91 lines
4.7 KiB
C
91 lines
4.7 KiB
C
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/****************************************************************
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* *
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* Copyright 2005, 2011 Fidelity Information Services, Inc *
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* *
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* This source code contains the intellectual property *
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* of its copyright holder(s), and is made available *
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* under a license. If you do not know the terms of *
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* the license, please stop and do not read further. *
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* *
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****************************************************************/
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#ifndef __JNL_GET_CHECKSUM_H_
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#define __JNL_GET_CHECKSUM_H_
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#define INIT_CHECKSUM_SEED 1
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#define CHKSUM_SEGLEN4 8
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#define ADJUST_CHECKSUM(sum, num4) (((sum) >> 4) + ((sum) << 4) + (num4))
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#ifdef UNIX
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/* Include the sequence number field of the journal record as part of the checksum computation. ADJUST_CHECKSUM
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* macro currently relies on 4 byte quanitites as inputs. But, the journal sequence number is an 8 byte quantity.
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* To avoid multiple calls to ADJUST_CHECKSUM to include the complete 8 byte sequence number, each of which might
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* take around 4-5 instructions, consider only the lower order order 4 bytes of the sequence number for the checksum
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* compuation. Given that the lower order bytes are the ones that will keep changing for every transaction, this
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* should suffice.
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*/
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#define ADJUST_CHECKSUM_WITH_SEQNO(IS_REPLICATED, CHECKSUM, SEQNO) \
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{ \
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seq_num rec_token_seq; \
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\
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if (IS_REPLICATED) \
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{ \
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rec_token_seq = SEQNO; \
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CHECKSUM = ADJUST_CHECKSUM(CHECKSUM, (rec_token_seq & 0x0000FFFF)); \
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} \
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}
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#else
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#define ADJUST_CHECKSUM_WITH_SEQNO(IS_REPLICATED, CHECKSUM, SEQNO)
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#endif
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/* This macro is to be used whenever we are computing the checksum of a block that has been acquired. */
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#define JNL_GET_CHECKSUM_ACQUIRED_BLK(cse, csd, csa, old_blk, bsize) \
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{ \
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cache_rec_ptr_t cr; \
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boolean_t cr_is_null; \
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\
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GBLREF uint4 dollar_tlevel; \
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\
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/* Record current database tn before computing checksum of acquired block. This is used \
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* later by the commit logic to determine if the block contents have changed (and hence \
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* if recomputation of checksum is necessary). For BG, we have two-phase commit where \
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* phase2 is done outside of crit. So it is possible that we note down the current database \
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* tn and then compute checksums outside of crit and then get crit and yet in the validation \
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* logic find the block header tn is LESSER than the noted dbtn (even though the block \
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* contents changed after the noted dbtn). This will cause us to falsely validate this block \
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* as not needing checksum recomputation. To ensure the checksum is recomputed inside crit, \
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* we note down a tn of 0 in case the block is locked for update (cr->in_tend is non-zero). \
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*/ \
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assert((gds_t_acquired == cse->mode) || (gds_t_create == cse->mode)); \
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assert(cse->old_block == (sm_uc_ptr_t)(old_blk)); \
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assert((bsize) <= csd->blk_size); \
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/* Since this macro is invoked only in case of before-image journaling and since MM does not \
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* support before-image journaling, we can safely assert that BG is the only access method. \
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*/ \
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assert(dba_bg == csd->acc_meth); \
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/* In rare cases cse->cr can be NULL even though this block is an acquired block. This is \
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* possible if we are in TP and this block was part of the tree in the initial phase of the \
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* transaction but was marked free (by another process concurrently) in the later phase of \
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* the same TP transaction. But this case is a sureshot restart situation so be safe and \
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* ensure recomputation happens inside of crit just in case we dont restart. Also add asserts \
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* (using donot_commit variable) to ensure we do restart this transaction. \
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*/ \
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cr = cse->cr; \
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cr_is_null = (NULL == cr); \
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assert(!cr_is_null || dollar_tlevel); \
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DEBUG_ONLY(if (cr_is_null) TREF(donot_commit) |= DONOTCOMMIT_JNLGETCHECKSUM_NULL_CR;) \
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cse->tn = ((cr_is_null || cr->in_tend) ? 0 : csd->trans_hist.curr_tn); \
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/* If cr is NULL, it is a restartable situation. So dont waste time computing checksums. Also \
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* if the db is encrypted, we cannot get at the encryption global buffer (jnl_get_checksum \
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* requires this) since we dont even have a regular global buffer corresponding to this block \
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* so there is no way jnl_get_checksum can proceed in that case. So it is actually necessary \
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* to avoid computing checksums if cr is NULL. \
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*/ \
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cse->blk_checksum = !cr_is_null ? jnl_get_checksum((uint4 *)(old_blk), csa, (bsize)) : 0; \
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}
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uint4 jnl_get_checksum(uint4 *buff, sgmnt_addrs *csa, int bufflen);
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uint4 jnl_get_checksum_entire(uint4 *buff, int bufflen);
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#endif
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