journal: add sd_journal_open_files

This allows the caller to explicitly specify which journal files
should be opened. The same functionality could be achieved before
by creating a directory and playing around with symlinks. It
is useful to debug stuff and explore the journal, and has been
requested before.

Waiting is supported, the journal will notice modifications on
the files supplied when opening the journal, but will not add
any new files.

src/journal/journal-internal.h

@@ -123,6 +123,7 @@ struct sd_journal {
         uint64_t unique_offset;
 
         bool on_network;
+        bool no_new_files;
 
         size_t data_threshold;
 

src/journal/libsystemd-journal.sym

@@ -104,3 +104,8 @@ LIBSYSTEMD_JOURNAL_202 {
 global:
         sd_journal_add_conjunction;
 } LIBSYSTEMD_JOURNAL_201;
+
+LIBSYSTEMD_JOURNAL_205 {
+global:
+        sd_journal_open_files;
+} LIBSYSTEMD_JOURNAL_202;

src/journal/sd-journal.c

@@ -33,6 +33,7 @@
 #include "journal-file.h"
 #include "hashmap.h"
 #include "list.h"
+#include "strv.h"
 #include "path-util.h"
 #include "lookup3.h"
 #include "compress.h"
@@ -1278,37 +1279,24 @@ static bool file_type_wanted(int flags, const char *filename) {
         return false;
 }
 
-static int add_file(sd_journal *j, const char *prefix, const char *filename) {
-        _cleanup_free_ char *path = NULL;
-        int r;
+static int add_any_file(sd_journal *j, const char *path) {
         JournalFile *f;
+        int r;
 
         assert(j);
-        assert(prefix);
-        assert(filename);
-
-        if (!file_type_wanted(j->flags, filename))
-                return 0;
-
-        path = strjoin(prefix, "/", filename, NULL);
-        if (!path)
-                return -ENOMEM;
+        assert(path);
 
         if (hashmap_get(j->files, path))
                 return 0;
 
         if (hashmap_size(j->files) >= JOURNAL_FILES_MAX) {
-                log_debug("Too many open journal files, not adding %s, ignoring.", path);
+                log_warning("Too many open journal files, not adding %s.", path);
                 return set_put_error(j, -ETOOMANYREFS);
         }
 
         r = journal_file_open(path, O_RDONLY, 0, false, false, NULL, j->mmap, NULL, &f);
-        if (r < 0) {
-                if (errno == ENOENT)
-                        return 0;
-
+        if (r < 0)
                 return r;
-        }
 
         /* journal_file_dump(f); */
 
@@ -1327,6 +1315,28 @@ static int add_file(sd_journal *j, const char *prefix, const char *filename) {
         return 0;
 }
 
+static int add_file(sd_journal *j, const char *prefix, const char *filename) {
+        _cleanup_free_ char *path = NULL;
+        int r;
+
+        assert(j);
+        assert(prefix);
+        assert(filename);
+
+        if (j->no_new_files ||
+            !file_type_wanted(j->flags, filename))
+                return 0;
+
+        path = strjoin(prefix, "/", filename, NULL);
+        if (!path)
+                return -ENOMEM;
+
+        r = add_any_file(j, path);
+        if (r == -ENOENT)
+                return 0;
+        return 0;
+}
+
 static int remove_file(sd_journal *j, const char *prefix, const char *filename) {
         char *path;
         JournalFile *f;
@@ -1507,6 +1517,9 @@ static int add_root_directory(sd_journal *j, const char *p) {
                         inotify_rm_watch(j->inotify_fd, m->wd);
         }
 
+        if (j->no_new_files)
+                return 0;
+
         for (;;) {
                 struct dirent *de;
                 union dirent_storage buf;
@@ -1587,6 +1600,36 @@ static int add_search_paths(sd_journal *j) {
         return 0;
 }
 
+static int add_current_paths(sd_journal *j) {
+        Iterator i;
+        JournalFile *f;
+
+        assert(j);
+        assert(j->no_new_files);
+
+        /* Simply adds all directories for files we have open as
+         * "root" directories. We don't expect errors here, so we
+         * treat them as fatal. */
+
+        HASHMAP_FOREACH(f, j->files, i) {
+                int r;
+                _cleanup_free_ char *dir;
+
+                dir = dirname_malloc(f->path);
+                if (!dir)
+                        return -ENOMEM;
+
+                r = add_root_directory(j, dir);
+                if (r < 0) {
+                        set_put_error(j, r);
+                        return r;
+                }
+        }
+
+        return 0;
+}
+
+
 static int allocate_inotify(sd_journal *j) {
         assert(j);
 
@@ -1697,6 +1740,40 @@ fail:
         return r;
 }
 
+_public_ int sd_journal_open_files(sd_journal **ret, const char **paths, int flags) {
+        sd_journal *j;
+        const char **path;
+        int r;
+
+        if (!ret)
+                return -EINVAL;
+
+        if (flags != 0)
+                return -EINVAL;
+
+        j = journal_new(flags, NULL);
+        if (!j)
+                return -ENOMEM;
+
+        STRV_FOREACH(path, paths) {
+                r = add_any_file(j, *path);
+                if (r < 0) {
+                        log_error("Failed to open %s: %s", *path, strerror(-r));
+                        goto fail;
+                }
+        }
+
+        j->no_new_files = true;
+
+        *ret = j;
+        return 0;
+
+fail:
+        sd_journal_close(j);
+
+        return r;
+}
+
 _public_ void sd_journal_close(sd_journal *j) {
         Directory *d;
         JournalFile *f;
@@ -2017,7 +2094,9 @@ _public_ int sd_journal_get_fd(sd_journal *j) {
 
         /* Iterate through all dirs again, to add them to the
          * inotify */
-        if (j->path)
+        if (j->no_new_files)
+                r = add_current_paths(j);
+        else if (j->path)
                 r = add_root_directory(j, j->path);
         else
                 r = add_search_paths(j);