sfdisk: make sure we do not overlap on --move

The area we need to move does not have to be aligned to optimal I/O
size (step size) -- we need to be sure we do not move data
after/before the area.

Addresses: https://github.com/karelzak/util-linux/issues/938
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/disk-utils/sfdisk.c b/disk-utils/sfdisk.c
index 0601c3bcf5ddf374a1fa397911c322177a5b962c..8f2edb87f79325b3926c8183a830d4f47155de97 100644 (file)
--- a/disk-utils/sfdisk.c
+++ b/disk-utils/sfdisk.c
@@ -374,7 +374,7 @@ static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_pa
        int ok = 0, fd, backward = 0;
        fdisk_sector_t nsectors, from, to, step, i, prev;
        size_t io, ss, step_bytes, cc;
-       uintmax_t src, dst;
+       uintmax_t src, dst, nbytes;
        int errsv, progress = 0;
        struct timeval prev_time;
        uint64_t bytes_per_sec = 0;
@@ -409,6 +409,7 @@ static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_pa
        from = fdisk_partition_get_start(orig_pa);
        to = fdisk_partition_get_start(pa);
 
+
        if ((to >= from && from + nsectors >= to) ||
            (from >= to && to + nsectors >= from)) {
                /* source and target overlay, check if we need to copy
@@ -434,6 +435,8 @@ static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_pa
        while (nsectors % step)
                step--;
 
+       nbytes = nsectors * ss;
+
        DBG(MISC, ul_debug(" step: %ju (%zu bytes)", (uintmax_t)step, step_bytes));
 
 #if defined(POSIX_FADV_SEQUENTIAL) && defined(HAVE_POSIX_FADVISE)
@@ -504,7 +507,7 @@ static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_pa
        gettimeofday(&prev_time, NULL);
        prev = 0;
 
-       for (cc = 1, i = 0; i < nsectors; i += step, cc++) {
+       for (cc = 1, i = 0; i < nsectors && nbytes > 0; i += step, cc++) {
                ssize_t rc;
 
                if (backward)
@@ -512,6 +515,13 @@ static int move_partition_data(struct sfdisk *sf, size_t partno, struct fdisk_pa
 
                DBG(MISC, ul_debug("#%05zu: src=%ju dst=%ju", cc, src, dst));
 
+               if (nbytes < step_bytes) {
+                       DBG(MISC, ul_debug(" aligning step from %ju to %ju",
+                                               step_bytes, nbytes));
+                       step_bytes = nbytes;
+               }
+               nbytes -= step_bytes;
+
                if (!sf->noact) {
                        /* read source */
                        if (lseek(fd, src, SEEK_SET) == (off_t) -1)