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Re: [Qemu-devel] [PATCH 11/22] qcow2-bitmap: add qcow2_store_persistent_
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH 11/22] qcow2-bitmap: add qcow2_store_persistent_bitmaps() |
Date: |
Fri, 7 Oct 2016 21:24:09 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 |
On 30.09.2016 12:53, Vladimir Sementsov-Ogievskiy wrote:
> Realize block bitmap stroing interface, to allow qcow2 images store
> persistent bitmaps.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> ---
> block/qcow2-bitmap.c | 241
> +++++++++++++++++++++++++++++++++++++++++++++++++++
> block/qcow2.c | 2 +
> block/qcow2.h | 2 +
> 3 files changed, 245 insertions(+)
>
> diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
> index 81520cd..a5be25a 100644
> --- a/block/qcow2-bitmap.c
> +++ b/block/qcow2-bitmap.c
> @@ -27,6 +27,7 @@
>
> #include "qemu/osdep.h"
> #include "qapi/error.h"
> +#include "qemu/cutils.h"
>
> #include "block/block_int.h"
> #include "block/qcow2.h"
> @@ -96,6 +97,15 @@ static inline void bitmap_table_to_cpu(uint64_t
> *bitmap_table, size_t size)
> }
> }
>
> +static inline void bitmap_table_to_be(uint64_t *bitmap_table, size_t size)
> +{
> + size_t i;
> +
> + for (i = 0; i < size; ++i) {
> + cpu_to_be64s(&bitmap_table[i]);
> + }
> +}
> +
> static inline int calc_dir_entry_size(size_t name_size, size_t
> extra_data_size)
> {
> return align_offset(sizeof(Qcow2BitmapDirEntry) +
> @@ -564,3 +574,234 @@ out:
>
> return ret;
> }
> +
> +/* store_bitmap_data()
> + * Store bitmap to image, filling bitamp table accordingly.
s/bitamp/bitmap/
> + */
> +static int store_bitmap_data(BlockDriverState *bs, BdrvDirtyBitmap *bitmap,
> + uint64_t *bitmap_table, uint32_t
> bitmap_table_size)
> +{
> + int ret;
> + BDRVQcow2State *s = bs->opaque;
> + uint64_t sector, dsc;
> + uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
> + int cl_size = s->cluster_size;
Once more, I don't think this variable is necessary, and I feel like it
makes reading the code more difficult for no gain.
> + uint8_t *buf = NULL;
> + uint32_t tb_size =
> + size_to_clusters(s,
> + bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size));
Should be uint64_t or you might accidentally get a truncation here. I'm
not sure how you would get such huge bitmaps but it's trivial to use
uint64_t.
> +
> + BdrvDirtyBitmapIter *dbi;
> +
> + if (tb_size != bitmap_table_size) {
> + return -EINVAL;
> + }
> +
> + memset(bitmap_table, 0, bitmap_table_size * sizeof(bitmap_table[0]));
On 32 bit machines, this multiplication can overflow. There should at
least be an assertion to prevent this. Other than that, of course, there
needs to be some place which limits bitmap_table_size to some sane value
and emits a real error if it exceeds that value.
> +
> + dbi = bdrv_dirty_iter_new(bitmap, 0);
> + buf = g_malloc(cl_size);
> + dsc = dirty_sectors_in_cluster(s, bitmap);
> +
> + while ((sector = bdrv_dirty_iter_next(dbi)) != -1) {
sector should be int64_t instead of uint64_t, then.
> + uint64_t cluster = sector / dsc;
> + sector = cluster * dsc;
Our coding style does not allow interleaving declarations and
non-declarations.
> + uint64_t end = MIN(bm_size, sector + dsc);
> + uint64_t write_size =
> + bdrv_dirty_bitmap_serialization_size(bitmap, sector, end -
> sector);
> +
> + int64_t off = qcow2_alloc_clusters(bs, cl_size);
> + if (off < 0) {
> + ret = off;
> + goto finish;
> + }
> + bitmap_table[cluster] = off;
> +
> + bdrv_dirty_bitmap_serialize_part(bitmap, buf, sector, end);
s/end/end - sector/?
> + if (write_size < cl_size) {
> + memset(buf + write_size, 0, cl_size - write_size);
> + }
> +
I guess there should be a metadata overlap check here.
> + ret = bdrv_pwrite(bs->file, off, buf, cl_size);
> + if (ret < 0) {
> + goto finish;
> + }
> +
> + if (end >= bm_size) {
> + break;
> + }
> +
> + bdrv_set_dirty_iter(dbi, end);
> + }
> + ret = 0; /* writes */
What is that comment supposed to mean?
> +
> +finish:
> + if (ret < 0) {
> + clear_bitmap_table(bs, bitmap_table, bitmap_table_size);
> + }
> + g_free(buf);
> + bdrv_dirty_iter_free(dbi);
> +
> + return ret;
In case you decide to keep BME_MAX_PHYS_SIZE, this function should check
somewhere that the physical size of the bitmap does not exceed that value.
> +}
> +
> +/* store_bitmap()
> + * Store bitmap to qcow2 and set bitmap_table. bitmap_table itself is not
> + * stored to qcow2.
First of all, there is no parameter called "bitmap_table", and second,
yes, the bitmap table is written to the qcow2 file.
> + */
> +static int store_bitmap(BlockDriverState *bs,
> + BdrvDirtyBitmap *bitmap,
> + Qcow2BitmapDirEntry *entry)
> +{
> + int ret;
> + BDRVQcow2State *s = bs->opaque;
> + uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
> + const char *bm_name = bdrv_dirty_bitmap_name(bitmap);
> +
> + uint64_t *tb;
> + int64_t tb_offset;
> + uint32_t tb_size =
> + size_to_clusters(s,
> + bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size));
As above, this variable should be of type uint64_t.
Also, you have to check that it does not exceed BME_MAX_TABLE_SIZE.
> +
> + tb = g_try_new(uint64_t, tb_size);
> + if (tb == NULL) {
> + return -ENOMEM;
> + }
> +
> + ret = store_bitmap_data(bs, bitmap, tb, tb_size);
> + if (ret < 0) {
> + g_free(tb);
> + return ret;
> + }
> +
> + tb_offset = qcow2_alloc_clusters(bs, tb_size * sizeof(tb[0]));
If you don't limit tb_size, then this multiplication can overflow on 32
bit machines.
> + if (tb_offset < 0) {
> + ret = tb_offset;
> + goto fail;
> + }
> +
There should be a metadata overlap check here.
> + bitmap_table_to_be(tb, tb_size);
> + ret = bdrv_pwrite(bs->file, tb_offset, tb, tb_size * sizeof(tb[0]));
> + if (ret < 0) {
> + goto fail;
> + }
> +
> + g_free(tb);
> +
> + entry->bitmap_table_offset = tb_offset;
> + entry->bitmap_table_size = tb_size;
> + entry->flags = bdrv_dirty_bitmap_granularity(bitmap) ? BME_FLAG_AUTO : 0;
s/granularity/get_autoload/
> + entry->type = BT_DIRTY_TRACKING_BITMAP;
> + entry->granularity_bits = ctz32(bdrv_dirty_bitmap_granularity(bitmap));
You should probably check somewhere that the resulting value for
entry->granularity_bits is in the BME_{MIN,MAX}_GRANULARITY_BITS range.
> + entry->name_size = strlen(bm_name);
And that this length does not exceed BME_MAX_NAME_SIZE.
> + entry->extra_data_size = 0;
> + memcpy(entry + 1, bm_name, entry->name_size);
> +
> + return 0;
> +
> +fail:
> + clear_bitmap_table(bs, tb, tb_size);
> +
> + if (tb_offset > 0) {
> + qcow2_free_clusters(bs, tb_offset, tb_size, QCOW2_DISCARD_ALWAYS);
As before, I'd vote for QCOW2_DISCARD_OTHER.
> + }
> +
> + g_free(tb);
> +
> + return ret;
> +}
> +
> +static Qcow2BitmapDirEntry *find_bitmap_by_name(uint8_t *bitmap_directory,
> + size_t size, const char
> *name)
> +{
> + Qcow2BitmapDirEntry *e;
> +
> + for_each_bitmap_dir_entry(e, bitmap_directory, size) {
> + if (strncmp((char *)(e + 1), name, e->name_size) == 0) {
> + return e;
> + }
> + }
> +
> + return NULL;
> +}
> +
> +void qcow2_store_persistent_bitmaps(BlockDriverState *bs, Error **errp)
> +{
> + BdrvDirtyBitmap *bm;
> + BDRVQcow2State *s = bs->opaque;
> + uint32_t new_nb_bitmaps = s->nb_bitmaps;
> + uint64_t new_dir_size = s->bitmap_directory_size;
> + uint8_t *dir = NULL, *new_dir = NULL;
> + int ret;
> + Qcow2BitmapDirEntry *new_pos;
> +
> + if (s->nb_bitmaps > 0) {
> + dir = directory_read(bs, s->bitmap_directory_offset,
> + s->bitmap_directory_size, errp);
> + if (dir == NULL) {
> + goto out;
> + }
> + }
> +
> + for (bm = bdrv_dirty_bitmap_next(bs, NULL); bm != NULL;
> + bm = bdrv_dirty_bitmap_next(bs, bm)) {
> + const char *name = bdrv_dirty_bitmap_name(bm);
> +
> + if (!bdrv_dirty_bitmap_get_persistance(bm)) {
> + continue;
> + }
> +
> + if (s->nb_bitmaps > 0 &&
> + find_bitmap_by_name(dir, s->bitmap_directory_size, name)) {
> + error_setg(errp,
> + "Can't store bitmap '%s' to '%s', as it already
> exists",
> + name, bdrv_get_device_or_node_name(bs));
> + goto out;
> + }
> +
> + new_nb_bitmaps++;
> + new_dir_size += calc_dir_entry_size(strlen(name), 0);
> + }
> +
> + if (s->nb_bitmaps == new_nb_bitmaps) {
> + /* No new bitmaps - nothing to do */
> + goto out;
> + }
> +
> + new_dir = g_try_malloc0(new_dir_size);
> + if (new_dir == NULL) {
> + error_setg(errp, "Can't allocate space for bitmap directory.");
> + goto out;
> + }
> +
> + memcpy(new_dir, dir, s->bitmap_directory_size);
> + new_pos = (Qcow2BitmapDirEntry *)(new_dir + s->bitmap_directory_size);
> +
> + for (bm = bdrv_dirty_bitmap_next(bs, NULL); bm != NULL;
> + bm = bdrv_dirty_bitmap_next(bs, bm)) {
> + if (!bdrv_dirty_bitmap_get_persistance(bm)) {
> + continue;
> + }
> +
> + ret = store_bitmap(bs, bm, new_pos);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Can't store bitmap '%s' to '%s'",
> + bdrv_dirty_bitmap_name(bm),
> + bdrv_get_device_or_node_name(bs));
> + goto out;
> + }
> + new_pos = next_dir_entry(new_pos);
> + }
> +
> + ret = directory_update(bs, new_dir, new_dir_size, new_nb_bitmaps);
> + if (ret < 0) {
> + error_setg_errno(errp, -ret, "Can't update bitmap directory in '%s'",
> + bdrv_get_device_or_node_name(bs));
> + goto out;
> + }
> +
> +out:
> + g_free(new_dir);
> + g_free(dir);
This error path leaks all the bitmaps that have been written
successfully (if any). I guess this is more or less fine if
directory_update() failed (because you can't really tell the state of
the image header after directory_update(), so better be safe) but it's
not so fine if just some store_bitmap() failed.
Max
> +}
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 02ec224..8238205 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c
> @@ -3493,6 +3493,8 @@ BlockDriver bdrv_qcow2 = {
>
> .bdrv_detach_aio_context = qcow2_detach_aio_context,
> .bdrv_attach_aio_context = qcow2_attach_aio_context,
> +
> + .bdrv_store_persistent_bitmaps = qcow2_store_persistent_bitmaps,
> };
>
> static void bdrv_qcow2_init(void)
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 482a29f..dfcf4c6 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -627,4 +627,6 @@ int qcow2_cache_get_empty(BlockDriverState *bs,
> Qcow2Cache *c, uint64_t offset,
> void **table);
> void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table);
>
> +void qcow2_store_persistent_bitmaps(BlockDriverState *bs, Error **errp);
> +
> #endif
>
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- Re: [Qemu-devel] [PATCH 11/22] qcow2-bitmap: add qcow2_store_persistent_bitmaps(),
Max Reitz <=