From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: Strange merge failure (would be overwritten by merge / cannot merge) Date: Sun, 6 Sep 2009 14:37:07 -0700 (PDT) Message-ID: References: <4AA17874.7090905@debian.org> <7vr5ul99o2.fsf@alter.siamese.dyndns.org> <20090904234552.GA43797@gmail.com> <7vab191dz1.fsf@alter.siamese.dyndns.org> <7vzl98vrmt.fsf@alter.siamese.dyndns.org> <7vvdjwbhzv.fsf@alter.siamese.dyndns.org> <7v3a6z3lsg.fsf@alter.siamese.dyndns.org> <7vws4bzu7w.fsf@alter.siamese.dyndns.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Git Mailing List To: Junio C Hamano X-From: git-owner@vger.kernel.org Sun Sep 06 23:37:20 2009 Return-path: Envelope-to: gcvg-git-2@lo.gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1MkPQF-0006iP-UY for gcvg-git-2@lo.gmane.org; Sun, 06 Sep 2009 23:37:20 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758438AbZIFVhJ (ORCPT ); Sun, 6 Sep 2009 17:37:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758287AbZIFVhI (ORCPT ); Sun, 6 Sep 2009 17:37:08 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:59558 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752401AbZIFVhH (ORCPT ); Sun, 6 Sep 2009 17:37:07 -0400 Received: from imap1.linux-foundation.org (imap1.linux-foundation.org [140.211.169.55]) by smtp1.linux-foundation.org (8.14.2/8.13.5/Debian-3ubuntu1.1) with ESMTP id n86Lb7cE019671 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sun, 6 Sep 2009 14:37:08 -0700 Received: from localhost (localhost [127.0.0.1]) by imap1.linux-foundation.org (8.13.5.20060308/8.13.5/Debian-3ubuntu1.1) with ESMTP id n86Lb7iL026696; Sun, 6 Sep 2009 14:37:07 -0700 X-X-Sender: torvalds@localhost.localdomain In-Reply-To: User-Agent: Alpine 2.01 (LFD 1184 2008-12-16) X-Spam-Status: No, hits=-3.459 required=5 tests=AWL,BAYES_00 X-Spam-Checker-Version: SpamAssassin 3.2.4-osdl_revision__1.47__ X-MIMEDefang-Filter: lf$Revision: 1.188 $ X-Scanned-By: MIMEDefang 2.63 on 140.211.169.13 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Sun, 6 Sep 2009, Linus Torvalds wrote: > > And it's not working, for some reason I'm not seeing, but I thought I'd > send it to you just as a way to show where I'm trying to take this. Maybe > you see what my thinko is. Duh. My thinko was that I wasn't testing the right thing. The patch works fine, my test failures came from the fact that I was working on a branch with some other broken experimental features. Now, the patch I sent out did have a buglet: when a conflict happens, 'mask' will not have the conflicting bits we just added to 'dirmask'. But that buglet doesn't actually seem to affect any of the traverse_tree() callers, and they are fine with 'dirmask' being separate from 'mask'. So here's a slightly updated version, and it passes all the tests. Again, an important note: this is _not_ meant to change semantics, it's really only meant to re-organize the code so that we _can_ do look-ahead in the trees for conflicts. But in its current form, the look-ahead is limited to the next entry, the same as the old code. So there should be no semantic changes from this patch. Just avoid using 'df_name_compare()' and create that 'find_df_conflict()' function that can be expanded to actually look ahead more. Linus --- tree-walk.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 69 insertions(+), 3 deletions(-) diff --git a/tree-walk.c b/tree-walk.c index 02e2aed..fb5ca1e 100644 --- a/tree-walk.c +++ b/tree-walk.c @@ -62,7 +62,7 @@ void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1) static int entry_compare(struct name_entry *a, struct name_entry *b) { - return df_name_compare( + return base_name_compare( a->path, tree_entry_len(a->path, a->sha1), a->mode, b->path, tree_entry_len(b->path, b->sha1), b->mode); } @@ -138,6 +138,68 @@ char *make_traverse_path(char *path, const struct traverse_info *info, const str return path; } +/* + * See if 'entry' may conflict with a later tree entry in 't': if so, + * fill in 'conflict' with the conflicting tree entry from 't'. + * + * NOTE! Right now we do _not_ create a create a private copy of the tree + * descriptor, so we can't actually walk it any further without losing + * our place. We should change it to a loop over a copy of the tree + * descriptor, but then we'd also have to remember the skipped entries, + * so this is a hacky simple case that only handles the case we used + * to handle historically (ie clash in the very first entry) + * + * Note that only a regular file 'entry' can conflict with a later + * directory, since a directory with the same name will sort later. + */ +static int find_df_conflict(struct tree_desc *t, struct name_entry *entry, struct name_entry *conflict) +{ + int len; + + if (S_ISDIR(entry->mode)) + return 0; + len = tree_entry_len(entry->path, entry->sha1); + + while (t->size) { + int nlen; + + entry_extract(t, conflict); + nlen = tree_entry_len(conflict->path, conflict->sha1); + + /* + * We can only have a future conflict if the entry matches the + * beginning of the name exactly, and if the next character is + * smaller than '/'. + * + * Break out otherwise. + */ + if (nlen < len) + break; + if (memcmp(conflict->path, entry->path, nlen)) + break; + + /* + * FIXME! This is the case where we'd like to mark the tree + * entry used in the original 't' rather than modify 't'! + */ + if (nlen == len) { + update_tree_entry(t); + return 1; + } + + if (conflict->path[len] > '/') + break; + /* + * FIXME! Here we'd really like to do 'update_tree_entry(©);' + * but that requires us to remember the conflict position specially + * so now we just punt and stop looking for conflicts + */ + break; + } + entry_clear(conflict); + return 0; +} + int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info) { int ret = 0; @@ -179,14 +241,18 @@ int traverse_trees(int n, struct tree_desc *t, struct traverse_info *info) dirmask &= mask; /* - * Clear all the unused name-entries. + * Clear all the unused name-entries, and look for + * conflicts. */ for (i = 0; i < n; i++) { if (mask & (1ul << i)) continue; entry_clear(entry + i); + if (find_df_conflict(t+i, entry+last, entry+i)) + dirmask |= (1ul << i); } - ret = info->fn(n, mask, dirmask, entry, info); + + ret = info->fn(n, mask | dirmask, dirmask, entry, info); if (ret < 0) break; if (ret)