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From: Duy Nguyen <pclouds@gmail.com>
To: Phillip Wood <phillip.wood@dunelm.org.uk>
Cc: "Michal Suchánek" <msuchanek@suse.de>,
	"Git Mailing List" <git@vger.kernel.org>,
	"Eric Sunshine" <sunshine@sunshineco.com>,
	"Marketa Calabkova" <mcalabkova@suse.cz>,
	"Junio C Hamano" <gitster@pobox.com>
Subject: Re: [PATCH 2/2] setup: don't fail if commondir reference is deleted.
Date: Fri, 22 Feb 2019 16:32:50 +0700	[thread overview]
Message-ID: <CACsJy8B2HRyBKQd+S7hjfU+xGFH+_y0YKcw8397znc2eGUBogQ@mail.gmail.com> (raw)
In-Reply-To: <adc0f7f9-aa41-780e-6fce-94d493fac318@talktalk.net>

On Fri, Feb 22, 2019 at 12:07 AM Phillip Wood <phillip.wood@talktalk.net> wrote:
>
> Hi Michal/Duy
>
> On 21/02/2019 13:50, Michal Suchánek wrote:
> > On Thu, 21 Feb 2019 17:50:38 +0700
> > Duy Nguyen <pclouds@gmail.com> wrote:
> >
> >> On Tue, Feb 19, 2019 at 12:05 AM Michal Suchanek <msuchanek@suse.de> wrote:
> >>>
> >>> When adding wotktrees git can die in get_common_dir_noenv while
> >>> examining existing worktrees because the commondir file does not exist.
> >>> Rather than testing if the file exists before reading it handle ENOENT.
> >>
> >> I don't think we could go around fixing every access to incomplete
> >> worktrees like this. If this is because of racy 'worktree add', then
> >> perhaps a better solution is make it absolutely clear it's not ready
> >> for anybody to access.
> >>
> >> For example, we can suffix the worktree directory name with ".lock"
> >> and make sure get_worktrees() ignores entries ending with ".lock".
> >> That should protect other commands while 'worktree add' is still
> >> running. Only when the worktree is complete that 'worktree add' should
> >> rename the directory to lose ".lock" and run external commands like
> >> git-checkout to populate the worktree.
> >
> > The problem is we don't forbid worktree names ending with ".lock".
> > Which means that if we start to forbid them now existing worktrees
> > might become inaccessible.
>
> I think it is also racy as the renaming breaks the use of mkdir erroring
> out if the directory already exists.

You mean the part where we see "fred" exists and decide to try the
name "fred1" instead (i.e. patch 1/2)?

I don't think it's the problem if that's the case. We mkdir
"fred.lock" _then_ check if "fred" exists. If it does, remove
fred.lock and move on to fred1.lock. Then we rename fred1.lock to
fred1 and error out if rename fails.
-- 
Duy

  parent reply	other threads:[~2019-02-22  9:33 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-18 17:04 [PATCH 0/2] worktree add race fix Michal Suchanek
2019-02-18 17:04 ` [PATCH 1/2] worktree: fix worktree add race Michal Suchanek
2019-02-18 17:04 ` [PATCH 2/2] setup: don't fail if commondir reference is deleted Michal Suchanek
2019-02-18 21:00   ` Eric Sunshine
2019-02-21 10:50   ` Duy Nguyen
2019-02-21 13:50     ` Michal Suchánek
2019-02-21 17:07       ` Phillip Wood
2019-02-21 17:12         ` Eric Sunshine
2019-02-21 17:27           ` Phillip Wood
2019-03-04 13:30             ` Michal Suchánek
2019-02-21 17:33           ` Michal Suchánek
2019-02-22  9:32         ` Duy Nguyen [this message]
2019-02-22 10:20           ` Phillip Wood
2019-02-22  9:26       ` Duy Nguyen
2019-02-20 16:16 ` [PATCH v3 1/2] worktree: fix worktree add race Michal Suchanek
2019-02-20 16:34   ` Eric Sunshine
2019-02-20 17:29     ` Michal Suchánek
2019-03-08  9:20   ` Duy Nguyen
2019-03-08  9:37     ` Eric Sunshine
2019-03-11  1:55     ` Junio C Hamano
2019-02-20 16:16 ` [PATCH v3 2/2] setup: don't fail if commondir reference is deleted Michal Suchanek
2019-02-20 16:55   ` Eric Sunshine
2019-02-20 17:16     ` Michal Suchánek
2019-02-20 18:35       ` Eric Sunshine
2019-02-21  9:27         ` Eric Sunshine
2019-02-21 11:13           ` Michal Suchánek
2019-02-21 11:19         ` Michal Suchánek

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