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Revert "Revert "journal: Make sd_journal_previous/next() return 0 at HEAD/TAIL""

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This reverts commit 1db6dbb1dc.

The original patch was reverted because of issue #25369. The issue was created
because it wrongly assumed that sd_journal_seek_tail() seeks to 'current' tail.
But in fact, only when a subsequent sd_journal_previous() is called that it's
pointing to the tail at that time. The concept of 'tail' in sd_journal_seek_tail()
only has a logical meaning, and a sd_journal_previous is needed. In fact, if we
look at the codes in journalctl, we can see sd_journal_seek_tail() is followed by
sd_journal_previous(). By contrary, a sd_journal_next() after a 'logical' tail does
not make much sense. So the original patch is correct, and projects that are
using 'sd_journal_next()' right after 'sd_journal_seek_tail()' should do fixes
as in https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2823#note_1637715.
This commit is contained in:
Chen Qi 2023-02-24 12:36:55 +08:00 committed by Yu Watanabe
parent a94149601a
commit 7a4ee86161
2 changed files with 20 additions and 30 deletions
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42
src/journal/test-journal-interleaving.c
View file

@ -188,24 +188,19 @@ static void test_skip_one(void (*setup)(void)) {
/* Seek to head, move to previous, then iterate down. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_head(j));
/* FIXME: calling sd_journal_previous() thrice (or >= number of journal files) here works as
* mostly equivalent to calling sd_journal_next(). */
assert_ret(sd_journal_previous(j));
assert_ret(sd_journal_previous(j));
assert_ret(sd_journal_previous(j)); /* pointing the first entry */
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(sd_journal_next(j)); /* pointing the first entry */
test_check_numbers_down(j, 9);
sd_journal_close(j);
/* Seek to head, walk several steps, then iterate down. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_head(j));
assert_ret(sd_journal_previous(j));
assert_ret(sd_journal_previous(j));
assert_ret(sd_journal_previous(j)); /* pointing the first entry */
assert_ret(sd_journal_next(j)); /* pointing the second entry */
/* FIXME: as calling sd_journal_previous() thrice works equivalent to sd_journal_next(),
* we need to call sd_journal_previous() here. */
assert_ret(sd_journal_previous(j)); /* pointing the first entry */
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(sd_journal_next(j)); /* pointing the first entry */
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(sd_journal_previous(j)); /* no-op */
test_check_numbers_down(j, 9);
sd_journal_close(j);
@ -220,22 +215,19 @@ static void test_skip_one(void (*setup)(void)) {
/* Seek to tail, move to next, then iterate up. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_tail(j));
/* FIXME: calling sd_journal_next() thrice (or >= number of journal files) here works as mostly
* equivalent to calling sd_journal_previous(). */
assert_ret(sd_journal_next(j));
assert_ret(sd_journal_next(j));
assert_ret(sd_journal_next(j)); /* pointing the last entry */
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(sd_journal_previous(j)); /* pointing the first entry */
test_check_numbers_up(j, 9);
sd_journal_close(j);
/* Seek to tail, walk several steps, then iterate up. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_tail(j));
assert_ret(sd_journal_next(j));
assert_ret(sd_journal_next(j));
assert_ret(sd_journal_next(j)); /* pointing the last entry */
assert_ret(sd_journal_previous(j)); /* pointing the previous of the last entry. */
assert_ret(sd_journal_next(j)); /* pointing the last entry */
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(sd_journal_previous(j)); /* pointing the last entry. */
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(sd_journal_next(j)); /* no-op */
test_check_numbers_up(j, 9);
sd_journal_close(j);
@ -251,8 +243,7 @@ static void test_skip_one(void (*setup)(void)) {
/* Seek to tail, skip to head in a more complext way, then iterate down. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_tail(j));
// FIXME: sd_journal_next() cannot be called here.
//assert_ret(sd_journal_next(j));
assert_ret(sd_journal_next(j)); /* no-op */
assert_ret(r = sd_journal_previous_skip(j, 4));
assert_se(r == 4);
assert_ret(r = sd_journal_previous_skip(j, 5));
@ -284,8 +275,7 @@ static void test_skip_one(void (*setup)(void)) {
/* Seek to head, skip to tail in a more complex way, then iterate up. */
assert_ret(sd_journal_open_directory(&j, t, 0));
assert_ret(sd_journal_seek_head(j));
// FIXME: sd_journal_previous() cannot be called here.
//assert_ret(sd_journal_previous(j));
assert_ret(sd_journal_previous(j)); /* no-op */
assert_ret(r = sd_journal_next_skip(j, 4));
assert_se(r == 4);
assert_ret(r = sd_journal_next_skip(j, 5));

8
src/libsystemd/sd-journal/sd-journal.c
View file

@ -660,9 +660,9 @@ static int find_location_for_match(
/* FIXME: missing: find by monotonic */
if (j->current_location.type == LOCATION_HEAD)
return journal_file_next_entry_for_data(f, d, DIRECTION_DOWN, ret, offset);
return direction == DIRECTION_DOWN ? journal_file_next_entry_for_data(f, d, DIRECTION_DOWN, ret, offset) : 0;
if (j->current_location.type == LOCATION_TAIL)
return journal_file_next_entry_for_data(f, d, DIRECTION_UP, ret, offset);
return direction == DIRECTION_UP ? journal_file_next_entry_for_data(f, d, DIRECTION_UP, ret, offset) : 0;
if (j->current_location.seqnum_set && sd_id128_equal(j->current_location.seqnum_id, f->header->seqnum_id))
return journal_file_move_to_entry_by_seqnum_for_data(f, d, j->current_location.seqnum, direction, ret, offset);
if (j->current_location.monotonic_set) {
@ -755,9 +755,9 @@ static int find_location_with_matches(
/* No matches is simple */
if (j->current_location.type == LOCATION_HEAD)
return journal_file_next_entry(f, 0, DIRECTION_DOWN, ret, offset);
return direction == DIRECTION_DOWN ? journal_file_next_entry(f, 0, DIRECTION_DOWN, ret, offset) : 0;
if (j->current_location.type == LOCATION_TAIL)
return journal_file_next_entry(f, 0, DIRECTION_UP, ret, offset);
return direction == DIRECTION_UP ? journal_file_next_entry(f, 0, DIRECTION_UP, ret, offset) : 0;
if (j->current_location.seqnum_set && sd_id128_equal(j->current_location.seqnum_id, f->header->seqnum_id))
return journal_file_move_to_entry_by_seqnum(f, j->current_location.seqnum, direction, ret, offset);
if (j->current_location.monotonic_set) {