Optimise error message write to _lvm_errmsg

Isn't usually perfomance critical - but log_error is used i.e.for debuging,
this code noticable slows down the processing.

Added 512KB limit to avoid memory exhastions in case of some endless loop.

TODO: use _lvm_errmsg buffer only when lvm2api needs it.

diff --git a/lib/log/log.c b/lib/log/log.c
index ec72b7aea0fe63c517f54959de4dae1ed885da7a..66cedfd3d695a5c56794e0c42ec0c059a32cce2d 100644 (file)
--- a/lib/log/log.c
+++ b/lib/log/log.c
@@ -43,6 +43,9 @@ static lvm2_log_fn_t _lvm2_log_fn = NULL;
 static int _lvm_errno = 0;
 static int _store_errmsg = 0;
 static char *_lvm_errmsg = NULL;
+static size_t _lvm_errmsg_size = 0;
+static size_t _lvm_errmsg_len = 0;
+#define MAX_ERRMSG_LEN (512 * 1024)  /* Max size of error buffer 512KB */
 
 void init_log_fn(lvm2_log_fn_t log_fn)
 {
@@ -154,6 +157,7 @@ void reset_lvm_errno(int store_errmsg)
        if (_lvm_errmsg) {
                dm_free(_lvm_errmsg);
                _lvm_errmsg = NULL;
+               _lvm_errmsg_size = _lvm_errmsg_len = 0;
        }
 
        _store_errmsg = store_errmsg;
@@ -189,6 +193,7 @@ void print_log(int level, const char *file, int line, int dm_errno,
        int use_stderr = level & _LOG_STDERR;
        int log_once = level & _LOG_ONCE;
        int fatal_internal_error = 0;
+       size_t msglen;
 
        level &= ~(_LOG_STDERR|_LOG_ONCE);
 
@@ -229,14 +234,24 @@ void print_log(int level, const char *file, int line, int dm_errno,
                message = &buf2[0];
        }
 
-       if (_store_errmsg && (level <= _LOG_ERR)) {
-               if (!_lvm_errmsg)
-                       _lvm_errmsg = dm_strdup(message);
-               else if ((newbuf = dm_realloc(_lvm_errmsg,
-                                             strlen(_lvm_errmsg) +
-                                             strlen(message) + 2))) {
-                       _lvm_errmsg = strcat(newbuf, "\n");
-                       _lvm_errmsg = strcat(newbuf, message);
+       if (_store_errmsg && (level <= _LOG_ERR) &&
+           _lvm_errmsg_len < MAX_ERRMSG_LEN) {
+               msglen = strlen(message);
+               if ((_lvm_errmsg_len + msglen + 1) >= _lvm_errmsg_size) {
+                       _lvm_errmsg_size = 2 * (_lvm_errmsg_len + msglen + 1);
+                       if ((newbuf = dm_realloc(_lvm_errmsg,
+                                                _lvm_errmsg_size)))
+                               _lvm_errmsg = newbuf;
+                       else
+                               _lvm_errmsg_size = _lvm_errmsg_len;
+               }
+               if (_lvm_errmsg &&
+                   (_lvm_errmsg_len + msglen + 2) < _lvm_errmsg_size) {
+                       /* prepend '\n' and copy with '\0' but do not count in */
+                        if (_lvm_errmsg_len)
+                               _lvm_errmsg[_lvm_errmsg_len++] = '\n';
+                       memcpy(_lvm_errmsg + _lvm_errmsg_len, message, msglen + 1);
+                       _lvm_errmsg_len += msglen;
                }
        }