pstore/zone: Provide way to skip "broken" zone for MTD devices

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/lkml/20200511233229.27745-8-keescook@chromium.org/
Co-developed-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: //lore.kernel.org/lkml/20200512173801.222666-1-colin.king@canonical.com
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
index e0d95fb..67343d6 100644 (file)
--- a/fs/pstore/blk.c
+++ b/fs/pstore/blk.c
@@ -109,9 +109,12 @@ 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 pstore_device_info {
        unsigned long total_size;
@@ -337,6 +340,9 @@ 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 2d9f452..add26b1 100644 (file)
--- a/fs/pstore/zone.c
+++ b/fs/pstore/zone.c
@@ -249,6 +249,9 @@ 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())
@@ -391,7 +394,11 @@ static int psz_kmsg_recover_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;
                }
@@ -725,24 +732,58 @@ 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->kmsg_write_cnt.
+ */
 static inline int notrace psz_kmsg_write_record(struct psz_context *cxt,
                struct pstore_record *record)
 {
        size_t size, hlen;
        struct pstore_zone *zone;
-       unsigned int zonenum;
+       unsigned int i;
 
-       zonenum = cxt->kmsg_write_cnt;
-       zone = cxt->kpszs[zonenum];
-       if (unlikely(!zone))
-               return -ENOSPC;
-       cxt->kmsg_write_cnt = (zonenum + 1) % cxt->kmsg_max_cnt;
+       for (i = 0; i < cxt->kmsg_max_cnt; i++) {
+               unsigned int zonenum, len;
+               int ret;
 
-       pr_debug("write %s to zone id %d\n", zone->name, zonenum);
-       psz_write_kmsg_hdr(zone, record);
-       hlen = sizeof(struct psz_kmsg_header);
-       size = min_t(size_t, record->size, zone->buffer_size - hlen);
-       return psz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
+               zonenum = (cxt->kmsg_write_cnt + i) % cxt->kmsg_max_cnt;
+               zone = cxt->kpszs[zonenum];
+               if (unlikely(!zone))
+                       return -ENOSPC;
+
+               /* avoid destroying 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_kmsg_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->kmsg_write_cnt = zonenum + 1;
+                       cxt->kmsg_write_cnt %= cxt->kmsg_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_kmsg_write(struct psz_context *cxt,

diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
index 4501977..ccba8c0 100644 (file)
--- 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 6f16b0d..e79a18e 100644 (file)
--- a/include/linux/pstore_zone.h
+++ b/include/linux/pstore_zone.h
@@ -23,11 +23,15 @@ typedef ssize_t (*pstore_zone_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;