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
This commit is contained in:
Junio C Hamano 2013-04-01 08:59:53 -07:00
commit c044bed8f0
4 changed files with 166 additions and 62 deletions

17
cache.h
View File

@ -132,7 +132,6 @@ struct cache_entry {
unsigned int ce_namelen;
unsigned char sha1[20];
struct cache_entry *next;
struct cache_entry *dir_next;
char name[FLEX_ARRAY]; /* more */
};
@ -268,25 +267,15 @@ struct index_state {
unsigned name_hash_initialized : 1,
initialized : 1;
struct hash_table name_hash;
struct hash_table dir_hash;
};
extern struct index_state the_index;
/* Name hashing */
extern void add_name_hash(struct index_state *istate, struct cache_entry *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.
*/
static inline void remove_name_hash(struct cache_entry *ce)
{
ce->ce_flags |= CE_UNHASHED;
}
extern void remove_name_hash(struct index_state *istate, struct cache_entry *ce);
extern void free_name_hash(struct index_state *istate);
#ifndef NO_THE_INDEX_COMPATIBILITY_MACROS

View File

@ -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;
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;
}
/* 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);
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);
}

View File

@ -46,7 +46,7 @@ static void replace_index_entry(struct index_state *istate, int nr, struct cache
{
struct cache_entry *old = istate->cache[nr];
remove_name_hash(old);
remove_name_hash(istate, old);
set_index_entry(istate, nr, ce);
istate->cache_changed = 1;
}
@ -460,7 +460,7 @@ int remove_index_entry_at(struct index_state *istate, int pos)
struct cache_entry *ce = istate->cache[pos];
record_resolve_undo(istate, ce);
remove_name_hash(ce);
remove_name_hash(istate, ce);
istate->cache_changed = 1;
istate->cache_nr--;
if (pos >= istate->cache_nr)
@ -483,7 +483,7 @@ void remove_marked_cache_entries(struct index_state *istate)
for (i = j = 0; i < istate->cache_nr; i++) {
if (ce_array[i]->ce_flags & CE_REMOVE)
remove_name_hash(ce_array[i]);
remove_name_hash(istate, ce_array[i]);
else
ce_array[j++] = ce_array[i];
}
@ -1515,8 +1515,7 @@ int discard_index(struct index_state *istate)
istate->cache_changed = 0;
istate->timestamp.sec = 0;
istate->timestamp.nsec = 0;
istate->name_hash_initialized = 0;
free_hash(&istate->name_hash);
free_name_hash(istate);
cache_tree_free(&(istate->cache_tree));
istate->initialized = 0;

20
t/t7062-wtstatus-ignorecase.sh Executable file
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@ -0,0 +1,20 @@
#!/bin/sh
test_description='git-status with core.ignorecase=true'
. ./test-lib.sh
test_expect_success 'status with hash collisions' '
# note: "V/", "V/XQANY/" and "WURZAUP/" produce the same hash code
# in name-hash.c::hash_name
mkdir V &&
mkdir V/XQANY &&
mkdir WURZAUP &&
touch V/XQANY/test &&
git config core.ignorecase true &&
git add . &&
# test is successful if git status completes (no endless loop)
git status
'
test_done