Nguyễn Thái Ngọc Duy <pclouds@xxxxxxxxx> writes:
> Locked paths are saved in a linked list so that if something wrong
> happens, *.lock are removed. This works fine if we keep cwd the same,
> which is true 99% of time except:
>
> - update-index and read-tree hold the lock on $GIT_DIR/index really
> early, then later on may call setup_work_tree() to move cwd.
>
> - Suppose a lock is being held (e.g. by "git add") then somewhere
> down the line, somebody calls real_path (e.g. "link_alt_odb_entry"),
> which temporarily moves cwd away and back.
>
> During that time when cwd is moved (either permanently or temporarily)
> and we decide to die(), attempts to remove relative *.lock will fail,
> and the next operation will complain that some files are still locked.
>
> Avoid this case by turning relative paths to absolute when chdir() is
> called (or soon to be called, in setup_git_directory_gently case).
The rationale makes sense.
> +extern void make_locked_paths_absolute(void);
> +static inline int chdir_safe(const char *path)
> +{
> + make_locked_paths_absolute();
> + return chdir(path);
> +}
Clever ;-). Instead of making paths absolute when you receive
requests to lock them, you lazily turn the ones relative to cwd()
absolute just before they are about to become invalid/problematic
because the program wants to chdir.
> diff --git a/lockfile.c b/lockfile.c
> index 8fbcb6a..a70d107 100644
> --- a/lockfile.c
> +++ b/lockfile.c
> @@ -280,3 +280,19 @@ void rollback_lock_file(struct lock_file *lk)
> }
> lk->filename[0] = 0;
> }
> +
> +void make_locked_paths_absolute(void)
> +{
> + struct lock_file *lk;
> + const char *abspath;
> + for (lk = lock_file_list; lk != NULL; lk = lk->next) {
> + if (!lk->filename[0] || lk->filename[0] == '/')
> + continue;
Do we have to worry about Windows?
> + abspath = absolute_path(lk->filename);
> + if (strlen(abspath) >= sizeof(lk->filename))
> + warning("locked path %s is relative when current directory "
> + "is changed", lk->filename);
Shouldn't this be a die() or an error return (which will kill the
caller anyway)?
> @@ -636,6 +636,7 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
> die_errno("Unable to read current working directory");
> offset = len = strlen(cwd);
>
> + make_locked_paths_absolute();
Just being curious, but this early in the start-up sequence, what
files do we have locks on?
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