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mdbx: rework mdbx_read_header().
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@ -278,8 +278,10 @@ typedef struct MDB_meta {
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#define MDB_DATASIGN_NONE 0u
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#define MDB_DATASIGN_WEAK 1u
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volatile uint64_t mm_datasync_sign;
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#define META_IS_WEAK(meta) ((meta)->mm_datasync_sign == MDB_DATASIGN_WEAK)
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#define META_IS_STEADY(meta) ((meta)->mm_datasync_sign > MDB_DATASIGN_WEAK)
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#define SIGN_IS_WEAK(sign) ((sign) == MDB_DATASIGN_WEAK)
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#define SIGN_IS_STEADY(sign) ((sign) > MDB_DATASIGN_WEAK)
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#define META_IS_WEAK(meta) SIGN_IS_WEAK((meta)->mm_datasync_sign)
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#define META_IS_STEADY(meta) SIGN_IS_STEADY((meta)->mm_datasync_sign)
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volatile mdbx_canary mm_canary;
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} MDB_meta;
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58
src/mdbx.c
58
src/mdbx.c
@ -3264,38 +3264,32 @@ fail:
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return rc;
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}
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/** Read the environment parameters of a DB environment before
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* mapping it into memory.
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* @param[in] env the environment handle
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* @param[out] meta address of where to store the meta information
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* @return 0 on success, non-zero on failure. */
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/* Read the environment parameters of a DB environment
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* before mapping it into memory. */
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static int __cold mdbx_read_header(MDB_env *env, MDB_meta *meta) {
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MDB_metabuf pbuf;
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MDB_page *p;
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MDB_meta *m;
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int i, rc, off;
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assert(offsetof(MDB_metabuf, mb_metabuf.mm_meta) == PAGEHDRSZ);
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/* We don't know the page size yet, so use a minimum value.
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* Read both meta pages so we can use the latest one. */
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meta->mm_datasync_sign = MDB_DATASIGN_WEAK;
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meta->mm_txnid = 0;
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for (i = off = 0; i < NUM_METAS; i++, off += meta->mm_psize) {
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rc = mdbx_pread(env->me_fd, &pbuf, sizeof(pbuf), off);
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off_t offset = 0;
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/* Read both meta pages so we can use the latest one. */
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for (int loops_left = 2; --loops_left >= 0;) {
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MDB_metabuf buf;
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/* We don't know the page size on first time, so use a minimum value. */
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int rc = mdbx_pread(env->me_fd, &buf, sizeof(buf), offset);
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if (rc != MDB_SUCCESS) {
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mdbx_debug("read: %s", mdbx_strerror(rc));
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return rc;
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}
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p = (MDB_page *)&pbuf;
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MDB_page *p = (MDB_page *)&buf;
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if (!F_ISSET(p->mp_flags, P_META)) {
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mdbx_debug("page %zu not a meta page", p->mp_pgno);
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return MDB_INVALID;
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}
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m = PAGEDATA(p);
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MDB_meta *m = PAGEDATA(p);
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if (m->mm_magic != MDB_MAGIC) {
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mdbx_debug("meta has invalid magic");
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return MDB_INVALID;
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@ -3307,22 +3301,38 @@ static int __cold mdbx_read_header(MDB_env *env, MDB_meta *meta) {
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return MDB_VERSION_MISMATCH;
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}
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if (m->mm_datasync_sign > MDB_DATASIGN_WEAK &&
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m->mm_datasync_sign != mdbx_meta_sign(m))
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/* LY: check signature as a checksum */
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if (META_IS_STEADY(m) && m->mm_datasync_sign != mdbx_meta_sign(m)) {
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mdbx_debug("steady-meta has invalid checksum");
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continue;
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}
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if (mdbx_meta_lt(meta, m))
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if (mdbx_meta_lt(meta, m)) {
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*meta = *m;
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if (META_IS_WEAK(meta))
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loops_left += 1; /* LY: should re-read to avoid race */
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}
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if (offset)
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offset = 0;
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else {
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offset = meta->mm_psize;
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if (!offset)
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offset = m->mm_psize;
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if (!offset)
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offset = env->me_os_psize;
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}
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}
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if (meta->mm_datasync_sign == MDB_DATASIGN_WEAK)
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/* LY: Both meta-pages are weak. */
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if (META_IS_WEAK(meta)) {
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mdbx_debug("both meta-pages are weak, database is corrupted");
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return MDB_CORRUPTED;
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}
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return MDB_SUCCESS;
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}
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/** Fill in most of the zeroed #MDB_meta for an empty database environment */
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/* Fill in most of the zeroed MDB_meta for an empty database environment */
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static void __cold mdbx_env_init_meta0(MDB_env *env, MDB_meta *meta) {
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meta->mm_magic = MDB_MAGIC;
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meta->mm_version = MDB_DATA_VERSION;
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