Long ago in 628522ec14 (sha1-lookup: more memory efficient
search in sorted list of SHA-1, 2007-12-29) we added
sha1_entry_pos(), a binary search that uses the uniform
distribution of sha1s to scale the selection of mid-points.
As this was a performance experiment, we tied it to the
GIT_USE_LOOKUP environment variable and never enabled it by
default.
This code was successful in reducing the number of steps in
each search. But the overhead of the scaling ends up making
it slower when the cache is warm. Here are best-of-five
timings for running rev-list on linux.git, which will have
to look up every object:
$ time git rev-list --objects --all >/dev/null
real 0m35.357s
user 0m35.016s
sys 0m0.340s
$ time GIT_USE_LOOKUP=1 git rev-list --objects --all >/dev/null
real 0m37.364s
user 0m37.045s
sys 0m0.316s
The USE_LOOKUP version might have more benefit on a cold
cache, as the time to fault in each page would dominate. But
that would be for a single lookup. In practice, most
operations tend to look up many objects, and the whole pack
.idx will end up warm.
It's possible that the code could be better optimized to
compete with a naive binary search for the warm-cache case,
and we could have the best of both worlds. But over the
years nobody has done so, and this is largely dead code that
is rarely run outside of the test suite. Let's drop it in
the name of simplicity.
This lets us remove sha1_entry_pos() entirely, as the .idx
lookup code was the only caller. Note that sha1-lookup.c
still contains sha1_pos(), which differs from
sha1_entry_pos() in two ways:
- it has a different interface; it uses a function pointer
to access sha1 entries rather than a size/offset pair
describing the table's memory layout
- it only scales the initial selection of "mi", rather
than each iteration of the search
We can't get rid of this function, as it's called from
several places. It may be that we could replace it with a
simple binary search, but that's out of scope for this patch
(and would need benchmarking).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Code clean-up.
* jk/pack-name-cleanups:
index-pack: make pointer-alias fallbacks safer
replace snprintf with odb_pack_name()
odb_pack_keep(): stop generating keepfile name
sha1_file.c: make pack-name helper globally accessible
move odb_* declarations out of git-compat-util.h
A leak in a codepath to read from a packed object in (rare) cases
has been plugged.
* rs/sha1-file-plug-fallback-base-leak:
sha1_file: release fallback base's memory in unpack_entry()
We provide sha1_pack_name() and sha1_pack_index_name(), but
the more generic form (which takes its own strbuf and an
arbitrary extension) is only used to implement the other
two. Let's make it available, but clean up a few things:
1. Name it odb_pack_name(), as the original
sha1_get_pack_name() is long but not all that
descriptive.
2. Switch the strbuf argument to the beginning, so that it
matches similar path-building functions like
git_path_buf().
3. Clean up the out-dated docstring and move it to the
public declaration.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a pack entry that's used as a delta base is corrupt, unpack_entry()
marks it as unusable and then searches the object again in the hope that
it can be found in another pack or in a loose file. The memory for this
external base object is never released. Free it after use.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A crashing bug introduced in v2.11 timeframe has been found (it is
triggerable only in fast-import) and fixed.
* jk/clear-delta-base-cache-fix:
clear_delta_base_cache(): don't modify hashmap while iterating
On Thu, Jan 19, 2017 at 03:03:46PM +0100, Ulrich Spörlein wrote:
> > I suspect the patch below may fix things for you. It works around it by
> > walking over the lru list (either is fine, as they both contain all
> > entries, and since we're clearing everything, we don't care about the
> > order).
>
> Confirmed. With the patch applied, I can import the whole 55G in one go
> without any crashes or aborts. Thanks much!
Thanks. Here it is rolled up with a commit message.
-- >8 --
Subject: clear_delta_base_cache(): don't modify hashmap while iterating
Removing entries while iterating causes fast-import to
access an already-freed `struct packed_git`, leading to
various confusing errors.
What happens is that clear_delta_base_cache() drops the
whole contents of the cache by iterating over the hashmap,
calling release_delta_base_cache() on each entry. That
function removes the item from the hashmap. The hashmap code
may then shrink the table, but the hashmap_iter struct
retains an offset from the old table.
As a result, the next call to hashmap_iter_next() may claim
that the iteration is done, even though some items haven't
been visited.
The only caller of clear_delta_base_cache() is fast-import,
which wants to clear the cache because it is discarding the
packed_git struct for its temporary pack. So by failing to
remove all of the entries, we still have references to the
freed packed_git.
To make things even more confusing, this doesn't seem to
trigger with the test suite, because it depends on
complexities like the size of the hash table, which entries
got cleared, whether we try to access them before they're
evicted from the cache, etc.
So I've been able to identify the problem with large
imports like freebsd's svn import, or a fast-export of
linux.git. But nothing that would be reasonable to run as
part of the normal test suite.
We can fix this easily by iterating over the lru linked list
instead of the hashmap. They both contain the same entries,
and we can use the "safe" variant of the list iterator,
which exists for exactly this case.
Let's also add a warning to the hashmap API documentation to
reduce the chances of getting bit by this again.
Reported-by: Ulrich Spörlein <uqs@freebsd.org>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git grep" has been taught to optionally recurse into submodules.
* bw/grep-recurse-submodules:
grep: search history of moved submodules
grep: enable recurse-submodules to work on <tree> objects
grep: optionally recurse into submodules
grep: add submodules as a grep source type
submodules: load gitmodules file from commit sha1
submodules: add helper to determine if a submodule is initialized
submodules: add helper to determine if a submodule is populated
real_path: canonicalize directory separators in root parts
real_path: have callers use real_pathdup and strbuf_realpath
real_path: create real_pathdup
real_path: convert real_path_internal to strbuf_realpath
real_path: resolve symlinks by hand
A recent update to receive-pack to make it easier to drop garbage
objects made it clear that GIT_ALTERNATE_OBJECT_DIRECTORIES cannot
have a pathname with a colon in it (no surprise!), and this in turn
made it impossible to push into a repository at such a path. This
has been fixed by introducing a quoting mechanism used when
appending such a path to the colon-separated list.
* jk/quote-env-path-list-component:
t5615-alternate-env: double-quotes in file names do not work on Windows
t5547-push-quarantine: run the path separator test on Windows, too
tmp-objdir: quote paths we add to alternates
alternates: accept double-quoted paths
When a loose tree or commit is read by fsck (or any git
program), unpack_sha1_rest() checks whether there is extra
cruft at the end of the object file, after the zlib data.
Blobs that are streamed, however, do not have this check.
For normal git operations, it's not a big deal. We know the
sha1 and size checked out, so we have the object bytes we
wanted. The trailing garbage doesn't affect what we're
trying to do.
But since the point of fsck is to find corruption or other
problems, it should be more thorough. This patch teaches its
loose-sha1 reader to detect extra bytes after the zlib
stream and complain.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It's surprisingly hard to ask the sha1_file code to open a
_specific_ incarnation of a loose object. Most of the
functions take a sha1, and loop over the various object
types (packed versus loose) and locations (local versus
alternates) at a low level.
However, some tools like fsck need to look at a specific
file. This patch gives them a function they can use to open
the loose object at a given path.
The implementation unfortunately ends up repeating bits of
related functions, but there's not a good way around it
without some major refactoring of the whole sha1_file stack.
We need to mmap the specific file, then partially read the
zlib stream to know whether we're streaming or not, and then
finally either stream it or copy the data to a buffer.
We can do that by assembling some of the more arcane
internal sha1_file functions, but we end up having to
essentially reimplement unpack_sha1_file(), along with the
streaming bits of check_sha1_signature().
Still, most of the ugliness is contained in the new
function, and the interface is clean enough that it may be
reusable (though it seems unlikely anything but git-fsck
would care about opening a specific file).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we fail to open a corrupt loose object, we report an
error and mention the filename via sha1_file_name().
However, that function will always give us a path in the
local repository, whereas the corrupt object may have come
from an alternate. The result is a very misleading error
message.
Teach the open_sha1_file() and stat_sha1_file() helpers to
pass back the path they found, so that we can report it
correctly.
Note that the pointers we return go to static storage (e.g.,
from sha1_file_name()), which is slightly dangerous.
However, these helpers are static local helpers, and the
names are used for immediately generating error messages.
The simplicity is an acceptable tradeoff for the danger.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The codeflow of setting NOATIME and CLOEXEC on file descriptors Git
opens has been simplified.
We may want to drop the tip one, but we'll see.
* jc/git-open-cloexec:
sha1_file: stop opening files with O_NOATIME
git_open_cloexec(): use fcntl(2) w/ FD_CLOEXEC fallback
git_open(): untangle possible NOATIME and CLOEXEC interactions
A recent update to receive-pack to make it easier to drop garbage
objects made it clear that GIT_ALTERNATE_OBJECT_DIRECTORIES cannot
have a pathname with a colon in it (no surprise!), and this in turn
made it impossible to push into a repository at such a path. This
has been fixed by introducing a quoting mechanism used when
appending such a path to the colon-separated list.
* jk/quote-env-path-list-component:
t5615-alternate-env: double-quotes in file names do not work on Windows
t5547-push-quarantine: run the path separator test on Windows, too
tmp-objdir: quote paths we add to alternates
alternates: accept double-quoted paths
Migrate callers of real_path() who duplicate the retern value to use
real_pathdup or strbuf_realpath.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We read lists of alternates from objects/info/alternates
files (delimited by newline), as well as from the
GIT_ALTERNATE_OBJECT_DIRECTORIES environment variable
(delimited by colon or semi-colon, depending on the
platform).
There's no mechanism for quoting the delimiters, so it's
impossible to specify an alternate path that contains a
colon in the environment, or one that contains a newline in
a file. We've lived with that restriction for ages because
both alternates and filenames with colons are relatively
rare, and it's only a problem when the two meet. But since
722ff7f87 (receive-pack: quarantine objects until
pre-receive accepts, 2016-10-03), which builds on the
alternates system, every push causes the receiver to set
GIT_ALTERNATE_OBJECT_DIRECTORIES internally.
It would be convenient to have some way to quote the
delimiter so that we can represent arbitrary paths.
The simplest thing would be an escape character before a
quoted delimiter (e.g., "\:" as a literal colon). But that
creates a backwards compatibility problem: any path which
uses that escape character is now broken, and we've just
shifted the problem. We could choose an unlikely escape
character (e.g., something from the non-printable ASCII
range), but that's awkward to use.
Instead, let's treat names as unquoted unless they begin
with a double-quote, in which case they are interpreted via
our usual C-stylke quoting rules. This also breaks
backwards-compatibility, but in a smaller way: it only
matters if your file has a double-quote as the very _first_
character in the path (whereas an escape character is a
problem anywhere in the path). It's also consistent with
many other parts of git, which accept either a bare pathname
or a double-quoted one, and the sender can choose to quote
or not as required.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix a corner-case regression in a topic that graduated during the
v2.11 cycle.
* jk/alt-odb-cleanup:
alternates: re-allow relative paths from environment
Commit 670c359da (link_alt_odb_entry: handle normalize_path
errors, 2016-10-03) regressed the handling of relative paths
in the GIT_ALTERNATE_OBJECT_DIRECTORIES variable. It's not
entirely clear this was ever meant to work, but it _has_
worked for several years, so this commit restores the
original behavior.
When we get a path in GIT_ALTERNATE_OBJECT_DIRECTORIES, we
add it the path to the list of alternate object directories
as if it were found in objects/info/alternates, but with one
difference: we do not provide the link_alt_odb_entry()
function with a base for relative paths. That function
doesn't turn it into an absolute path, and we end up feeding
the relative path to the strbuf_normalize_path() function.
Most relative paths break out of the top-level directory
(e.g., "../foo.git/objects"), and thus normalizing fails.
Prior to 670c359da, we simply ignored the error, and due to
the way normalize_path_copy() was implemented it happened to
return the original path in this case. We then accessed the
alternate objects using this relative path.
By storing the relative path in the alt_odb list, the path
is relative to wherever we happen to be at the time we do an
object lookup. That means we look from $GIT_DIR in a bare
repository, and from the top of the worktree in a non-bare
repository.
If this were being designed from scratch, it would make
sense to pick a stable location (probably $GIT_DIR, or even
the object directory) and use that as the relative base,
turning the result into an absolute path. However, given
the history, at this point the minimal fix is to match the
pre-670c359da behavior.
We can do this simply by ignoring the error when we have no
relative base and using the original value (which we now
reliably have, thanks to strbuf_normalize_path()).
That still leaves us with a relative path that foils our
duplicate detection, and may act strangely if we ever
chdir() later in the process. We could solve that by storing
an absolute path based on getcwd(). That may be a good
future direction; for now we'll do just the minimum to fix
the regression.
The new t5615 script demonstrates the fix in its final three
tests. Since we didn't have any tests of the alternates
environment variable at all, it also adds some tests of
absolute paths.
Reported-by: Bryan Turner <bturner@atlassian.com>
Signed-off-by: Jeff King <peff@peff.net>
When we open object files, we try to do so with O_NOATIME.
This dates back to 144bde78e9 (Use O_NOATIME when opening
the sha1 files., 2005-04-23), which is an optimization to
avoid creating a bunch of dirty inodes when we're accessing
many objects. But a few things have changed since then:
1. In June 2005, git learned about packfiles, which means
we would do a lot fewer atime updates (rather than one
per object access, we'd generally get one per packfile).
2. In late 2006, Linux learned about "relatime", which is
generally the default on modern installs. So
performance around atimes updates is a non-issue there
these days.
All the world isn't Linux, but as it turns out, Linux
is the only platform to implement O_NOATIME in the
first place.
So it's very unlikely that this code is helping anybody
these days.
Helped-by: Jeff King <peff@peff.net>
[jc: took idea and log message from peff]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A platform might not support open(2) with O_CLOEXEC but may support
telling the same with fcntl(2) to flip FD_CLOEXEC bit on on an open
file descriptor. It is a fallback that is inherently racy and this
may not be worth doing, though.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git generally does not explicitly close file descriptors that were
open in the parent process when spawning a child process, but most
of the time the child does not want to access them. As Windows does
not allow removing or renaming a file that has a file descriptor
open, a slow-to-exit child can even break the parent process by
holding onto them. Use O_CLOEXEC flag to open files in various
codepaths.
* ls/git-open-cloexec:
read-cache: make sure file handles are not inherited by child processes
sha1_file: open window into packfiles with O_CLOEXEC
sha1_file: rename git_open_noatime() to git_open()
When fetching from a remote that has many tags that are irrelevant
to branches we are following, we used to waste way too many cycles
when checking if the object pointed at by a tag (that we are not
going to fetch!) exists in our repository too carefully.
* jk/fetch-quick-tag-following:
fetch: use "quick" has_sha1_file for tag following
The way we structured the fallback/retry mechanism for opening with
O_NOATIME and O_CLOEXEC meant that if we failed due to lack of
support to open the file with O_NOATIME option (i.e. EINVAL), we
would still try to drop O_CLOEXEC first and retry, and then drop
O_NOATIME. A platform on which O_NOATIME is defined in the header
without support from the kernel wouldn't have a chance to open with
O_CLOEXEC option due to this code structure.
Arguably, O_CLOEXEC is more important than O_NOATIME, as the latter
is mostly about performance, while the former can affect correctness.
Instead use O_CLOEXEC to open the file, and then use fcntl(2) to set
O_NOATIME on the resulting file descriptor. open(2) itself does not
cause atime to be updated according to Linus [*1*].
The helper to do the former can be usable in the codepath in
ce_compare_data() that was recently added to open a file descriptor
with O_CLOEXEC; use it while we are at it.
*1* <CA+55aFw83E+zOd+z5h-CA-3NhrLjVr-anL6pubrSWttYx3zu8g@mail.gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Updates the way approximate count of total objects is computed
while attempting to come up with a unique abbreviated object name,
which in turn needs to estimate how many hexdigits are necessary to
ensure uniqueness.
* jk/abbrev-auto:
find_unique_abbrev: move logic out of get_short_sha1()
When fetching from a remote that has many tags that are irrelevant
to branches we are following, we used to waste way too many cycles
when checking if the object pointed at by a tag (that we are not
going to fetch!) exists in our repository too carefully.
* jk/fetch-quick-tag-following:
fetch: use "quick" has_sha1_file for tag following
All processes that the Git main process spawns inherit the open file
descriptors of the main process. These leaked file descriptors can
cause problems.
Use the O_CLOEXEC flag similar to 05d1ed61 to fix the leaked file
descriptors.
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This function is meant to be used when reading from files in the
object store, and the original objective was to avoid smudging atime
of loose object files too often, hence its name. Because we'll be
extending its role in the next commit to also arrange the file
descriptors they return auto-closed in the child processes, rename
it to lose "noatime" part that is too specific.
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Codepaths involved in interacting alternate object store have
been cleaned up.
* jk/alt-odb-cleanup:
alternates: use fspathcmp to detect duplicates
sha1_file: always allow relative paths to alternates
count-objects: report alternates via verbose mode
fill_sha1_file: write into a strbuf
alternates: store scratch buffer as strbuf
fill_sha1_file: write "boring" characters
alternates: use a separate scratch space
alternates: encapsulate alt->base munging
alternates: provide helper for allocating alternate
alternates: provide helper for adding to alternates list
link_alt_odb_entry: refactor string handling
link_alt_odb_entry: handle normalize_path errors
t5613: clarify "too deep" recursion tests
t5613: do not chdir in main process
t5613: whitespace/style cleanups
t5613: use test_must_fail
t5613: drop test_valid_repo function
t5613: drop reachable_via function
When we auto-follow tags in a fetch, we look at all of the
tags advertised by the remote and fetch ones where we don't
already have the tag, but we do have the object it peels to.
This involves a lot of calls to has_sha1_file(), some of
which we can reasonably expect to fail. Since 45e8a74
(has_sha1_file: re-check pack directory before giving up,
2013-08-30), this may cause many calls to
reprepare_packed_git(), which is potentially expensive.
This has gone unnoticed for several years because it
requires a fairly unique setup to matter:
1. You need to have a lot of packs on the client side to
make reprepare_packed_git() expensive (the most
expensive part is finding duplicates in an unsorted
list, which is currently quadratic).
2. You need a large number of tag refs on the server side
that are candidates for auto-following (i.e., that the
client doesn't have). Each one triggers a re-read of
the pack directory.
3. Under normal circumstances, the client would
auto-follow those tags and after one large fetch, (2)
would no longer be true. But if those tags point to
history which is disconnected from what the client
otherwise fetches, then it will never auto-follow, and
those candidates will impact it on every fetch.
So when all three are true, each fetch pays an extra
O(nr_tags * nr_packs^2) cost, mostly in string comparisons
on the pack names. This was exacerbated by 47bf4b0
(prepare_packed_git_one: refactor duplicate-pack check,
2014-06-30) which uses a slightly more expensive string
check, under the assumption that the duplicate check doesn't
happen very often (and it shouldn't; the real problem here
is how often we are calling reprepare_packed_git()).
This patch teaches fetch to use HAS_SHA1_QUICK to sacrifice
accuracy for speed, in cases where we might be racy with a
simultaneous repack. This is similar to the fix in 0eeb077
(index-pack: avoid excessive re-reading of pack directory,
2015-06-09). As with that case, it's OK for has_sha1_file()
occasionally say "no I don't have it" when we do, because
the worst case is not a corruption, but simply that we may
fail to auto-follow a tag that points to it.
Here are results from the included perf script, which sets
up a situation similar to the one described above:
Test HEAD^ HEAD
----------------------------------------------------------
5550.4: fetch 11.21(10.42+0.78) 0.08(0.04+0.02) -99.3%
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Codepaths that read from an on-disk loose object were too loose in
validating what they are reading is a proper object file and
sometimes read past the data they read from the disk, which has
been corrected. H/t to Gustavo Grieco for reporting.
* jc/verify-loose-object-header:
unpack_sha1_header(): detect malformed object header
streaming: make sure to notice corrupt object
"git pack-objects" in a repository with many packfiles used to
spend a lot of time looking for/at objects in them; the accesses to
the packfiles are now optimized by checking the most-recently-used
packfile first.
* jk/pack-objects-optim-mru:
pack-objects: use mru list when iterating over packs
pack-objects: break delta cycles before delta-search phase
sha1_file: make packed_object_info public
provide an initializer for "struct object_info"
On a case-insensitive filesystem, we should realize that
"a/objects" and "A/objects" are the same path. We already
use fspathcmp() to check against the main object directory,
but until recently we couldn't use it for comparing against
other alternates (because their paths were not
NUL-terminated strings). But now we can, so let's do so.
Note that we also need to adjust count-objects to load the
config, so that it can see the setting of core.ignorecase
(this is required by the test, but is also a general bugfix
for users of count-objects).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We recursively expand alternates repositories, so that if A
borrows from B which borrows from C, A can see all objects.
For the root object database, we allow relative paths, so A
can point to B as "../B/objects". However, we currently do
not allow relative paths when recursing, so B must use an
absolute path to reach C.
That is an ancient protection from c2f493a (Transitively
read alternatives, 2006-05-07) that tries to avoid adding
the same alternate through two different paths. Since
5bdf0a8 (sha1_file: normalize alt_odb path before comparing
and storing, 2011-09-07), we use a normalized absolute path
for each alt_odb entry.
This means that in most cases the protection is no longer
necessary; we will detect the duplicate no matter how we got
there (but see below). And it's a good idea to get rid of
it, as it creates an unnecessary complication when setting
up recursive alternates (B has to know that A is going to
borrow from it and make sure to use an absolute path).
Note that our normalization doesn't actually look at the
filesystem, so it can still be fooled by crossing symbolic
links. But that's also true of absolute paths, so it's not a
good reason to disallow only relative paths (it's
potentially a reason to switch to real_path(), but that's a
separate and non-trivial change).
We adjust the test script here to demonstrate that this now
works, and add new tests to show that the normalization does
indeed suppress duplicates.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It's currently the responsibility of the caller to give
fill_sha1_file() enough bytes to write into, leading them to
manually compute the required lengths. Instead, let's just
write into a strbuf so that it's impossible to get this
wrong.
The alt_odb caller already has a strbuf, so this makes
things strictly simpler. The other caller, sha1_file_name(),
uses a static PATH_MAX buffer and dies when it would
overflow. We can convert this to a static strbuf, which
means our allocation cost is amortized (and as a bonus, we
no longer have to worry about PATH_MAX being too short for
normal use).
This does introduce some small overhead in fill_sha1_file(),
as each strbuf_addchar() will check whether it needs to
grow. However, between the optimization in fec501d
(strbuf_addch: avoid calling strbuf_grow, 2015-04-16) and
the fact that this is not generally called in a tight loop
(after all, the next step is typically to access the file!)
this probably doesn't matter. And even if it did, the right
place to micro-optimize is inside fill_sha1_file(), by
calling a single strbuf_grow() there.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We pre-size the scratch buffer to hold a loose object
filename of the form "xx/yyyy...", which leads to allocation
code that is hard to verify. We have to use some magic
numbers during the initial allocation, and then writers must
blindly assume that the buffer is big enough. Using a strbuf
makes it more clear that we cannot overflow.
Unfortunately, we do still need some magic numbers to grow
our strbuf before calling fill_sha1_path(), but the strbuf
growth is much closer to the point of use. This makes it
easier to see that it's correct, and opens the possibility
of pushing it even further down if fill_sha1_path() learns
to work on strbufs.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This function forms a sha1 as "xx/yyyy...", but skips over
the slot for the slash rather than writing it, leaving it to
the caller to do so. It also does not bother to put in a
trailing NUL, even though every caller would want it (we're
forming a path which by definition is not a directory, so
the only thing to do with it is feed it to a system call).
Let's make the lives of our callers easier by just writing
out the internal "/" and the NUL.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The alternate_object_database struct uses a single buffer
both for storing the path to the alternate, and as a scratch
buffer for forming object names. This is efficient (since
otherwise we'd end up storing the path twice), but it makes
life hard for callers who just want to know the path to the
alternate. They have to remember to stop reading after
"alt->name - alt->base" bytes, and to subtract one for the
trailing '/'.
It would be much simpler if they could simply access a
NUL-terminated path string. We could encapsulate this in a
function which puts a NUL in the scratch buffer and returns
the string, but that opens up questions about the lifetime
of the result. The first time another caller uses the
alternate, the scratch buffer may get other data tacked onto
it.
Let's instead just store the root path separately from the
scratch buffer. There aren't enough alternates being stored
for the duplicated data to matter for performance, and this
keeps things simple and safe for the callers.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The alternate_object_database struct holds a path to the
alternate objects, but we also use that buffer as scratch
space for forming loose object filenames. Let's pull that
logic into a helper function so that we can more easily
modify it.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Allocating a struct alternate_object_database is tricky, as
we must over-allocate the buffer to provide scratch space,
and then put in particular '/' and NUL markers.
Let's encapsulate this in a function so that the complexity
doesn't leak into callers (and so that we can modify it
later).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The submodule code wants to temporarily add an alternate
object store to our in-memory alt_odb list, but does it
manually. Let's provide a helper so it can reuse the code in
link_alt_odb_entry().
While we're adding our new add_to_alternates_memory(), let's
document add_to_alternates_file(), as the two are related.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The string handling in link_alt_odb_entry() is mostly an
artifact of the original version, which took the path as a
ptr/len combo, and did not have a NUL-terminated string
until we created one in the alternate_object_database
struct. But since 5bdf0a8 (sha1_file: normalize alt_odb
path before comparing and storing, 2011-09-07), the first
thing we do is put the path into a strbuf, which gives us
some easy opportunities for cleanup.
In particular:
- we call strlen(pathbuf.buf), which is silly; we can look
at pathbuf.len.
- even though we have a strbuf, we don't maintain its
"len" field when chomping extra slashes from the
end, and instead keep a separate "pfxlen" variable. We
can fix this and then drop "pfxlen" entirely.
- we don't check whether the path is usable until after we
allocate the new struct, making extra cleanup work for
ourselves. Since we have a NUL-terminated string, we can
bump the "is it usable" checks higher in the function.
While we're at it, we can move that logic to its own
helper, which makes the flow of link_alt_odb_entry()
easier to follow.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we add a new alternate to the list, we try to normalize
out any redundant "..", etc. However, we do not look at the
return value of normalize_path_copy(), and will happily
continue with a path that could not be normalized. Worse,
the normalizing process is done in-place, so we are left
with whatever half-finished working state the normalizing
function was in.
Fortunately, this cannot cause us to read past the end of
our buffer, as that working state will always leave the
NUL from the original path in place. And we do tend to
notice problems when we check is_directory() on the path.
But you can see the nonsense that we feed to is_directory
with an entry like:
this/../../is/../../way/../../too/../../deep/../../to/../../resolve
in your objects/info/alternates, which yields:
error: object directory
/to/e/deep/too/way//ects/this/../../is/../../way/../../too/../../deep/../../to/../../resolve
does not exist; check .git/objects/info/alternates.
We can easily fix this just by checking the return value.
But that makes it hard to generate a good error message,
since we're normalizing in-place and our input value has
been overwritten by cruft.
Instead, let's provide a strbuf helper that does an in-place
normalize, but restores the original contents on error. This
uses a second buffer under the hood, which is slightly less
efficient, but this is not a performance-critical code path.
The strbuf helper can also properly set the "len" parameter
of the strbuf before returning. Just doing:
normalize_path_copy(buf.buf, buf.buf);
will shorten the string, but leave buf.len at the original
length. That may be confusing to later code which uses the
strbuf.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The get_short_sha1() is only about reading short sha1s; we
do call it in a loop to check "is this long enough" for each
object, but otherwise it should not need to know about
things like our default_abbrev setting.
So instead of asking it to set default_automatic_abbrev as a
side-effect, let's just have find_unique_abbrev() pick the
right place to start its loop. This requires a separate
approximate_object_count() function, but that naturally
belongs with the rest of sha1_file.c.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Codepaths that read from an on-disk loose object were too loose in
validating what they are reading is a proper object file and
sometimes read past the data they read from the disk, which has
been corrected. H/t to Gustavo Grieco for reporting.
* jc/verify-loose-object-header:
unpack_sha1_header(): detect malformed object header
streaming: make sure to notice corrupt object
When opening a loose object file, we often do this sequence:
- prepare a short buffer for the object header (on stack)
- call unpack_sha1_header() and have early part of the object data
inflated, enough to fill the buffer
- parse that data in the short buffer, assuming that the first part
of the object is <typename> SP <length> NUL
Because the parsing function parse_sha1_header_extended() is not
given the number of bytes inflated into the header buffer, it you
craft a file whose early part inflates a garbage sequence without SP
or NUL, and replace a loose object with it, it will end up reading
past the end of the inflated data.
To correct this, do the following four things:
- rename unpack_sha1_header() to unpack_sha1_short_header() and
have unpack_sha1_header_to_strbuf() keep calling that as its
helper function. This will detect and report zlib errors, but is
not aware of the format of a loose object (as before).
- introduce unpack_sha1_header() that calls the same helper
function, and when zlib reports it inflated OK into the buffer,
check if the inflated data has NUL. This would ensure that
parsing function will terminate within the buffer that holds the
inflated header.
- update unpack_sha1_header_to_strbuf() to check if the resulting
buffer has NUL for the same effect.
- update parse_sha1_header_extended() to make sure that its loop to
find the SP that terminates the <typename> stops at NUL.
Essentially, this makes unpack_*() functions that are asked to
unpack a loose object header to be a bit more strict and detect an
input that cannot possibly be a valid object header, even before the
parsing function kicks in.
Reported-by: Gustavo Grieco <gustavo.grieco@imag.fr>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Recently we updated the code to manage the in-core cache that holds
objects that have recently been used to reconstitute other objects
that are stored as deltas against them, but the update used an
incorrect API function to manage the list of these objects. This
has been fixed.
* jk/delta-base-cache:
add_delta_base_cache: use list_for_each_safe
Sort the linked list of packs directly using llist_mergesort() instead
of building an array, calling qsort(3) and fixing up the list pointers.
This is shorter and less complicated.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "git diff --submodule={short,log}" mechanism has been enhanced
to allow "--submodule=diff" to show the patch between the submodule
commits bound to the superproject.
* jk/diff-submodule-diff-inline:
diff: teach diff to display submodule difference with an inline diff
submodule: refactor show_submodule_summary with helper function
submodule: convert show_submodule_summary to use struct object_id *
allow do_submodule_path to work even if submodule isn't checked out
diff: prepare for additional submodule formats
graph: add support for --line-prefix on all graph-aware output
diff.c: remove output_prefix_length field
cache: add empty_tree_oid object and helper function
