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    Subject[PATCH 07/11] pstore/blk: skip broken zone for mtd device
    Date
    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@allwinnertech.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 58418d429c55..aea6d2664a22 100644
    --- a/Documentation/admin-guide/pstore-block.rst
    +++ b/Documentation/admin-guide/pstore-block.rst
    @@ -185,7 +185,8 @@ The parameter @offset 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 a14b1b3d9053..7c6bf14f7e7d 100644
    --- a/fs/pstore/blkzone.c
    +++ b/fs/pstore/blkzone.c
    @@ -222,6 +222,9 @@ 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())
    @@ -375,7 +378,11 @@ 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;
    }
    @@ -665,24 +672,58 @@ 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,
    @@ -806,7 +847,6 @@ 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;
    @@ -867,7 +907,7 @@ 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);

    @@ -892,7 +932,7 @@ 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;
    @@ -906,7 +946,7 @@ 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);
    @@ -956,7 +996,7 @@ 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))
    +
    /**
    * 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
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