[Devel] [PATCH] dm-qcow2: parse bitmap extension
Andrey Zhadchenko
andrey.zhadchenko at virtuozzo.com
Wed Feb 19 19:17:25 MSK 2025
If qcow2 file has only inactive bitmaps, we should not reset
QCOW2_AUTOCLEAR_BITMAPS bit. Bitmaps are already allocated and
we are not expected to change them.
Still reset this bit if we encounter enabled bitmap.
https://virtuozzo.atlassian.net/browse/VSTOR-99404
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
drivers/md/dm-qcow2-target.c | 125 ++++++++++++++++++++++++++++++++++-
drivers/md/dm-qcow2.h | 42 ++++++++++++
2 files changed, 165 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c
index 276eab9acc4f..9b85d79fb02c 100644
--- a/drivers/md/dm-qcow2-target.c
+++ b/drivers/md/dm-qcow2-target.c
@@ -555,7 +555,7 @@ static int qcow2_check_convert_hdr(struct dm_target *ti,
return 0;
hdr->incompatible_features = be64_to_cpu(raw_hdr->incompatible_features);
- hdr->autoclear_features = be64_to_cpu(raw_hdr->autoclear_features);
+ hdr->autoclear_features = 0;
hdr->refcount_order = be32_to_cpu(raw_hdr->refcount_order);
hdr->header_length = be32_to_cpu(raw_hdr->header_length);
@@ -631,7 +631,7 @@ int qcow2_set_image_file_features(struct qcow2 *qcow2, bool dirty)
return -EIO;
raw_hdr = kmap(md->page);
- qcow2->hdr.autoclear_features = raw_hdr->autoclear_features = 0;
+ raw_hdr->autoclear_features = cpu_to_be64(qcow2->hdr.autoclear_features);
if (kernel_sets_dirty_bit) {
if (dirty)
raw_hdr->incompatible_features |= dirty_mask;
@@ -709,12 +709,117 @@ static int qcow2_attach_file(struct dm_target *ti, struct qcow2_target *tgt,
}
ALLOW_ERROR_INJECTION(qcow2_attach_file, ERRNO);
+static int qcow2_parse_bitmap_ext(struct dm_target *ti, struct qcow2 *qcow2,
+ struct Qcow2BitmapHeaderExt *ext)
+{
+ struct Qcow2BitmapDirEntry entry;
+ u64 index, size, offset;
+ struct page **pages = NULL;
+ char *addr = NULL;
+ int i, ret;
+ bool clear_bitmaps = false;
+
+ ext->bitmap_directory_offset = be64_to_cpu(ext->bitmap_directory_offset);
+ ext->bitmap_directory_size = be64_to_cpu(ext->bitmap_directory_size);
+ ext->nb_bitmaps = be32_to_cpu(ext->nb_bitmaps);
+
+ if (!ext->nb_bitmaps ||
+ ext->nb_bitmaps > QCOW2_MAX_BITMAPS ||
+ ext->bitmap_directory_size > QCOW2_MAX_BITMAP_DIRECTORY_SIZE ||
+ ext->bitmap_directory_offset % PAGE_SIZE)
+ return -EINVAL;
+
+ index = ext->bitmap_directory_offset >> PAGE_SHIFT;
+ size = round_up(ext->bitmap_directory_size, PAGE_SIZE);
+
+ addr = kvmalloc(size, GFP_KERNEL);
+ if (!addr)
+ return -ENOMEM;
+
+ pages = kvmalloc((size / PAGE_SIZE) * sizeof(*pages), GFP_KERNEL);
+ if (!pages) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ for (i = 0; i < size >> PAGE_SHIFT; i++)
+ pages[i] = virt_to_page(addr + i * PAGE_SIZE);
+
+ ret = qcow2_rw_pages_sync(READ, qcow2, index, pages, size >> PAGE_SHIFT);
+ if (ret)
+ goto out;
+
+ offset = 0;
+ while (offset < ext->bitmap_directory_size) {
+ memcpy(&entry, addr + offset, sizeof(entry));
+
+ entry.flags = be32_to_cpu(entry.flags);
+ entry.name_size = be16_to_cpu(entry.name_size);
+ entry.extra_data_size = be32_to_cpu(entry.extra_data_size);
+
+ if (entry.flags & BME_FLAG_AUTO)
+ clear_bitmaps = true;
+
+ offset += round_up(sizeof(entry) + entry.name_size + entry.extra_data_size, 8);
+ }
+
+ if (!clear_bitmaps)
+ qcow2->hdr.autoclear_features |= QCOW2_AUTOCLEAR_BITMAPS;
+
+ ret = 0;
+out:
+ kvfree(pages);
+ kvfree(addr);
+ return ret;
+}
+
+static int qcow2_parse_extensions(struct dm_target *ti, struct qcow2 *qcow2,
+ loff_t start, loff_t end, void *addr)
+{
+ loff_t offset;
+ struct QCowExtension ext;
+
+ offset = start;
+ while (offset < end) {
+ memcpy(&ext, (char *)addr + offset, sizeof(ext));
+ ext.magic = be32_to_cpu(ext.magic);
+ ext.len = be32_to_cpu(ext.len);
+ offset += sizeof(ext);
+
+ switch (ext.magic) {
+ case QCOW2_EXT_MAGIC_BITMAPS:
+ struct Qcow2BitmapHeaderExt bitmaps_ext;
+
+ if (ext.len != sizeof(bitmaps_ext)) {
+ QC_ERR(ti, "dm-qcow2: unexpected bitmap extension size\n");
+ return -EINVAL;
+ }
+
+ memcpy(&bitmaps_ext, (char *)addr + offset,
+ sizeof(bitmaps_ext));
+ if (qcow2_parse_bitmap_ext(ti, qcow2, &bitmaps_ext))
+ return -EINVAL;
+ break;
+ case QCOW2_EXT_MAGIC_END:
+ return 0;
+ default:
+ /* Skip all other extensions */
+ break;
+ }
+
+ offset += ((ext.len + 7) & ~7);
+ }
+
+ return 0;
+}
+
static int qcow2_parse_header(struct dm_target *ti, struct qcow2 *qcow2,
struct qcow2 *upper, bool is_bottom)
{
struct QCowHeader *raw_hdr, *hdr = &qcow2->hdr;
loff_t min_len, max_len, new_size;
struct file *file = qcow2->file;
+ loff_t ext_start, ext_end;
struct md_page *md;
int ret;
@@ -779,6 +884,22 @@ static int qcow2_parse_header(struct dm_target *ti, struct qcow2 *qcow2,
ret = -EFBIG;
if (qcow2->reftable_max_file_size < qcow2->file_size)
goto out;
+
+ ext_start = hdr->header_length;
+ if (hdr->backing_file_offset)
+ ext_end = hdr->backing_file_offset;
+ else
+ ext_end = PAGE_SIZE;
+
+ if (ext_end > PAGE_SIZE) {
+ QC_INFO(ti, "dm-qcow2: extensions are too long, skipping them\n");
+ } else {
+ ret = qcow2_parse_extensions(ti, qcow2, ext_start, ext_end, raw_hdr);
+ if (ret) {
+ QC_ERR(ti, "dm-qcow2: failed to parse extensions\n");
+ goto out;
+ }
+ }
ret = 0;
out:
return ret;
diff --git a/drivers/md/dm-qcow2.h b/drivers/md/dm-qcow2.h
index 42f041a82a5b..d9bcbead0657 100644
--- a/drivers/md/dm-qcow2.h
+++ b/drivers/md/dm-qcow2.h
@@ -43,6 +43,9 @@ struct QCowHeader {
#define INCOMPATIBLE_FEATURES_EXTL2_BIT (1 << 4)
uint64_t incompatible_features;
uint64_t compatible_features;
+
+#define QCOW2_AUTOCLEAR_BITMAPS (1 << 0)
+#define QCOW2_AUTOCLEAR_DATA_FILE_RAW (1 << 1)
uint64_t autoclear_features;
uint32_t refcount_order;
@@ -57,6 +60,45 @@ struct QCowHeader {
uint8_t padding[7];
} __packed;
+#define QCOW2_EXT_MAGIC_END 0
+#define QCOW2_EXT_MAGIC_BITMAPS 0x23852875
+
+struct QCowExtension {
+ uint32_t magic;
+ uint32_t len;
+} __packed;
+
+/* Bitmap header extension constraints */
+#define QCOW2_MAX_BITMAPS 65535
+#define QCOW2_MAX_BITMAP_DIRECTORY_SIZE (1024 * QCOW2_MAX_BITMAPS)
+
+struct Qcow2BitmapHeaderExt {
+ uint32_t nb_bitmaps;
+ uint32_t reserved32;
+ uint64_t bitmap_directory_size;
+ uint64_t bitmap_directory_offset;
+} __packed;
+
+/* Bitmap directory entry flags */
+#define BME_RESERVED_FLAGS 0xfffffffcU
+#define BME_FLAG_IN_USE (1U << 0)
+#define BME_FLAG_AUTO (1U << 1)
+
+struct Qcow2BitmapDirEntry {
+ /* header is 8 byte aligned */
+ uint64_t bitmap_table_offset;
+
+ uint32_t bitmap_table_size;
+ uint32_t flags;
+
+ uint8_t type;
+ uint8_t granularity_bits;
+ uint16_t name_size;
+ uint32_t extra_data_size;
+ /* extra data follows */
+ /* name follows */
+} __packed;
+
struct wb_desc {
struct md_page *md;
#define LX_INDEXES_PER_PAGE (PAGE_SIZE / sizeof(u64))
--
2.39.3
More information about the Devel
mailing list