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fast-import: Avoid infinite loop after reset
Johannes Sixt noticed that a 'reset' command applied to a branch that is already active in the branch LRU cache can cause fast-import to relink the same branch into the LRU cache twice. This will cause the LRU cache to contain a cycle, making unload_one_branch run in an infinite loop as it tries to select the oldest branch for eviction. I have trivially fixed the problem by adding an active bit to each branch object; this bit indicates if the branch is already in the LRU and allows us to avoid trying to add it a second time. Converting the pack_id field into a bitfield makes this change take up no additional memory. Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
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@ -220,7 +220,8 @@ struct branch
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const char *name;
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struct tree_entry branch_tree;
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uintmax_t last_commit;
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unsigned int pack_id;
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unsigned active : 1;
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unsigned pack_id : PACK_ID_BITS;
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unsigned char sha1[20];
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};
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@ -528,6 +529,7 @@ static struct branch *new_branch(const char *name)
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b->table_next_branch = branch_table[hc];
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b->branch_tree.versions[0].mode = S_IFDIR;
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b->branch_tree.versions[1].mode = S_IFDIR;
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b->active = 0;
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b->pack_id = MAX_PACK_ID;
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branch_table[hc] = b;
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branch_count++;
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@ -1547,6 +1549,7 @@ static void unload_one_branch(void)
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e = active_branches;
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active_branches = e->active_next_branch;
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}
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e->active = 0;
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e->active_next_branch = NULL;
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if (e->branch_tree.tree) {
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release_tree_content_recursive(e->branch_tree.tree);
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@ -1559,10 +1562,13 @@ static void unload_one_branch(void)
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static void load_branch(struct branch *b)
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{
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load_tree(&b->branch_tree);
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b->active_next_branch = active_branches;
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active_branches = b;
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cur_active_branches++;
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branch_load_count++;
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if (!b->active) {
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b->active = 1;
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b->active_next_branch = active_branches;
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active_branches = b;
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cur_active_branches++;
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branch_load_count++;
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}
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}
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static void file_change_m(struct branch *b)
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