELEMENT_TYPE *) SH_ALLOCATE(tb, sizeof(SH_ELEMENT_TYPE) * tb->size);
tb->data = (SH_ELEMENT_TYPE *) SH_ALLOCATE(tb, sizeof(SH_ELEMENT_TYPE) * size);
SH_UPDATE_PARAMETERS(tb, size);
return tb;
}
@ -490,10 +504,15 @@ SH_GROW(SH_TYPE * tb, uint64 newsize)
Assert(oldsize != SH_MAX_SIZE);
Assert(oldsize < newsize);
/* compute parameters for new table */
SH_COMPUTE_PARAMETERS(tb, newsize);
newsize = SH_COMPUTE_SIZE(newsize);
tb->data = (SH_ELEMENT_TYPE *) SH_ALLOCATE(tb, sizeof(SH_ELEMENT_TYPE) * tb->size);
tb->data = (SH_ELEMENT_TYPE *) SH_ALLOCATE(tb, sizeof(SH_ELEMENT_TYPE) * newsize);
/*
* Update parameters for new table after allocation succeeds to avoid
* inconsistent state on OOM.
*/
SH_UPDATE_PARAMETERS(tb, newsize);
newdata = tb->data;
@ -1173,7 +1192,8 @@ SH_STAT(SH_TYPE * tb)
#undef SH_STAT
/* internal function names */
#undef SH_COMPUTE_PARAMETERS
#undef SH_COMPUTE_SIZE
#undef SH_UPDATE_PARAMETERS
#undef SH_COMPARE_KEYS
#undef SH_INITIAL_BUCKET
#undef SH_NEXT