[PATCH v2 17/25] write_sha1_file: freshen existing objects
- From
Jeff King <peff@peff.net>
- Date
- Oct 15, 2014, 22:42 UTC
- Message-ID
- <20141015224222.GQ25630@peff.net>
- In-Reply-To
- <20141015223244.GA25368@peff.net>
When we try to write a loose object file, we first check whether that object already exists. If so, we skip the write as an optimization. However, this can interfere with prune's strategy of using mtimes to mark files in progress.
For example, if a branch contains a particular tree object and is deleted, that tree object may become unreachable, and have an old mtime. If a new operation then tries to write the same tree, this ends up as a noop; we notice we already have the object and do nothing. A prune running simultaneously with this operation will see the object as old, and may delete it.
We can solve this by "freshening" objects that we avoid writing by updating their mtime. The algorithm for doing so is essentially the same as that of has_sha1_file. Therefore we provide a new (static) interface "check_and_freshen", which finds and optionally freshens the object. It's trivial to implement freshening and simple checking by tweaking a single parameter.
Signed-off-by: Jeff King <peff@peff.net> --- sha1_file.c | 51 +++++++++++++++++++++++++++++++++++++++------- t/t6501-freshen-objects.sh | 27 ++++++++++++++++++++++++ 2 files changed, 71 insertions(+), 7 deletions(-)
diff --git a/sha1_file.c b/sha1_file.c index eb410a2..d7f1838 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -443,27 +443,53 @@ void prepare_alt_odb(void) read_info_alternates(get_object_directory(), 0); } -static int has_loose_object_local(const unsigned char *sha1) +static int freshen_file(const char *fn) { - return !access(sha1_file_name(sha1), F_OK); + struct utimbuf t; + t.actime = t.modtime = time(NULL); + return !utime(fn, &t); } -int has_loose_object_nonlocal(const unsigned char *sha1) +static int check_and_freshen_file(const char *fn, int freshen) +{ + if (access(fn, F_OK)) + return 0; + if (freshen && freshen_file(fn)) + return 0; + return 1; +} + +static int check_and_freshen_local(const unsigned char *sha1, int freshen) +{ + return check_and_freshen_file(sha1_file_name(sha1), freshen); +} + +static int check_and_freshen_nonlocal(const unsigned char *sha1, int freshen) { struct alternate_object_database *alt; prepare_alt_odb(); for (alt = alt_odb_list; alt; alt = alt->next) { fill_sha1_path(alt->name, sha1); - if (!access(alt->base, F_OK)) + if (check_and_freshen_file(alt->base, freshen)) return 1; } return 0; } +static int check_and_freshen(const unsigned char *sha1, int freshen) +{ + return check_and_freshen_local(sha1, freshen) || + check_and_freshen_nonlocal(sha1, freshen); +} + +int has_loose_object_nonlocal(const unsigned char *sha1) +{ + return check_and_freshen_nonlocal(sha1, 0); +} + static int has_loose_object(const unsigned char *sha1) { - return has_loose_object_local(sha1) || - has_loose_object_nonlocal(sha1); + return check_and_freshen(sha1, 0); } static unsigned int pack_used_ctr; @@ -2966,6 +2992,17 @@ static int write_loose_object(const unsigned char *sha1, char *hdr, int hdrlen, return move_temp_to_file(tmp_file, filename); } +static int freshen_loose_object(const unsigned char *sha1) +{ + return check_and_freshen(sha1, 1); +} + +static int freshen_packed_object(const unsigned char *sha1) +{ + struct pack_entry e; + return find_pack_entry(sha1, &e) && freshen_file(e.p->pack_name); +} + int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *returnsha1) { unsigned char sha1[20]; @@ -2978,7 +3015,7 @@ int write_sha1_file(const void *buf, unsigned long len, const char *type, unsign write_sha1_file_prepare(buf, len, type, sha1, hdr, &hdrlen); if (returnsha1) hashcpy(returnsha1, sha1); - if (has_sha1_file(sha1)) + if (freshen_loose_object(sha1) || freshen_packed_object(sha1)) return 0; return write_loose_object(sha1, hdr, hdrlen, buf, len, 0); } diff --git a/t/t6501-freshen-objects.sh b/t/t6501-freshen-objects.sh index e25c47d..157f3f9 100755 --- a/t/t6501-freshen-objects.sh +++ b/t/t6501-freshen-objects.sh @@ -100,6 +100,33 @@ for repack in '' true; do test_expect_success "repository passes fsck ($title)" ' git fsck ' + + test_expect_success "abandon objects again ($title)" ' + git reset --hard HEAD^ && + find .git/objects -type f | + xargs test-chmtime -v -86400 + ' + + test_expect_success "start writing new commit with same tree ($title)" ' + tree=$( + GIT_INDEX_FILE=index.tmp && + export GIT_INDEX_FILE && + git read-tree HEAD && + add abandon && + add unrelated && + git write-tree + ) + ' + + test_expect_success "simultaneous gc ($title)" ' + git gc --prune=12.hours.ago + ' + + # tree should have been refreshed by write-tree + test_expect_success "finish writing out commit ($title)" ' + commit=$(echo foo | git commit-tree -p HEAD $tree) && + git update-ref HEAD $commit + ' done test_done
-- 2.1.2.596.g7379948