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qcow2: Separate qcow2_check_read_snapshot_table()

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Reading the snapshot table can fail.  That is a problem when we want to
repair the image.

Therefore, stop reading the snapshot table in qcow2_do_open() in check
mode.  Instead, add a new function qcow2_check_read_snapshot_table()
that reads the snapshot table at a later point.  In the future, we want
to handle errors here and fix them.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-id: 20191011152814.14791-9-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2019-10-11 17:28:06 +02:00
parent 0a85af351d
commit 8bc584fe03
3 changed files with 120 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
block/qcow2-snapshot.c
View File

@ -322,6 +322,64 @@ fail:
return ret;
}
int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
BdrvCheckResult *result,
BdrvCheckMode fix)
{
BDRVQcow2State *s = bs->opaque;
Error *local_err = NULL;
int ret;
struct {
uint32_t nb_snapshots;
uint64_t snapshots_offset;
} QEMU_PACKED snapshot_table_pointer;
/* qcow2_do_open() discards this information in check mode */
ret = bdrv_pread(bs->file, offsetof(QCowHeader, nb_snapshots),
&snapshot_table_pointer, sizeof(snapshot_table_pointer));
if (ret < 0) {
result->check_errors++;
fprintf(stderr, "ERROR failed to read the snapshot table pointer from "
"the image header: %s\n", strerror(-ret));
return ret;
}
s->snapshots_offset = be64_to_cpu(snapshot_table_pointer.snapshots_offset);
s->nb_snapshots = be32_to_cpu(snapshot_table_pointer.nb_snapshots);
ret = qcow2_validate_table(bs, s->snapshots_offset, s->nb_snapshots,
sizeof(QCowSnapshotHeader),
sizeof(QCowSnapshotHeader) * QCOW_MAX_SNAPSHOTS,
"snapshot table", &local_err);
if (ret < 0) {
result->check_errors++;
error_reportf_err(local_err, "ERROR ");
/* We did not read the snapshot table, so invalidate this information */
s->snapshots_offset = 0;
s->nb_snapshots = 0;
return ret;
}
qemu_co_mutex_unlock(&s->lock);
ret = qcow2_read_snapshots(bs, &local_err);
qemu_co_mutex_lock(&s->lock);
if (ret < 0) {
result->check_errors++;
error_reportf_err(local_err,
"ERROR failed to read the snapshot table: ");
/* We did not read the snapshot table, so invalidate this information */
s->snapshots_offset = 0;
s->nb_snapshots = 0;
return ret;
}
return 0;
}
static void find_new_snapshot_id(BlockDriverState *bs,
char *id_str, int id_str_size)
{

76
block/qcow2.c
View File

@ -570,11 +570,40 @@ int qcow2_mark_consistent(BlockDriverState *bs)
return 0;
}
static void qcow2_add_check_result(BdrvCheckResult *out,
const BdrvCheckResult *src,
bool set_allocation_info)
{
out->corruptions += src->corruptions;
out->leaks += src->leaks;
out->check_errors += src->check_errors;
out->corruptions_fixed += src->corruptions_fixed;
out->leaks_fixed += src->leaks_fixed;
if (set_allocation_info) {
out->image_end_offset = src->image_end_offset;
out->bfi = src->bfi;
}
}
static int coroutine_fn qcow2_co_check_locked(BlockDriverState *bs,
BdrvCheckResult *result,
BdrvCheckMode fix)
{
int ret = qcow2_check_refcounts(bs, result, fix);
BdrvCheckResult snapshot_res = {};
BdrvCheckResult refcount_res = {};
int ret;
memset(result, 0, sizeof(*result));
ret = qcow2_check_read_snapshot_table(bs, &snapshot_res, fix);
qcow2_add_check_result(result, &snapshot_res, false);
if (ret < 0) {
return ret;
}
ret = qcow2_check_refcounts(bs, &refcount_res, fix);
qcow2_add_check_result(result, &refcount_res, true);
if (ret < 0) {
return ret;
}
@ -1410,17 +1439,22 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
goto fail;
}
/* The total size in bytes of the snapshot table is checked in
* qcow2_read_snapshots() because the size of each snapshot is
* variable and we don't know it yet.
* Here we only check the offset and number of snapshots. */
ret = qcow2_validate_table(bs, header.snapshots_offset,
header.nb_snapshots,
sizeof(QCowSnapshotHeader),
sizeof(QCowSnapshotHeader) * QCOW_MAX_SNAPSHOTS,
"Snapshot table", errp);
if (ret < 0) {
goto fail;
if (!(flags & BDRV_O_CHECK)) {
/*
* The total size in bytes of the snapshot table is checked in
* qcow2_read_snapshots() because the size of each snapshot is
* variable and we don't know it yet.
* Here we only check the offset and number of snapshots.
*/
ret = qcow2_validate_table(bs, header.snapshots_offset,
header.nb_snapshots,
sizeof(QCowSnapshotHeader),
sizeof(QCowSnapshotHeader) *
QCOW_MAX_SNAPSHOTS,
"Snapshot table", errp);
if (ret < 0) {
goto fail;
}
}
/* read the level 1 table */
@ -1580,13 +1614,19 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
s->image_backing_file = g_strdup(bs->auto_backing_file);
}
/* Internal snapshots */
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
/*
* Internal snapshots; skip reading them in check mode, because
* we do not need them then, and we do not want to abort because
* of a broken table.
*/
if (!(flags & BDRV_O_CHECK)) {
s->snapshots_offset = header.snapshots_offset;
s->nb_snapshots = header.nb_snapshots;
ret = qcow2_read_snapshots(bs, errp);
if (ret < 0) {
goto fail;
ret = qcow2_read_snapshots(bs, errp);
if (ret < 0) {
goto fail;
}
}
/* Clear unknown autoclear feature bits */

4
block/qcow2.h
View File

@ -718,6 +718,10 @@ void qcow2_free_snapshots(BlockDriverState *bs);
int qcow2_read_snapshots(BlockDriverState *bs, Error **errp);
int qcow2_write_snapshots(BlockDriverState *bs);
int coroutine_fn qcow2_check_read_snapshot_table(BlockDriverState *bs,
BdrvCheckResult *result,
BdrvCheckMode fix);
/* qcow2-cache.c functions */
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
unsigned table_size);