1 files changed, 71 insertions, 59 deletions

diff --git a/packfile.c b/packfile.c
index f0dc63e92f..6ab5233613 100644
--- a/packfile.c
+++ b/packfile.c
@@ -178,6 +178,7 @@ int load_idx(const char *path, const unsigned int hashsz, void *idx_map,
 		     */
 		    (sizeof(off_t) <= 4))
 			return error("pack too large for current definition of off_t in %s", path);
+		p->crc_offset = 8 + 4 * 256 + nr * hashsz;
 	}
 
 	p->index_version = version;
@@ -510,7 +511,6 @@ static int open_packed_git_1(struct packed_git *p)
 	struct pack_header hdr;
 	unsigned char hash[GIT_MAX_RAWSZ];
 	unsigned char *idx_hash;
-	long fd_flag;
 	ssize_t read_result;
 	const unsigned hashsz = the_hash_algo->rawsz;
 
@@ -554,16 +554,6 @@ static int open_packed_git_1(struct packed_git *p)
 	} else if (p->pack_size != st.st_size)
 		return error("packfile %s size changed", p->pack_name);
 
-	/* We leave these file descriptors open with sliding mmap;
-	 * there is no point keeping them open across exec(), though.
-	 */
-	fd_flag = fcntl(p->pack_fd, F_GETFD, 0);
-	if (fd_flag < 0)
-		return error("cannot determine file descriptor flags");
-	fd_flag |= FD_CLOEXEC;
-	if (fcntl(p->pack_fd, F_SETFD, fd_flag) == -1)
-		return error("cannot set FD_CLOEXEC");
-
 	/* Verify we recognize this pack file format. */
 	read_result = read_in_full(p->pack_fd, &hdr, sizeof(hdr));
 	if (read_result < 0)
@@ -587,9 +577,8 @@ static int open_packed_git_1(struct packed_git *p)
 			     " while index indicates %"PRIu32" objects",
 			     p->pack_name, ntohl(hdr.hdr_entries),
 			     p->num_objects);
-	if (lseek(p->pack_fd, p->pack_size - hashsz, SEEK_SET) == -1)
-		return error("end of packfile %s is unavailable", p->pack_name);
-	read_result = read_in_full(p->pack_fd, hash, hashsz);
+	read_result = pread_in_full(p->pack_fd, hash, hashsz,
+					p->pack_size - hashsz);
 	if (read_result < 0)
 		return error_errno("error reading from %s", p->pack_name);
 	if (read_result != hashsz)
@@ -1016,12 +1005,14 @@ void reprepare_packed_git(struct repository *r)
 {
 	struct object_directory *odb;
 
+	obj_read_lock();
 	for (odb = r->objects->odb; odb; odb = odb->next)
 		odb_clear_loose_cache(odb);
 
 	r->objects->approximate_object_count_valid = 0;
 	r->objects->packed_git_initialized = 0;
 	prepare_packed_git(r);
+	obj_read_unlock();
 }
 
 struct packed_git *get_packed_git(struct repository *r)
@@ -1098,7 +1089,23 @@ unsigned long get_size_from_delta(struct packed_git *p,
 	do {
 		in = use_pack(p, w_curs, curpos, &stream.avail_in);
 		stream.next_in = in;
+		/*
+		 * Note: the window section returned by use_pack() must be
+		 * available throughout git_inflate()'s unlocked execution. To
+		 * ensure no other thread will modify the window in the
+		 * meantime, we rely on the packed_window.inuse_cnt. This
+		 * counter is incremented before window reading and checked
+		 * before window disposal.
+		 *
+		 * Other worrying sections could be the call to close_pack_fd(),
+		 * which can close packs even with in-use windows, and to
+		 * reprepare_packed_git(). Regarding the former, mmap doc says:
+		 * "closing the file descriptor does not unmap the region". And
+		 * for the latter, it won't re-open already available packs.
+		 */
+		obj_read_unlock();
 		st = git_inflate(&stream, Z_FINISH);
+		obj_read_lock();
 		curpos += stream.next_in - in;
 	} while ((st == Z_OK || st == Z_BUF_ERROR) &&
 		 stream.total_out < sizeof(delta_head));
@@ -1174,11 +1181,11 @@ const struct packed_git *has_packed_and_bad(struct repository *r,
 	return NULL;
 }
 
-static off_t get_delta_base(struct packed_git *p,
-				    struct pack_window **w_curs,
-				    off_t *curpos,
-				    enum object_type type,
-				    off_t delta_obj_offset)
+off_t get_delta_base(struct packed_git *p,
+		     struct pack_window **w_curs,
+		     off_t *curpos,
+		     enum object_type type,
+		     off_t delta_obj_offset)
 {
 	unsigned char *base_info = use_pack(p, w_curs, *curpos, NULL);
 	off_t base_offset;
@@ -1219,30 +1226,32 @@ static off_t get_delta_base(struct packed_git *p,
  * the final object lookup), but more expensive for OFS deltas (we
  * have to load the revidx to convert the offset back into a sha1).
  */
-static const unsigned char *get_delta_base_sha1(struct packed_git *p,
-						struct pack_window **w_curs,
-						off_t curpos,
-						enum object_type type,
-						off_t delta_obj_offset)
+static int get_delta_base_oid(struct packed_git *p,
+			      struct pack_window **w_curs,
+			      off_t curpos,
+			      struct object_id *oid,
+			      enum object_type type,
+			      off_t delta_obj_offset)
 {
 	if (type == OBJ_REF_DELTA) {
 		unsigned char *base = use_pack(p, w_curs, curpos, NULL);
-		return base;
+		oidread(oid, base);
+		return 0;
 	} else if (type == OBJ_OFS_DELTA) {
 		struct revindex_entry *revidx;
 		off_t base_offset = get_delta_base(p, w_curs, &curpos,
 						   type, delta_obj_offset);
 
 		if (!base_offset)
-			return NULL;
+			return -1;
 
 		revidx = find_pack_revindex(p, base_offset);
 		if (!revidx)
-			return NULL;
+			return -1;
 
-		return nth_packed_object_sha1(p, revidx->nr);
+		return nth_packed_object_id(oid, p, revidx->nr);
 	} else
-		return NULL;
+		return -1;
 }
 
 static int retry_bad_packed_offset(struct repository *r,
@@ -1255,7 +1264,7 @@ static int retry_bad_packed_offset(struct repository *r,
 	revidx = find_pack_revindex(p, obj_offset);
 	if (!revidx)
 		return OBJ_BAD;
-	nth_packed_object_oid(&oid, p, revidx->nr);
+	nth_packed_object_id(&oid, p, revidx->nr);
 	mark_bad_packed_object(p, oid.hash);
 	type = oid_object_info(r, &oid, NULL);
 	if (type <= OBJ_NONE)
@@ -1457,6 +1466,14 @@ static void add_delta_base_cache(struct packed_git *p, off_t base_offset,
 	struct delta_base_cache_entry *ent = xmalloc(sizeof(*ent));
 	struct list_head *lru, *tmp;
 
+	/*
+	 * Check required to avoid redundant entries when more than one thread
+	 * is unpacking the same object, in unpack_entry() (since its phases I
+	 * and III might run concurrently across multiple threads).
+	 */
+	if (in_delta_base_cache(p, base_offset))
+		return;
+
 	delta_base_cached += base_size;
 
 	list_for_each_safe(lru, tmp, &delta_base_cache_lru) {
@@ -1542,20 +1559,16 @@ int packed_object_info(struct repository *r, struct packed_git *p,
 		}
 	}
 
-	if (oi->delta_base_sha1) {
+	if (oi->delta_base_oid) {
 		if (type == OBJ_OFS_DELTA || type == OBJ_REF_DELTA) {
-			const unsigned char *base;
-
-			base = get_delta_base_sha1(p, &w_curs, curpos,
-						   type, obj_offset);
-			if (!base) {
+			if (get_delta_base_oid(p, &w_curs, curpos,
+					       oi->delta_base_oid,
+					       type, obj_offset) < 0) {
 				type = OBJ_BAD;
 				goto out;
 			}
-
-			hashcpy(oi->delta_base_sha1, base);
 		} else
-			hashclr(oi->delta_base_sha1);
+			oidclr(oi->delta_base_oid);
 	}
 
 	oi->whence = in_delta_base_cache(p, obj_offset) ? OI_DBCACHED :
@@ -1586,7 +1599,15 @@ static void *unpack_compressed_entry(struct packed_git *p,
 	do {
 		in = use_pack(p, w_curs, curpos, &stream.avail_in);
 		stream.next_in = in;
+		/*
+		 * Note: we must ensure the window section returned by
+		 * use_pack() will be available throughout git_inflate()'s
+		 * unlocked execution. Please refer to the comment at
+		 * get_size_from_delta() to see how this is done.
+		 */
+		obj_read_unlock();
 		st = git_inflate(&stream, Z_FINISH);
+		obj_read_lock();
 		if (!stream.avail_out)
 			break; /* the payload is larger than it should be */
 		curpos += stream.next_in - in;
@@ -1671,7 +1692,7 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 			off_t len = revidx[1].offset - obj_offset;
 			if (check_pack_crc(p, &w_curs, obj_offset, len, revidx->nr)) {
 				struct object_id oid;
-				nth_packed_object_oid(&oid, p, revidx->nr);
+				nth_packed_object_id(&oid, p, revidx->nr);
 				error("bad packed object CRC for %s",
 				      oid_to_hex(&oid));
 				mark_bad_packed_object(p, oid.hash);
@@ -1760,7 +1781,7 @@ void *unpack_entry(struct repository *r, struct packed_git *p, off_t obj_offset,
 			struct object_id base_oid;
 			revidx = find_pack_revindex(p, obj_offset);
 			if (revidx) {
-				nth_packed_object_oid(&base_oid, p, revidx->nr);
+				nth_packed_object_id(&base_oid, p, revidx->nr);
 				error("failed to read delta base object %s"
 				      " at offset %"PRIuMAX" from %s",
 				      oid_to_hex(&base_oid), (uintmax_t)obj_offset,
@@ -1847,36 +1868,27 @@ int bsearch_pack(const struct object_id *oid, const struct packed_git *p, uint32
 			    index_lookup, index_lookup_width, result);
 }
 
-const unsigned char *nth_packed_object_sha1(struct packed_git *p,
-					    uint32_t n)
+int nth_packed_object_id(struct object_id *oid,
+			 struct packed_git *p,
+			 uint32_t n)
 {
 	const unsigned char *index = p->index_data;
 	const unsigned int hashsz = the_hash_algo->rawsz;
 	if (!index) {
 		if (open_pack_index(p))
-			return NULL;
+			return -1;
 		index = p->index_data;
 	}
 	if (n >= p->num_objects)
-		return NULL;
+		return -1;
 	index += 4 * 256;
 	if (p->index_version == 1) {
-		return index + (hashsz + 4) * n + 4;
+		oidread(oid, index + (hashsz + 4) * n + 4);
 	} else {
 		index += 8;
-		return index + hashsz * n;
+		oidread(oid, index + hashsz * n);
 	}
-}
-
-const struct object_id *nth_packed_object_oid(struct object_id *oid,
-					      struct packed_git *p,
-					      uint32_t n)
-{
-	const unsigned char *hash = nth_packed_object_sha1(p, n);
-	if (!hash)
-		return NULL;
-	hashcpy(oid->hash, hash);
-	return oid;
+	return 0;
 }
 
 void check_pack_index_ptr(const struct packed_git *p, const void *vptr)
@@ -2055,7 +2067,7 @@ int for_each_object_in_pack(struct packed_git *p,
 		else
 			pos = i;
 
-		if (!nth_packed_object_oid(&oid, p, pos))
+		if (nth_packed_object_id(&oid, p, pos) < 0)
 			return error("unable to get sha1 of object %u in %s",
 				     pos, p->pack_name);