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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
2023-05-22 02:54:40 +09:00
committed by Yu Watanabe
parent a94149601a
commit 7a4ee86161
2 changed files with 20 additions and 30 deletions
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src/journal/test-journal-interleaving.c
+16 -26
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@@ -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));