libfdisk: (gpt) move backup header after device resize

Addresses: https://github.com/karelzak/util-linux/issues/532
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libfdisk/src/gpt.c b/libfdisk/src/gpt.c
index 26d04f1d881fe47292d3811c9715e7a8b7b4412f..56bd373cd0fd7b937ac18ff6b5d234a0e9e8051c 100644 (file)
--- a/libfdisk/src/gpt.c
+++ b/libfdisk/src/gpt.c
@@ -525,6 +525,40 @@ static int gpt_mknew_pmbr(struct fdisk_context *cxt)
        return 0;
 }
 
+/* Move backup header to the end of the device */
+static void gpt_fix_alternative_lba(struct fdisk_context *cxt, struct fdisk_gpt_label *gpt)
+{
+       struct gpt_header *p, *b;
+       uint64_t esz, esects, last;
+
+       if (!cxt)
+               return;
+
+       p = gpt->pheader;       /* primary */
+       b = gpt->bheader;       /* backup */
+
+       /* count size of partitions array */
+       esz = (uint64_t) le32_to_cpu(p->npartition_entries) * sizeof(struct gpt_entry);
+       esects = (esz + cxt->sector_size - 1) / cxt->sector_size;
+
+       /* reference from primary to backup */
+       p->alternative_lba = cpu_to_le64(cxt->total_sectors - 1ULL);
+
+       /* reference from backup to primary */
+       b->alternative_lba = p->my_lba;
+       b->my_lba = p->alternative_lba;
+
+       /* fix backup partitions array address */
+       b->partition_entry_lba = cpu_to_le64(cxt->total_sectors - 1ULL - esects);
+
+       /* update last usable LBA */
+       last = cxt->total_sectors - 2ULL - esects;
+       p->last_usable_lba  = cpu_to_le64(last);
+       b->last_usable_lba  = cpu_to_le64(last);
+
+       DBG(LABEL, ul_debug("Alternative-LBA updated to: %"PRIu64, le64_to_cpu(p->alternative_lba)));
+}
+
 /* some universal differences between the headers */
 static void gpt_mknew_header_common(struct fdisk_context *cxt,
                                    struct gpt_header *header, uint64_t lba)
@@ -824,9 +858,15 @@ static int valid_pmbr(struct fdisk_context *cxt)
        if (ret == GPT_MBR_PROTECTIVE) {
                uint64_t sz_lba = (uint64_t) le32_to_cpu(pmbr->partition_record[part].size_in_lba);
                if (sz_lba != cxt->total_sectors - 1ULL && sz_lba != 0xFFFFFFFFULL) {
+
                        fdisk_warnx(cxt, _("GPT PMBR size mismatch (%"PRIu64" != %"PRIu64") "
-                                          "will be corrected by w(rite)."),
+                                          "will be corrected by write."),
                                        sz_lba, cxt->total_sectors - 1ULL);
+
+                       /* Note that gpt_write_pmbr() overwrites PMBR, but we want to keep it valid already 
+                        * in memory too to disable warnings when valid_pmbr() called next time */
+                       pmbr->partition_record[part].size_in_lba  =
+                               cpu_to_le32((uint32_t) min( cxt->total_sectors - 1ULL, 0xFFFFFFFFULL) );
                        fdisk_label_set_changed(cxt->label, 1);
                }
        }
@@ -1525,6 +1565,7 @@ static int gpt_probe_label(struct fdisk_context *cxt)
                if (!gpt->bheader)
                        goto failed;
                gpt_recompute_crc(gpt->bheader, gpt->ents);
+               fdisk_label_set_changed(cxt->label, 1);
 
        /* primary corrupted, backup OK -- recovery */
        } else if (!gpt->pheader && gpt->bheader) {
@@ -1534,6 +1575,20 @@ static int gpt_probe_label(struct fdisk_context *cxt)
                if (!gpt->pheader)
                        goto failed;
                gpt_recompute_crc(gpt->pheader, gpt->ents);
+               fdisk_label_set_changed(cxt->label, 1);
+       }
+
+       /* The headers make be correct, but Backup do not have to be on the end
+        * of the device (due to device resize, etc.). Let's fix this issue. */
+       if (le64_to_cpu(gpt->pheader->alternative_lba) > cxt->total_sectors ||
+           le64_to_cpu(gpt->pheader->alternative_lba) < cxt->total_sectors - 1ULL) {
+               fdisk_warnx(cxt, _("The backup GPT table is not on the end of the device. "
+                                  "This problem will be corrected by write."));
+
+               gpt_fix_alternative_lba(cxt, gpt);
+               gpt_recompute_crc(gpt->bheader, gpt->ents);
+               gpt_recompute_crc(gpt->pheader, gpt->ents);
+               fdisk_label_set_changed(cxt->label, 1);
        }
 
        cxt->label->nparts_max = gpt_get_nentries(gpt);
@@ -1991,7 +2046,6 @@ static int gpt_write_disklabel(struct fdisk_context *cxt)
 
        /* check that the backup header is properly placed */
        if (le64_to_cpu(gpt->pheader->alternative_lba) < cxt->total_sectors - 1ULL)
-               /* TODO: correct this (with user authorization) and write */
                goto err0;
 
        if (check_overlap_partitions(gpt))