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authorJeff King <peff@peff.net>2014-02-27 05:56:31 -0500
committerJunio C Hamano <gitster@pobox.com>2014-02-27 12:04:23 -0800
commit0cc77c386cea7afebb54a5e7263ca37569ecfe7a (patch)
treee718edef67b0e74a1cdcb3850b0479aedb226585 /shallow.c
parent5f95c9f850b19b368c43ae399cc831b17a26a5ac (diff)
downloadgit-0cc77c386cea7afebb54a5e7263ca37569ecfe7a.tar.gz
shallow: use stat_validity to check for up-to-date file
When we are about to write the shallow file, we check that it has not changed since we last read it. Instead of hand-rolling this, we can use stat_validity. This is built around the index stat-check, so it is more robust than just checking the mtime, as we do now (it uses the same check as we do for index files). The new code also handles the case of a shallow file appearing unexpectedly. With the current code, two simultaneous processes making us shallow (e.g., two "git fetch --depth=1" running at the same time in a non-shallow repository) can race to overwrite each other. As a bonus, we also remove a race in determining the stat information of what we read (we stat and then open, leaving a race window; instead we should open and then fstat the descriptor). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'shallow.c')
-rw-r--r--shallow.c24
1 files changed, 7 insertions, 17 deletions
diff --git a/shallow.c b/shallow.c
index bbc98b55c0..1a6f022fa8 100644
--- a/shallow.c
+++ b/shallow.c
@@ -10,7 +10,7 @@
#include "commit-slab.h"
static int is_shallow = -1;
-static struct stat shallow_stat;
+static struct stat_validity shallow_stat;
static char *alternate_shallow_file;
void set_alternate_shallow_file(const char *path, int override)
@@ -52,12 +52,12 @@ int is_repository_shallow(void)
* shallow file should be used. We could just open it and it
* will likely fail. But let's do an explicit check instead.
*/
- if (!*path ||
- stat(path, &shallow_stat) ||
- (fp = fopen(path, "r")) == NULL) {
+ if (!*path || (fp = fopen(path, "r")) == NULL) {
+ stat_validity_clear(&shallow_stat);
is_shallow = 0;
return is_shallow;
}
+ stat_validity_update(&shallow_stat, fileno(fp));
is_shallow = 1;
while (fgets(buf, sizeof(buf), fp)) {
@@ -137,21 +137,11 @@ struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
void check_shallow_file_for_update(void)
{
- struct stat st;
-
- if (!is_shallow)
- return;
- else if (is_shallow == -1)
+ if (is_shallow == -1)
die("BUG: shallow must be initialized by now");
- if (stat(git_path("shallow"), &st))
- die("shallow file was removed during fetch");
- else if (st.st_mtime != shallow_stat.st_mtime
-#ifdef USE_NSEC
- || ST_MTIME_NSEC(st) != ST_MTIME_NSEC(shallow_stat)
-#endif
- )
- die("shallow file was changed during fetch");
+ if (!stat_validity_check(&shallow_stat, git_path("shallow")))
+ die("shallow file has changed since we read it");
}
#define SEEN_ONLY 1