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From: Elijah Newren <newren@gmail.com>
To: Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
	Junio C Hamano <gitster@pobox.com>,
	Derrick Stolee <dstolee@microsoft.com>
Subject: Re: [PATCH v3 16/17] sparse-checkout: write using lockfile
Date: Sat, 12 Oct 2019 15:59:15 -0700
Message-ID: <CABPp-BGCNpZWoWk4coNEpA0zS2g0HXi5Kzb+QVusyLRt0fy=zw@mail.gmail.com> (raw)
In-Reply-To: <8927494b8c418e43f5bbd6e1eb108be5a0a263fc.1570478905.git.gitgitgadget@gmail.com>

On Mon, Oct 7, 2019 at 1:08 PM Derrick Stolee via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> From: Derrick Stolee <dstolee@microsoft.com>
>
> If two 'git sparse-checkout set' subcommands are launched at the
> same time, the behavior can be unexpected as they compete to write
> the sparse-checkout file and update the working directory.
>
> Take a lockfile around the writes to the sparse-checkout file. In
> addition, acquire this lock around the working directory update
> to avoid two commands updating the working directory in different
> ways.

Wow, there's something I never would have thought to check.  Did you
have folks run into this, or is this just some defensive programming?
Either way, I'm impressed.

>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  builtin/sparse-checkout.c          | 15 ++++++++++++---
>  t/t1091-sparse-checkout-builtin.sh |  7 +++++++
>  2 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/sparse-checkout.c b/builtin/sparse-checkout.c
> index 542d57fac6..9b313093cd 100644
> --- a/builtin/sparse-checkout.c
> +++ b/builtin/sparse-checkout.c
> @@ -308,6 +308,8 @@ static int write_patterns_and_update(struct pattern_list *pl)
>  {
>         char *sparse_filename;
>         FILE *fp;
> +       int fd;
> +       struct lock_file lk = LOCK_INIT;
>         int result;
>
>         if (!core_apply_sparse_checkout) {
> @@ -317,21 +319,28 @@ static int write_patterns_and_update(struct pattern_list *pl)
>
>         result = update_working_directory(pl);
>
> +       sparse_filename = get_sparse_checkout_filename();
> +       fd = hold_lock_file_for_update(&lk, sparse_filename,
> +                                     LOCK_DIE_ON_ERROR);
> +
> +       result = update_working_directory(pl);
>         if (result) {
> +               rollback_lock_file(&lk);
> +               free(sparse_filename);
>                 clear_pattern_list(pl);
>                 update_working_directory(NULL);
>                 return result;
>         }
>
> -       sparse_filename = get_sparse_checkout_filename();
> -       fp = fopen(sparse_filename, "w");
> +       fp = fdopen(fd, "w");
>
>         if (core_sparse_checkout_cone)
>                 write_cone_to_file(fp, pl);
>         else
>                 write_patterns_to_file(fp, pl);
>
> -       fclose(fp);
> +       fflush(fp);
> +       commit_lock_file(&lk);
>
>         free(sparse_filename);
>         clear_pattern_list(pl);
> diff --git a/t/t1091-sparse-checkout-builtin.sh b/t/t1091-sparse-checkout-builtin.sh
> index 82eb5fb2f8..f22a4afbea 100755
> --- a/t/t1091-sparse-checkout-builtin.sh
> +++ b/t/t1091-sparse-checkout-builtin.sh
> @@ -262,4 +262,11 @@ test_expect_success 'revert to old sparse-checkout on bad update' '
>         test_cmp dir expect
>  '
>
> +test_expect_success 'fail when lock is taken' '
> +       test_when_finished rm -rf repo/.git/info/sparse-checkout.lock &&
> +       touch repo/.git/info/sparse-checkout.lock &&
> +       test_must_fail git -C repo sparse-checkout set deep 2>err &&
> +       test_i18ngrep "File exists" err
> +'
> +
>  test_done
> --
> gitgitgadget
>

  reply index

Thread overview: 93+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-20 15:11 [PATCH 0/9] [RFC] New sparse-checkout builtin and "cone" mode Derrick Stolee via GitGitGadget
2019-08-20 15:11 ` [PATCH 1/9] sparse-checkout: create builtin with 'list' subcommand Derrick Stolee via GitGitGadget
2019-08-23 22:30   ` Elijah Newren
2019-08-20 15:11 ` [PATCH 2/9] sparse-checkout: create 'init' subcommand Derrick Stolee via GitGitGadget
2019-08-23 23:02   ` Elijah Newren
2019-09-11 14:27     ` Derrick Stolee
2019-09-11 20:28     ` Derrick Stolee
2019-08-20 15:11 ` [PATCH 3/9] clone: add --sparse mode Derrick Stolee via GitGitGadget
2019-08-23 23:17   ` Elijah Newren
2019-09-18 13:51     ` Derrick Stolee
2019-08-20 15:11 ` [PATCH 4/9] sparse-checkout: 'add' subcommand Derrick Stolee via GitGitGadget
2019-08-23 23:30   ` Elijah Newren
2019-09-18 13:55     ` Derrick Stolee
2019-09-18 14:56       ` Elijah Newren
2019-09-18 17:23         ` Derrick Stolee
2019-08-20 15:11 ` [PATCH 5/9] sparse-checkout: create 'disable' subcommand Derrick Stolee via GitGitGadget
2019-08-23 23:50   ` Elijah Newren
2019-08-20 15:11 ` [PATCH 6/9] trace2:experiment: clear_ce_flags_1 Jeff Hostetler via GitGitGadget
2019-08-24  0:08   ` Elijah Newren
2019-08-20 15:11 ` [PATCH 7/9] sparse-checkout: add 'cone' mode Derrick Stolee via GitGitGadget
2019-08-24  0:31   ` Elijah Newren
2019-08-20 15:11 ` [PATCH 8/9] sparse-checkout: use hashmaps for cone patterns Derrick Stolee via GitGitGadget
2019-08-24  4:56   ` Elijah Newren
2019-08-20 15:11 ` [PATCH 9/9] sparse-checkout: init and add in cone mode Derrick Stolee via GitGitGadget
2019-08-24  5:07   ` Elijah Newren
2019-08-21 21:52 ` [PATCH 0/9] [RFC] New sparse-checkout builtin and "cone" mode Elijah Newren
2019-08-22 13:10   ` Derrick Stolee
2019-08-22 14:25     ` Derrick Stolee
2019-08-24  5:40     ` Elijah Newren
2019-08-26 13:29       ` Derrick Stolee
2019-08-26 18:16         ` Elijah Newren
2019-08-26 19:16           ` Derrick Stolee
2019-09-02 17:55       ` Eric Sunshine
2019-09-19 14:43 ` [PATCH v2 00/11] " Derrick Stolee via GitGitGadget
2019-09-19 14:43   ` [PATCH v2 01/11] sparse-checkout: create builtin with 'list' subcommand Derrick Stolee via GitGitGadget
2019-10-05 19:22     ` Elijah Newren
2019-09-19 14:43   ` [PATCH v2 02/11] sparse-checkout: create 'init' subcommand Derrick Stolee via GitGitGadget
2019-10-05 19:34     ` Elijah Newren
2019-09-19 14:43   ` [PATCH v2 03/11] clone: add --sparse mode Derrick Stolee via GitGitGadget
2019-10-05 19:40     ` Elijah Newren
2019-10-07 13:56       ` Derrick Stolee
2019-09-19 14:43   ` [PATCH v2 05/11] sparse-checkout: add '--stdin' option to set subcommand Derrick Stolee via GitGitGadget
2019-09-19 14:43   ` [PATCH v2 04/11] sparse-checkout: 'set' subcommand Derrick Stolee via GitGitGadget
2019-10-05 22:44     ` Elijah Newren
2019-10-06  0:30       ` Elijah Newren
2019-10-07 18:26         ` Derrick Stolee
2019-10-11 22:24           ` Elijah Newren
2019-09-19 14:43   ` [PATCH v2 06/11] sparse-checkout: create 'disable' subcommand Derrick Stolee via GitGitGadget
2019-10-06  4:10     ` Elijah Newren
2019-10-07 19:12       ` Derrick Stolee
2019-09-19 14:43   ` [PATCH v2 07/11] trace2: add region in clear_ce_flags Jeff Hostetler via GitGitGadget
2019-10-06  4:13     ` Elijah Newren
2019-09-19 14:43   ` [PATCH v2 08/11] sparse-checkout: add 'cone' mode Derrick Stolee via GitGitGadget
2019-10-06  4:22     ` Elijah Newren
2019-10-07 19:15       ` Derrick Stolee
2019-09-19 14:43   ` [PATCH v2 09/11] sparse-checkout: use hashmaps for cone patterns Derrick Stolee via GitGitGadget
2019-09-19 20:59     ` Derrick Stolee
2019-09-20 14:37       ` Derrick Stolee
2019-09-19 14:43   ` [PATCH v2 10/11] sparse-checkout: init and set in cone mode Derrick Stolee via GitGitGadget
2019-09-19 14:43   ` [PATCH v2 11/11] unpack-trees: hash less " Derrick Stolee via GitGitGadget
2019-10-01 13:40   ` [PATCH v2 00/11] New sparse-checkout builtin and "cone" mode Derrick Stolee
2019-10-01 16:54     ` Elijah Newren
2019-10-01 18:15       ` Derrick Stolee
2019-10-03 22:28     ` Junio C Hamano
2019-10-07 20:08   ` [PATCH v3 00/17] " Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 01/17] sparse-checkout: create builtin with 'list' subcommand Derrick Stolee via GitGitGadget
2019-10-11 22:01       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 02/17] sparse-checkout: create 'init' subcommand Derrick Stolee via GitGitGadget
2019-10-11 22:14       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 03/17] clone: add --sparse mode Derrick Stolee via GitGitGadget
2019-10-11 22:20       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 04/17] sparse-checkout: 'set' subcommand Derrick Stolee via GitGitGadget
2019-10-11 22:26       ` Elijah Newren
2019-10-11 22:30         ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 05/17] sparse-checkout: add '--stdin' option to set subcommand Derrick Stolee via GitGitGadget
2019-10-11 22:27       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 06/17] sparse-checkout: create 'disable' subcommand Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 07/17] trace2: add region in clear_ce_flags Jeff Hostetler via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 08/17] sparse-checkout: add 'cone' mode Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 09/17] sparse-checkout: use hashmaps for cone patterns Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 10/17] sparse-checkout: init and set in cone mode Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 11/17] unpack-trees: hash less " Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 12/17] unpack-trees: add progress to clear_ce_flags() Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 13/17] read-tree: show progress by default Derrick Stolee via GitGitGadget
2019-10-12 22:16       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 14/17] sparse-checkout: sanitize for nested folders Derrick Stolee via GitGitGadget
2019-10-07 20:08     ` [PATCH v3 15/17] sparse-checkout: update working directory in-process Derrick Stolee via GitGitGadget
2019-10-12 22:57       ` Elijah Newren
2019-10-07 20:08     ` [PATCH v3 16/17] sparse-checkout: write using lockfile Derrick Stolee via GitGitGadget
2019-10-12 22:59       ` Elijah Newren [this message]
2019-10-07 20:08     ` [PATCH v3 17/17] sparse-checkout: cone mode should not interact with .gitignore Derrick Stolee via GitGitGadget
2019-10-12 23:00       ` Elijah Newren
2019-10-12 23:22     ` [PATCH v3 00/17] New sparse-checkout builtin and "cone" mode Elijah Newren

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