nftl.c

讲述linux的初始化过程

					       "in Virtual Unit Chain %d for block %d\n",
					       thisVUC, block);
				break;
			case SECTOR_IGNORE:
			case SECTOR_DELETED:
				break;
			default:
				printk("Unknown status for block %d in EUN %d: %x\n",
				       block, thisEUN, status);
			}
		}

		if (!silly--) {
			printk(KERN_WARNING "Infinite loop in Virtual Unit Chain 0x%x\n",
			       thisVUC);
			return BLOCK_NIL;
		}
		
		thisEUN = nftl->ReplUnitTable[thisEUN];
	}

	if (inplace) {
		/* We're being asked to be a fold-in-place. Check
		   that all blocks are either present or SECTOR_FREE
		   in the target block. If not, we're going to have
		   to fold out-of-place anyway.
		*/
		for (block = 0; block < nftl->EraseSize / 512 ; block++) {
			if (BlockLastState[block] != SECTOR_FREE &&
			    BlockMap[block] != targetEUN) {
				DEBUG(MTD_DEBUG_LEVEL1, "Setting inplace to 0. VUC %d, "
				      "block %d was %x lastEUN, "
				      "and is in EUN %d (%s) %d\n",
				      thisVUC, block, BlockLastState[block],
				      BlockMap[block], 
				      BlockMap[block]== targetEUN ? "==" : "!=",
				      targetEUN);
				inplace = 0;
				break;
			}
		}

		if (pendingblock >= (thisVUC * (nftl->EraseSize / 512)) &&
		    pendingblock < ((thisVUC + 1)* (nftl->EraseSize / 512)) &&
		    BlockLastState[pendingblock - (thisVUC * (nftl->EraseSize / 512))] !=
		    SECTOR_FREE) {
			DEBUG(MTD_DEBUG_LEVEL1, "Pending write not free in EUN %d. "
			      "Folding out of place.\n", targetEUN);
			inplace = 0;
		}
	}
	
	if (!inplace) {
		DEBUG(MTD_DEBUG_LEVEL1, "Cannot fold Virtual Unit Chain %d in place. "
		      "Trying out-of-place\n", thisVUC);
		/* We need to find a targetEUN to fold into. */
		targetEUN = NFTL_findfreeblock(nftl, 1);
		if (targetEUN == BLOCK_NIL) {
			/* Ouch. Now we're screwed. We need to do a 
			   fold-in-place of another chain to make room
			   for this one. We need a better way of selecting
			   which chain to fold, because makefreeblock will 
			   only ask us to fold the same one again.
			*/
			printk(KERN_WARNING
			       "NFTL_findfreeblock(desperate) returns 0xffff.\n");
			return BLOCK_NIL;
		}
	} else {
            /* We put a fold mark in the chain we are folding only if
               we fold in place to help the mount check code. If we do
               not fold in place, it is possible to find the valid
               chain by selecting the longer one */
            oob.u.c.FoldMark = oob.u.c.FoldMark1 = cpu_to_le16(FOLD_MARK_IN_PROGRESS);
            oob.u.c.unused = 0xffffffff;
            MTD_WRITEOOB(nftl->mtd, (nftl->EraseSize * targetEUN) + 2 * 512 + 8, 
                         8, &retlen, (char *)&oob.u);
        }

	/* OK. We now know the location of every block in the Virtual Unit Chain,
	   and the Erase Unit into which we are supposed to be copying.
	   Go for it.
	*/
	DEBUG(MTD_DEBUG_LEVEL1,"Folding chain %d into unit %d\n", thisVUC, targetEUN);
	for (block = 0; block < nftl->EraseSize / 512 ; block++) {
		unsigned char movebuf[512];
		int ret;

		/* If it's in the target EUN already, or if it's pending write, do nothing */
		if (BlockMap[block] == targetEUN ||
		    (pendingblock == (thisVUC * (nftl->EraseSize / 512) + block))) {
			continue;
		}

                /* copy only in non free block (free blocks can only
                   happen in case of media errors or deleted blocks) */
                if (BlockMap[block] == BLOCK_NIL)
                        continue;
                
                ret = MTD_READECC(nftl->mtd, (nftl->EraseSize * BlockMap[block])
                                  + (block * 512), 512, &retlen, movebuf, (char *)&oob); 
                if (ret < 0) {
                    ret = MTD_READECC(nftl->mtd, (nftl->EraseSize * BlockMap[block])
                                      + (block * 512), 512, &retlen,
                                      movebuf, (char *)&oob); 
                    if (ret != -EIO) 
                        printk("Error went away on retry.\n");
                }
                MTD_WRITEECC(nftl->mtd, (nftl->EraseSize * targetEUN) + (block * 512),
                             512, &retlen, movebuf, (char *)&oob);
	}
        
        /* add the header so that it is now a valid chain */
        oob.u.a.VirtUnitNum = oob.u.a.SpareVirtUnitNum
                = cpu_to_le16(thisVUC);
        oob.u.a.ReplUnitNum = oob.u.a.SpareReplUnitNum = 0xffff;
        
        MTD_WRITEOOB(nftl->mtd, (nftl->EraseSize * targetEUN) + 8, 
                     8, &retlen, (char *)&oob.u);

	/* OK. We've moved the whole lot into the new block. Now we have to free the original blocks. */

	/* At this point, we have two different chains for this Virtual Unit, and no way to tell 
	   them apart. If we crash now, we get confused. However, both contain the same data, so we
	   shouldn't actually lose data in this case. It's just that when we load up on a medium which
	   has duplicate chains, we need to free one of the chains because it's not necessary any more.
	*/
	thisEUN = nftl->EUNtable[thisVUC];
	DEBUG(MTD_DEBUG_LEVEL1,"Want to erase\n");

	/* For each block in the old chain (except the targetEUN of course), 
	   free it and make it available for future use */
	while (thisEUN <= nftl->lastEUN && thisEUN != targetEUN) {
		unsigned int EUNtmp;

                EUNtmp = nftl->ReplUnitTable[thisEUN];

                if (NFTL_formatblock(nftl, thisEUN) < 0) {
			/* could not erase : mark block as reserved
			 * FixMe: Update Bad Unit Table on disk
			 */
			nftl->ReplUnitTable[thisEUN] = BLOCK_RESERVED;
                } else {
			/* correctly erased : mark it as free */
			nftl->ReplUnitTable[thisEUN] = BLOCK_FREE;
			nftl->numfreeEUNs++;
                }
                thisEUN = EUNtmp;
	}
	
	/* Make this the new start of chain for thisVUC */
	nftl->ReplUnitTable[targetEUN] = BLOCK_NIL;
	nftl->EUNtable[thisVUC] = targetEUN;

	return targetEUN;
}

u16 NFTL_makefreeblock( struct NFTLrecord *nftl , unsigned pendingblock)
{
	/* This is the part that needs some cleverness applied. 
	   For now, I'm doing the minimum applicable to actually
	   get the thing to work.
	   Wear-levelling and other clever stuff needs to be implemented
	   and we also need to do some assessment of the results when
	   the system loses power half-way through the routine.
	*/
	u16 LongestChain = 0;
	u16 ChainLength = 0, thislen;
	u16 chain, EUN;

	for (chain = 0; chain < nftl->MediaHdr.FormattedSize / nftl->EraseSize; chain++) {
		EUN = nftl->EUNtable[chain];
		thislen = 0;

		while (EUN <= nftl->lastEUN) {
			thislen++;
			//printk("VUC %d reaches len %d with EUN %d\n", chain, thislen, EUN);
			EUN = nftl->ReplUnitTable[EUN] & 0x7fff;
			if (thislen > 0xff00) {
				printk("Endless loop in Virtual Chain %d: Unit %x\n",
				       chain, EUN);
			}
			if (thislen > 0xff10) {
				/* Actually, don't return failure. Just ignore this chain and
				   get on with it. */
				thislen = 0;
				break;
			}
		}

		if (thislen > ChainLength) {
			//printk("New longest chain is %d with length %d\n", chain, thislen);
			ChainLength = thislen;
			LongestChain = chain;
		}
	}

	if (ChainLength < 2) {
		printk(KERN_WARNING "No Virtual Unit Chains available for folding. "
		       "Failing request\n");
		return 0xffff;
	}

	return NFTL_foldchain (nftl, LongestChain, pendingblock);
}

/* NFTL_findwriteunit: Return the unit number into which we can write 
                       for this block. Make it available if it isn't already
*/
static inline u16 NFTL_findwriteunit(struct NFTLrecord *nftl, unsigned block)
{
	u16 lastEUN;
	u16 thisVUC = block / (nftl->EraseSize / 512);
	unsigned int writeEUN;
	unsigned long blockofs = (block * 512) & (nftl->EraseSize -1);
	size_t retlen;
	int silly, silly2 = 3;
	struct nftl_oob oob;

	do {
		/* Scan the media to find a unit in the VUC which has
		   a free space for the block in question.
		*/

		/* This condition catches the 0x[7f]fff cases, as well as 
		   being a sanity check for past-end-of-media access
		*/
		lastEUN = BLOCK_NIL;
		writeEUN = nftl->EUNtable[thisVUC];
                silly = MAX_LOOPS;
		while (writeEUN <= nftl->lastEUN) {
			struct nftl_bci bci;
			size_t retlen;
                        unsigned int status;

			lastEUN = writeEUN;

			MTD_READOOB(nftl->mtd, (writeEUN * nftl->EraseSize) + blockofs,
				    8, &retlen, (char *)&bci);
			
			DEBUG(MTD_DEBUG_LEVEL2, "Status of block %d in EUN %d is %x\n",
			      block , writeEUN, le16_to_cpu(bci.Status));

                        status = bci.Status | bci.Status1;
			switch(status) {
			case SECTOR_FREE:
				return writeEUN;

			case SECTOR_DELETED:
			case SECTOR_USED:
			case SECTOR_IGNORE:
				break;
			default:
				// Invalid block. Don't use it any more. Must implement.
				break;			
			}
			
			if (!silly--) { 
				printk(KERN_WARNING
				       "Infinite loop in Virtual Unit Chain 0x%x\n",
				       thisVUC);
				return 0xffff;
			}

			/* Skip to next block in chain */
			writeEUN = nftl->ReplUnitTable[writeEUN];
		}

		/* OK. We didn't find one in the existing chain, or there 
		   is no existing chain. */

		/* Try to find an already-free block */
		writeEUN = NFTL_findfreeblock(nftl, 0);

		if (writeEUN == BLOCK_NIL) {
			/* That didn't work - there were no free blocks just
			   waiting to be picked up. We're going to have to fold
			   a chain to make room.
			*/

			/* First remember the start of this chain */
			//u16 startEUN = nftl->EUNtable[thisVUC];
			
			//printk("Write to VirtualUnitChain %d, calling makefreeblock()\n", thisVUC);
			writeEUN = NFTL_makefreeblock(nftl, 0xffff);
			
			if (writeEUN == BLOCK_NIL) {
				/* Ouch. This should never happen - we should
				   always be able to make some room somehow. 
				   If we get here, we've allocated more storage 
				   space than actual media, or our makefreeblock
				   routine is missing something.
				*/
				printk(KERN_WARNING "Cannot make free space.\n");
				return BLOCK_NIL;
			}			
			//printk("Restarting scan\n");
			lastEUN = BLOCK_NIL;
			continue;
		}

		/* We've found a free block. Insert it into the chain. */
		
		if (lastEUN != BLOCK_NIL) {
                    thisVUC |= 0x8000; /* It's a replacement block */
		} else {
                    /* The first block in a new chain */
                    nftl->EUNtable[thisVUC] = writeEUN;
		}

		/* set up the actual EUN we're writing into */
		/* Both in our cache... */
		nftl->ReplUnitTable[writeEUN] = BLOCK_NIL;

		/* ... and on the flash itself */
		MTD_READOOB(nftl->mtd, writeEUN * nftl->EraseSize + 8, 8,
			    &retlen, (char *)&oob.u);

		oob.u.a.VirtUnitNum = oob.u.a.SpareVirtUnitNum = cpu_to_le16(thisVUC);

		MTD_WRITEOOB(nftl->mtd, writeEUN * nftl->EraseSize + 8, 8,
                             &retlen, (char *)&oob.u);

                /* we link the new block to the chain only after the
                   block is ready. It avoids the case where the chain
                   could point to a free block */
                if (lastEUN != BLOCK_NIL) {
			/* Both in our cache... */
			nftl->ReplUnitTable[lastEUN] = writeEUN;
			/* ... and on the flash itself */
			MTD_READOOB(nftl->mtd, (lastEUN * nftl->EraseSize) + 8,
				    8, &retlen, (char *)&oob.u);

			oob.u.a.ReplUnitNum = oob.u.a.SpareReplUnitNum
				= cpu_to_le16(writeEUN);

			MTD_WRITEOOB(nftl->mtd, (lastEUN * nftl->EraseSize) + 8,
				     8, &retlen, (char *)&oob.u);
		}

		return writeEUN;

	} while (silly2--);

	printk(KERN_WARNING "Error folding to make room for Virtual Unit Chain 0x%x\n",
	       thisVUC);
	return 0xffff;
}

static int NFTL_writeblock(struct NFTLrecord *nftl, unsigned block, char *buffer)
{
	u16 writeEUN;
	unsigned long blockofs = (block * 512) & (nftl->EraseSize - 1);
	size_t retlen;
	u8 eccbuf[6];

	writeEUN = NFTL_findwriteunit(nftl, block);

	if (writeEUN == BLOCK_NIL) {
		printk(KERN_WARNING
		       "NFTL_writeblock(): Cannot find block to write to\n");
		/* If we _still_ haven't got a block to use, we're screwed */
		return 1;
	}

	MTD_WRITEECC(nftl->mtd, (writeEUN * nftl->EraseSize) + blockofs,
		     512, &retlen, (char *)buffer, (char *)eccbuf);
        /* no need to write SECTOR_USED flags since they are written in mtd_writeecc */

	return 0;
}