From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Matt McCutchen <matt@mattmccutchen.net>, git <git@vger.kernel.org>
Subject: Re: Protecting old temporary objects being reused from concurrent "git gc"?
Date: Tue, 15 Nov 2016 12:01:35 -0800 [thread overview]
Message-ID: <xmqqk2c4tsv4.fsf@gitster.mtv.corp.google.com> (raw)
In-Reply-To: <20161115174028.zvohfcw4jse3jrmm@sigill.intra.peff.net> (Jeff King's message of "Tue, 15 Nov 2016 12:40:29 -0500")
Jeff King <peff@peff.net> writes:
> I suspect the issue is that read-tree populates the cache-tree index
> extension, and then write-tree omits the object write before it even
> gets to write_sha1_file(). The solution is that it should probably be
> calling one of the freshen() functions (possibly just replacing
> has_sha1_file() with check_and_freshen(), but I haven't looked).
I think the final writing always happens via write_sha1_file(), but
an earlier cache-tree update that says "if we have a tree object
already, then use it, otherwise even though we know the object name
for this subtree, do not record it in the cache-tree" codepath may
decide to record the subtree's sha1 without refreshing the referent.
A fix may look like this.
cache-tree.c | 2 +-
cache.h | 1 +
sha1_file.c | 9 +++++++--
3 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/cache-tree.c b/cache-tree.c
index 345ea35963..3ae6d056b4 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -401,7 +401,7 @@ static int update_one(struct cache_tree *it,
if (repair) {
unsigned char sha1[20];
hash_sha1_file(buffer.buf, buffer.len, tree_type, sha1);
- if (has_sha1_file(sha1))
+ if (freshen_object(sha1))
hashcpy(it->sha1, sha1);
else
to_invalidate = 1;
diff --git a/cache.h b/cache.h
index 5cdea6833e..1f5694f308 100644
--- a/cache.h
+++ b/cache.h
@@ -1126,6 +1126,7 @@ extern int sha1_object_info(const unsigned char *, unsigned long *);
extern int hash_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1);
extern int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *return_sha1);
extern int hash_sha1_file_literally(const void *buf, unsigned long len, const char *type, unsigned char *sha1, unsigned flags);
+extern int freshen_object(const unsigned char *);
extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *);
extern int force_object_loose(const unsigned char *sha1, time_t mtime);
extern int git_open_cloexec(const char *name, int flags);
diff --git a/sha1_file.c b/sha1_file.c
index e030805497..1daeb05dcd 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -3275,6 +3275,11 @@ static int freshen_packed_object(const unsigned char *sha1)
return 1;
}
+int freshen_object(const unsigned char *sha1)
+{
+ return freshen_packed_object(sha1) || freshen_loose_object(sha1);
+}
+
int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1)
{
char hdr[32];
@@ -3284,7 +3289,7 @@ int write_sha1_file(const void *buf, unsigned long len, const char *type, unsign
* it out into .git/objects/??/?{38} file.
*/
write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen);
- if (freshen_packed_object(sha1) || freshen_loose_object(sha1))
+ if (freshen_object(sha1))
return 0;
return write_loose_object(sha1, hdr, hdrlen, buf, len, 0);
}
@@ -3302,7 +3307,7 @@ int hash_sha1_file_literally(const void *buf, unsigned long len, const char *typ
if (!(flags & HASH_WRITE_OBJECT))
goto cleanup;
- if (freshen_packed_object(sha1) || freshen_loose_object(sha1))
+ if (freshen_object(sha1))
goto cleanup;
status = write_loose_object(sha1, header, hdrlen, buf, len, 0);
next prev parent reply other threads:[~2016-11-15 20:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-15 14:13 Protecting old temporary objects being reused from concurrent "git gc"? Matt McCutchen
2016-11-15 17:06 ` Jeff King
2016-11-15 17:33 ` Matt McCutchen
2016-11-15 17:40 ` Jeff King
2016-11-15 19:08 ` [PATCH] git-gc.txt: expand discussion of races with other processes Matt McCutchen
2016-11-15 19:12 ` Protecting old temporary objects being reused from concurrent "git gc"? Matt McCutchen
2016-11-15 20:01 ` Junio C Hamano [this message]
2016-11-16 8:07 ` Jeff King
2016-11-16 18:18 ` Junio C Hamano
2016-11-16 18:58 ` Junio C Hamano
2016-11-17 1:04 ` Jeff King
2016-11-17 1:35 ` Re* " Junio C Hamano
2016-11-17 1:43 ` Jeff King
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