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    Subject[PATCH v4 09/12] pstore/zone: Provide way to skip "broken" zone for MTD devices
    Date
    From: WeiXiong Liao <liaoweixiong@allwinnertech.com>

    One requirement to support MTD devices in pstore/zone is having a
    way to declare certain regions as broken. Add this support to
    pstore/zone.

    The MTD driver should return -ENOMSG when encountering a bad region,
    which tells pstore/zone to skip and try the next one.

    Signed-off-by: WeiXiong Liao <liaoweixiong@allwinnertech.com>
    Link: https://lore.kernel.org/r/1585126506-18635-9-git-send-email-liaoweixiong@allwinnertech.com
    Signed-off-by: Kees Cook <keescook@chromium.org>
    ---
    fs/pstore/blk.c | 10 ++++--
    fs/pstore/zone.c | 65 ++++++++++++++++++++++++++++++-------
    include/linux/pstore_blk.h | 3 +-
    include/linux/pstore_zone.h | 12 ++++---
    4 files changed, 71 insertions(+), 19 deletions(-)

    diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
    index 5db811b7018d..e33e58afd4cb 100644
    --- a/fs/pstore/blk.c
    +++ b/fs/pstore/blk.c
    @@ -101,9 +101,12 @@ static struct bdev_info {
    * means error.
    * @write: The same as @read, but the following error number:
    * -EBUSY means try to write again later.
    + * -ENOMSG means to try next zone.
    * @panic_write:The write operation only used for panic case. It's optional
    - * if you do not care panic log. The parameters and return value
    - * are the same as @read.
    + * if you do not care panic log. The parameters are relative
    + * value to storage.
    + * On success, the number of bytes should be returned, others
    + * excluding -ENOMSG mean error. -ENOMSG means to try next zone.
    */
    struct psblk_device {
    unsigned long total_size;
    @@ -315,6 +318,9 @@ static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
    /* size and off must align to SECTOR_SIZE for block device */
    ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
    size >> SECTOR_SHIFT);
    + /* try next zone */
    + if (ret == -ENOMSG)
    + return ret;
    return ret ? -EIO : size;
    }

    diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
    index 36d78c63bd20..43d44d016039 100644
    --- a/fs/pstore/zone.c
    +++ b/fs/pstore/zone.c
    @@ -247,6 +247,9 @@ static int psz_zone_write(struct pstore_zone *zone,

    return 0;
    dirty:
    + /* no need to mark dirty if going to try next zone */
    + if (wcnt == -ENOMSG)
    + return -ENOMSG;
    atomic_set(&zone->dirty, true);
    /* flush dirty zones nicely */
    if (wcnt == -EBUSY && !is_on_panic())
    @@ -382,7 +385,11 @@ static int psz_recover_oops_meta(struct psz_context *cxt)
    return -EINVAL;

    rcnt = info->read((char *)buf, len, zone->off);
    - if (rcnt != len) {
    + if (rcnt == -ENOMSG) {
    + 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;
    }
    @@ -717,24 +724,58 @@ static void psz_write_kmsg_hdr(struct pstore_zone *zone,
    hdr->counter = 0;
    }

    +/*
    + * In case zone is broken, which may occur to MTD device, we try each zones,
    + * start at cxt->oops_write_cnt.
    + */
    static inline int notrace psz_oops_write_record(struct psz_context *cxt,
    struct pstore_record *record)
    {
    + int ret = -EBUSY;
    size_t size, hlen;
    struct pstore_zone *zone;
    - unsigned int zonenum;
    + unsigned int i;

    - zonenum = cxt->oops_write_cnt;
    - zone = cxt->opszs[zonenum];
    - if (unlikely(!zone))
    - return -ENOSPC;
    - cxt->oops_write_cnt = (zonenum + 1) % cxt->oops_max_cnt;
    + for (i = 0; i < cxt->oops_max_cnt; i++) {
    + unsigned int zonenum, len;
    +
    + zonenum = (cxt->oops_write_cnt + i) % cxt->oops_max_cnt;
    + zone = cxt->opszs[zonenum];
    + if (unlikely(!zone))
    + return -ENOSPC;

    - pr_debug("write %s to zone id %d\n", zone->name, zonenum);
    - psz_write_kmsg_hdr(zone, record);
    - hlen = sizeof(struct psz_oops_header);
    - size = min_t(size_t, record->size, zone->buffer_size - hlen);
    - return psz_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);
    + psz_write_kmsg_hdr(zone, record);
    + hlen = sizeof(struct psz_oops_header);
    + size = min_t(size_t, record->size, zone->buffer_size - hlen);
    + ret = psz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
    + if (likely(!ret || ret != -ENOMSG)) {
    + cxt->oops_write_cnt = zonenum + 1;
    + cxt->oops_write_cnt %= cxt->oops_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 psz_oops_write(struct psz_context *cxt,
    diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
    index d8f609e60288..828b0763d477 100644
    --- a/include/linux/pstore_blk.h
    +++ b/include/linux/pstore_blk.h
    @@ -14,7 +14,8 @@
    * @start_sect: start sector to block device
    * @sects: sectors count on buf
    *
    - * Return: On success, zero should be returned. Others mean error.
    + * Return: On success, zero should be returned. Others excluding -ENOMSG
    + * mean error. -ENOMSG means to try next zone.
    *
    * Panic write to block device must be aligned to SECTOR_SIZE.
    */
    diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
    index 94f441b8b616..ddb3dfea4ea6 100644
    --- a/include/linux/pstore_zone.h
    +++ b/include/linux/pstore_zone.h
    @@ -23,11 +23,15 @@ typedef ssize_t (*psz_write_op)(const char *, size_t, loff_t);
    * @read: The general read operation. Both of the function parameters
    * @size and @offset are relative value to storage.
    * On success, the number of bytes should be returned, others
    - * means error.
    - * @write: The same as @read, but -EBUSY means try to write again later.
    + * mean error.
    + * @write: The same as @read, but the following error number:
    + * -EBUSY means try to write again later.
    + * -ENOMSG means to try next zone.
    * @panic_write:The write operation only used for panic case. It's optional
    - * if you do not care panic log. The parameters and return value
    - * are the same as @read.
    + * if you do not care panic log. The parameters are relative
    + * value to storage.
    + * On success, the number of bytes should be returned, others
    + * excluding -ENOMSG mean error. -ENOMSG means to try next zone.
    */
    struct pstore_zone_info {
    struct module *owner;
    --
    2.20.1
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