[PATCH v3 8/8] jffs2: add runtime toggle for write verification
From: zhouminqiang <hidden>
Date: 2026-09-01 13:13:20
Also in:
linux-arm-kernel, lkml
Subsystem:
filesystems (vfs and infrastructure), journalling flash file system v2 (jffs2), the rest · Maintainers:
Alexander Viro, Christian Brauner, David Woodhouse, Richard Weinberger, Linus Torvalds
Write verification is a diagnostic facility that adds read-back overhead to every write. In production, this overhead is undesirable unless fault isolation is required. Add a module parameter jffs2.write_verify (bool, 0644) that defaults to off when CONFIG_JFFS2_FS_WRITE_VERIFY is enabled. The verification entry checks READ_ONCE(jffs2_write_verify) and returns immediately when disabled, avoiding any overhead. The parameter can be toggled at runtime via /sys/module/jffs2/parameters/write_verify or set at boot/modprobe time. Signed-off-by: zhouminqiang <redacted> --- fs/jffs2/Kconfig | 8 ++++++++ fs/jffs2/writev.c | 23 +++++++++++++++++++++++ 2 files changed, 31 insertions(+)
diff --git a/fs/jffs2/Kconfig b/fs/jffs2/Kconfig
index 556025a5d438..03dadbd003cd 100644
--- a/fs/jffs2/Kconfig
+++ b/fs/jffs2/Kconfig@@ -61,6 +61,14 @@ config JFFS2_FS_WRITE_VERIFY tell transport/program-time corruption from post-commit media damage. + Verification defaults to off when this option is selected and can + be enabled at runtime via sysfs: + + /sys/module/jffs2/parameters/write_verify + + Write 0 to disable, 1 to enable. Boot/modprobe parameter + jffs2.write_verify=0|1 is also supported. + If unsure, say 'N'. config JFFS2_SUMMARY
diff --git a/fs/jffs2/writev.c b/fs/jffs2/writev.c
index 604a14bb5710..342c413be95c 100644
--- a/fs/jffs2/writev.c
+++ b/fs/jffs2/writev.c@@ -9,12 +9,32 @@ * */ +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include <linux/kernel.h> +#include <linux/module.h> #include <linux/slab.h> #include <linux/mtd/mtd.h> #include "nodelist.h" #ifdef CONFIG_JFFS2_FS_WRITE_VERIFY +/* + * Optional read-back after writes. + * + * Catch cases where data is corrupted after node CRCs are calculated but + * before it is correctly programmed -- e.g. in RAM or during DMA/bus + * transfer to the flash controller -- so mtd_write() succeeds while the + * medium does not match the in-memory image. + * + * Runtime toggle: /sys/module/jffs2/parameters/write_verify + * (also boot/modprobe: jffs2.write_verify=0|1) + */ +static bool jffs2_write_verify; +module_param_named(write_verify, jffs2_write_verify, bool, 0644); +MODULE_PARM_DESC(write_verify, + "Verify flash writes by reading back (default: N)"); + + int jffs2_verify_write(struct jffs2_sb_info *c, const unsigned char *buf, uint32_t ofs, size_t len) {
@@ -23,6 +43,9 @@ int jffs2_verify_write(struct jffs2_sb_info *c, const unsigned char *buf, char *eccstr; void *verify_buf; + if (!READ_ONCE(jffs2_write_verify)) + return 0; + verify_buf = kmalloc(len, GFP_NOFS | __GFP_NOWARN); if (!verify_buf) { pr_warn("%s(): verify buffer allocation failed, skipping verification\n",
--
2.52.0