Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes: > Btw, even with Shawn's patch, I wonder if the index_data usage is correct. Hmph. gfi uses data in a "pack" in two quite different ways. A new object is written to an unfinalized pack. Such a pack already has "struct packed_git" allocated for it and a pointer to it is held in pack_data. As far as the core part of git (that is, sha1_file.c) is concerned, however, this pack does not even exist. It is still not part of packed_git list in sha1_file.c, and read_sha1_file() will not see objects in it, as no idx into the packfile exists yet. gfi has a table of objects in this pack and uses gfi_unpack_entry() function to retrieve data from it. A packfile is finalized in end_packfile(). The pack header and footer is recomputed, an idx file is written, and the pack is finally registered. Before that time p->index_data is not even used for that pack (it is initialized with NULL). So I do not think "index_data usage" can be incorrect, as there won't be any index_data usage with unfinalized pack, and the core part of git would not even have any mmap(2) (nor open fd) into its idx file before it is finalized. By the way, I was quite puzzled how the gfi_unpack_entry() function manages to work correctly when it has to read an object it deltified based on another object it wrote into the same unfinalized pack earlier. It knows where in the unfinalized pack it wrote the object, so it can find from its own "struct object_entry" the offset for the object, and calls unpack_entry() defined in the core to do the rest. However, most of the core does not really know about the other objects in this half-built pack. If the object is a delta, unpack_delta_entry() needs to find the delta base. And it needs to do that without having the idx. The trick (the code really needs a bit more documentation) is that gfi never writes anything but OFS_DELTA. So the core, even though it does not have the corresponding idx file, does not have to look up the object (in fact it does not even know what object to look up for the base, it only knows the offset). - To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
