Messages in this thread Patch in this message | | | From | Michał Kępień <> | Subject | [PATCH v2 5/5] mtdchar: extend MEMREAD ioctl to return ECC statistics | Date | Thu, 16 Dec 2021 09:34:18 +0100 |
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While returning -EUCLEAN or -EBADMSG is a valid signal for user space that the ECC algorithm detected errors during a read operation, that signal is not granular enough to cover all use cases. For example, knowing the maximum number of bitflips detected in a single ECC step during a read operation performed on a given page may be useful when dealing with an MTD partition whose ECC layout varies across pages (e.g. a partition consisting of a bootloader area using a "custom" ECC layout followed by data pages using a "standard" ECC layout).
Extend struct mtd_read_req with a newly introduced struct mtd_read_req_ecc_stats and set the fields of that structure in mtdchar_read_ioctl(). Use ECC statistics to ensure the error code returned by the MEMREAD ioctl accounts for all ECC errors detected during the read operation.
Link: https://www.infradead.org/pipermail/linux-mtd/2016-April/067085.html
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com> Signed-off-by: Michał Kępień <kernel@kempniu.pl> --- drivers/mtd/mtdchar.c | 26 ++++++++++++++++++++++++++ include/uapi/mtd/mtd-abi.h | 21 +++++++++++++++++++++ 2 files changed, 47 insertions(+)
diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c index 6ad59c9eed2f..68cc91d82a5d 100644 --- a/drivers/mtd/mtdchar.c +++ b/drivers/mtd/mtdchar.c @@ -714,6 +714,10 @@ static int mtdchar_read_ioctl(struct mtd_info *mtd, if (!usr_oob) req.ooblen = 0; + req.ecc_stats.uncorrectable_errors = 0; + req.ecc_stats.corrected_bitflips = 0; + req.ecc_stats.max_bitflips = 0; + if (req.start + req.len > mtd->size) { ret = -EINVAL; goto out; @@ -738,12 +742,14 @@ static int mtdchar_read_ioctl(struct mtd_info *mtd, } while (req.len > 0 || (!usr_data && req.ooblen > 0)) { + struct mtd_req_stats stats; struct mtd_oob_ops ops = { .mode = req.mode, .len = min_t(size_t, req.len, datbuf_len), .ooblen = min_t(size_t, req.ooblen, oobbuf_len), .datbuf = datbuf, .oobbuf = oobbuf, + .stats = &stats, }; /* @@ -757,6 +763,13 @@ static int mtdchar_read_ioctl(struct mtd_info *mtd, ops.len -= mtd_mod_by_ws(req.start + ops.len, mtd); ret = mtd_read_oob(mtd, (loff_t)req.start, &ops); + + req.ecc_stats.uncorrectable_errors += + stats.uncorrectable_errors; + req.ecc_stats.corrected_bitflips += stats.corrected_bitflips; + req.ecc_stats.max_bitflips = + max(req.ecc_stats.max_bitflips, stats.max_bitflips); + if (ret && !mtd_is_bitflip_or_eccerr(ret)) break; @@ -774,6 +787,19 @@ static int mtdchar_read_ioctl(struct mtd_info *mtd, usr_oob += ops.oobretlen; } + /* + * As multiple iterations of the above loop (and therefore multiple + * mtd_read_oob() calls) may be necessary to complete the read request, + * adjust the final return code to ensure it accounts for all detected + * ECC errors. + */ + if (!ret || mtd_is_bitflip(ret)) { + if (req.ecc_stats.uncorrectable_errors > 0) + ret = -EBADMSG; + else if (req.ecc_stats.corrected_bitflips > 0) + ret = -EUCLEAN; + } + out: req.len = orig_len - req.len; req.ooblen = orig_ooblen - req.ooblen; diff --git a/include/uapi/mtd/mtd-abi.h b/include/uapi/mtd/mtd-abi.h index 337e6e597fad..bc68f266c174 100644 --- a/include/uapi/mtd/mtd-abi.h +++ b/include/uapi/mtd/mtd-abi.h @@ -91,6 +91,25 @@ struct mtd_write_req { __u8 padding[7]; }; +/** + * struct mtd_read_req_ecc_stats - ECC statistics for a read operation + * + * @uncorrectable_errors: the number of uncorrectable errors that happened + * during the read operation + * @corrected_bitflips: the number of bitflips corrected during the read + * operation + * @max_bitflips: the maximum number of bitflips detected in any single ECC + * step for the data read during the operation; this information + * can be used to decide whether the data stored in a specific + * region of the MTD device should be moved somewhere else to + * avoid data loss. + */ +struct mtd_read_req_ecc_stats { + __u32 uncorrectable_errors; + __u32 corrected_bitflips; + __u32 max_bitflips; +}; + /** * struct mtd_read_req - data structure for requesting a read operation * @@ -101,6 +120,7 @@ struct mtd_write_req { * @usr_oob: user-provided OOB buffer * @mode: MTD mode (see "MTD operation modes") * @padding: reserved, must be set to 0 + * @ecc_stats: ECC statistics for the read operation * * This structure supports ioctl(MEMREAD) operations, allowing data and/or OOB * reads in various modes. To read from OOB-only, set @usr_data == NULL, and to @@ -115,6 +135,7 @@ struct mtd_read_req { __u64 usr_oob; __u8 mode; __u8 padding[7]; + struct mtd_read_req_ecc_stats ecc_stats; }; #define MTD_ABSENT 0 -- 2.34.1
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