Commit 509a1977 authored by Howard Chu's avatar Howard Chu
Browse files

Change default mem init behavior

Init malloc'd memory by default, use #MDB_NOMEMINIT to disable.
Bump version to 0.9.10
parent 92f71f50
......@@ -70,11 +70,15 @@
* 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.
......@@ -180,7 +184,7 @@ typedef int mdb_filehandle_t;
/** 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))
......@@ -190,7 +194,7 @@ typedef int mdb_filehandle_t;
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 ")"
......@@ -283,8 +287,8 @@ typedef void (MDB_rel_func)(MDB_val *item, void *oldptr, void *newptr, void *rel
#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
......@@ -554,22 +558,25 @@ int mdb_env_create(MDB_env **env);
* 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.
......@@ -1155,8 +1162,8 @@ int mdb_get(MDB_txn *txn, MDB_dbi dbi, MDB_val *key, MDB_val *data);
* 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
......
......@@ -1323,7 +1323,7 @@ mdb_page_malloc(MDB_txn *txn, unsigned num)
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.
......@@ -1341,7 +1341,7 @@ mdb_page_malloc(MDB_txn *txn, unsigned num)
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;
}
......@@ -2508,9 +2508,9 @@ mdb_freelist_save(MDB_txn *txn)
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 */
......@@ -3965,7 +3965,7 @@ fail:
* 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)
......
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