标签：des style color 使用 os strong
对于yaffs2文件系统来说，坏块管理无疑是最关键的问题；下面就Yaffs2文件系统读、写操作来分析坏块产生记。{
int attempts = 0;int write_ok = 0;int chunk;/*删除checkpt的数据，其实也就是无效掉checkpt的数据*/
yaffs2_checkpt_invalidate(dev);do {struct yaffs_block_info *bi = 0;int erased_ok = 0;
/*申请一个没有使用的chunk*/
chunk = yaffs_alloc_chunk(dev, use_reserver, &bi);if (chunk < 0) {
/*进入到这里表示flash里面已经没有使用空间，没有使用空间，整个文件系统进入自读状态*/
/* no space */break;
}
/* First check this chunk is erased, if it needs
每个异常关机后再开机后，每个申请块的第一个chunk必须进行异常检查这里仅仅是第一个申请到的chunk,除非是强制所有的都要检查，不然只检查上面的内容。
* checking. The checking policy (unless forced* always on) is as follows:*
/*检查第一个申请的chunk，如果检查通过，其它的chunk都不用再进行检查了；如果检查失败，则再次检查；如果块被擦除，则不需要检查。
* Check the first page we try to write in a block.* If the check passes then we don‘t need to check any* more. If the check fails, we check again...* If the block has been erased, we don‘t need to check.** However, if the block has been prioritised for gc,* then we think there might be something odd about* this block and stop using it.** Rationale: We should only ever see chunks that have* not been erased if there was a partially written* chunk due to power loss. This checking policy should* catch that case with very few checks and thus save a* lot of checks that are most likely not needed.** Mods to the above* If an erase check fails or the write fails we skip the* rest of the block.
/* let‘s give it a try */attempts++;
/*如果dev->param.always_check_erased置位，表示所有chunk都检查*/
if (dev->param.always_check_erased)bi->skip_erased_check = 0;
/*第一次的要进行检查*/
if (!bi->skip_erased_check) {
/*对当前申请的chunk进行检查，检查的原则是，先检查tag数据中的ecc是否正确，检查无异常则erased为1，否则erased为0*/
erased_ok = yaffs_check_chunk_erased(dev, chunk);if (erased_ok != YAFFS_OK) {
/*进入到这里表示数据检查不通过，回收这个异常chunk*/
yaffs_trace(YAFFS_TRACE_ERROR,"**>> yaffs chunk %d was not erased",chunk);/* If not erased, delete this one,* skip rest of block and* try another chunk */
/*下面两个函数目前不想太过考虑*/
yaffs_chunk_del(dev, chunk, 1, __LINE__);yaffs_skip_rest_of_block(dev);continue;}}
/*写数据到chunk，同时写oob区*/
write_ok = yaffs_wr_chunk_tags_nand(dev, chunk, data, tags);
/*表示不跳过检查*/
if (!bi->skip_erased_check)write_ok =
/*这里对写入的数据进行检查，原则是先把main区的数据全部读出来，然后再进行memcmp比较，比较完后再对oob的16个字节yaffs2数据也进行对比，全部正常则表示写正常*/
yaffs_verify_chunk_written(dev, chunk, data, tags);
if (write_ok != YAFFS_OK) {
/*如果写不正常，则进行下面的回收操作,下面对这个问题再另行分析*/
yaffs_handle_chunk_wr_error(dev, chunk, erased_ok);
continue;}
/*置位，这个块只检查一次*/
bi->skip_erased_check = 1;/* Copy the data into the robustification buffer */yaffs_handle_chunk_wr_ok(dev, chunk, data, tags);} while (write_ok != YAFFS_OK &&(yaffs_wr_attempts <= 0 || attempts <= yaffs_wr_attempts));if (!write_ok)chunk = -1;if (attempts > 1) {yaffs_trace(YAFFS_TRACE_ERROR,"**>> yaffs write required %d attempts",attempts);
/*计算写异常次数*/
dev->n_retired_writes += (attempts - 1);}return chunk;
int flash_block = nand_chunk / dev->param.chunks_per_block;struct yaffs_block_info *bi = yaffs_get_block_info(dev, flash_block);/*操作这个块优先进行垃圾回收,下面紧接着分析这个函数*/
yaffs_handle_chunk_error(dev, bi);if (erased_ok) {/* Was an actual write failure,* so mark the block for retirement.*/
/*这里置位，直接表示这个块会被标记为坏块*/
bi->needs_retiring = 1;yaffs_trace(YAFFS_TRACE_ERROR | YAFFS_TRACE_BAD_BLOCKS,"**>> Block %d needs retiring", flash_block);}/* Delete the chunk */yaffs_chunk_del(dev, nand_chunk, 1, __LINE__);yaffs_skip_rest_of_block(dev);
if (!bi->gc_prioritise) {/*表示这个块上有出现过ecc校验出错，* 回收时优先回收这一块*/bi->gc_prioritise = 1;/*表示这个设备上有优先可以回收的块*/dev->has_pending_prioritised_gc = 1;/*记录ecc错误的次数*/bi->chunk_error_strikes++;
/*如果ecc异常超过3次以上，那么表示这个块也就是坏块了*/
if (bi->chunk_error_strikes > 3) {bi->needs_retiring = 1; /* Too many stikes, so retire *//*这里是我要检验的一个点，就是有ecc出错的情况下* 这里会有打印信息*/yaffs_trace(YAFFS_TRACE_ALWAYS,"yaffs: Block struck out");}}
struct yaffs_block_info *bi = yaffs_get_block_info(dev, block_no);int erased_ok = 0;int i;/* If the block is still healthy erase it and mark as clean.* If the block has had a data failure, then retire it.*/yaffs_trace(YAFFS_TRACE_GC | YAFFS_TRACE_ERASE,"yaffs_block_became_dirty block %d state %d %s",block_no, bi->block_state,(bi->needs_retiring) ? "needs retiring" : "");/*清除当前最旧的块序列号*/yaffs2_clear_oldest_dirty_seq(dev, bi);/*当前块可回收*/bi->block_state = YAFFS_BLOCK_STATE_DIRTY;/* If this is the block being garbage collected then stop gc‘ing *//*是不是表示当前的这个块正在进行回收,个人认为这里就是表示当前块正在被回收*/if (block_no == dev->gc_block)dev->gc_block = 0;/* If this block is currently the best candidate for gc* then drop as a candidate *//*如果这是存储的最脏的擦除块，那么直接丢弃它*/if (block_no == dev->gc_dirtiest) {dev->gc_dirtiest = 0;dev->gc_pages_in_use = 0;}/*数据有错误在这个块上???*//*这个块上出现过三次以上的ecc错误*/if (!bi->needs_retiring) {/*使checkpt无效？*/yaffs2_checkpt_invalidate(dev);/*调用mtd的nand flash接口擦除*/erased_ok = yaffs_erase_block(dev, block_no);if (!erased_ok) {dev->n_erase_failures++;yaffs_trace(YAFFS_TRACE_ERROR | YAFFS_TRACE_BAD_BLOCKS,"**>> Erasure failed %d", block_no);}}
/*上面如果bi->needs_retiring置位了，表示这个块直接被标记为坏块*/
/* Verify erasure if needed *//*检查是否擦除成功*/if (erased_ok &&((yaffs_trace_mask & YAFFS_TRACE_ERASE) ||!yaffs_skip_verification(dev))) {for (i = 0; i < dev->param.chunks_per_block; i++) {if (!yaffs_check_chunk_erased(dev,block_no * dev->param.chunks_per_block + i)) {yaffs_trace(YAFFS_TRACE_ERROR,">>Block %d erasure supposedly OK, but chunk %d not erased",block_no, i);}}}/*如果是这样，表示整个块均不能用了，*/if (!erased_ok) {/* We lost a block of free space *//*能用空间减去一个单位的block*/dev->n_free_chunks -= dev->param.chunks_per_block;
/*下面函数将会直接调用标记坏块接口,下面具体分析这个函数*/
yaffs_retire_block(dev, block_no);yaffs_trace(YAFFS_TRACE_ERROR | YAFFS_TRACE_BAD_BLOCKS,"**>> Block %d retired", block_no);return;}/* Clean it up... *//*块的状态为空*/bi->block_state = YAFFS_BLOCK_STATE_EMPTY;/*序列号为空*/bi->seq_number = 0;/*可用块++*/dev->n_erased_blocks++;/*这个块中被使用的chunk为０*/bi->pages_in_use = 0;bi->soft_del_pages = 0;bi->has_shrink_hdr = 0;bi->skip_erased_check = 1; /* Clean, so no need to check */bi->gc_prioritise = 0;bi->has_summary=0;/*整个块均处理完成了，把这个块的所有的chunk位清除*/yaffs_clear_chunk_bits(dev, block_no);yaffs_trace(YAFFS_TRACE_ERASE, "Erased block %d", block_no);
struct yaffs_block_info *bi = yaffs_get_block_info(dev, flash_block);yaffs2_checkpt_invalidate(dev);yaffs2_clear_oldest_dirty_seq(dev, bi);/*标志为坏块*/if (yaffs_mark_bad(dev, flash_block) != YAFFS_OK) {if (yaffs_erase_block(dev, flash_block) != YAFFS_OK) {yaffs_trace(YAFFS_TRACE_ALWAYS,"yaffs: Failed to mark bad and erase block %d",flash_block);} else {struct yaffs_ext_tags tags;int chunk_id =flash_block * dev->param.chunks_per_block;u8 *buffer = yaffs_get_temp_buffer(dev);memset(buffer, 0xff, dev->data_bytes_per_chunk);memset(&tags, 0, sizeof(tags));tags.seq_number = YAFFS_SEQUENCE_BAD_BLOCK;if (dev->param.write_chunk_tags_fn(dev, chunk_id -dev->chunk_offset,buffer,&tags) != YAFFS_OK)yaffs_trace(YAFFS_TRACE_ALWAYS,"yaffs: Failed to write bad block marker to block %d",flash_block);yaffs_release_temp_buffer(dev, buffer);}}bi->block_state = YAFFS_BLOCK_STATE_DEAD;bi->gc_prioritise = 0;bi->needs_retiring = 0;dev->n_retired_blocks++;
yaffs2文件系统坏块产生记,码迷,mamicode.com
标签：des style color 使用 os strong
原文地址：http://blog.csdn.net/xingtian19880101/article/details/24691129
