In
yaffs_rd_chunk_tags_nand, if the result isn’t
YAFFS_ECC_RESULT_NO_ERROR, it will call
yaffs_handle_chunk_error to mark that’s an error.
Here is my question. Why
also consider that’s an error when the result is
YAFFS_ECC_RESULT_FIXED?
It only calls yaffshandle_chunk_error() if the result from the read
shows error correction was required. A read that required ECC
correction shows that page is having trouble retaining accurate
data, and if (many) repeated reads of the same page are done the
data will eventually go bad (resulting in an uncorrectable error
correction) thereby losing the data. To prevent this if enough ECC
corrections are made within a block yaffs_handle_chunk_error will
force the block to be garbage collected (which copies out any good
data into another block and erases the block). This is done to
handle read disturb errors whereby the process of reading data
multiple times can disturb bits.