Karsten Blees <karsten.bl...@gmail.com> writes:
> With core.ignorecase=true, name-hash.c builds a case insensitive index of
> all tracked directories. Currently, the existing cache entry structures are
> added multiple times to the same hashtable (with different name lengths and
> hash codes). However, there's only one dir_next pointer, which gets
> completely messed up in case of hash collisions. In the worst case, this
> causes an endless loop if ce == ce->dir_next:
>
> ---8<---
> # "V/", "V/XQANY/" and "WURZAUP/" all have the same hash_name
> mkdir V
> mkdir V/XQANY
> mkdir WURZAUP
> touch V/XQANY/test
> git init
> git config core.ignorecase true
> git add .
> git status
> ---8<---
Instead of using the scissors mark to confuse "am -c", indenting
this block would have been easier to later readers.
Also it is somewhat a shame that we do not use the above sample
collisions in a new test case.
> +static struct dir_entry *hash_dir_entry(struct index_state *istate,
> + struct cache_entry *ce, int namelen, int add)
> {
> /*
> * Throw each directory component in the hash for quick lookup
> * during a git status. Directory components are stored with their
> - * closing slash. Despite submodules being a directory, they never
> - * reach this point, because they are stored without a closing slash
> - * in the cache.
Is the description of submodule no longer relevant?
> - * Note that the cache_entry stored with the directory does not
> - * represent the directory itself. It is a pointer to an existing
> - * filename, and its only purpose is to represent existence of the
> - * directory in the cache. It is very possible multiple directory
> - * hash entries may point to the same cache_entry.
Is this paragraph no longer relevant? It seems to me that it still
holds true, given the way how dir->ce points at the given ce.
> + * closing slash.
> */
> + struct dir_entry *dir, *p;
> +
> + /* get length of parent directory */
> + while (namelen > 0 && !is_dir_sep(ce->name[namelen - 1]))
> + namelen--;
> + if (namelen <= 0)
> + return NULL;
> +
> + /* lookup existing entry for that directory */
> + dir = find_dir_entry(istate, ce->name, namelen);
> + if (add && !dir) {
> ...
> }
> +
> + /* add or release reference to this entry (and parents if 0) */
> + p = dir;
> + if (add) {
> + while (p && !(p->nr++))
> + p = p->parent;
> + } else {
> + while (p && p->nr && !(--p->nr))
> + p = p->parent;
> + }
Can we free the entry when its refcnt goes down to zero? If yes, is
it worth doing so?
> +
> + return dir;
> }
>
> static void hash_index_entry(struct index_state *istate, struct cache_entry
> *ce)
> @@ -74,7 +111,7 @@ static void hash_index_entry(struct index_state *istate,
> struct cache_entry *ce)
> if (ce->ce_flags & CE_HASHED)
> return;
> ce->ce_flags |= CE_HASHED;
> - ce->next = ce->dir_next = NULL;
> + ce->next = NULL;
> hash = hash_name(ce->name, ce_namelen(ce));
> pos = insert_hash(hash, ce, &istate->name_hash);
> if (pos) {
> @@ -82,8 +119,8 @@ static void hash_index_entry(struct index_state *istate,
> struct cache_entry *ce)
> *pos = ce;
> }
>
> - if (ignore_case)
> - hash_index_entry_directories(istate, ce);
> + if (ignore_case && !(ce->ce_flags & CE_UNHASHED))
> + hash_dir_entry(istate, ce, ce_namelen(ce), 1);
> }
>
> static void lazy_init_name_hash(struct index_state *istate)
> @@ -99,11 +136,33 @@ static void lazy_init_name_hash(struct index_state
> *istate)
>
> void add_name_hash(struct index_state *istate, struct cache_entry *ce)
> {
> + /* if already hashed, add reference to directory entries */
> + if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_STATE_MASK)
> + hash_dir_entry(istate, ce, ce_namelen(ce), 1);
Instead of a single function with "are we adding or removing?"
parameter, it would be a lot easier to read the callers if they are
wrapped in two helpers, add_dir_entry() and del_dir_entry() or
something, especially when the add=[0|1] parameter is constant for
each and every callsite (i.e. the codeflow determines it, not the
data).
> ce->ce_flags &= ~CE_UNHASHED;
> if (istate->name_hash_initialized)
> hash_index_entry(istate, ce);
> }
>
> +/*
> + * We don't actually *remove* it, we can just mark it invalid so that
> + * we won't find it in lookups.
> + *
> + * Not only would we have to search the lists (simple enough), but
> + * we'd also have to rehash other hash buckets in case this makes the
> + * hash bucket empty (common). So it's much better to just mark
> + * it.
> + */
> +void remove_name_hash(struct index_state *istate, struct cache_entry *ce)
> +{
> + /* if already hashed, release reference to directory entries */
> + if (ignore_case && (ce->ce_flags & CE_STATE_MASK) == CE_HASHED)
> + hash_dir_entry(istate, ce, ce_namelen(ce), 0);
And here as well.
> +
> + ce->ce_flags |= CE_UNHASHED;
> +}
> +
> static int slow_same_name(const char *name1, int len1, const char *name2,
> int len2)
> {
> if (len1 != len2)
> @@ -137,18 +196,7 @@ static int same_name(const struct cache_entry *ce, const
> char *name, int namelen
> if (!icase)
> return 0;
>
> - /*
> - * If the entry we're comparing is a filename (no trailing slash), then
> compare
> - * the lengths exactly.
> - */
> - if (name[namelen - 1] != '/')
> - return slow_same_name(name, namelen, ce->name, len);
> -
> - /*
> - * For a directory, we point to an arbitrary cache_entry filename. Just
> - * make sure the directory portion matches.
> - */
> - return slow_same_name(name, namelen, ce->name, namelen < len ? namelen
> : len);
> + return slow_same_name(name, namelen, ce->name, len);
Hmph, what is this change about? Nobody calls same_name() with a
directory name anymore or something?
Thanks.
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