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SubjectRe: [PATCH v2 07/11] pstore/blk: skip broken zone for mtd device
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hi Kees Cook,

On 2020/3/19 AM 2:35, Kees Cook wrote:
> 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@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 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?
>

ENOMSG is OK.

>> +
>> /**
>> * 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
>>
>

--
WeiXiong Liao

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