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commit_lock_file_to(): refactor a helper out of commit_lock_file()

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commit_locked_index(), when writing to an alternate index file,
duplicates (poorly) the code in commit_lock_file(). And anyway, it
shouldn't have to know so much about the internal workings of lockfile
objects. So extract a new function commit_lock_file_to() that does the
work common to the two functions, and call it from both
commit_lock_file() and commit_locked_index().

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Michael Haggerty 2014-10-01 12:28:36 +02:00 committed by Junio C Hamano
parent 0c0d6e8601
commit 751bacedaa
4 changed files with 50 additions and 38 deletions
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34
Documentation/technical/api-lockfile.txt
View File

@ -49,14 +49,14 @@ The caller:
When finished writing, the caller can:
* Close the file descriptor and rename the lockfile to its final
destination by calling `commit_lock_file`.
destination by calling `commit_lock_file` or `commit_lock_file_to`.
* Close the file descriptor and remove the lockfile by calling
`rollback_lock_file`.
* Close the file descriptor without removing or renaming the lockfile
by calling `close_lock_file`, and later call `commit_lock_file`,
`rollback_lock_file`, or `reopen_lock_file`.
`commit_lock_file_to`, `rollback_lock_file`, or `reopen_lock_file`.
Even after the lockfile is committed or rolled back, the `lock_file`
object must not be freed or altered by the caller. However, it may be
@ -64,20 +64,19 @@ reused; just pass it to another call of `hold_lock_file_for_update` or
`hold_lock_file_for_append`.
If the program exits before you have called one of `commit_lock_file`,
`rollback_lock_file`, or `close_lock_file`, an `atexit(3)` handler
will close and remove the lockfile, rolling back any uncommitted
changes.
`commit_lock_file_to`, `rollback_lock_file`, or `close_lock_file`, an
`atexit(3)` handler will close and remove the lockfile, rolling back
any uncommitted changes.
If you need to close the file descriptor you obtained from a
`hold_lock_file_*` function yourself, do so by calling
`close_lock_file`. You should never call `close(2)` yourself!
Otherwise the `struct lock_file` structure would still think that the
file descriptor needs to be closed, and a later call to
`commit_lock_file` or `rollback_lock_file` or program exit would
file descriptor needs to be closed, and a commit or rollback would
result in duplicate calls to `close(2)`. Worse yet, if you `close(2)`
and then later open another file descriptor for a completely different
purpose, then a call to `commit_lock_file` or `rollback_lock_file`
might close that unrelated file descriptor.
purpose, then a commit or rollback might close that unrelated file
descriptor.
Error handling
@ -100,9 +99,9 @@ unable_to_lock_die::
Emit an appropriate error message and `die()`.
Similarly, `commit_lock_file` and `close_lock_file` return 0 on
success. On failure they set `errno` appropriately, do their best to
roll back the lockfile, and return -1.
Similarly, `commit_lock_file`, `commit_lock_file_to`, and
`close_lock_file` return 0 on success. On failure they set `errno`
appropriately, do their best to roll back the lockfile, and return -1.
Flags
@ -156,6 +155,12 @@ commit_lock_file::
`commit_lock_file` for a `lock_file` object that is not
currently locked.
commit_lock_file_to::
Like `commit_lock_file()`, except that it takes an explicit
`path` argument to which the lockfile should be renamed. The
`path` must be on the same filesystem as the lock file.
rollback_lock_file::
Take a pointer to the `struct lock_file` initialized with an
@ -172,8 +177,9 @@ close_lock_file::
`hold_lock_file_for_append`, and close the file descriptor.
Return 0 upon success. On failure to `close(2)`, return a
negative value and roll back the lock file. Usually
`commit_lock_file` or `rollback_lock_file` should eventually
be called if `close_lock_file` succeeds.
`commit_lock_file`, `commit_lock_file_to`, or
`rollback_lock_file` should eventually be called if
`close_lock_file` succeeds.
reopen_lock_file::

1
cache.h
View File

@ -590,6 +590,7 @@ extern void unable_to_lock_message(const char *path, int err,
extern NORETURN void unable_to_lock_die(const char *path, int err);
extern int hold_lock_file_for_update(struct lock_file *, const char *path, int);
extern int hold_lock_file_for_append(struct lock_file *, const char *path, int);
extern int commit_lock_file_to(struct lock_file *, const char *path);
extern int commit_lock_file(struct lock_file *);
extern int reopen_lock_file(struct lock_file *);
extern void update_index_if_able(struct index_state *, struct lock_file *);

40
lockfile.c
View File

@ -43,9 +43,9 @@
* Same as the previous state, except that the lockfile is closed
* and fd is -1.
*
* - Unlocked (after commit_lock_file(), rollback_lock_file(), a
* failed attempt to lock, or a failed close_lock_file()). In this
* state:
* - Unlocked (after commit_lock_file(), commit_lock_file_to(),
* rollback_lock_file(), a failed attempt to lock, or a failed
* close_lock_file()). In this state:
* - active is unset
* - filename is empty (usually, though there are transitory
* states in which this condition doesn't hold). Client code should
@ -284,23 +284,15 @@ int reopen_lock_file(struct lock_file *lk)
return lk->fd;
}
int commit_lock_file(struct lock_file *lk)
int commit_lock_file_to(struct lock_file *lk, const char *path)
{
static struct strbuf result_file = STRBUF_INIT;
int err;
if (!lk->active)
die("BUG: attempt to commit unlocked object");
die("BUG: attempt to commit unlocked object to \"%s\"", path);
if (close_lock_file(lk))
return -1;
/* 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) {
if (rename(lk->filename.buf, path)) {
int save_errno = errno;
rollback_lock_file(lk);
errno = save_errno;
@ -312,6 +304,26 @@ int commit_lock_file(struct lock_file *lk)
return 0;
}
int commit_lock_file(struct lock_file *lk)
{
static struct strbuf result_file = STRBUF_INIT;
int err;
if (!lk->active)
die("BUG: attempt to commit unlocked object");
if (lk->filename.len <= LOCK_SUFFIX_LEN ||
strcmp(lk->filename.buf + lk->filename.len - LOCK_SUFFIX_LEN, LOCK_SUFFIX))
die("BUG: lockfile filename corrupt");
/* remove ".lock": */
strbuf_add(&result_file, lk->filename.buf,
lk->filename.len - LOCK_SUFFIX_LEN);
err = commit_lock_file_to(lk, result_file.buf);
strbuf_reset(&result_file);
return err;
}
int hold_locked_index(struct lock_file *lk, int die_on_error)
{
return hold_lock_file_for_update(lk, get_index_file(),

13
read-cache.c
View File

@ -2041,17 +2041,10 @@ void set_alternate_index_output(const char *name)
static int commit_locked_index(struct lock_file *lk)
{
if (alternate_index_output) {
if (close_lock_file(lk))
return -1;
if (rename(lk->filename.buf, alternate_index_output))
return -1;
lk->active = 0;
strbuf_reset(&lk->filename);
return 0;
} else {
if (alternate_index_output)
return commit_lock_file_to(lk, alternate_index_output);
else
return commit_lock_file(lk);
}
}
static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,