From 7cdaee9caaf96564237e4cfa8279699a36942624 Mon Sep 17 00:00:00 2001 From: Karina Litskevich Date: Tue, 14 Feb 2023 17:18:30 +0300 Subject: [PATCH v1 2/2] Better comments and variable name in AllocSetRealloc() --- src/backend/utils/mmgr/aset.c | 46 ++++++++++++++++++++--------------- 1 file changed, 27 insertions(+), 19 deletions(-) diff --git a/src/backend/utils/mmgr/aset.c b/src/backend/utils/mmgr/aset.c index 1ff0bb83cb..35007750a9 100644 --- a/src/backend/utils/mmgr/aset.c +++ b/src/backend/utils/mmgr/aset.c @@ -1112,7 +1112,7 @@ AllocSetRealloc(void *pointer, Size size) AllocBlock block; AllocSet set; MemoryChunk *chunk = PointerGetMemoryChunk(pointer); - Size oldsize; + Size oldchksize; int fidx; /* Allow access to private part of chunk header. */ @@ -1140,11 +1140,11 @@ AllocSetRealloc(void *pointer, Size size) set = block->aset; - oldsize = block->endptr - (char *) pointer; + oldchksize = block->endptr - (char *) pointer; #ifdef MEMORY_CONTEXT_CHECKING /* Test for someone scribbling on unused space in chunk */ - Assert(chunk->requested_size < oldsize); + Assert(chunk->requested_size < oldchksize); if (!sentinel_ok(pointer, chunk->requested_size)) elog(WARNING, "detected write past chunk end in %s %p", set->header.name, chunk); @@ -1194,14 +1194,17 @@ AllocSetRealloc(void *pointer, Size size) #endif /* - * realloc() (or randomize_mem()) will have left any newly-allocated - * part UNDEFINED, but we may need to adjust trailing bytes from the - * old allocation. + * If this is an increase, realloc() (or randomize_mem()) will have left + * any newly-allocated part UNDEFINED, but we may need to adjust + * trailing bytes from the old allocation as they are marked NOACCESS. */ #ifdef USE_VALGRIND - if (size > chunk->requested_size && oldsize > chunk->requested_size) + if (size > chunk->requested_size && oldchksize > chunk->requested_size) + { + Assert(chksize >= oldchksize); VALGRIND_MAKE_MEM_UNDEFINED((char *) pointer + chunk->requested_size, - oldsize - chunk->requested_size); + oldchksize - chunk->requested_size); + } #endif chunk->requested_size = size; @@ -1211,12 +1214,15 @@ AllocSetRealloc(void *pointer, Size size) #else /* !MEMORY_CONTEXT_CHECKING */ /* - * We don't know how much of the old chunk size was the actual - * allocation; it could have been as small as one byte. We have to be - * conservative and just mark the entire old portion DEFINED. + * We may need to adjust marking of bytes from the old allocation as + * some of them may be marked NOACCESS. We don't know how much of the + * old chunk size was the requested size; it could have been as small as + * one byte. We have to be conservative and just mark the entire old + * portion DEFINED. Make sure not to mark memory behind the new + * allocation in case it's smaller than old one. */ - if (size >= oldsize) - VALGRIND_MAKE_MEM_DEFINED(pointer, oldsize); + if (size >= oldchksize) + VALGRIND_MAKE_MEM_DEFINED(pointer, oldchksize); else VALGRIND_MAKE_MEM_DEFINED(pointer, size); #endif @@ -1243,11 +1249,11 @@ AllocSetRealloc(void *pointer, Size size) fidx = MemoryChunkGetValue(chunk); Assert(FreeListIdxIsValid(fidx)); - oldsize = GetChunkSizeFromFreeListIdx(fidx); + oldchksize = GetChunkSizeFromFreeListIdx(fidx); #ifdef MEMORY_CONTEXT_CHECKING /* Test for someone scribbling on unused space in chunk */ - if (chunk->requested_size < oldsize) + if (chunk->requested_size < oldchksize) if (!sentinel_ok(pointer, chunk->requested_size)) elog(WARNING, "detected write past chunk end in %s %p", set->header.name, chunk); @@ -1258,7 +1264,7 @@ AllocSetRealloc(void *pointer, Size size) * allocated area already is >= the new size. (In particular, we will * fall out here if the requested size is a decrease.) */ - if (oldsize >= size) + if (oldchksize >= size) { #ifdef MEMORY_CONTEXT_CHECKING Size oldrequest = chunk->requested_size; @@ -1281,10 +1287,10 @@ AllocSetRealloc(void *pointer, Size size) size - oldrequest); else VALGRIND_MAKE_MEM_NOACCESS((char *) pointer + size, - oldsize - size); + oldchksize - size); /* set mark to catch clobber of "unused" space */ - if (size < oldsize) + if (size < oldchksize) set_sentinel(pointer, size); #else /* !MEMORY_CONTEXT_CHECKING */ @@ -1293,7 +1299,7 @@ AllocSetRealloc(void *pointer, Size size) * the old request or shrinking it, so we conservatively mark the * entire new allocation DEFINED. */ - VALGRIND_MAKE_MEM_NOACCESS(pointer, oldsize); + VALGRIND_MAKE_MEM_NOACCESS(pointer, oldchksize); VALGRIND_MAKE_MEM_DEFINED(pointer, size); #endif @@ -1316,6 +1322,7 @@ AllocSetRealloc(void *pointer, Size size) * memory indefinitely. See pgsql-hackers archives for 2007-08-11.) */ AllocPointer newPointer; + Size oldsize; /* allocate new chunk */ newPointer = AllocSetAlloc((MemoryContext) set, size); @@ -1340,6 +1347,7 @@ AllocSetRealloc(void *pointer, Size size) #ifdef MEMORY_CONTEXT_CHECKING oldsize = chunk->requested_size; #else + oldsize = oldchksize; VALGRIND_MAKE_MEM_DEFINED(pointer, oldsize); #endif -- 2.25.1