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Message-ID: <202003181131.3A8F861F@keescook>
Date: Wed, 18 Mar 2020 11:35:43 -0700
From: Kees Cook <keescook@...omium.org>
To: WeiXiong Liao <liaoweixiong@...winnertech.com>
Cc: Anton Vorontsov <anton@...msg.org>,
Colin Cross <ccross@...roid.com>,
Tony Luck <tony.luck@...el.com>,
Jonathan Corbet <corbet@....net>,
Miquel Raynal <miquel.raynal@...tlin.com>,
Richard Weinberger <richard@....at>,
Vignesh Raghavendra <vigneshr@...com>,
Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
"David S. Miller" <davem@...emloft.net>,
Rob Herring <robh@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mtd@...ts.infradead.org
Subject: Re: [PATCH v2 07/11] pstore/blk: skip broken zone for mtd device
On Fri, Feb 07, 2020 at 08:25:51PM +0800, WeiXiong Liao wrote:
> It's one of a series of patches for adaptive to MTD device.
>
> MTD device is not block device. As the block of flash (MTD device) will
> be broken, it's necessary for pstore/blk to skip the broken block
> (bad block).
>
> If device drivers return -ENEXT, pstore/blk will try next zone of dmesg.
>
> Signed-off-by: WeiXiong Liao <liaoweixiong@...winnertech.com>
> ---
> Documentation/admin-guide/pstore-block.rst | 3 +-
> fs/pstore/blkzone.c | 74 +++++++++++++++++++++++-------
> include/linux/blkoops.h | 4 +-
> include/linux/pstore_blk.h | 4 ++
> 4 files changed, 66 insertions(+), 19 deletions(-)
>
> diff --git a/Documentation/admin-guide/pstore-block.rst b/Documentation/admin-guide/pstore-block.rst
> index c8a5f68960c3..be865dfc1a28 100644
> --- a/Documentation/admin-guide/pstore-block.rst
> +++ b/Documentation/admin-guide/pstore-block.rst
> @@ -188,7 +188,8 @@ The parameter @offset of these interface is the relative position of the device.
> Normally the number of bytes read/written should be returned, while for error,
> negative number will be returned. The following return numbers mean more:
>
> --EBUSY: pstore/blk should try again later.
> +1. -EBUSY: pstore/blk should try again later.
> +#. -ENEXT: this zone is used or broken, pstore/blk should try next one.
>
> panic_write (for non-block device)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> diff --git a/fs/pstore/blkzone.c b/fs/pstore/blkzone.c
> index 442e5a5bbfda..205aeff28992 100644
> --- a/fs/pstore/blkzone.c
> +++ b/fs/pstore/blkzone.c
> @@ -207,6 +207,9 @@ static int blkz_zone_write(struct blkz_zone *zone,
>
> return 0;
> set_dirty:
> + /* no need to mark dirty if going to try next zone */
> + if (wcnt == -ENEXT)
> + return -ENEXT;
> atomic_set(&zone->dirty, true);
> /* flush dirty zones nicely */
> if (wcnt == -EBUSY && !is_on_panic())
> @@ -360,7 +363,11 @@ static int blkz_recover_dmesg_meta(struct blkz_context *cxt)
> return -EINVAL;
>
> rcnt = info->read((char *)buf, len, zone->off);
> - if (rcnt != len) {
> + if (rcnt == -ENEXT) {
> + pr_debug("%s with id %lu may be broken, skip\n",
> + zone->name, i);
> + continue;
> + } else if (rcnt != len) {
> pr_err("read %s with id %lu failed\n", zone->name, i);
> return (int)rcnt < 0 ? (int)rcnt : -EIO;
> }
> @@ -650,24 +657,58 @@ static void blkz_write_kmsg_hdr(struct blkz_zone *zone,
> hdr->counter = 0;
> }
>
> +/*
> + * In case zone is broken, which may occur to MTD device, we try each zones,
> + * start at cxt->dmesg_write_cnt.
> + */
> static inline int notrace blkz_dmesg_write_do(struct blkz_context *cxt,
> struct pstore_record *record)
> {
> + int ret = -EBUSY;
> size_t size, hlen;
> struct blkz_zone *zone;
> - unsigned int zonenum;
> + unsigned int i;
>
> - zonenum = cxt->dmesg_write_cnt;
> - zone = cxt->dbzs[zonenum];
> - if (unlikely(!zone))
> - return -ENOSPC;
> - cxt->dmesg_write_cnt = (zonenum + 1) % cxt->dmesg_max_cnt;
> + for (i = 0; i < cxt->dmesg_max_cnt; i++) {
> + unsigned int zonenum, len;
> +
> + zonenum = (cxt->dmesg_write_cnt + i) % cxt->dmesg_max_cnt;
> + zone = cxt->dbzs[zonenum];
> + if (unlikely(!zone))
> + return -ENOSPC;
>
> - pr_debug("write %s to zone id %d\n", zone->name, zonenum);
> - blkz_write_kmsg_hdr(zone, record);
> - hlen = sizeof(struct blkz_dmesg_header);
> - size = min_t(size_t, record->size, zone->buffer_size - hlen);
> - return blkz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
> + /* avoid destorying old data, allocate a new one */
> + len = zone->buffer_size + sizeof(*zone->buffer);
> + zone->oldbuf = zone->buffer;
> + zone->buffer = kzalloc(len, GFP_KERNEL);
> + if (!zone->buffer) {
> + zone->buffer = zone->oldbuf;
> + return -ENOMEM;
> + }
> + zone->buffer->sig = zone->oldbuf->sig;
> +
> + pr_debug("write %s to zone id %d\n", zone->name, zonenum);
> + blkz_write_kmsg_hdr(zone, record);
> + hlen = sizeof(struct blkz_dmesg_header);
> + size = min_t(size_t, record->size, zone->buffer_size - hlen);
> + ret = blkz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
> + if (likely(!ret || ret != -ENEXT)) {
> + cxt->dmesg_write_cnt = zonenum + 1;
> + cxt->dmesg_write_cnt %= cxt->dmesg_max_cnt;
> + /* no need to try next zone, free last zone buffer */
> + kfree(zone->oldbuf);
> + zone->oldbuf = NULL;
> + return ret;
> + }
> +
> + pr_debug("zone %u may be broken, try next dmesg zone\n",
> + zonenum);
> + kfree(zone->buffer);
> + zone->buffer = zone->oldbuf;
> + zone->oldbuf = NULL;
> + }
> +
> + return -EBUSY;
> }
>
> static int notrace blkz_dmesg_write(struct blkz_context *cxt,
> @@ -791,7 +832,6 @@ static int notrace blkz_pstore_write(struct pstore_record *record)
> }
> }
>
> -#define READ_NEXT_ZONE ((ssize_t)(-1024))
> static struct blkz_zone *blkz_read_next_zone(struct blkz_context *cxt)
> {
> struct blkz_zone *zone = NULL;
> @@ -852,7 +892,7 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
> if (blkz_read_dmesg_hdr(zone, record)) {
> atomic_set(&zone->buffer->datalen, 0);
> atomic_set(&zone->dirty, 0);
> - return READ_NEXT_ZONE;
> + return -ENEXT;
> }
> size -= sizeof(struct blkz_dmesg_header);
>
> @@ -877,7 +917,7 @@ static ssize_t blkz_dmesg_read(struct blkz_zone *zone,
> if (unlikely(blkz_zone_read(zone, record->buf + hlen, size,
> sizeof(struct blkz_dmesg_header)) < 0)) {
> kfree(record->buf);
> - return READ_NEXT_ZONE;
> + return -ENEXT;
> }
>
> return size + hlen;
> @@ -891,7 +931,7 @@ static ssize_t blkz_record_read(struct blkz_zone *zone,
>
> buf = (struct blkz_buffer *)zone->oldbuf;
> if (!buf)
> - return READ_NEXT_ZONE;
> + return -ENEXT;
>
> size = atomic_read(&buf->datalen);
> start = atomic_read(&buf->start);
> @@ -943,7 +983,7 @@ static ssize_t blkz_pstore_read(struct pstore_record *record)
> }
>
> ret = readop(zone, record);
> - if (ret == READ_NEXT_ZONE)
> + if (ret == -ENEXT)
> goto next_zone;
> return ret;
> }
> diff --git a/include/linux/blkoops.h b/include/linux/blkoops.h
> index 8f40f225545d..71c596fd4cc8 100644
> --- a/include/linux/blkoops.h
> +++ b/include/linux/blkoops.h
> @@ -27,6 +27,7 @@
> * On error, negative number should be returned. The following returning
> * number means more:
> * -EBUSY: pstore/blk should try again later.
> + * -ENEXT: this zone is used or broken, pstore/blk should try next one.
> * @panic_write:
> * The write operation only used for panic.
> *
> @@ -45,7 +46,8 @@ struct blkoops_device {
>
> /*
> * Panic write for block device who should write alignmemt to SECTOR_SIZE.
> - * On success, zero should be returned. Others mean error.
> + * On success, zero should be returned. Others mean error except that -ENEXT
> + * means the zone is used or broken, pstore/blk should try next one.
> */
> typedef int (*blkoops_blk_panic_write_op)(const char *buf, sector_t start_sect,
> sector_t sects);
> diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
> index 77704c1b404a..bbbe4fe37f7c 100644
> --- a/include/linux/pstore_blk.h
> +++ b/include/linux/pstore_blk.h
> @@ -6,6 +6,9 @@
> #include <linux/types.h>
> #include <linux/blkdev.h>
>
> +/* read/write function return -ENEXT means try next zone */
> +#define ENEXT ((ssize_t)(1024))
I really don't like inventing errno numbers. Can you just reuse an
existing (but non-block) errno like ESRCH or ENOMSG or something?
> +
> /**
> * struct blkz_info - backend blkzone driver structure
> *
> @@ -42,6 +45,7 @@
> * On error, negative number should be returned. The following returning
> * number means more:
> * -EBUSY: pstore/blk should try again later.
> + * -ENEXT: this zone is used or broken, pstore/blk should try next one.
> * @panic_write:
> * The write operation only used for panic. It's optional if you do not
> * care panic record. If panic occur but blkzone do not recover yet, the
> --
> 1.9.1
>
--
Kees Cook
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