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    Subject[PATCH v3 2/3] mtd: mtdoops: Create a header structure for the saved mtdoops.
    From
    Create a dump header to enable the addition of fields without having
    to modify the rest of the code.

    Reported-by: kernel test robot <lkp@intel.com>
    Signed-off-by: Jean-Marc Eurin <jmeurin@google.com>
    ---
    drivers/mtd/mtdoops.c | 55 +++++++++++++++++++++++--------------------
    1 file changed, 30 insertions(+), 25 deletions(-)

    diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
    index 09a26747f490..f80468ef31c6 100644
    --- a/drivers/mtd/mtdoops.c
    +++ b/drivers/mtd/mtdoops.c
    @@ -22,9 +22,6 @@
    /* Maximum MTD partition size */
    #define MTDOOPS_MAX_MTD_SIZE (8 * 1024 * 1024)

    -#define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
    -#define MTDOOPS_HEADER_SIZE 8
    -
    static unsigned long record_size = 4096;
    module_param(record_size, ulong, 0400);
    MODULE_PARM_DESC(record_size,
    @@ -40,6 +37,13 @@ module_param(dump_oops, int, 0600);
    MODULE_PARM_DESC(dump_oops,
    "set to 1 to dump oopses, 0 to only dump panics (default 1)");

    +#define MTDOOPS_KERNMSG_MAGIC 0x5d005d00
    +
    +struct mtdoops_hdr {
    + u32 seq;
    + u32 magic;
    +} __packed;
    +
    static struct mtdoops_context {
    struct kmsg_dumper dump;

    @@ -178,16 +182,16 @@ static void mtdoops_write(struct mtdoops_context *cxt, int panic)
    {
    struct mtd_info *mtd = cxt->mtd;
    size_t retlen;
    - u32 *hdr;
    + struct mtdoops_hdr *hdr;
    int ret;

    if (test_and_set_bit(0, &cxt->oops_buf_busy))
    return;

    /* Add mtdoops header to the buffer */
    - hdr = cxt->oops_buf;
    - hdr[0] = cxt->nextcount;
    - hdr[1] = MTDOOPS_KERNMSG_MAGIC;
    + hdr = (struct mtdoops_hdr *)cxt->oops_buf;
    + hdr->seq = cxt->nextcount;
    + hdr->magic = MTDOOPS_KERNMSG_MAGIC;

    if (panic) {
    ret = mtd_panic_write(mtd, cxt->nextpage * record_size,
    @@ -222,8 +226,9 @@ static void mtdoops_workfunc_write(struct work_struct *work)
    static void find_next_position(struct mtdoops_context *cxt)
    {
    struct mtd_info *mtd = cxt->mtd;
    + struct mtdoops_hdr hdr;
    int ret, page, maxpos = 0;
    - u32 count[MTDOOPS_HEADER_SIZE/sizeof(u32)], maxcount = 0xffffffff;
    + u32 maxcount = 0xffffffff;
    size_t retlen;

    for (page = 0; page < cxt->oops_pages; page++) {
    @@ -231,32 +236,31 @@ static void find_next_position(struct mtdoops_context *cxt)
    continue;
    /* Assume the page is used */
    mark_page_used(cxt, page);
    - ret = mtd_read(mtd, page * record_size, MTDOOPS_HEADER_SIZE,
    - &retlen, (u_char *)&count[0]);
    - if (retlen != MTDOOPS_HEADER_SIZE ||
    + ret = mtd_read(mtd, page * record_size, sizeof(hdr),
    + &retlen, (u_char *)&hdr);
    + if (retlen != sizeof(hdr) ||
    (ret < 0 && !mtd_is_bitflip(ret))) {
    - printk(KERN_ERR "mtdoops: read failure at %ld (%td of %d read), err %d\n",
    - page * record_size, retlen,
    - MTDOOPS_HEADER_SIZE, ret);
    + printk(KERN_ERR "mtdoops: read failure at %ld (%td of %ld read), err %d\n",
    + page * record_size, retlen, sizeof(hdr), ret);
    continue;
    }

    - if (count[0] == 0xffffffff && count[1] == 0xffffffff)
    + if (hdr.seq == 0xffffffff && hdr.magic == 0xffffffff)
    mark_page_unused(cxt, page);
    - if (count[0] == 0xffffffff || count[1] != MTDOOPS_KERNMSG_MAGIC)
    + if (hdr.seq == 0xffffffff || hdr.magic != MTDOOPS_KERNMSG_MAGIC)
    continue;
    if (maxcount == 0xffffffff) {
    - maxcount = count[0];
    + maxcount = hdr.seq;
    maxpos = page;
    - } else if (count[0] < 0x40000000 && maxcount > 0xc0000000) {
    - maxcount = count[0];
    + } else if (hdr.seq < 0x40000000 && maxcount > 0xc0000000) {
    + maxcount = hdr.seq;
    maxpos = page;
    - } else if (count[0] > maxcount && count[0] < 0xc0000000) {
    - maxcount = count[0];
    + } else if (hdr.seq > maxcount && hdr.seq < 0xc0000000) {
    + maxcount = hdr.seq;
    maxpos = page;
    - } else if (count[0] > maxcount && count[0] > 0xc0000000
    + } else if (hdr.seq > maxcount && hdr.seq > 0xc0000000
    && maxcount > 0x80000000) {
    - maxcount = count[0];
    + maxcount = hdr.seq;
    maxpos = page;
    }
    }
    @@ -287,8 +291,9 @@ static void mtdoops_do_dump(struct kmsg_dumper *dumper,

    if (test_and_set_bit(0, &cxt->oops_buf_busy))
    return;
    - kmsg_dump_get_buffer(&iter, true, cxt->oops_buf + MTDOOPS_HEADER_SIZE,
    - record_size - MTDOOPS_HEADER_SIZE, NULL);
    + kmsg_dump_get_buffer(&iter, true,
    + cxt->oops_buf + sizeof(struct mtdoops_hdr),
    + record_size - sizeof(struct mtdoops_hdr), NULL);
    clear_bit(0, &cxt->oops_buf_busy);

    if (reason != KMSG_DUMP_OOPS) {
    --
    2.36.0.rc0.470.gd361397f0d-goog
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