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Message-Id: <20250902080117.3658372-1-wangzhaolong@huaweicloud.com>
Date: Tue, 2 Sep 2025 16:01:17 +0800
From: Wang Zhaolong <wangzhaolong@...weicloud.com>
To: miquel.raynal@...tlin.com,
richard@....at,
vigneshr@...com
Cc: linux-mtd@...ts.infradead.org,
linux-kernel@...r.kernel.org,
chengzhihao1@...wei.com,
yi.zhang@...wei.com,
yangerkun@...wei.com
Subject: [PATCH] mtd: core: only increment ecc_stats.badblocks on confirmed good->bad transition
Repeatedly marking the same eraseblock bad inflates
mtd->ecc_stats.badblocks because mtd_block_markbad() unconditionally
increments the counter on success, while some implementations (e.g.
NAND) return 0 both when the block was already bad and when it has just
been marked[1].
Fix by probing the bad-block state before and after calling
->_block_markbad() (when _block_isbad is available) and only increment
the counter on a confirmed good->bad transition. If _block_isbad is not
implemented, be conservative and do not increment.
Keep the logic centralized in mtdcore; the markbad path is not a hot
path, so the extra IO is acceptable.
Link: https://lore.kernel.org/all/ef573188-9815-4a6b-bad1-3d8ff7c9b16f@huaweicloud.com/ [1]
Signed-off-by: Wang Zhaolong <wangzhaolong@...weicloud.com>
---
drivers/mtd/mtdcore.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 5ba9a741f5ac..a6d38da651e9 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -2338,10 +2338,12 @@ EXPORT_SYMBOL_GPL(mtd_block_isbad);
int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
struct mtd_info *master = mtd_get_master(mtd);
int ret;
+ loff_t moffs;
+ int oldbad = -1;
if (!master->_block_markbad)
return -EOPNOTSUPP;
if (ofs < 0 || ofs >= mtd->size)
return -EINVAL;
@@ -2349,17 +2351,35 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
return -EROFS;
if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
- ret = master->_block_markbad(master, mtd_get_master_ofs(mtd, ofs));
+ moffs = mtd_get_master_ofs(mtd, ofs);
+
+ /* Pre-check: remember current state if available. */
+ if (master->_block_isbad)
+ oldbad = master->_block_isbad(master, moffs);
+
+ ret = master->_block_markbad(master, moffs);
if (ret)
return ret;
- while (mtd->parent) {
- mtd->ecc_stats.badblocks++;
- mtd = mtd->parent;
+ /*
+ * Post-check and bump stats only on a confirmed good->bad transition.
+ * If _block_isbad is not implemented, be conservative and do not bump.
+ */
+ if (master->_block_isbad) {
+ /* If it was already bad, nothing to do. */
+ if (oldbad > 0)
+ return 0;
+
+ if (master->_block_isbad(master, moffs) > 0) {
+ while (mtd->parent) {
+ mtd->ecc_stats.badblocks++;
+ mtd = mtd->parent;
+ }
+ }
}
return 0;
}
EXPORT_SYMBOL_GPL(mtd_block_markbad);
--
2.39.2
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