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authorJunio C Hamano <gitster@pobox.com>2013-04-01 15:59:53 (GMT)
committerJunio C Hamano <gitster@pobox.com>2013-04-01 15:59:53 (GMT)
commitc044bed8f0ed0275792cf66201579e42c0de7171 (patch)
treef39c9e19c58b25b9e88a25f3f5648fd496d7a1b6 /name-hash.c
parente81890548c2deff5a642ba1917e31742bfb15b96 (diff)
parent2092678cd5265e40dfb2b8e3adc8f2075faeece4 (diff)
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Merge branch 'kb/name-hash'
The code to keep track of what directory names are known to Git on platforms with case insensitive filesystems can get confused upon a hash collision between these pathnames and looped forever. * kb/name-hash: name-hash.c: fix endless loop with core.ignorecase=true
Diffstat (limited to 'name-hash.c')
-rw-r--r--name-hash.c182
1 files changed, 139 insertions, 43 deletions
diff --git a/name-hash.c b/name-hash.c
index 9bac31a..617c86c 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -32,38 +32,96 @@ static unsigned int hash_name(const char *name, int namelen)
return hash;
}
-static void hash_index_entry_directories(struct index_state *istate, struct cache_entry *ce)
+struct dir_entry {
+ struct dir_entry *next;
+ struct dir_entry *parent;
+ struct cache_entry *ce;
+ int nr;
+ unsigned int namelen;
+};
+
+static struct dir_entry *find_dir_entry(struct index_state *istate,
+ const char *name, unsigned int namelen)
+{
+ unsigned int hash = hash_name(name, namelen);
+ struct dir_entry *dir;
+
+ for (dir = lookup_hash(hash, &istate->dir_hash); dir; dir = dir->next)
+ if (dir->namelen == namelen &&
+ !strncasecmp(dir->ce->name, name, namelen))
+ return dir;
+ return NULL;
+}
+
+static struct dir_entry *hash_dir_entry(struct index_state *istate,
+ struct cache_entry *ce, int namelen)
{
/*
* 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.
+ * in index_state.name_hash (as ordinary cache_entries).
*
- * 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.
+ * Note that the cache_entry stored with the dir_entry merely
+ * supplies the name of the directory (up to dir_entry.namelen). We
+ * track the number of 'active' files in a directory in dir_entry.nr,
+ * so we can tell if the directory is still relevant, e.g. for git
+ * status. However, if cache_entries are removed, we cannot pinpoint
+ * an exact cache_entry that's still active. It is very possible that
+ * multiple dir_entries point to the same cache_entry.
*/
- unsigned int hash;
- void **pos;
+ struct dir_entry *dir;
+
+ /* 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 (!dir) {
+ /* not found, create it and add to hash table */
+ void **pdir;
+ unsigned int hash = hash_name(ce->name, namelen);
- const char *ptr = ce->name;
- while (*ptr) {
- while (*ptr && *ptr != '/')
- ++ptr;
- if (*ptr == '/') {
- ++ptr;
- hash = hash_name(ce->name, ptr - ce->name);
- pos = insert_hash(hash, ce, &istate->name_hash);
- if (pos) {
- ce->dir_next = *pos;
- *pos = ce;
- }
+ dir = xcalloc(1, sizeof(struct dir_entry));
+ dir->namelen = namelen;
+ dir->ce = ce;
+
+ pdir = insert_hash(hash, dir, &istate->dir_hash);
+ if (pdir) {
+ dir->next = *pdir;
+ *pdir = dir;
}
+
+ /* recursively add missing parent directories */
+ dir->parent = hash_dir_entry(istate, ce, namelen - 1);
}
+ return dir;
+}
+
+static void add_dir_entry(struct index_state *istate, struct cache_entry *ce)
+{
+ /* Add reference to the directory entry (and parents if 0). */
+ struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
+ while (dir && !(dir->nr++))
+ dir = dir->parent;
+}
+
+static void remove_dir_entry(struct index_state *istate, struct cache_entry *ce)
+{
+ /*
+ * Release reference to the directory entry (and parents if 0).
+ *
+ * Note: we do not remove / free the entry because there's no
+ * hash.[ch]::remove_hash and dir->next may point to other entries
+ * that are still valid, so we must not free the memory.
+ */
+ struct dir_entry *dir = hash_dir_entry(istate, ce, ce_namelen(ce));
+ while (dir && dir->nr && !(--dir->nr))
+ dir = dir->parent;
}
static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
@@ -74,7 +132,7 @@ 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 +140,8 @@ 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))
+ add_dir_entry(istate, ce);
}
static void lazy_init_name_hash(struct index_state *istate)
@@ -101,11 +159,33 @@ 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)
+ add_dir_entry(istate, ce);
+
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)
+ remove_dir_entry(istate, ce);
+
+ ce->ce_flags |= CE_UNHASHED;
+}
+
static int slow_same_name(const char *name1, int len1, const char *name2, int len2)
{
if (len1 != len2)
@@ -139,18 +219,7 @@ 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);
}
struct cache_entry *index_name_exists(struct index_state *istate, const char *name, int namelen, int icase)
@@ -166,27 +235,54 @@ struct cache_entry *index_name_exists(struct index_state *istate, const char *na
if (same_name(ce, name, namelen, icase))
return ce;
}
- if (icase && name[namelen - 1] == '/')
- ce = ce->dir_next;
- else
- ce = ce->next;
+ ce = ce->next;
}
/*
- * Might be a submodule. Despite submodules being directories,
+ * When looking for a directory (trailing '/'), it might be a
+ * submodule or a directory. Despite submodules being directories,
* they are stored in the name hash without a closing slash.
- * When ignore_case is 1, directories are stored in the name hash
- * with their closing slash.
+ * When ignore_case is 1, directories are stored in a separate hash
+ * table *with* their closing slash.
*
* The side effect of this storage technique is we have need to
+ * lookup the directory in a separate hash table, and if not found
* remove the slash from name and perform the lookup again without
* the slash. If a match is made, S_ISGITLINK(ce->mode) will be
* true.
*/
if (icase && name[namelen - 1] == '/') {
+ struct dir_entry *dir = find_dir_entry(istate, name, namelen);
+ if (dir && dir->nr)
+ return dir->ce;
+
ce = index_name_exists(istate, name, namelen - 1, icase);
if (ce && S_ISGITLINK(ce->ce_mode))
return ce;
}
return NULL;
}
+
+static int free_dir_entry(void *entry, void *unused)
+{
+ struct dir_entry *dir = entry;
+ while (dir) {
+ struct dir_entry *next = dir->next;
+ free(dir);
+ dir = next;
+ }
+ return 0;
+}
+
+void free_name_hash(struct index_state *istate)
+{
+ if (!istate->name_hash_initialized)
+ return;
+ istate->name_hash_initialized = 0;
+ if (ignore_case)
+ /* free directory entries */
+ for_each_hash(&istate->dir_hash, free_dir_entry, NULL);
+
+ free_hash(&istate->name_hash);
+ free_hash(&istate->dir_hash);
+}