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Re: [PATCH v3 00/25] Lockfile correctness and refactoring

From
Torsten Bögershausen <tboegi@web.de>
Date
Apr 15, 2014, 18:40 UTC
Message-ID
<534D7D2E.7060100@web.de>
In-Reply-To
<1397483695-10888-1-git-send-email-mhagger@alum.mit.edu>
refs.c:
int close_ref(struct ref_lock *lock)
{
	if (close_lock_file(lock->lk))
		return -1;
	lock->lock_fd = -1;
	return 0;
}
When the close() fails, fd is still >= 0, even if the file is closed.
Could it be written like this ?
int close_ref(struct ref_lock *lock)
{
	return close_lock_file(lock->lk);
}
=====================
lockfile.c, line 49
 *   - filename holds the filename of the lockfile
I think we have a strbuf here? (which is a good thing),
should we write:
 *   - strbuf filename holds the filename of the lockfile
----------
(and at some places filename[0] is mentioned,
should that be filename.buf[0] ?)
=========================
int commit_lock_file(struct lock_file *lk)
{
	static struct strbuf result_file = STRBUF_INIT;
	int err;
	if (lk->fd >= 0 && close_lock_file(lk))
		return -1;
##What happens if close() fails and close_lock_file() returns != 0?
##Is the lk now in a good shaped state?
I think the file which had been open by lk->fd is in an unkown state,
and should not be used for anything.
When I remember it right, an error on close() can mean "the file could not
be written and closed as expected, it can be truncated or corrupted.
This can happen on a network file system like NFS, or probably even other FS.
For me the failing of close() means I smell a need for a rollback.
	if (!lk->active)
		die("BUG: attempt to commit unlocked object");
	/* remove ".lock": */
	strbuf_add(&result_file, lk->filename.buf,
		   lk->filename.len - LOCK_SUFFIX_LEN);
	err = rename(lk->filename.buf, result_file.buf);
	strbuf_reset(&result_file);
	if (err)
		return -1;
	lk->active = 0;
	strbuf_reset(&lk->filename);
	return 0;
}

================ Please treat my comments more than questions rather than answers, thanks for an interesting reading

Previous: Michael HaggertyNext: Michael Haggerty
Message 31 of 32 in “Lockfile correctness and refactoring”
  1. 00/25 Lockfile correctness and refactoringMichael Haggerty, Apr 14, 2014
  2. 01/25 unable_to_lock_die(): rename function from unable_to_lock_index_die()Michael Haggerty, Apr 14, 2014
  3. 02/25 api-lockfile: expand the documentationMichael Haggerty, Apr 14, 2014
  4. 03/25 rollback_lock_file(): do not clear filename redundantlyMichael Haggerty, Apr 14, 2014
  5. 04/25 rollback_lock_file(): set fd to -1Michael Haggerty, Apr 14, 2014
  6. 05/25 lockfile: unlock file if lockfile permissions cannot be adjustedMichael Haggerty, Apr 14, 2014
  7. 06/25 hold_lock_file_for_append(): release lock on errorsMichael Haggerty, Apr 14, 2014
  8. 07/25 lock_file(): always add lock_file object to lock_file_listMichael Haggerty, Apr 14, 2014
  9. 08/25 lockfile.c: document the various states of lock_file objectsMichael Haggerty, Apr 14, 2014
  10. 09/25 cache.h: define constants LOCK_SUFFIX and LOCK_SUFFIX_LENMichael Haggerty, Apr 14, 2014
  11. 10/25 delete_ref_loose(): don't muck around in the lock_file's filenameMichael Haggerty, Apr 14, 2014
  12. 11/25 prepare_index(): declare return value to be (const char *)Michael Haggerty, Apr 14, 2014
  13. 12/25 write_packed_entry_fn(): convert cb_data into a (const int *)Michael Haggerty, Apr 14, 2014
  14. 13/25 lock_file(): exit early if lockfile cannot be openedMichael Haggerty, Apr 14, 2014
  15. 14/25 remove_lock_file(): call rollback_lock_file()Michael Haggerty, Apr 14, 2014
  16. 15/25 commit_lock_file(): inline temporary variableMichael Haggerty, Apr 14, 2014
  17. 16/25 commit_lock_file(): die() if called for unlocked lockfile objectMichael Haggerty, Apr 14, 2014
  18. Johannes SixtApr 15, 2014
  19. Michael HaggertyApr 16, 2014
  20. 17/25 lockfile: avoid transitory invalid statesMichael Haggerty, Apr 14, 2014
  21. 18/25 struct lock_file: declare some fields volatileMichael Haggerty, Apr 14, 2014
  22. Johannes SixtApr 15, 2014
  23. Michael HaggertyApr 16, 2014
  24. 19/25 try_merge_strategy(): remove redundant lock_file allocationMichael Haggerty, Apr 14, 2014
  25. 20/25 try_merge_strategy(): use a statically-allocated lock_file objectMichael Haggerty, Apr 14, 2014
  26. 21/25 commit_lock_file(): use a strbuf to manage temporary spaceMichael Haggerty, Apr 14, 2014
  27. 22/25 Change lock_file::filename into a strbufMichael Haggerty, Apr 14, 2014
  28. 23/25 resolve_symlink(): use a strbuf for internal scratch spaceMichael Haggerty, Apr 14, 2014
  29. 24/25 resolve_symlink(): take a strbuf parameterMichael Haggerty, Apr 14, 2014
  30. 25/25 trim_last_path_elm(): replace last_path_elm()Michael Haggerty, Apr 14, 2014
  31. Torsten BögershausenApr 15, 2014
  32. Michael HaggertyApr 16, 2014

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