* access to locks and lock file. Exceptions: On read-only filesystems
* or with the #MDB_NOLOCK flag described under #mdb_env_open().
*
- * - By default, unused portions of the datafile may receive garbage data
- * from memory freed by other code. (This does not happen when using
- * the #MDB_WRITEMAP flag.) Applications handling sensitive data
+ * - By default, in versions before 0.9.10, unused portions of the data
+ * file might receive garbage data from memory freed by other code.
+ * (This did not happen when using the #MDB_WRITEMAP flag.) As of
+ * 0.9.10 the default behavior is to initialize such memory before
+ * writing to the data file. Since there may be a slight performance
+ * cost due to this initialization, applications may disable it using
+ * the #MDB_NOMEMINIT flag. Applications handling sensitive data
* which must not be written, and which don't use #MDB_WRITEMAP,
- * need to prevent this with the #MDB_CLEANMEM flag.
+ * should not use this flag.
*
* - A thread can only use one transaction at a time, plus any child
* transactions. Each transaction belongs to one thread. See below.
/** Library minor version */
#define MDB_VERSION_MINOR 9
/** Library patch version */
-#define MDB_VERSION_PATCH 9
+#define MDB_VERSION_PATCH 10
/** Combine args a,b,c into a single integer for easy version comparisons */
#define MDB_VERINT(a,b,c) (((a) << 24) | ((b) << 16) | (c))
MDB_VERINT(MDB_VERSION_MAJOR,MDB_VERSION_MINOR,MDB_VERSION_PATCH)
/** The release date of this library version */
-#define MDB_VERSION_DATE "October 24, 2013"
+#define MDB_VERSION_DATE "November 11, 2013"
/** A stringifier for the version info */
#define MDB_VERSTR(a,b,c,d) "MDB " #a "." #b "." #c ": (" d ")"
#define MDB_NOLOCK 0x400000
/** don't do readahead (no effect on Windows) */
#define MDB_NORDAHEAD 0x800000
- /** don't write uninitialized malloc'd memory to datafile */
-#define MDB_CLEANMEM 0x1000000
+ /** don't initialize malloc'd memory before writing to datafile */
+#define MDB_NOMEMINIT 0x1000000
/** @} */
/** @defgroup mdb_dbi_open Database Flags
* supports it. Turning it off may help random read performance
* when the DB is larger than RAM and system RAM is full.
* The option is not implemented on Windows.
- * <li>#MDB_CLEANMEM
- * Don't write uninitialized memory to unused spaces in the datafile.
- * By default, memory for pages written to the datafile is obtained
- * using malloc, and only the portions that LMDB uses are modified.
- * Unused portions of a page may contain leftover data from other
- * code that used the heap and subsequently freed that memory.
- * That can be a problem for applications which handle sensitive data
- * like passwords, and it makes memory checkers like Valgrind noisy.
- * With this flag, unused portions of pages will be initialized to
- * zero. This flag is not needed with #MDB_WRITEMAP, which writes
- * directly to the mmap instead of using malloc for pages. The
+ * <li>#MDB_NOMEMINIT
+ * Don't initialize malloc'd memory before writing to unused spaces
+ * in the data file. By default, memory for pages written to the data
+ * file is obtained using malloc. While these pages may be reused in
+ * subsequent transactions, freshly malloc'd pages will be initialized
+ * to zeroes before use. This avoids persisting leftover data from other
+ * code (that used the heap and subsequently freed the memory) into the
+ * data file. Note that many other system libraries may allocate
+ * and free memory from the heap for arbitrary uses. E.g., stdio may
+ * use the heap for file I/O buffers. This initialization step comes
+ * at some performance cost so some applications may want to disable
+ * it using this flag. This option can be a problem for applications
+ * which handle sensitive data like passwords, and it makes memory
+ * checkers like Valgrind noisy. This flag is not needed with #MDB_WRITEMAP,
+ * which writes directly to the mmap instead of using malloc for pages. The
* initialization is also skipped if #MDB_RESERVE is used; the
* caller is expected to overwrite all of the memory that was
* reserved in that case.
* This flag may be changed at any time using #mdb_env_set_flags().
- * It comes at some performance cost.
* </ul>
* @param[in] mode The UNIX permissions to set on created files. This parameter
* is ignored on Windows.
* reserved space, which the caller can fill in later - before
* the next update operation or the transaction ends. This saves
* an extra memcpy if the data is being generated later.
- * MDB does nothing else with this memory, even if #MDB_CLEANMEM is
- * set - the caller is expected to modify all of the space requested.
+ * MDB does nothing else with this memory, the caller is expected
+ * to modify all of the space requested.
* <li>#MDB_APPEND - append the given key/data pair to the end of the
* database. No key comparisons are performed. This option allows
* fast bulk loading when keys are already known to be in the
MDB_env *env = txn->mt_env;
MDB_page *ret = env->me_dpages;
size_t psize = env->me_psize, sz = psize, off;
- /* For #MDB_CLEANMEM, psize counts how much to init.
+ /* For ! #MDB_NOMEMINIT, psize counts how much to init.
* For a single page alloc, we init everything after the page header.
* For multi-page, we init the final page; if the caller needed that
* many pages they will be filling in at least up to the last page.
off = sz - psize;
}
if ((ret = malloc(sz)) != NULL) {
- if (env->me_flags & MDB_CLEANMEM) {
+ if (!(env->me_flags & MDB_NOMEMINIT)) {
memset((char *)ret + off, 0, psize);
ret->mp_pad = 0;
}
return rc;
}
- /* MDB_RESERVE cancels CLEANMEM in ovpage malloc (when no WRITEMAP) */
- clean_limit = (env->me_flags & (MDB_CLEANMEM|MDB_WRITEMAP)) == MDB_CLEANMEM
- ? maxfree_1pg : SSIZE_MAX;
+ /* MDB_RESERVE cancels meminit in ovpage malloc (when no WRITEMAP) */
+ clean_limit = (env->me_flags & (MDB_NOMEMINIT|MDB_WRITEMAP))
+ ? SSIZE_MAX : maxfree_1pg;
for (;;) {
/* Come back here after each Put() in case freelist changed */
* at runtime. Changing other flags requires closing the
* environment and re-opening it with the new flags.
*/
-#define CHANGEABLE (MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_CLEANMEM)
+#define CHANGEABLE (MDB_NOSYNC|MDB_NOMETASYNC|MDB_MAPASYNC|MDB_NOMEMINIT)
#define CHANGELESS (MDB_FIXEDMAP|MDB_NOSUBDIR|MDB_RDONLY|MDB_WRITEMAP| \
MDB_NOTLS|MDB_NOLOCK|MDB_NORDAHEAD)
projects / openldap / commitdiff