]> git.ipfire.org Git - thirdparty/mdadm.git/blobdiff - Grow.c
Create missing /dev files where needed.
[thirdparty/mdadm.git] / Grow.c
diff --git a/Grow.c b/Grow.c
index d669a4e2465495a851ca1acb65c771ceac91f72d..de53df18559c69fabcabe2f8daa5d627b594e6a1 100644 (file)
--- a/Grow.c
+++ b/Grow.c
@@ -92,13 +92,13 @@ int Grow_Add_device(char *devname, int fd, char *newdev)
                                d);
                        return 1;
                }
-               dv = map_dev(disk.major, disk.minor);
+               dv = map_dev(disk.major, disk.minor, 1);
                if (!dv) {
                        fprintf(stderr, Name ": cannot find device file for device %d\n",
                                d);
                        return 1;
                }
-               fd2 = open(dv, O_RDWR);
+               fd2 = dev_open(dv, O_RDWR);
                if (!fd2) {
                        fprintf(stderr, Name ": cannot open device file %s\n", dv);
                        return 1;
@@ -154,13 +154,13 @@ int Grow_Add_device(char *devname, int fd, char *newdev)
                                d);
                        return 1;
                }
-               dv = map_dev(disk.major, disk.minor);
+               dv = map_dev(disk.major, disk.minor, 1);
                if (!dv) {
                        fprintf(stderr, Name ": cannot find device file for device %d\n",
                                d);
                        return 1;
                }
-               fd2 = open(dv, O_RDWR);
+               fd2 = dev_open(dv, O_RDWR);
                if (fd2 < 0) {
                        fprintf(stderr, Name ": cannot open device file %s\n", dv);
                        return 1;
@@ -192,7 +192,7 @@ int Grow_Add_device(char *devname, int fd, char *newdev)
        return 0;
 }
 
-int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int write_behind)
+int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int write_behind, int force)
 {
        /*
         * First check that array doesn't have a bitmap
@@ -208,7 +208,7 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
        struct supertype *st;
        int major = BITMAP_MAJOR_HI;
        int vers = md_get_version(fd);
-       unsigned long long bitmapsize;
+       unsigned long long bitmapsize, array_size;
 
        if (vers < 9003) {
                major = BITMAP_MAJOR_HOSTENDIAN;
@@ -219,7 +219,7 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
        }
 
        if (ioctl(fd, GET_BITMAP_FILE, &bmf) != 0) {
-               if (errno == ENOMEM) 
+               if (errno == ENOMEM)
                        fprintf(stderr, Name ": Memory allocation failure.\n");
                else
                        fprintf(stderr, Name ": bitmaps not supported by this kernel.\n");
@@ -255,7 +255,22 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
                        devname);
                return 1;
        }
-       bitmapsize = array.size * 2;
+       bitmapsize = array.size;
+       bitmapsize <<= 1;
+#ifdef BLKGETSIZE64
+       if (ioctl(fd, BLKGETSIZE64, &array_size) == 0 &&
+           array_size > (0x7fffffffULL<<9)) {
+               /* Array is big enough that we cannot trust array.size
+                * try other approaches
+                */
+               bitmapsize = get_component_size(fd);
+       }
+#endif
+       if (bitmapsize == 0) {
+               fprintf(stderr, Name ": Cannot reliably determine size of array to create bitmap - sorry.\n");
+               return 1;
+       }
+
        if (array.level == 10) {
                int ncopies = (array.layout&255)*(array.layout>>8);
                bitmapsize = bitmapsize * array.raid_disks / ncopies;
@@ -283,17 +298,22 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
                                continue;
                        if ((disk.state & (1<<MD_DISK_SYNC))==0)
                                continue;
-                       dv = map_dev(disk.major, disk.minor);
+                       dv = map_dev(disk.major, disk.minor, 1);
                        if (dv) {
                                void *super;
-                               int fd2 = open(dv, O_RDWR);
+                               int fd2 = dev_open(dv, O_RDWR);
                                if (fd2 < 0)
                                        continue;
                                if (st->ss->load_super(st, fd2, &super, NULL)==0) {
-                                       st->ss->add_internal_bitmap(st, super,
-                                                                   chunk, delay, write_behind,
-                                                                   bitmapsize, 0, major);
-                                       st->ss->write_bitmap(st, fd2, super);
+                                       if (st->ss->add_internal_bitmap(st, super,
+                                                                       chunk, delay, write_behind,
+                                                                       bitmapsize, 0, major))
+                                               st->ss->write_bitmap(st, fd2, super);
+                                       else {
+                                               fprintf(stderr, Name ": failed to create internal bitmap - chunksize problem.\n");
+                                               close(fd2);
+                                               return 1;
+                                       }
                                }
                                close(fd2);
                        }
@@ -323,9 +343,9 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
                        if ((disk.major==0 && disk.minor==0) ||
                            (disk.state & (1<<MD_DISK_REMOVED)))
                                continue;
-                       dv = map_dev(disk.major, disk.minor);
+                       dv = map_dev(disk.major, disk.minor, 1);
                        if (!dv) continue;
-                       fd2 = open(dv, O_RDONLY);
+                       fd2 = dev_open(dv, O_RDONLY);
                        if (fd2 >= 0 &&
                            st->ss->load_super(st, fd2, &super, NULL) == 0) {
                                close(fd2);
@@ -338,13 +358,13 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
                        fprintf(stderr, Name ": cannot find UUID for array!\n");
                        return 1;
                }
-               if (CreateBitmap(file, 0, (char*)uuid, chunk,
+               if (CreateBitmap(file, force, (char*)uuid, chunk,
                                 delay, write_behind, bitmapsize, major)) {
                        return 1;
                }
                bitmap_fd = open(file, O_RDWR);
                if (bitmap_fd < 0) {
-                       fprintf(stderr, Name ": weird: %s cannot be openned\n",
+                       fprintf(stderr, Name ": weird: %s cannot be opened\n",
                                file);
                        return 1;
                }
@@ -358,4 +378,580 @@ int Grow_addbitmap(char *devname, int fd, char *file, int chunk, int delay, int
        return 0;
 }
 
+
+/*
+ * When reshaping an array we might need to backup some data.
+ * This is written to all spares with a 'super_block' describing it.
+ * The superblock goes 1K form the end of the used space on the
+ * device.
+ * It if written after the backup is complete.
+ * It has the following structure.
+ */
+
+struct mdp_backup_super {
+       char    magic[16];  /* md_backup_data-1 */
+       __u8    set_uuid[16];
+       __u64   mtime;
+       /* start/sizes in 512byte sectors */
+       __u64   devstart;
+       __u64   arraystart;
+       __u64   length;
+       __u32   sb_csum;        /* csum of preceeding bytes. */
+};
+
+int bsb_csum(char *buf, int len)
+{
+       int i;
+       int csum = 0;
+       for (i=0; i<len; i++)
+               csum = (csum<<3) + buf[0];
+       return __cpu_to_le32(csum);
+}
+
+int Grow_reshape(char *devname, int fd, int quiet, char *backup_file,
+                long long size,
+                int level, int layout, int chunksize, int raid_disks)
+{
+       /* Make some changes in the shape of an array.
+        * The kernel must support the change.
+        * Different reshapes have subtly different meaning for different
+        * levels, so we need to check the current state of the array
+        * and go from there.
+        */
+       struct mdu_array_info_s array;
+       char *c;
+
+       struct mdp_backup_super bsb;
+       struct supertype *st;
+
+       int nlevel, olevel;
+       int nchunk, ochunk;
+       int nlayout, olayout;
+       int ndisks, odisks;
+       int ndata, odata;
+       unsigned long long nstripe, ostripe, last_block;
+       int *fdlist;
+       unsigned long long *offsets;
+       int d, i, spares;
+       int nrdisks;
+       int err;
+       void *super = NULL;
+
+       struct sysarray *sra;
+       struct sysdev *sd;
+
+       if (ioctl(fd, GET_ARRAY_INFO, &array) < 0) {
+               fprintf(stderr, Name ": %s is not an active md array - aborting\n",
+                       devname);
+               return 1;
+       }
+       c = map_num(pers, array.level);
+       if (c == NULL) c = "-unknown-";
+       switch(array.level) {
+       default: /* raid0, linear, multipath cannot be reconfigured */
+               fprintf(stderr, Name ": %s array %s cannot be reshaped.\n",
+                       c, devname);
+               return 1;
+
+       case LEVEL_FAULTY: /* only 'layout' change is permitted */
+
+               if (size >= 0) {
+                       fprintf(stderr, Name ": %s: Cannot change size of a 'faulty' array\n",
+                               devname);
+                       return 1;
+               }
+               if (level != UnSet && level != LEVEL_FAULTY) {
+                       fprintf(stderr, Name ": %s: Cannot change RAID level of a 'faulty' array\n",
+                               devname);
+                       return 1;
+               }
+               if (chunksize  || raid_disks) {
+                       fprintf(stderr, Name ": %s: Cannot change chunksize or disks of a 'faulty' array\n",
+                               devname);
+                       return 1;
+               }
+               if (layout == UnSet)
+                       return 0; /* nothing to do.... */
+
+               array.layout = layout;
+               if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
+                       fprintf(stderr, Name ": Cannot set layout for %s: %s\n",
+                               devname, strerror(errno));
+                       return 1;
+               }
+               if (!quiet)
+                       printf("layout for %s set to %d\n", devname, array.layout);
+               return 0;
+
+       case 1: /* raid_disks and size can each be changed.  They are independant */
+
+               if (level != UnSet && level != 1) {
+                       fprintf(stderr, Name ": %s: Cannot change RAID level of a RAID1 array.\n",
+                               devname);
+                       return 1;
+               }
+               if (chunksize || layout != UnSet) {
+                       fprintf(stderr, Name ": %s: Cannot change chunk size of layout for a RAID1 array.\n",
+                               devname);
+                       return 1;
+               }
+
+               /* Each can trigger a resync/recovery which will block the
+                * other from happening.  Later we could block
+                * resync for the duration via 'sync_action'...
+                */
+               if (raid_disks >= 0)
+                       array.raid_disks = raid_disks;
+               if (size >= 0)
+                       array.size = size;
+               if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
+                       fprintf(stderr, Name ": Cannot set device size/shape for %s: %s\n",
+                               devname, strerror(errno));
+                       return 1;
+               }
+               return 0;
+
+       case 4:
+       case 5:
+       case 6:
+               st = super_by_version(array.major_version,
+                                     array.minor_version);
+               /* size can be changed independantly.
+                * layout/chunksize/raid_disks/level can be changed
+                * though the kernel may not support it all.
+                * If 'suspend_lo' is not present in devfs, then
+                * these cannot be changed.
+                */
+               if (size >= 0) {
+                       /* Cannot change other details as well.. */
+                       if (layout != UnSet ||
+                           chunksize != 0 ||
+                           raid_disks != 0 ||
+                           level != UnSet) {
+                               fprintf(stderr, Name ": %s: Cannot change shape as well as size of a %s array.\n",
+                                       devname, c);
+                               return 1;
+                       }
+                       array.size = size;
+                       if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
+                               fprintf(stderr, Name ": Cannot set device size/shape for %s: %s\n",
+                                       devname, strerror(errno));
+                               return 1;
+                       }
+                       return 0;
+               }
+               /* Ok, just change the shape. This can be awkward.
+                *  There are three possibilities.
+                * 1/ The array will shrink.  We don't support this
+                *    possibility.  Maybe one day...
+                * 2/ The array will not change size.  This is easy enough
+                *    to do, but not reliably.  If the process is aborted
+                *    the array *will* be corrupted.  So maybe we can allow
+                *    this but only if the user is really certain.  e.g.
+                *    --really-risk-everything
+                * 3/ The array will grow. This can be reliably achieved.
+                *    However the kernel's restripe routines will cheerfully
+                *    overwrite some early data before it is safe.  So we
+                *    need to make a backup of the early parts of the array
+                *    and be ready to restore it if rebuild aborts very early.
+                *
+                *    We backup data by writing it to all spares (there must be
+                *    at least 1, so even raid6->raid5 requires a spare to be
+                *    present).
+                *
+                *    So: we enumerate the devices in the array and
+                *    make sure we can open all of them.
+                *    Then we freeze the early part of the array and
+                *    backup to the various spares.
+                *    Then we request changes and start the reshape.
+                *    Monitor progress until it has passed the danger zone.
+                *    and finally invalidate the copied data and unfreeze the
+                *    start of the array.
+                *
+                *    Before we can do this we need to decide:
+                *     - will the array grow?  Just calculate size
+                *     - how much needs to be saved: count stripes.
+                *     - where to save data... good question.
+                *
+                */
+               nlevel = olevel = array.level;
+               nchunk = ochunk = array.chunk_size;
+               nlayout = olayout = array.layout;
+               ndisks = odisks = array.raid_disks;
+
+               if (level != UnSet) nlevel = level;
+               if (chunksize) nchunk = chunksize;
+               if (layout != UnSet) nlayout = layout;
+               if (raid_disks) ndisks = raid_disks;
+
+               odata = odisks-1;
+               if (olevel == 6) odata--; /* number of data disks */
+               ndata = ndisks-1;
+               if (nlevel == 6) ndata--;
+
+               if (ndata < odata) {
+                       fprintf(stderr, Name ": %s: Cannot reduce number of data disks (yet).\n",
+                               devname);
+                       return 1;
+               }
+               if (ndata == odata) {
+                       fprintf(stderr, Name ": %s: Cannot reshape array without increasing size (yet).\n",
+                               devname);
+                       return 1;
+               }
+               /* Well, it is growing... so how much do we need to backup.
+                * Need to backup a full number of new-stripes, such that the
+                * last one does not over-write any place that it would be read
+                * from
+                */
+               nstripe = ostripe = 0;
+               while (nstripe >= ostripe) {
+                       nstripe += nchunk/512;
+                       last_block = nstripe * ndata;
+                       ostripe = last_block / odata / (ochunk/512) * (ochunk/512);
+               }
+               printf("mdadm: Need to backup %lluK of critical section..\n", last_block/2);
+
+               sra = sysfs_read(fd, 0,
+                                GET_COMPONENT|GET_DEVS|GET_OFFSET|GET_STATE);
+               if (!sra) {
+                       fprintf(stderr, Name ": %s: Cannot get array details from sysfs\n",
+                               devname);
+                       return 1;
+               }
+
+               if (last_block >= sra->component_size/2) {
+                       fprintf(stderr, Name ": %s: Something wrong - reshape aborted\n",
+                               devname);
+                       return 1;
+               }
+               if (sra->spares == 0 && backup_file == NULL) {
+                       fprintf(stderr, Name ": %s: Cannot grow - need a spare or backup-file to backup critical section\n",
+                               devname);
+                       return 1;
+               }
+
+               nrdisks = array.nr_disks + sra->spares;
+               /* Now we need to open all these devices so we can read/write.
+                */
+               fdlist = malloc((1+nrdisks) * sizeof(int));
+               offsets = malloc((1+nrdisks) * sizeof(offsets[0]));
+               if (!fdlist || !offsets) {
+                       fprintf(stderr, Name ": malloc failed: grow aborted\n");
+                       return 1;
+               }
+               for (d=0; d <= nrdisks; d++)
+                       fdlist[d] = -1;
+               d = array.raid_disks;
+               for (sd = sra->devs; sd; sd=sd->next) {
+                       if (sd->state & (1<<MD_DISK_FAULTY))
+                               continue;
+                       if (sd->state & (1<<MD_DISK_SYNC)) {
+                               char *dn = map_dev(sd->major, sd->minor, 1);
+                               fdlist[sd->role] = dev_open(dn, O_RDONLY);
+                               offsets[sd->role] = sd->offset;
+                               if (fdlist[sd->role] < 0) {
+                                       fprintf(stderr, Name ": %s: cannot open component %s\n",
+                                               devname, dn);
+                                       goto abort;
+                               }
+                       } else {
+                               /* spare */
+                               char *dn = map_dev(sd->major, sd->minor, 1);
+                               fdlist[d] = dev_open(dn, O_RDWR);
+                               offsets[d] = sd->offset;
+                               if (fdlist[d]<0) {
+                                       fprintf(stderr, Name ": %s: cannot open component %s\n",
+                                               devname, dn);
+                                       goto abort;
+                               }
+                               d++;
+                       }
+               }
+               for (i=0 ; i<array.raid_disks; i++)
+                       if (fdlist[i] < 0) {
+                               fprintf(stderr, Name ": %s: failed to find device %d. Array might be degraded.\n"
+                                       " --grow aborted\n", devname, i);
+                               goto abort;
+                       }
+               spares = sra->spares;
+               if (backup_file) {
+                       fdlist[d] = open(backup_file, O_RDWR|O_CREAT|O_EXCL, 0600);
+                       if (fdlist[d] < 0) {
+                               fprintf(stderr, Name ": %s: cannot create backup file %s: %s\n",
+                                       devname, backup_file, strerror(errno));
+                               goto abort;
+                       }
+                       offsets[d] = 8;
+                       d++;
+                       spares++;
+               }
+               if (fdlist[array.raid_disks] < 0) {
+                       fprintf(stderr, Name ": %s: failed to find a spare and no backup-file given - --grow aborted\n",
+                               devname);
+                       goto abort;
+               }
+
+               /* Find a superblock */
+               if (st->ss->load_super(st, fdlist[0], &super, NULL)) {
+                       fprintf(stderr, Name ": %s: Cannot find a superblock\n",
+                               devname);
+                       goto abort;
+               }
+
+
+               memcpy(bsb.magic, "md_backup_data-1", 16);
+               st->ss->uuid_from_super((int*)&bsb.set_uuid, super);
+               bsb.mtime = __cpu_to_le64(time(0));
+               bsb.arraystart = 0;
+               bsb.length = __cpu_to_le64(last_block);
+
+               /* Decide offset for the backup, llseek the spares, and write
+                * a leading superblock 4K earlier.
+                */
+               for (i=array.raid_disks; i<d; i++) {
+                       char buf[4096];
+                       if (i==d-1 && backup_file) {
+                               /* This is the backup file */
+                               offsets[i] = 8;
+                       } else
+                               offsets[i] += sra->component_size - last_block - 8;
+                       if (lseek64(fdlist[i], (offsets[i]<<9) - 4096, 0)
+                           != (offsets[i]<<9) - 4096) {
+                               fprintf(stderr, Name ": could not seek...\n");
+                               goto abort;
+                       }
+                       memset(buf, 0, sizeof(buf));
+                       bsb.devstart = __cpu_to_le64(offsets[i]);
+                       bsb.sb_csum = bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb));
+                       memcpy(buf, &bsb, sizeof(bsb));
+                       if (write(fdlist[i], buf, 4096) != 4096) {
+                               fprintf(stderr, Name ": could not write leading superblock\n");
+                               goto abort;
+                       }
+               }
+               array.level = nlevel;
+               array.raid_disks = ndisks;
+               array.chunk_size = nchunk;
+               array.layout = nlayout;
+               if (ioctl(fd, SET_ARRAY_INFO, &array) != 0) {
+                       fprintf(stderr, Name ": Cannot set device size/shape for %s: %s\n",
+                               devname, strerror(errno));
+                       goto abort;
+               }
+
+               /* suspend the relevant region */
+               sysfs_set_num(sra, NULL, "suspend_hi", 0); /* just in case */
+               if (sysfs_set_num(sra, NULL, "suspend_lo", 0) < 0 ||
+                   sysfs_set_num(sra, NULL, "suspend_hi", last_block) < 0) {
+                       fprintf(stderr, Name ": %s: failed to suspend device.\n",
+                               devname);
+                       goto abort_resume;
+               }
+
+
+               err = save_stripes(fdlist, offsets,
+                                  odisks, ochunk, olevel, olayout,
+                                  spares, fdlist+odisks,
+                                  0ULL, last_block*512);
+
+               /* abort if there was an error */
+               if (err < 0) {
+                       fprintf(stderr, Name ": %s: failed to save critical region\n",
+                               devname);
+                       goto abort_resume;
+               }
+
+               for (i=odisks; i<d ; i++) {
+                       bsb.devstart = __cpu_to_le64(offsets[i]);
+                       bsb.sb_csum = bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb));
+                       if (lseek64(fdlist[i], (offsets[i]+last_block)<<9, 0) < 0 ||
+                           write(fdlist[i], &bsb, sizeof(bsb)) != sizeof(bsb) ||
+                           fsync(fdlist[i]) != 0) {
+                               fprintf(stderr, Name ": %s: fail to save metadata for critical region backups.\n",
+                                       devname);
+                               goto abort_resume;
+                       }
+               }
+
+               /* start the reshape happening */
+               if (sysfs_set_str(sra, NULL, "sync_action", "reshape") < 0) {
+                       fprintf(stderr, Name ": %s: failed to initiate reshape\n",
+                               devname);
+                       goto abort_resume;
+               }
+               /* wait for reshape to pass the critical region */
+               while(1) {
+                       unsigned long long comp;
+                       if (sysfs_get_ll(sra, NULL, "sync_completed", &comp)<0) {
+                               sleep(5);
+                               break;
+                       }
+                       if (comp >= nstripe)
+                               break;
+                       sleep(1);
+               }
                
+               /* invalidate superblocks */
+               memset(&bsb, 0, sizeof(bsb));
+               for (i=odisks; i<d ; i++) {
+                       lseek64(fdlist[i], (offsets[i]+last_block)<<9, 0);
+                       write(fdlist[i], &bsb, sizeof(bsb));
+               }
+
+               /* unsuspend. */
+               sysfs_set_num(sra, NULL, "suspend_lo", last_block);
+
+               for (i=0; i<d; i++)
+                       if (fdlist[i] >= 0)
+                               close(fdlist[i]);
+               free(fdlist);
+               free(offsets);
+               if (backup_file)
+                       unlink(backup_file);
+
+               printf(Name ": ... critical section passed.\n");
+               break;
+       }
+       return 0;
+
+
+ abort_resume:
+       sysfs_set_num(sra, NULL, "suspend_lo", last_block);
+ abort:
+       for (i=0; i<array.nr_disks; i++)
+               if (fdlist[i] >= 0)
+                       close(fdlist[i]);
+       free(fdlist);
+       free(offsets);
+       if (backup_file)
+               unlink(backup_file);
+       return 1;
+
+}
+
+/*
+ * If any spare contains md_back_data-1 which is recent wrt mtime,
+ * write that data into the array and update the super blocks with
+ * the new reshape_progress
+ */
+int Grow_restart(struct supertype *st, struct mdinfo *info, int *fdlist, int cnt, char *backup_file)
+{
+       int i, j;
+       int old_disks;
+       int err = 0;
+       unsigned long long *offsets;
+
+       if (info->delta_disks < 0)
+               return 1; /* cannot handle a shrink */
+       if (info->new_level != info->array.level ||
+           info->new_layout != info->array.layout ||
+           info->new_chunk != info->array.chunk_size)
+               return 1; /* Can only handle change in disks */
+
+       old_disks = info->array.raid_disks - info->delta_disks;
+
+       for (i=old_disks-(backup_file?1:0); i<cnt; i++) {
+               void *super = NULL;
+               struct mdinfo dinfo;
+               struct mdp_backup_super bsb;
+               char buf[4096];
+               int fd;
+
+               /* This was a spare and may have some saved data on it.
+                * Load the superblock, find and load the
+                * backup_super_block.
+                * If either fail, go on to next device.
+                * If the backup contains no new info, just return
+                * else restore data and update all superblocks
+                */
+               if (i == old_disks-1) {
+                       fd = open(backup_file, O_RDONLY);
+                       if (fd<0)
+                               continue;
+                       if (lseek(fd, 4096, 0) != 4096)
+                               continue;
+               } else {
+                       fd = fdlist[i];
+                       if (fd < 0)
+                               continue;
+                       if (st->ss->load_super(st, fd, &super, NULL))
+                               continue;
+
+                       st->ss->getinfo_super(&dinfo, super);
+                       free(super); super = NULL;
+                       if (lseek64(fd,
+                                   (dinfo.data_offset + dinfo.component_size - 8) <<9,
+                                   0) < 0)
+                               continue; /* Cannot seek */
+               }
+               if (read(fd, &bsb, sizeof(bsb)) != sizeof(bsb))
+                       continue; /* Cannot read */
+               if (memcmp(bsb.magic, "md_backup_data-1", 16) != 0)
+                       continue;
+               if (bsb.sb_csum != bsb_csum((char*)&bsb, ((char*)&bsb.sb_csum)-((char*)&bsb)))
+                       continue; /* bad checksum */
+               if (memcmp(bsb.set_uuid,info->uuid, 16) != 0)
+                       continue; /* Wrong uuid */
+
+               if (info->array.utime > __le64_to_cpu(bsb.mtime) + 3600 ||
+                   info->array.utime < __le64_to_cpu(bsb.mtime))
+                       continue; /* time stamp is too bad */
+
+               if (__le64_to_cpu(bsb.arraystart) != 0)
+                       continue; /* Can only handle backup from start of array */
+               if (__le64_to_cpu(bsb.length) <
+                   info->reshape_progress)
+                       continue; /* No new data here */
+
+               if (lseek64(fd, __le64_to_cpu(bsb.devstart)*512, 0)< 0)
+                       continue; /* Cannot seek */
+               /* There should be a duplicate backup superblock 4k before here */
+               if (lseek64(fd, -4096, 1) < 0 ||
+                   read(fd, buf, 4096) != 4096 ||
+                   memcmp(buf, &bsb, sizeof(buf)) != 0)
+                       continue; /* Cannot find leading superblock */
+
+               /* Now need the data offsets for all devices. */
+               offsets = malloc(sizeof(*offsets)*info->array.raid_disks);
+               for(j=0; j<info->array.raid_disks; j++) {
+                       if (fdlist[j] < 0)
+                               continue;
+                       if (st->ss->load_super(st, fdlist[j], &super, NULL))
+                               /* FIXME should be this be an error */
+                               continue;
+                       st->ss->getinfo_super(&dinfo, super);
+                       free(super); super = NULL;
+                       offsets[j] = dinfo.data_offset;
+               }
+               printf(Name ": restoring critical section\n");
+
+               if (restore_stripes(fdlist, offsets,
+                                   info->array.raid_disks,
+                                   info->new_chunk,
+                                   info->new_level,
+                                   info->new_layout,
+                                   fd, __le64_to_cpu(bsb.devstart)*512,
+                                   0, __le64_to_cpu(bsb.length)*512)) {
+                       /* didn't succeed, so giveup */
+                       return -1;
+               }
+
+               /* Ok, so the data is restored. Let's update those superblocks. */
+
+               for (j=0; j<info->array.raid_disks; j++) {
+                       if (fdlist[j] < 0) continue;
+                       if (st->ss->load_super(st, fdlist[j], &super, NULL))
+                               continue;
+                       st->ss->getinfo_super(&dinfo, super);
+                       dinfo.reshape_progress = __le64_to_cpu(bsb.length);
+                       st->ss->update_super(&dinfo, super, "_reshape_progress",NULL,0);
+                       st->ss->store_super(st, fdlist[j], super);
+                       free(super);
+               }
+
+               /* And we are done! */
+               return 0;
+       }
+       return err;
+}