Граф коммитов

25 Коммитов

Автор SHA1 Сообщение Дата
Kevin Willford 2a1bd45b2e name-hash: fix buffer overrun
Add check for the end of the entries for the thread partition.
Add test for lazy init name hash with specific directory structure

The lazy init hash name was causing a buffer overflow when the last
entry in the index was multiple folder deep with parent folders that
did not have any files in them.

This adds a test for the boundary condition of the thread partitions
with the folder structure that was triggering the buffer overflow.

The fix was to check if it is the last entry for the thread partition
in the handle_range_dir and not try to use the next entry in the cache.

Signed-off-by: Kevin Willford <kewillf@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-31 20:57:18 -07:00
Jeff Hostetler 846df809bc name-hash: perf improvement for lazy_init_name_hash
Improve performance of lazy_init_name_hash() when
ignore_case is set.  Teach name-hash to build the
istate.name_hash and istate.dir_hash simultaneously
using a forward-diving technique on the pathname
of the index_entry, rather than adding name_hash
entries and then searching backwards in the pathname
for parent directories.

This borrows algorithm ideas from clear_ce_flags_{1,dir}.

Multiple threads are used with the new algorithm to
speed hashmap construction.

This new code path is only used when threads are present
(a compiler settings) and when the index is large enough
to warrant the pthread complexity.

The code in clear_ce_flags_dir() uses a linear search to
find the adjacent index entries with the same prefix; a
binary search is used here handle_range_dir() to further
speed things up.

The size of LAZY_THREAD_COST was determined from rough
analysis using:
    t/helper/test-lazy-init-name-hash --analyze

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-24 11:00:03 -07:00
Jeff Hostetler 16f9b4cdd3 name-hash: specify initial size for istate.dir_hash table
Specify an initial size for the istate.dir_hash HashMap matching
the size of the istate.name_hash.

Previously hashmap_init() was given 0, causing a 64 bucket
hashmap to be created.  When working with very large
repositories, this would cause numerous rehash() calls to
realloc and rebalance the hashmap. This is especially true
when the worktree is deep, with many directories containing
a few files.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-22 13:41:41 -07:00
Jeff King 96ffc06f72 convert trivial cases to FLEX_ARRAY macros
Using FLEX_ARRAY macros reduces the amount of manual
computation size we have to do. It also ensures we don't
overflow size_t, and it makes sure we write the same number
of bytes that we allocated.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2016-02-22 14:51:09 -08:00
David Turner 41284eb0f9 name-hash: don't reuse cache_entry in dir_entry
Stop reusing cache_entry in dir_entry; doing so causes a
use-after-free bug.

During merges, we free entries that we no longer need in the
destination index.  But those entries might have also been stored in
the dir_entry cache, and when a later call to add_to_index found them,
they would be used after being freed.

To prevent this, change dir_entry to store a copy of the name instead
of a pointer to a cache_entry.  This entails some refactoring of code
that expects the cache_entry.

Keith McGuigan <kmcguigan@twitter.com> diagnosed this bug and wrote
the initial patch, but this version does not use any of Keith's code.

Helped-by: Keith McGuigan <kmcguigan@twitter.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: David Turner <dturner@twopensource.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-10-21 12:47:38 -07:00
Karsten Blees ab73a9d119 hashmap: add simplified hashmap_get_from_hash() API
Hashmap entries are typically looked up by just a key. The hashmap_get()
API expects an initialized entry structure instead, to support compound
keys. This flexibility is currently only needed by find_dir_entry() in
name-hash.c (and compat/win32/fscache.c in the msysgit fork). All other
(currently five) call sites of hashmap_get() have to set up a near emtpy
entry structure, resulting in duplicate code like this:

  struct hashmap_entry keyentry;
  hashmap_entry_init(&keyentry, hash(key));
  return hashmap_get(map, &keyentry, key);

Add a hashmap_get_from_hash() API that allows hashmap lookups by just
specifying the key and its hash code, i.e.:

  return hashmap_get_from_hash(map, hash(key), key);

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-07 13:56:35 -07:00
Jeremiah Mahler be99ec97c8 name-hash.c: replace cache_name_compare() with memcmp(3)
The same_name() private function wants a quick-and-exact check to
see if they two names are byte-for-byte identical first and then
fall back to the slow path.  Use memcmp(3) for the former to make it
clear that we do not want any "name" specific comparison.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-20 10:08:10 -07:00
Eric Sunshine 7b359ea6b3 name-hash: retire unused index_name_exists()
db5360f3f4 (name-hash: refactor polymorphic index_name_exists();
2013-09-17) split index_name_exists() into index_file_exists() and
index_dir_exists() but retained index_name_exists() as a thin wrapper
to avoid disturbing possible in-flight topics. Since this change
landed in 'master' some time ago and there are no in-flight topics
referencing index_name_exists(), retire it.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-02-24 15:26:33 -08:00
Karsten Blees 419a597f64 name-hash.c: remove cache entries instead of marking them CE_UNHASHED
The new hashmap implementation supports remove, so really remove unused
cache entries from the name hashmap instead of just marking them.

The CE_UNHASHED flag and CE_STATE_MASK are no longer needed.

Keep the CE_HASHED flag to prevent adding entries twice.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-11-18 13:04:24 -08:00
Karsten Blees 8b013788a1 name-hash.c: use new hash map implementation for cache entries
Note: the "ce->next = NULL;" in unpack-trees.c::do_add_entry can safely be
removed, as ce->next (now ce->ent.next) is always properly initialized in
name-hash.c::hash_index_entry.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-11-18 13:04:24 -08:00
Karsten Blees 1c8cca190a name-hash.c: remove unreferenced directory entries
The new hashmap implementation supports remove, so remove and free
directory entries that are no longer referenced by active cache entries.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-11-18 13:04:24 -08:00
Karsten Blees e05881a457 name-hash.c: use new hash map implementation for directories
Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-11-18 13:04:23 -08:00
Eric Sunshine d28eec2673 name-hash: stop storing trailing '/' on paths in index_state.dir_hash
When 5102c617 (Add case insensitivity support for directories when using
git status, 2010-10-03) added directories to the name-hash there was
only a single hash table in which both real cache entries and leading
directory prefixes were registered. To distinguish between the two types
of entries, directories were stored with a trailing '/'.

2092678c (name-hash.c: fix endless loop with core.ignorecase=true,
2013-02-28), however, moved directories to a separate hash table
(index_state.dir_hash) but retained the (now) redundant trailing '/',
thus callers continue to bear the burden of ensuring the slash's
presence before searching the index for a directory. Eliminate this
redundancy by storing paths in the dir-hash without the trailing '/'.

An important benefit of this change is that it eliminates undocumented
and dangerous behavior of dir.c:directory_exists_in_index_icase() in
which it assumes not only that it can validly access one character
beyond the end of its incoming directory argument, but also that that
character will unconditionally be a '/'. This perilous behavior was
"tolerated" because the string passed in by its lone caller always had a
'/' in that position, however, things broke [1] when 2eac2a4c (ls-files
-k: a directory only can be killed if the index has a non-directory,
2013-08-15) added a new caller which failed to respect the undocumented
assumption.

[1]: http://thread.gmane.org/gmane.comp.version-control.git/232727

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-09-17 10:08:07 -07:00
Eric Sunshine db5360f3f4 name-hash: refactor polymorphic index_name_exists()
Depending upon the absence or presence of a trailing '/' on the incoming
pathname, index_name_exists() checks either if a file is present in the
index or if a directory is represented within the index. Each caller
explicitly chooses the mode of operation by adding or removing a
trailing '/' before invoking index_name_exists().

Since these two modes of operations are disjoint and have no code in
common (one searches index_state.name_hash; the other dir_hash), they
can be represented more naturally as distinct functions: one to search
for a file, and one for a directory.

Splitting index searching into two functions relieves callers of the
artificial burden of having to add or remove a slash to select the mode
of operation; instead they just call the desired function. A subsequent
patch will take advantage of this benefit in order to eliminate the
requirement that the incoming pathname for a directory search must have
a trailing slash.

(In order to avoid disturbing in-flight topics, index_name_exists() is
retained as a thin wrapper dispatching either to index_dir_exists() or
index_file_exists().)

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-09-17 10:07:13 -07:00
Junio C Hamano c044bed8f0 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
2013-04-01 08:59:53 -07:00
Junio C Hamano c241e285e5 Merge branch 'nd/preallocate-hash'
When we know approximately how many entries we will have in the
hash-table, it makes sense to size the hash table to that number
from the beginning to avoid unnecessary rehashing.

* nd/preallocate-hash:
  Preallocate hash tables when the number of inserts are known in advance
2013-03-21 14:02:19 -07:00
Nguyễn Thái Ngọc Duy c73592812d Preallocate hash tables when the number of inserts are known in advance
This avoids unnecessary re-allocations and reinsertions. On webkit.git
(i.e. about 182k inserts to the name hash table), this reduces about
100ms out of 3s user time.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-16 22:57:29 -07:00
Karsten Blees 2092678cd5 name-hash.c: fix endless loop with core.ignorecase=true
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 (see t7062).

Use a separate hashtable and separate structures for the directory index
so that each directory entry has its own next pointer. Use reference
counting to track which directory entry contains files.

There are only slight changes to the name-hash.c API:
- new free_name_hash() used by read_cache.c::discard_index()
- remove_name_hash() takes an additional index_state parameter
- index_name_exists() for a directory (trailing '/') may return a cache
  entry that has been removed (CE_UNHASHED). This is not a problem as the
  return value is only used to check if the directory exists (dir.c) or to
  normalize casing of directory names (read-cache.c).

Getting rid of cache_entry.dir_next reduces memory consumption, especially
with core.ignorecase=false (which doesn't use that member at all).

With core.ignorecase=true, building the directory index is slightly faster
as we add / check the parent directory first (instead of going through all
directory levels for each file in the index). E.g. with WebKit (~200k
files, ~7k dirs), time spent in lazy_init_name_hash is reduced from 176ms
to 130ms.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-02-27 23:29:04 -08:00
Junio C Hamano c19387e799 name-hash: allow hashing an empty string
Usually we do not pass an empty string to the function hash_name()
because we almost always ask for hash values for a path that is a
candidate to be added to the index. However, check-ignore (and most
likely check-attr, but I didn't check) apparently has a callchain
to ask the hash value for an empty path when it was given a "." from
the top-level directory to ask "Is the path . excluded by default?"

Make sure that hash_name() does not overrun the end of the given
pathname even when it is empty.

Remove a sweep-the-issue-under-the-rug conditional in check-ignore
that avoided to pass an empty string to the callchain while at it.
It is a valid question to ask for check-ignore if the top-level is
set to be ignored by default, even though the answer is most likely
no, if only because there is currently no way to specify such an
entry in the .gitignore file. But it is an unusual thing to ask and
it is not worth optimizing for it by special casing at the top level
of the call chain.

Signed-off-by: Adam Spiers <git@adamspiers.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-02-19 14:00:12 -08:00
Johannes Sixt 395c73560b name-hash.c: always initialize dir_next pointer
Test t2021-checkout-overwrite.sh reveals a segfault in 'git add' on a
case-insensitive file system when git is compiled with XMALLOC_POISON
defined. The reason is that 2548183b (fix phantom untracked files when
core.ignorecase is set) added a new member dir_next to struct cache_entry,
but forgot to initialize it in all cases.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-11-01 15:29:18 -07:00
Jeff King 2548183bad fix phantom untracked files when core.ignorecase is set
When core.ignorecase is turned on and there are stale index
entries, "git commit" can sometimes report directories as
untracked, even though they contain tracked files.

You can see an example of this with:

    # make a case-insensitive repo
    git init repo && cd repo &&
    git config core.ignorecase true &&

    # with some tracked files in a subdir
    mkdir subdir &&
    > subdir/one &&
    > subdir/two &&
    git add . &&
    git commit -m base &&

    # now make the index entries stale
    touch subdir/* &&

    # and then ask commit to update those entries and show
    # us the status template
    git commit -a

which will report "subdir/"  as untracked, even though it
clearly contains two tracked files. What is happening in the
commit program is this:

  1. We load the index, and for each entry, insert it into the index's
     name_hash. In addition, if ignorecase is turned on, we make an
     entry in the name_hash for the directory (e.g., "contrib/"), which
     uses the following code from 5102c61's hash_index_entry_directories:

        hash = hash_name(ce->name, ptr - ce->name);
        if (!lookup_hash(hash, &istate->name_hash)) {
                pos = insert_hash(hash, &istate->name_hash);
		if (pos) {
			ce->next = *pos;
			*pos = ce;
		}
        }

     Note that we only add the directory entry if there is not already an
     entry.

  2. We run add_files_to_cache, which gets updated information for each
     cache entry. It helpfully inserts this information into the cache,
     which calls replace_index_entry. This in turn calls
     remove_name_hash() on the old entry, and add_name_hash() on the new
     one. But remove_name_hash doesn't actually remove from the hash, it
     only marks it as "no longer interesting" (from cache.h):

      /*
       * 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;
      }

     This is OK in the specific-file case, since the entries in the hash
     form a linked list, and we can just skip the "not here anymore"
     entries during lookup.

     But for the directory hash entry, we will _not_ write a new entry,
     because there is already one there: the old one that is actually no
     longer interesting!

  3. While traversing the directories, we end up in the
     directory_exists_in_index_icase function to see if a directory is
     interesting. This in turn checks index_name_exists, which will
     look up the directory in the index's name_hash. We see the old,
     deleted record, and assume there is nothing interesting. The
     directory gets marked as untracked, even though there are index
     entries in it.

The problem is in the code I showed above:

        hash = hash_name(ce->name, ptr - ce->name);
        if (!lookup_hash(hash, &istate->name_hash)) {
                pos = insert_hash(hash, &istate->name_hash);
		if (pos) {
			ce->next = *pos;
			*pos = ce;
		}
        }

Having a single cache entry that represents the directory is
not enough; that entry may go away if the index is changed.
It may be tempting to say that the problem is in our removal
method; if we removed the entry entirely instead of simply
marking it as "not here anymore", then we would know we need
to insert a new entry. But that only covers this particular
case of remove-replace. In the more general case, consider
something like this:

  1. We add "foo/bar" and "foo/baz" to the index. Each gets
     their own entry in name_hash, plus we make a "foo/"
     entry that points to "foo/bar".

  2. We remove the "foo/bar" entry from the index, and from
     the name_hash.

  3. We ask if "foo/" exists, and see no entry, even though
     "foo/baz" exists.

So we need that directory entry to have the list of _all_
cache entries that indicate that the directory is tracked.
So that implies making a linked list as we do for other
entries, like:

  hash = hash_name(ce->name, ptr - ce->name);
  pos = insert_hash(hash, &istate->name_hash);
  if (pos) {
	  ce->next = *pos;
	  *pos = ce;
  }

But that's not right either. In fact, it shows a second bug
in the current code, which is that the "ce->next" pointer is
supposed to be linking entries for a specific filename
entry, but here we are overwriting it for the directory
entry. So the same cache entry ends up in two linked lists,
but they share the same "next" pointer.

As it turns out, this second bug can't be triggered in the
current code. The "if (pos)" conditional is totally dead
code; pos will only be non-NULL if there was an existing
hash entry, and we already checked that there wasn't one
through our call to lookup_hash.

But fixing the first bug means taking out that call to
lookup_hash, which is going to activate the buggy dead code,
and we'll end up splicing the two linked lists together.

So we need to have a separate next pointer for the list in
the directory bucket, and we need to traverse that list in
index_name_exists when we are looking up a directory.

This bloats "struct cache_entry" by a few bytes. Which is
annoying, because it's only necessary when core.ignorecase
is enabled. There's not an easy way around it, short of
separating out the "next" pointers from cache_entry entirely
(i.e., having a separate "cache_entry_list" struct that gets
stored in the name_hash). In practice, it probably doesn't
matter; we have thousands of cache entries, compared to the
millions of objects (where adding 4 bytes to the struct
actually does impact performance).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2011-10-07 17:54:04 -07:00
Joshua Jensen 5102c6173c Add case insensitivity support for directories when using git status
When using a case preserving but case insensitive file system, directory
case can differ but still refer to the same physical directory.  git
status reports the directory with the alternate case as an Untracked
file.  (That is, when mydir/filea.txt is added to the repository and
then the directory on disk is renamed from mydir/ to MyDir/, git status
shows MyDir/ as being untracked.)

Support has been added in name-hash.c for hashing directories with a
terminating slash into the name hash. When index_name_exists() is called
with a directory (a name with a terminating slash), the name is not
found via the normal cache_name_compare() call, but it is found in the
slow_same_name() function.

Additionally, in dir.c, directory_exists_in_index_icase() allows newly
added directories deeper in the directory chain to be identified.

Ultimately, it would be better if the file list was read in case
insensitive alphabetical order from disk, but this change seems to
suffice for now.

The end result is the directory is looked up in a case insensitive
manner and does not show in the Untracked files list.

Signed-off-by: Joshua Jensen <jjensen@workspacewhiz.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2010-10-06 11:19:58 -07:00
Linus Torvalds cd2fef59ed Make hash_name_lookup able to do case-independent lookups
Right now nobody uses it, but "index_name_exists()" gets a flag so
you can enable it on a case-by-case basis.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-04-09 01:22:25 -07:00
Linus Torvalds df292c791a Make "index_name_exists()" return the cache_entry it found
This allows verify_absent() in unpack_trees() to use the hash chains
rather than looking it up using the binary search.

Perhaps more importantly, it's also going to be useful for the next phase,
where we actually start looking at the cache entry when we do
case-insensitive lookups and checking the result.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-04-09 01:22:25 -07:00
Linus Torvalds 96872bc200 Move name hashing functions into a file of its own
It's really totally separate functionality, and if we want to start
doing case-insensitive hash lookups, I'd rather do it when it's
separated out.

It also renames "remove_index_entry()" to "remove_name_hash()", because
that really describes the thing better. It doesn't actually remove the
index entry, that's done by "remove_index_entry_at()", which is something
very different, despite the similarity in names.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2008-04-09 01:22:25 -07:00