When writing both loose and packed references to disk we first create a
lockfile, write the updated values into that lockfile, and on commit we
rename the file into place. According to filesystem developers, this
behaviour is broken because applications should always sync data to disk
before doing the final rename to ensure data consistency [1][2][3]. If
applications fail to do this correctly, a hard crash of the machine can
easily result in corrupted on-disk data.
This kind of corruption can in fact be easily observed with Git when the
machine hard-resets shortly after writing references to disk. On
machines with ext4, this will likely lead to the "empty files" problem:
the file has been renamed, but its data has not been synced to disk. The
result is that the reference is corrupt, and in the worst case this can
lead to data loss.
Implement a new option to harden references so that users and admins can
avoid this scenario by syncing locked loose and packed references to
disk before we rename them into place.
[1]: https://thunk.org/tytso/blog/2009/03/15/dont-fear-the-fsync/
[2]: https://btrfs.wiki.kernel.org/index.php/FAQ (What are the crash guarantees of overwrite-by-rename)
[3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/admin-guide/ext4.rst (see auto_da_alloc)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit adds aggregate options for the core.fsync setting that are
more user-friendly. These options are specified in terms of 'levels of
safety', indicating which Git operations are considered to be sync
points for durability.
The new documentation is also included here in its entirety for ease of
review.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This change introduces code to parse the core.fsync setting and
configure the fsync_components variable.
core.fsync is configured as a comma-separated list of component names to
sync. Each time a core.fsync variable is encountered in the
configuration heirarchy, we start off with a clean state with the
platform default value. Passing 'none' resets the value to indicate
nothing will be synced. We gather all negative and positive entries from
the comma separated list and then compute the new value by removing all
the negative entries and adding all of the positive entries.
We issue a warning for components that are not recognized so that the
configuration code is compatible with configs from future versions of
Git with more repo components.
Complete documentation for the new setting is included in a later patch
in the series so that it can be reviewed once in final form.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit introduces the `core.fsyncMethod` configuration
knob, which can currently be set to `fsync` or `writeout-only`.
The new writeout-only mode attempts to tell the operating system to
flush its in-memory page cache to the storage hardware without issuing a
CACHE_FLUSH command to the storage controller.
Writeout-only fsync is significantly faster than a vanilla fsync on
common hardware, since data is written to a disk-side cache rather than
all the way to a durable medium. Later changes in this patch series will
take advantage of this primitive to implement batching of hardware
flushes.
When git_fsync is called with FSYNC_WRITEOUT_ONLY, it may fail and the
caller is expected to do an ordinary fsync as needed.
On Apple platforms, the fsync system call does not issue a CACHE_FLUSH
directive to the storage controller. This change updates fsync to do
fcntl(F_FULLFSYNC) to make fsync actually durable. We maintain parity
with existing behavior on Apple platforms by setting the default value
of the new core.fsyncMethod option.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The configuration variable 'core.abbrev' can be set to 'no' to
force no abbreviation regardless of the hash algorithm.
* ew/decline-core-abbrev:
core.abbrev=no disables abbreviations
This allows users to write hash-agnostic scripts and configs by
disabling abbreviations. Using "-c core.abbrev=40" will be
insufficient with SHA-256, and "-c core.abbrev=64" won't work with
SHA-1 repos today.
Signed-off-by: Eric Wong <e@80x24.org>
[jc: tweaked implementation, added doc and a test]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The core.multiPackIndex setting has been around since c4d25228eb
(config: create core.multiPackIndex setting, 2018-07-12), but has been
disabled by default. If a user wishes to use the multi-pack-index
feature, then they must enable this config and run 'git multi-pack-index
write'.
The multi-pack-index feature is relatively stable now, so make the
config option true by default. For users that do not use a
multi-pack-index, the only extra cost will be a file lookup to see if a
multi-pack-index file exists (once per process, per object directory).
Also, this config option will be referenced by an upcoming
"incremental-repack" task in the maintenance builtin, so move the config
option into the repository settings struct. Note that if
GIT_TEST_MULTI_PACK_INDEX=1, then we want to ignore the config option
and treat core.multiPackIndex as enabled.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Clarify that core.deltaBaseCacheLimit is per-thread, as can be seen from
the fact that cache usage (base_cache_used in struct thread_local in
builtin/index-pack.c) is tracked individually for each thread and
compared against delta_base_cache_limit.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A new config value for core.fsmonitorHookVersion was added to be able
to force the version of the fsmonitor hook. Possible values are 1 or 2.
When this is not set the code will use a value of -1 and attempt to use
version 2 of the hook first and if that fails will attempt version 1.
Signed-off-by: Kevin Willford <Kevin.Willford@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Management of sparsely checked-out working tree has gained a
dedicated "sparse-checkout" command.
* ds/sparse-cone: (21 commits)
sparse-checkout: improve OS ls compatibility
sparse-checkout: respect core.ignoreCase in cone mode
sparse-checkout: check for dirty status
sparse-checkout: update working directory in-process for 'init'
sparse-checkout: cone mode should not interact with .gitignore
sparse-checkout: write using lockfile
sparse-checkout: use in-process update for disable subcommand
sparse-checkout: update working directory in-process
sparse-checkout: sanitize for nested folders
unpack-trees: add progress to clear_ce_flags()
unpack-trees: hash less in cone mode
sparse-checkout: init and set in cone mode
sparse-checkout: use hashmaps for cone patterns
sparse-checkout: add 'cone' mode
trace2: add region in clear_ce_flags
sparse-checkout: create 'disable' subcommand
sparse-checkout: add '--stdin' option to set subcommand
sparse-checkout: 'set' subcommand
clone: add --sparse mode
sparse-checkout: create 'init' subcommand
...
Turns out that it don't work so well on Vista, see
https://github.com/git-for-windows/git/issues/1742 for details.
According to https://devblogs.microsoft.com/oldnewthing/?p=8873, it
*should* work on Windows Vista and later.
But apparently there are issues on Windows Vista when pipes are
involved. Given that Windows Vista is past its end of life (official
support ended on April 11th, 2017), let's not spend *too* much time on
this issue and just disable the file handle inheritance restriction on
any Windows version earlier than Windows 7.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The sparse-checkout feature can have quadratic performance as
the number of patterns and number of entries in the index grow.
If there are 1,000 patterns and 1,000,000 entries, this time can
be very significant.
Create a new Boolean config option, core.sparseCheckoutCone, to
indicate that we expect the sparse-checkout file to contain a
more limited set of patterns. This is a separate config setting
from core.sparseCheckout to avoid breaking older clients by
introducing a tri-state option.
The config option does nothing right now, but will be expanded
upon in a later commit.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The feature.manyFiles setting is suitable for repos with many
files in the working directory. By setting index.version=4 and
core.untrackedCache=true, commands such as 'git status' should
improve.
While adding this setting, modify the index version precedence
tests to check how this setting overrides the default for
index.version is unset.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The commit-graph feature has seen a lot of activity in the past
year or so since it was introduced. The feature is a critical
performance enhancement for medium- to large-sized repos, and
does not significantly hurt small repos.
Change the defaults for core.commitGraph and gc.writeCommitGraph
to true so users benefit from this feature by default.
There are several places in the test suite where the environment
variable GIT_TEST_COMMIT_GRAPH is disabled to avoid reading a
commit-graph, if it exists. The config option overrides the
environment, so swap these. Some GIT_TEST_COMMIT_GRAPH assignments
remain, and those are to avoid writing a commit-graph when a new
commit is created.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Applying CodingGuidelines about monospace on pathnames and URLs.
See Documentation/CodingGuidelines.txt for more information.
Signed-off-by: Corentin BOMPARD <corentin.bompard@etu.univ-lyon1.fr>
Signed-off-by: Nathan BERBEZIER <nathan.berbezier@etu.univ-lyon1.fr>
Signed-off-by: Pablo CHABANNE <pablo.chabanne@etu.univ-lyon1.fr>
Signed-off-by: Matthieu MOY <matthieu.moy@univ-lyon1.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The word "property" is vague here. Let's spell out that we mean the path
must be marked with the text attribute.
While we're here, let's make the paragraph a little easier to read by
de-emphasizing the "when core.autocrlf is false" bit. Putting it in the
first sentence obscures the main content, and many readers won't care
about autocrlf (i.e., anyone who is just following the gitattributes(7)
advice, which mainly discusses "text" and "core.eol").
Helped-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Split the overly large Documentation/config.txt file into million
little pieces. This potentially allows each individual piece
included into the manual page of the command it affects more easily.
* nd/config-split: (81 commits)
config.txt: remove config/dummy.txt
config.txt: move worktree.* to a separate file
config.txt: move web.* to a separate file
config.txt: move versionsort.* to a separate file
config.txt: move user.* to a separate file
config.txt: move url.* to a separate file
config.txt: move uploadpack.* to a separate file
config.txt: move uploadarchive.* to a separate file
config.txt: move transfer.* to a separate file
config.txt: move tag.* to a separate file
config.txt: move submodule.* to a separate file
config.txt: move stash.* to a separate file
config.txt: move status.* to a separate file
config.txt: move splitIndex.* to a separate file
config.txt: move showBranch.* to a separate file
config.txt: move sequencer.* to a separate file
config.txt: move sendemail-config.txt to config/
config.txt: move reset.* to a separate file
config.txt: move rerere.* to a separate file
config.txt: move repack.* to a separate file
...
Patrick Steinhardt
Neeraj Singh
Junio C Hamano
Eric Wong
Derrick Stolee
Jonathan Tan
Kevin Willford
Johannes Schindelin
Corentin BOMPARD
Jeff King
Nguyễn Thái Ngọc Duy