qemu-img: Add salvaging mode to convert
This adds a salvaging mode (--salvage) to qemu-img convert which ignores
read errors and treats the respective areas as containing only zeroes.
This can be used for instance to at least partially recover the data
from terminally corrupted qcow2 images.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190507203508.18026-3-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/qemu-img.c b/qemu-img.c
index e15e617..158b3a5 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -69,6 +69,7 @@
OPTION_SIZE = 264,
OPTION_PREALLOCATION = 265,
OPTION_SHRINK = 266,
+ OPTION_SALVAGE = 267,
};
typedef enum OutputFormat {
@@ -1581,6 +1582,7 @@
int64_t target_backing_sectors; /* negative if unknown */
bool wr_in_order;
bool copy_range;
+ bool salvage;
bool quiet;
int min_sparse;
int alignment;
@@ -1628,25 +1630,44 @@
}
if (s->sector_next_status <= sector_num) {
- int64_t count = n * BDRV_SECTOR_SIZE;
+ uint64_t offset = (sector_num - src_cur_offset) * BDRV_SECTOR_SIZE;
+ int64_t count;
- if (s->target_has_backing) {
+ do {
+ count = n * BDRV_SECTOR_SIZE;
- ret = bdrv_block_status(blk_bs(s->src[src_cur]),
- (sector_num - src_cur_offset) *
- BDRV_SECTOR_SIZE,
- count, &count, NULL, NULL);
- } else {
- ret = bdrv_block_status_above(blk_bs(s->src[src_cur]), NULL,
- (sector_num - src_cur_offset) *
- BDRV_SECTOR_SIZE,
- count, &count, NULL, NULL);
- }
- if (ret < 0) {
- error_report("error while reading block status of sector %" PRId64
- ": %s", sector_num, strerror(-ret));
- return ret;
- }
+ if (s->target_has_backing) {
+ ret = bdrv_block_status(blk_bs(s->src[src_cur]), offset,
+ count, &count, NULL, NULL);
+ } else {
+ ret = bdrv_block_status_above(blk_bs(s->src[src_cur]), NULL,
+ offset, count, &count, NULL,
+ NULL);
+ }
+
+ if (ret < 0) {
+ if (s->salvage) {
+ if (n == 1) {
+ if (!s->quiet) {
+ warn_report("error while reading block status at "
+ "offset %" PRIu64 ": %s", offset,
+ strerror(-ret));
+ }
+ /* Just try to read the data, then */
+ ret = BDRV_BLOCK_DATA;
+ count = BDRV_SECTOR_SIZE;
+ } else {
+ /* Retry on a shorter range */
+ n = DIV_ROUND_UP(n, 4);
+ }
+ } else {
+ error_report("error while reading block status at offset "
+ "%" PRIu64 ": %s", offset, strerror(-ret));
+ return ret;
+ }
+ }
+ } while (ret < 0);
+
n = DIV_ROUND_UP(count, BDRV_SECTOR_SIZE);
if (ret & BDRV_BLOCK_ZERO) {
@@ -1683,6 +1704,7 @@
static int coroutine_fn convert_co_read(ImgConvertState *s, int64_t sector_num,
int nb_sectors, uint8_t *buf)
{
+ uint64_t single_read_until = 0;
int n, ret;
assert(nb_sectors <= s->buf_sectors);
@@ -1690,6 +1712,7 @@
BlockBackend *blk;
int src_cur;
int64_t bs_sectors, src_cur_offset;
+ uint64_t offset;
/* In the case of compression with multiple source files, we can get a
* nb_sectors that spreads into the next part. So we must be able to
@@ -1698,13 +1721,29 @@
blk = s->src[src_cur];
bs_sectors = s->src_sectors[src_cur];
- n = MIN(nb_sectors, bs_sectors - (sector_num - src_cur_offset));
+ offset = (sector_num - src_cur_offset) << BDRV_SECTOR_BITS;
- ret = blk_co_pread(
- blk, (sector_num - src_cur_offset) << BDRV_SECTOR_BITS,
- n << BDRV_SECTOR_BITS, buf, 0);
+ n = MIN(nb_sectors, bs_sectors - (sector_num - src_cur_offset));
+ if (single_read_until > offset) {
+ n = 1;
+ }
+
+ ret = blk_co_pread(blk, offset, n << BDRV_SECTOR_BITS, buf, 0);
if (ret < 0) {
- return ret;
+ if (s->salvage) {
+ if (n > 1) {
+ single_read_until = offset + (n << BDRV_SECTOR_BITS);
+ continue;
+ } else {
+ if (!s->quiet) {
+ warn_report("error while reading offset %" PRIu64
+ ": %s", offset, strerror(-ret));
+ }
+ memset(buf, 0, BDRV_SECTOR_SIZE);
+ }
+ } else {
+ return ret;
+ }
}
sector_num += n;
@@ -2035,6 +2074,7 @@
{"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
{"force-share", no_argument, 0, 'U'},
{"target-image-opts", no_argument, 0, OPTION_TARGET_IMAGE_OPTS},
+ {"salvage", no_argument, 0, OPTION_SALVAGE},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, ":hf:O:B:Cco:l:S:pt:T:qnm:WU",
@@ -2152,6 +2192,9 @@
case OPTION_IMAGE_OPTS:
image_opts = true;
break;
+ case OPTION_SALVAGE:
+ s.salvage = true;
+ break;
case OPTION_TARGET_IMAGE_OPTS:
tgt_image_opts = true;
break;
@@ -2178,6 +2221,11 @@
goto fail_getopt;
}
+ if (s.copy_range && s.salvage) {
+ error_report("Cannot use copy offloading in salvaging mode");
+ goto fail_getopt;
+ }
+
if (tgt_image_opts && !skip_create) {
error_report("--target-image-opts requires use of -n flag");
goto fail_getopt;
