libfdisk: (gpt) improve and cleanup recovery code

 * use AlternativeLBA rather than hardcoded offset to backup GPT
 * create gpt_copy_header()

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libfdisk/src/gpt.c b/libfdisk/src/gpt.c
index 3a256e6dc033454ce2e53687e135ecf9e1b5f42a..68eddeb80aff5053399de747c67ba8f224368b06 100644 (file)
--- a/libfdisk/src/gpt.c
+++ b/libfdisk/src/gpt.c
@@ -413,6 +413,46 @@ static int gpt_mknew_header_from_bkp(struct fdisk_context *cxt,
        return 0;
 }
 
+static struct gpt_header *gpt_copy_header(struct fdisk_context *cxt,
+                          struct gpt_header *src)
+{
+       struct gpt_header *res;
+
+       if (!cxt || !src)
+               return NULL;
+
+       res = calloc(1, sizeof(*res));
+       if (!res) {
+               fdisk_warn(cxt, _("failed to allocate GPT header"));
+               return NULL;
+       }
+
+       res->my_lba                 = src->alternative_lba;
+       res->alternative_lba        = src->my_lba;
+
+       res->signature              = src->signature;
+       res->revision               = src->revision;
+       res->size                   = src->size;
+       res->npartition_entries     = src->npartition_entries;
+       res->sizeof_partition_entry = src->sizeof_partition_entry;
+       res->first_usable_lba       = src->first_usable_lba;
+       res->last_usable_lba        = src->last_usable_lba;
+
+       memcpy(&res->disk_guid, &src->disk_guid, sizeof(src->disk_guid));
+
+
+       if (res->my_lba == GPT_PRIMARY_PARTITION_TABLE_LBA)
+               res->partition_entry_lba = cpu_to_le64(2);
+       else {
+               uint64_t esz = le32_to_cpu(src->npartition_entries) * sizeof(struct gpt_entry);
+               uint64_t esects = (esz + cxt->sector_size - 1) / cxt->sector_size;
+
+               res->partition_entry_lba = cpu_to_le64(cxt->total_sectors - 1 - esects);
+       }
+
+       return res;
+}
+
 /*
  * Builds a clean new GPT header (currently under revision 1.0).
  *
@@ -779,10 +819,13 @@ static struct gpt_header *gpt_read_header(struct fdisk_context *cxt,
        else
                free(ents);
 
+       DBG(LABEL, dbgprint("found valid GPT Header on LBA %ju", lba));
        return header;
 invalid:
        free(header);
        free(ents);
+
+       DBG(LABEL, dbgprint("read GPT Header on LBA %ju failed", lba));
        return NULL;
 }
 
@@ -1106,9 +1149,15 @@ static int gpt_probe_label(struct fdisk_context *cxt)
        /* primary header */
        gpt->pheader = gpt_read_header(cxt, GPT_PRIMARY_PARTITION_TABLE_LBA,
                                       &gpt->ents);
-       /* backup header */
-       gpt->bheader = gpt_read_header(cxt, last_lba(cxt),
-                                       gpt->pheader ? NULL : &gpt->ents);
+
+       if (gpt->pheader)
+               /* primary OK, try backup from alternative LBA */
+               gpt->bheader = gpt_read_header(cxt,
+                                       le64_to_cpu(gpt->pheader->alternative_lba),
+                                       NULL);
+       else
+               /* primary corrupted -- try last LBA */
+               gpt->bheader = gpt_read_header(cxt, last_lba(cxt), &gpt->ents);
 
        if (!gpt->pheader && !gpt->bheader)
                goto failed;
@@ -1117,26 +1166,18 @@ static int gpt_probe_label(struct fdisk_context *cxt)
        if (gpt->pheader && !gpt->bheader) {
                fdisk_warnx(cxt, _("The backup GPT table is corrupt, but the "
                                  "primary appears OK, so that will be used."));
-               gpt->bheader = calloc(1, sizeof(*gpt->bheader));
-               if (!gpt->bheader) {
-                       fdisk_warn(cxt, _("failed to allocate GPT header"));
+               gpt->bheader = gpt_copy_header(cxt, gpt->pheader);
+               if (!gpt->bheader)
                        goto failed;
-               }
-               gpt_mknew_header_from_bkp(cxt, gpt->bheader,
-                               last_lba(cxt), gpt->pheader);
                gpt_recompute_crc(gpt->bheader, gpt->ents);
 
        /* primary corrupted, backup OK -- recovery */
        } else if (!gpt->pheader && gpt->bheader) {
                fdisk_warnx(cxt, _("The primary GPT table is corrupt, but the "
                                  "backup appears OK, so that will be used."));
-               gpt->pheader = calloc(1, sizeof(*gpt->bheader));
-               if (!gpt->pheader) {
-                       fdisk_warn(cxt, _("failed to allocate GPT header"));
+               gpt->pheader = gpt_copy_header(cxt, gpt->bheader);
+               if (!gpt->pheader)
                        goto failed;
-               }
-               gpt_mknew_header_from_bkp(cxt, gpt->pheader,
-                               GPT_PRIMARY_PARTITION_TABLE_LBA, gpt->bheader);
                gpt_recompute_crc(gpt->pheader, gpt->ents);
        }