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From 7204e7f9ea3067bda7e5658a06e91b67c736f8ab Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Mon, 12 Feb 2018 16:14:58 +0100
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Subject: [PATCH] sd-journal: properly handle inotify queue overflow
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This adds proper handling of IN_Q_OVERFLOW: when the inotify queue runs
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over we'll reiterate all directories we are looking at. At the same time
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we'll mark all files and directories we encounter that way with a
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generation counter we first increased. All files and directories not
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marked like this are then unloaded.
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With this logic we do the best when the inotify queue overflows: we
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synchronize our in-memory state again with what's on disk.  This
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contains some refactoring of the directory logic, to share more code
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between uuid directories and "root" directories and generally make
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things a bit more readable by splitting things up into smaller bits.
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See: #7998 #8032
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(cherry-picked from commit 858749f7312bd0adb5433075a92e1c35a2fb56ac)
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Resolves: #1540538
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---
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 src/journal/journal-file.h     |   2 +
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 src/journal/journal-internal.h |   2 +
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 src/journal/sd-journal.c       | 237 ++++++++++++++++++++++++++-------
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 src/shared/path-util.c         |  14 ++
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 src/shared/path-util.h         |   2 +
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 5 files changed, 206 insertions(+), 51 deletions(-)
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diff --git a/src/journal/journal-file.h b/src/journal/journal-file.h
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index c74ad5fc58..dd8ef52d2a 100644
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--- a/src/journal/journal-file.h
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+++ b/src/journal/journal-file.h
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@@ -121,6 +121,8 @@ typedef struct JournalFile {
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         void *fsprg_seed;
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         size_t fsprg_seed_size;
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+
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+        unsigned last_seen_generation;
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 #endif
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 } JournalFile;
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diff --git a/src/journal/journal-internal.h b/src/journal/journal-internal.h
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index eb23ac28ad..999e9d8cb6 100644
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--- a/src/journal/journal-internal.h
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+++ b/src/journal/journal-internal.h
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@@ -81,6 +81,7 @@ struct Directory {
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         char *path;
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         int wd;
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         bool is_root;
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+        unsigned last_seen_generation;
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 };
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 struct sd_journal {
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@@ -102,6 +103,7 @@ struct sd_journal {
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         int inotify_fd;
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         unsigned current_invalidate_counter, last_invalidate_counter;
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         usec_t last_process_usec;
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+        unsigned generation;
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         char *unique_field;
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         JournalFile *unique_file;
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diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
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index 14b65cfedd..9186f5188e 100644
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--- a/src/journal/sd-journal.c
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+++ b/src/journal/sd-journal.c
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@@ -1229,8 +1229,16 @@ static int add_any_file(sd_journal *j, const char *path) {
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         assert(j);
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         assert(path);
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-        if (ordered_hashmap_get(j->files, path))
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-                return 0;
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+        if (path) {
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+                f = ordered_hashmap_get(j->files, path);
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+                if (f) {
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+                        /* Mark this file as seen in this generation. This is used to GC old files in
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+                         * process_q_overflow() to detect journal files that are still and discern them from those who
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+                         * are gone. */
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+                        f->last_seen_generation = j->generation;
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+                        return 0;
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+                }
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+        }
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         if (ordered_hashmap_size(j->files) >= JOURNAL_FILES_MAX) {
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                 log_debug("Too many open journal files, not adding %s.", path);
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@@ -1252,6 +1260,8 @@ static int add_any_file(sd_journal *j, const char *path) {
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                 goto fail;
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         }
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+        f->last_seen_generation = j->generation;
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+
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         log_debug("File %s added.", f->path);
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         check_network(j, f->fd);
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@@ -1346,10 +1356,96 @@ static int dirname_is_machine_id(const char *fn) {
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         return sd_id128_equal(id, machine);
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 }
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+static bool dirent_is_journal_file(const struct dirent *de) {
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+        assert(de);
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+
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+        if (!IN_SET(de->d_type, DT_REG, DT_LNK, DT_UNKNOWN))
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+                return false;
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+
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+        return endswith(de->d_name, ".journal") ||
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+                endswith(de->d_name, ".journal~");
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+}
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+
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+static bool dirent_is_id128_subdir(const struct dirent *de) {
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+        assert(de);
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+
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+        if (!IN_SET(de->d_type, DT_DIR, DT_LNK, DT_UNKNOWN))
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+                return false;
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+
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+        return id128_is_valid(de->d_name);
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+}
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+
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+static int directory_open(sd_journal *j, const char *path, DIR **ret) {
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+        DIR *d;
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+
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+        assert(j);
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+        assert(path);
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+        assert(ret);
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+
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+        d = opendir(path);
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+        if (!d)
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+                return -errno;
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+
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+        *ret = d;
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+        return 0;
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+}
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+
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+static int add_directory(sd_journal *j, const char *prefix, const char *dirname);
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+
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+static void directory_enumerate(sd_journal *j, Directory *m, DIR *d) {
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+        struct dirent *de;
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+
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+        assert(j);
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+        assert(m);
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+        assert(d);
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+
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+        FOREACH_DIRENT_ALL(de, d, goto fail) {
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+                if (dirent_is_journal_file(de))
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+                        (void) add_file(j, m->path, de->d_name);
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+
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+                if (m->is_root && dirent_is_id128_subdir(de))
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+                        (void) add_directory(j, m->path, de->d_name);
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+        }
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+
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+        return;
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+
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+fail:
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+        log_debug_errno(errno, "Failed to enumerate directory %s, ignoring: %m", m->path);
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+}
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+
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+static void directory_watch(sd_journal *j, Directory *m, int fd, uint32_t mask) {
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+        int r;
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+
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+        assert(j);
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+        assert(m);
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+        assert(fd >= 0);
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+
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+        /* Watch this directory if that's enabled and if it not being watched yet. */
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+
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+        if (m->wd > 0) /* Already have a watch? */
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+                return;
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+        if (j->inotify_fd < 0) /* Not watching at all? */
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+                return;
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+
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+        m->wd = inotify_add_watch_fd(j->inotify_fd, fd, mask);
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+        if (m->wd < 0) {
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+                log_debug_errno(errno, "Failed to watch journal directory '%s', ignoring: %m", m->path);
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+                return;
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+        }
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+
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+        r = hashmap_put(j->directories_by_wd, INT_TO_PTR(m->wd), m);
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+        if (r == -EEXIST)
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+                log_debug_errno(r, "Directory '%s' already being watched under a different path, ignoring: %m", m->path);
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+        if (r < 0) {
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+                log_debug_errno(r, "Failed to add watch for journal directory '%s' to hashmap, ignoring: %m", m->path);
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+                (void) inotify_rm_watch(j->inotify_fd, m->wd);
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+                m->wd = -1;
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+        }
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+}
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+
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 static int add_directory(sd_journal *j, const char *prefix, const char *dirname) {
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         _cleanup_free_ char *path = NULL;
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         _cleanup_closedir_ DIR *d = NULL;
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-        struct dirent *de = NULL;
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         Directory *m;
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         int r, k;
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@@ -1357,7 +1453,7 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
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         assert(prefix);
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         assert(dirname);
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-        log_debug("Considering %s/%s.", prefix, dirname);
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+        log_debug("Considering '%s/%s'.", prefix, dirname);
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         if ((j->flags & SD_JOURNAL_LOCAL_ONLY) &&
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             !(dirname_is_machine_id(dirname) > 0 || path_startswith(prefix, "/run")))
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@@ -1369,9 +1465,9 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
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                 goto fail;
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         }
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-        d = opendir(path);
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-        if (!d) {
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-                r = log_debug_errno(errno, "Failed to open directory %s: %m", path);
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+        r = directory_open(j, path, &d);
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+        if (r < 0) {
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+                r = log_debug_errno(errno, "Failed to open directory '%s': %m", path);
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                 goto fail;
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         }
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@@ -1398,25 +1494,17 @@ static int add_directory(sd_journal *j, const char *prefix, const char *dirname)
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                 log_debug("Directory %s added.", m->path);
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         } else if (m->is_root)
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-                return 0;
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-
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-        if (m->wd <= 0 && j->inotify_fd >= 0) {
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-
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-                m->wd = inotify_add_watch(j->inotify_fd, m->path,
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-                                          IN_CREATE|IN_MOVED_TO|IN_MODIFY|IN_ATTRIB|IN_DELETE|
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-                                          IN_DELETE_SELF|IN_MOVE_SELF|IN_UNMOUNT|IN_MOVED_FROM|
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-                                          IN_ONLYDIR);
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+                return 0; /* Don't 'downgrade' from root directory */
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-                if (m->wd > 0 && hashmap_put(j->directories_by_wd, INT_TO_PTR(m->wd), m) < 0)
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-                        inotify_rm_watch(j->inotify_fd, m->wd);
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-        }
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+        m->last_seen_generation = j->generation;
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-        FOREACH_DIRENT_ALL(de, d, return log_debug_errno(errno, "Failed to read directory %s: %m", m->path)) {
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+        directory_watch(j, m, dirfd(d),
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+                        IN_CREATE|IN_MOVED_TO|IN_MODIFY|IN_ATTRIB|IN_DELETE|
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+                        IN_DELETE_SELF|IN_MOVE_SELF|IN_UNMOUNT|IN_MOVED_FROM|
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+                        IN_ONLYDIR);
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-                if (dirent_is_file_with_suffix(de, ".journal") ||
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-                    dirent_is_file_with_suffix(de, ".journal~"))
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-                        (void) add_file(j, m->path, de->d_name);
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-        }
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+        if (!j->no_new_files)
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+                directory_enumerate(j, m, d);
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         check_network(j, dirfd(d));
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@@ -1432,13 +1520,14 @@ fail:
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 static int add_root_directory(sd_journal *j, const char *p, bool missing_ok) {
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         _cleanup_closedir_ DIR *d = NULL;
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-        struct dirent *de;
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         Directory *m;
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         int r, k;
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         assert(j);
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         assert(p);
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+        log_debug("Considering root directory '%s'.", p);
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+
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         if ((j->flags & SD_JOURNAL_RUNTIME_ONLY) &&
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             !path_startswith(p, "/run"))
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                 return -EINVAL;
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@@ -1446,12 +1535,11 @@ static int add_root_directory(sd_journal *j, const char *p, bool missing_ok) {
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         if (j->prefix)
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                 p = strjoina(j->prefix, p);
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-        d = opendir(p);
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-        if (!d) {
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-                if (errno == ENOENT && missing_ok)
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-                        return 0;
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-
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-                r = log_debug_errno(errno, "Failed to open root directory %s: %m", p);
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+        r = directory_open(j, p, &d);
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+        if (r == -ENOENT && missing_ok)
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+                return 0;
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+        if (r < 0) {
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+                log_debug_errno(r, "Failed to open root directory %s: %m", p);
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                 goto fail;
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         }
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@@ -1495,19 +1583,12 @@ static int add_root_directory(sd_journal *j, const char *p, bool missing_ok) {
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                         inotify_rm_watch(j->inotify_fd, m->wd);
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         }
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-        if (j->no_new_files)
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-                return 0;
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-
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-        FOREACH_DIRENT_ALL(de, d, return log_debug_errno(errno, "Failed to read directory %s: %m", m->path)) {
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-                sd_id128_t id;
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+        directory_watch(j, m, dirfd(d),
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+                        IN_CREATE|IN_MOVED_TO|IN_MODIFY|IN_ATTRIB|IN_DELETE|
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+                        IN_ONLYDIR);
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-                if (dirent_is_file_with_suffix(de, ".journal") ||
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-                    dirent_is_file_with_suffix(de, ".journal~"))
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-                        (void) add_file(j, m->path, de->d_name);
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-                else if (IN_SET(de->d_type, DT_DIR, DT_LNK, DT_UNKNOWN) &&
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-                         sd_id128_from_string(de->d_name, &id) >= 0)
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-                        (void) add_directory(j, m->path, de->d_name);
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-        }
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+        if (!j->no_new_files)
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+                directory_enumerate(j, m, d);
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         check_network(j, dirfd(d));
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@@ -2068,6 +2149,18 @@ _public_ void sd_journal_restart_data(sd_journal *j) {
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         j->current_field = 0;
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 }
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+static int reiterate_all_paths(sd_journal *j) {
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+        assert(j);
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+
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+        if (j->no_new_files)
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+                return add_current_paths(j);
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+
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+        if (j->path)
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+                return add_root_directory(j, j->path, true);
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+
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+        return add_search_paths(j);
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+}
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+
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 _public_ int sd_journal_get_fd(sd_journal *j) {
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         int r;
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@@ -2081,15 +2174,11 @@ _public_ int sd_journal_get_fd(sd_journal *j) {
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         if (r < 0)
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                 return r;
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-        /* Iterate through all dirs again, to add them to the
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-         * inotify */
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-        if (j->no_new_files)
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-                r = add_current_paths(j);
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-        else if (j->path)
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-                r = add_root_directory(j, j->path, true);
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-        else
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-                r = add_search_paths(j);
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-        if (r < 0)
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+         log_debug("Reiterating files to get inotify watches established.");
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+
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+        /* Iterate through all dirs again, to add them to the inotify */
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+        r = reiterate_all_paths(j);
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+         if (r < 0)
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                 return r;
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         return j->inotify_fd;
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@@ -2131,12 +2220,58 @@ _public_ int sd_journal_get_timeout(sd_journal *j, uint64_t *timeout_usec) {
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         return 1;
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 }
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+static void process_q_overflow(sd_journal *j) {
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+        JournalFile *f;
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+        Directory *m;
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+        Iterator i;
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+
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+        assert(j);
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+
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+        /* When the inotify queue overruns we need to enumerate and re-validate all journal files to bring our list
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+         * back in sync with what's on disk. For this we pick a new generation counter value. It'll be assigned to all
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+         * journal files we encounter. All journal files and all directories that don't carry it after reenumeration
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+         * are subject for unloading. */
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+
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+        log_debug("Inotify queue overrun, reiterating everything.");
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+
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+        j->generation++;
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+        (void) reiterate_all_paths(j);
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+
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+        ORDERED_HASHMAP_FOREACH(f, j->files, i) {
de541a
+
de541a
+                if (f->last_seen_generation == j->generation)
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+                        continue;
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+
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+                log_debug("File '%s' hasn't been seen in this enumeration, removing.", f->path);
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+                remove_file_real(j, f);
de541a
+        }
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+
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+        HASHMAP_FOREACH(m, j->directories_by_path, i) {
de541a
+
de541a
+                if (m->last_seen_generation == j->generation)
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+                        continue;
de541a
+
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+                if (m->is_root) /* Never GC root directories */
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+                        continue;
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+
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+                log_debug("Directory '%s' hasn't been seen in this enumeration, removing.", f->path);
de541a
+                remove_directory(j, m);
de541a
+        }
de541a
+
de541a
+        log_debug("Reiteration complete.");
de541a
+}
de541a
+
de541a
 static void process_inotify_event(sd_journal *j, struct inotify_event *e) {
de541a
         Directory *d;
de541a
 
de541a
         assert(j);
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         assert(e);
de541a
 
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+        if (e->mask & IN_Q_OVERFLOW) {
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+                process_q_overflow(j);
de541a
+                return;
de541a
+        }
de541a
+
de541a
         /* Is this a subdirectory we watch? */
de541a
         d = hashmap_get(j->directories_by_wd, INT_TO_PTR(e->wd));
de541a
         if (d) {
de541a
diff --git a/src/shared/path-util.c b/src/shared/path-util.c
c62b8e
index 5d4de9ec4d..fcc591686f 100644
de541a
--- a/src/shared/path-util.c
de541a
+++ b/src/shared/path-util.c
dd65c9
@@ -861,3 +861,17 @@ char *prefix_root(const char *root, const char *path) {
de541a
         strcpy(p, path);
de541a
         return n;
de541a
 }
de541a
+
de541a
+int inotify_add_watch_fd(int fd, int what, uint32_t mask) {
de541a
+        char path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
de541a
+        int r;
de541a
+
de541a
+        /* This is like inotify_add_watch(), except that the file to watch is not referenced by a path, but by an fd */
de541a
+        xsprintf(path, "/proc/self/fd/%i", what);
de541a
+
de541a
+        r = inotify_add_watch(fd, path, mask);
de541a
+        if (r < 0)
de541a
+                return -errno;
de541a
+
de541a
+        return r;
de541a
+}
de541a
diff --git a/src/shared/path-util.h b/src/shared/path-util.h
c62b8e
index 34c016229c..96490e12b1 100644
de541a
--- a/src/shared/path-util.h
de541a
+++ b/src/shared/path-util.h
dd65c9
@@ -66,6 +66,8 @@ int fsck_exists(const char *fstype);
de541a
 
de541a
 char *prefix_root(const char *root, const char *path);
de541a
 
de541a
+int inotify_add_watch_fd(int fd, int what, uint32_t mask);
de541a
+
de541a
 /* Similar to prefix_root(), but returns an alloca() buffer, or
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  * possibly a const pointer into the path parameter */
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 #define prefix_roota(root, path)                                        \