From 5788ccf3c84f5587418a80128a3653aa35abf00b Mon Sep 17 00:00:00 2001 From: Xiaoming Ni Date: Tue, 31 Mar 2020 09:31:59 +0800 Subject: [PATCH] mtd: clear cache_state to avoid writing to bad blocks repeatedly The function call process is as follows: mtd_blktrans_work() while (1) do_blktrans_request() mtdblock_writesect() do_cached_write() write_cached_data() /*if cache_state is STATE_DIRTY*/ erase_write() write_cached_data() returns failure without modifying cache_state and cache_offset. So when do_cached_write() is called again, write_cached_data() will be called again to perform erase_write() on the same cache_offset. But if this cache_offset points to a bad block, erase_write() will always return -EIO. Writing to this mtdblk is equivalent to losing the current data, and repeatedly writing to the bad block. Repeatedly writing a bad block has no real benefits, but brings some negative effects: 1 Lost subsequent data 2 Loss of flash device life 3 erase_write() bad blocks are very time-consuming. For example: the function do_erase_oneblock() in chips/cfi_cmdset_0020.c or chips/cfi_cmdset_0002.c may take more than 20 seconds to return Therefore, when erase_write() returns -EIO in write_cached_data(), clear cache_state to avoid writing to bad blocks repeatedly. Signed-off-by: Xiaoming Ni Reviewed-by: Miquel Raynal Signed-off-by: Richard Weinberger --- drivers/mtd/mtdblock.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c index 078e0f6..32e52d8 100644 --- a/drivers/mtd/mtdblock.c +++ b/drivers/mtd/mtdblock.c @@ -89,8 +89,6 @@ static int write_cached_data (struct mtdblk_dev *mtdblk) ret = erase_write (mtd, mtdblk->cache_offset, mtdblk->cache_size, mtdblk->cache_data); - if (ret) - return ret; /* * Here we could arguably set the cache state to STATE_CLEAN. @@ -98,9 +96,14 @@ static int write_cached_data (struct mtdblk_dev *mtdblk) * be notified if this content is altered on the flash by other * means. Let's declare it empty and leave buffering tasks to * the buffer cache instead. + * + * If this cache_offset points to a bad block, data cannot be + * written to the device. Clear cache_state to avoid writing to + * bad blocks repeatedly. */ - mtdblk->cache_state = STATE_EMPTY; - return 0; + if (ret == 0 || ret == -EIO) + mtdblk->cache_state = STATE_EMPTY; + return ret; } -- 2.7.4