[PATCH] read-cache.c: fix index memory allocation
- From
René Scharfe <rene.scharfe@lsrfire.ath.cx>
- Date
- Oct 24, 2011, 01:01 UTC
- Message-ID
- <4EA4B8E7.5070106@lsrfire.ath.cx>
- In-Reply-To
- <4EA453D3.7080002@lsrfire.ath.cx>
estimate_cache_size() tries to guess how much memory is needed for the in-memory representation of an index file. It does that by using the file size, the number of entries and the difference of the sizes of the on-disk and in-memory structs -- without having to check the length of the name of each entry, which varies for each entry, but their sums are the same no matter the representation.
Except there can be a difference. First of all, the size is really calculated by ce_size and ondisk_ce_size based on offsetof(..., name), not sizeof, which can be different. And entries are padded with 1 to 8 NULs at the end (after the variable name) to make their total length a multiple of eight.
So in order to allocate enough memory to hold the index, change the delta calculation to be based on offsetof(..., name) and round up to the next multiple of eight.
On a 32-bit Linux, this delta was used before:
sizeof(struct cache_entry) == 72 sizeof(struct ondisk_cache_entry) == 64 --- 8
The actual difference for an entry with a filename length of one was, however (find the definitions are in cache.h):
offsetof(struct cache_entry, name) == 72 offsetof(struct ondisk_cache_entry, name) == 62
ce_size == (72 + 1 + 8) & ~7 == 80 ondisk_ce_size == (62 + 1 + 8) & ~7 == 64 --- 16
So eight bytes less had been allocated for such entries. The new formula yields the correct delta:
(72 - 62 + 7) & ~7 == 16
Reported-by: John Hsing <tsyj2007@gmail.com> Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx> --- read-cache.c | 6 ++-- t/t7510-status-index.sh | 50 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 53 insertions(+), 3 deletions(-) create mode 100755 t/t7510-status-index.sh
diff --git a/read-cache.c b/read-cache.c index 01a0e25..5790a91 100644 --- a/read-cache.c +++ b/read-cache.c @@ -1249,9 +1249,9 @@ static void convert_from_disk(struct ondisk_cache_entry *ondisk, struct cache_en static inline size_t estimate_cache_size(size_t ondisk_size, unsigned int entries) { - long per_entry; - - per_entry = sizeof(struct cache_entry) - sizeof(struct ondisk_cache_entry); + size_t fix_size_mem = offsetof(struct cache_entry, name); + size_t fix_size_dsk = offsetof(struct ondisk_cache_entry, name); + long per_entry = (fix_size_mem - fix_size_dsk + 7) & ~7; /* * Alignment can cause differences. This should be "alignof", but diff --git a/t/t7510-status-index.sh b/t/t7510-status-index.sh new file mode 100755 index 0000000..bca359d --- /dev/null +++ b/t/t7510-status-index.sh @@ -0,0 +1,50 @@ +#!/bin/sh + +test_description='git status with certain file name lengths' + +. ./test-lib.sh + +files="0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v w x y z" + +check() { + len=$1 + prefix=$2 + + for i in $files + do + : >$prefix$i + done + + test_expect_success "status, filename length $len" " + git add $prefix* && + git status + " + rm $prefix* .git/index +} + +check 1 +check 2 p +check 3 pr +check 4 pre +check 5 pref +check 6 prefi +check 7 prefix +check 8 prefix- +check 9 prefix-p +check 10 prefix-pr +check 11 prefix-pre +check 12 prefix-pref +check 13 prefix-prefi +check 14 prefix-prefix +check 15 prefix-prefix- +check 16 prefix-prefix-p +check 17 prefix-prefix-pr +check 18 prefix-prefix-pre +check 19 prefix-prefix-pref +check 20 prefix-prefix-prefi +check 21 prefix-prefix-prefix +check 22 prefix-prefix-prefix- +check 23 prefix-prefix-prefix-p +check 24 prefix-prefix-prefix-pr + +test_done
-- 1.7.7