diff options
| -rw-r--r-- | read-cache.c | 140 | ||||
| -rwxr-xr-x | t/t0010-racy-git.sh | 24 |
2 files changed, 110 insertions, 54 deletions
diff --git a/read-cache.c b/read-cache.c index 693273620..780601f07 100644 --- a/read-cache.c +++ b/read-cache.c @@ -6,6 +6,7 @@ #include "cache.h" struct cache_entry **active_cache = NULL; +static time_t index_file_timestamp; unsigned int active_nr = 0, active_alloc = 0, active_cache_changed = 0; /* @@ -28,6 +29,64 @@ void fill_stat_cache_info(struct cache_entry *ce, struct stat *st) ce->ce_size = htonl(st->st_size); } +static int ce_compare_data(struct cache_entry *ce, struct stat *st) +{ + int match = -1; + int fd = open(ce->name, O_RDONLY); + + if (fd >= 0) { + unsigned char sha1[20]; + if (!index_fd(sha1, fd, st, 0, NULL)) + match = memcmp(sha1, ce->sha1, 20); + close(fd); + } + return match; +} + +static int ce_compare_link(struct cache_entry *ce, unsigned long expected_size) +{ + int match = -1; + char *target; + void *buffer; + unsigned long size; + char type[10]; + int len; + + target = xmalloc(expected_size); + len = readlink(ce->name, target, expected_size); + if (len != expected_size) { + free(target); + return -1; + } + buffer = read_sha1_file(ce->sha1, type, &size); + if (!buffer) { + free(target); + return -1; + } + if (size == expected_size) + match = memcmp(buffer, target, size); + free(buffer); + free(target); + return match; +} + +static int ce_modified_check_fs(struct cache_entry *ce, struct stat *st) +{ + switch (st->st_mode & S_IFMT) { + case S_IFREG: + if (ce_compare_data(ce, st)) + return DATA_CHANGED; + break; + case S_IFLNK: + if (ce_compare_link(ce, st->st_size)) + return DATA_CHANGED; + break; + default: + return TYPE_CHANGED; + } + return 0; +} + int ce_match_stat(struct cache_entry *ce, struct stat *st) { unsigned int changed = 0; @@ -83,57 +142,37 @@ int ce_match_stat(struct cache_entry *ce, struct stat *st) if (ce->ce_size != htonl(st->st_size)) changed |= DATA_CHANGED; - return changed; -} - -static int ce_compare_data(struct cache_entry *ce, struct stat *st) -{ - int match = -1; - int fd = open(ce->name, O_RDONLY); - if (fd >= 0) { - unsigned char sha1[20]; - if (!index_fd(sha1, fd, st, 0, NULL)) - match = memcmp(sha1, ce->sha1, 20); - close(fd); - } - return match; -} - -static int ce_compare_link(struct cache_entry *ce, unsigned long expected_size) -{ - int match = -1; - char *target; - void *buffer; - unsigned long size; - char type[10]; - int len; + /* + * Within 1 second of this sequence: + * echo xyzzy >file && git-update-index --add file + * running this command: + * echo frotz >file + * would give a falsely clean cache entry. The mtime and + * length match the cache, and other stat fields do not change. + * + * We could detect this at update-index time (the cache entry + * being registered/updated records the same time as "now") + * and delay the return from git-update-index, but that would + * effectively mean we can make at most one commit per second, + * which is not acceptable. Instead, we check cache entries + * whose mtime are the same as the index file timestamp more + * careful than others. + */ + if (!changed && + index_file_timestamp && + index_file_timestamp <= ntohl(ce->ce_mtime.sec)) + changed |= ce_modified_check_fs(ce, st); - target = xmalloc(expected_size); - len = readlink(ce->name, target, expected_size); - if (len != expected_size) { - free(target); - return -1; - } - buffer = read_sha1_file(ce->sha1, type, &size); - if (!buffer) { - free(target); - return -1; - } - if (size == expected_size) - match = memcmp(buffer, target, size); - free(buffer); - free(target); - return match; + return changed; } int ce_modified(struct cache_entry *ce, struct stat *st) { - int changed; + int changed, changed_fs; changed = ce_match_stat(ce, st); if (!changed) return 0; - /* * If the mode or type has changed, there's no point in trying * to refresh the entry - it's not going to match @@ -148,18 +187,9 @@ int ce_modified(struct cache_entry *ce, struct stat *st) if ((changed & DATA_CHANGED) && ce->ce_size != htonl(0)) return changed; - switch (st->st_mode & S_IFMT) { - case S_IFREG: - if (ce_compare_data(ce, st)) - return changed | DATA_CHANGED; - break; - case S_IFLNK: - if (ce_compare_link(ce, st->st_size)) - return changed | DATA_CHANGED; - break; - default: - return changed | TYPE_CHANGED; - } + changed_fs = ce_modified_check_fs(ce, st); + if (changed_fs) + return changed | changed_fs; return 0; } @@ -471,6 +501,7 @@ int read_cache(void) return active_nr; errno = ENOENT; + index_file_timestamp = 0; fd = open(get_index_file(), O_RDONLY); if (fd < 0) { if (errno == ENOENT) @@ -504,6 +535,7 @@ int read_cache(void) offset = offset + ce_size(ce); active_cache[i] = ce; } + index_file_timestamp = st.st_mtime; return active_nr; unmap: diff --git a/t/t0010-racy-git.sh b/t/t0010-racy-git.sh new file mode 100755 index 000000000..eb175b780 --- /dev/null +++ b/t/t0010-racy-git.sh @@ -0,0 +1,24 @@ +#!/bin/sh + +test_description='racy GIT' + +. ./test-lib.sh + +# This test can give false success if your machine is sufficiently +# slow or your trial happened to happen on second boundary. + +for trial in 0 1 2 3 4 5 6 7 8 9 +do + rm -f .git/index + echo frotz >infocom + echo xyzzy >activision + git update-index --add infocom activision + echo xyzzy >infocom + + files=`git diff-files -p` + test_expect_success \ + "Racy GIT trial #$trial" \ + 'test "" != "$files"' +done + +test_done |