[PATCH v5 0/9] block: Fix resize (extending) of short overlays

[PATCH v5 0/9] block: Fix resize (extending) of short overlays

[Kevin Wolf]

v5:
- Fixed file-win32 [Patchew]
- Fixed zeroing in qcow2 for unaligned requests + tests [Vladimir]
- Made raw-format code more consistent [Eric]
- Leave output for existing iotests cases unchanged [Vladimir]

v4:
- Rewrote the series to move the actual zeroing to the block drivers so
  that error paths can work correctly and potentially long-running
  fallback to writing explicit zeroes is avoided.
- Fixed output filtering order in the test case [Max]

v3:
- Don't allow blocking the monitor for a zero write in block_resize
  (even though we can already blockfor other reasons there). This is
  mainly responsible for the increased complexity compared to v2.
  Personally, I think this is not an improvement over v2, but if this is
  what it takes to fix a corruption issue in 4.2... [Max]
- Don't use huge image files in the test case [Vladimir]

v2:
- Switched order of bs->total_sectors update and zero write [Vladimir]
- Fixed coding style [Vladimir]
- Changed the commit message to contain what was in the cover letter
- Test all preallocation modes
- Test allocation status with qemu-io 'map' [Vladimir]

Kevin Wolf (9):
  block: Add flags to BlockDriver.bdrv_co_truncate()
  block: Add flags to bdrv(_co)_truncate()
  block-backend: Add flags to blk_truncate()
  qcow2: Support BDRV_REQ_ZERO_WRITE for truncate
  raw-format: Support BDRV_REQ_ZERO_WRITE for truncate
  file-posix: Support BDRV_REQ_ZERO_WRITE for truncate
  block: truncate: Don't make backing file data visible
  iotests: Filter testfiles out in filter_img_info()
  iotests: Test committing to short backing file

 include/block/block.h          |   5 +-
 include/block/block_int.h      |  10 +-
 include/sysemu/block-backend.h |   2 +-
 block.c                        |   3 +-
 block/block-backend.c          |   4 +-
 block/commit.c                 |   4 +-
 block/crypto.c                 |   7 +-
 block/file-posix.c             |   6 +-
 block/file-win32.c             |   2 +-
 block/gluster.c                |   1 +
 block/io.c                     |  32 +++-
 block/iscsi.c                  |   2 +-
 block/mirror.c                 |   2 +-
 block/nfs.c                    |   3 +-
 block/parallels.c              |   6 +-
 block/qcow.c                   |   4 +-
 block/qcow2-refcount.c         |   2 +-
 block/qcow2.c                  |  51 +++++--
 block/qed.c                    |   3 +-
 block/raw-format.c             |   6 +-
 block/rbd.c                    |   1 +
 block/sheepdog.c               |   4 +-
 block/ssh.c                    |   2 +-
 block/vdi.c                    |   2 +-
 block/vhdx-log.c               |   2 +-
 block/vhdx.c                   |   6 +-
 block/vmdk.c                   |   8 +-
 block/vpc.c                    |   2 +-
 blockdev.c                     |   2 +-
 qemu-img.c                     |   2 +-
 qemu-io-cmds.c                 |   2 +-
 tests/test-block-iothread.c    |   9 +-
 tests/qemu-iotests/iotests.py  |   5 +-
 tests/qemu-iotests/274         | 157 ++++++++++++++++++++
 tests/qemu-iotests/274.out     | 260 +++++++++++++++++++++++++++++++++
 tests/qemu-iotests/group       |   1 +
 36 files changed, 558 insertions(+), 62 deletions(-)
 create mode 100755 tests/qemu-iotests/274
 create mode 100644 tests/qemu-iotests/274.out

-- 
2.25.3

[PATCH v5 1/9] block: Add flags to BlockDriver.bdrv_co_truncate()

[Kevin Wolf]

This adds a new BdrvRequestFlags parameter to the .bdrv_co_truncate()
driver callbacks, and a supported_truncate_flags field in
BlockDriverState that allows drivers to advertise support for request
flags in the context of truncate.

For now, we always pass 0 and no drivers declare support for any flag.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 include/block/block_int.h   | 10 +++++++++-
 block/crypto.c              |  3 ++-
 block/file-posix.c          |  2 +-
 block/file-win32.c          |  2 +-
 block/gluster.c             |  1 +
 block/io.c                  |  8 +++++++-
 block/iscsi.c               |  2 +-
 block/nfs.c                 |  3 ++-
 block/qcow2.c               |  2 +-
 block/qed.c                 |  1 +
 block/raw-format.c          |  2 +-
 block/rbd.c                 |  1 +
 block/sheepdog.c            |  4 ++--
 block/ssh.c                 |  2 +-
 tests/test-block-iothread.c |  3 ++-
 15 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 4c3587ea19..92335f33c7 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -355,7 +355,7 @@ struct BlockDriver {
      */
     int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
                                          bool exact, PreallocMode prealloc,
-                                         Error **errp);
+                                         BdrvRequestFlags flags, Error **errp);
 
     int64_t (*bdrv_getlength)(BlockDriverState *bs);
     bool has_variable_length;
@@ -847,6 +847,14 @@ struct BlockDriverState {
     /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
      * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED) */
     unsigned int supported_zero_flags;
+    /*
+     * Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
+     *
+     * If BDRV_REQ_ZERO_WRITE is given, the truncate operation must make sure
+     * that any added space reads as all zeros. If this can't be guaranteed,
+     * the operation must fail.
+     */
+    unsigned int supported_truncate_flags;
 
     /* the following member gives a name to every node on the bs graph. */
     char node_name[32];
diff --git a/block/crypto.c b/block/crypto.c
index d577f89659..3721a8495c 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -299,7 +299,8 @@ static int block_crypto_co_create_generic(BlockDriverState *bs,
 
 static int coroutine_fn
 block_crypto_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                         PreallocMode prealloc, Error **errp)
+                         PreallocMode prealloc, BdrvRequestFlags flags,
+                         Error **errp)
 {
     BlockCrypto *crypto = bs->opaque;
     uint64_t payload_offset =
diff --git a/block/file-posix.c b/block/file-posix.c
index 7e19bbff5f..53f475ed61 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2080,7 +2080,7 @@ raw_regular_truncate(BlockDriverState *bs, int fd, int64_t offset,
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     struct stat st;
diff --git a/block/file-win32.c b/block/file-win32.c
index 15859839a1..a6b0dda5c3 100644
--- a/block/file-win32.c
+++ b/block/file-win32.c
@@ -469,7 +469,7 @@ static void raw_close(BlockDriverState *bs)
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
     LONG low, high;
diff --git a/block/gluster.c b/block/gluster.c
index 0aa1f2cda4..d06df900f6 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1228,6 +1228,7 @@ static coroutine_fn int qemu_gluster_co_truncate(BlockDriverState *bs,
                                                  int64_t offset,
                                                  bool exact,
                                                  PreallocMode prealloc,
+                                                 BdrvRequestFlags flags,
                                                  Error **errp)
 {
     BDRVGlusterState *s = bs->opaque;
diff --git a/block/io.c b/block/io.c
index aba67f66b9..04ac5cf023 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3344,6 +3344,7 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
     BdrvTrackedRequest req;
+    BdrvRequestFlags flags = 0;
     int64_t old_size, new_bytes;
     int ret;
 
@@ -3394,7 +3395,12 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
     }
 
     if (drv->bdrv_co_truncate) {
-        ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, errp);
+        if (flags & ~bs->supported_truncate_flags) {
+            error_setg(errp, "Block driver does not support requested flags");
+            ret = -ENOTSUP;
+            goto out;
+        }
+        ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, flags, errp);
     } else if (bs->file && drv->is_filter) {
         ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
     } else {
diff --git a/block/iscsi.c b/block/iscsi.c
index 0b4b7210df..914a1de9fb 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -2124,7 +2124,7 @@ static void iscsi_reopen_commit(BDRVReopenState *reopen_state)
 
 static int coroutine_fn iscsi_co_truncate(BlockDriverState *bs, int64_t offset,
                                           bool exact, PreallocMode prealloc,
-                                          Error **errp)
+                                          BdrvRequestFlags flags, Error **errp)
 {
     IscsiLun *iscsilun = bs->opaque;
     int64_t cur_length;
diff --git a/block/nfs.c b/block/nfs.c
index cc2413d5ab..2393fbfe6b 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -755,7 +755,8 @@ static int64_t nfs_get_allocated_file_size(BlockDriverState *bs)
 
 static int coroutine_fn
 nfs_file_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                     PreallocMode prealloc, Error **errp)
+                     PreallocMode prealloc, BdrvRequestFlags flags,
+                     Error **errp)
 {
     NFSClient *client = bs->opaque;
     int ret;
diff --git a/block/qcow2.c b/block/qcow2.c
index b524b0c53f..0b406b22fb 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3964,7 +3964,7 @@ fail:
 
 static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
                                           bool exact, PreallocMode prealloc,
-                                          Error **errp)
+                                          BdrvRequestFlags flags, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t old_length;
diff --git a/block/qed.c b/block/qed.c
index 1af9b3cb1d..fb6100bd20 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1467,6 +1467,7 @@ static int coroutine_fn bdrv_qed_co_truncate(BlockDriverState *bs,
                                              int64_t offset,
                                              bool exact,
                                              PreallocMode prealloc,
+                                             BdrvRequestFlags flags,
                                              Error **errp)
 {
     BDRVQEDState *s = bs->opaque;
diff --git a/block/raw-format.c b/block/raw-format.c
index 93b25e1b6b..9331368f43 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -371,7 +371,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
 
 static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVRawState *s = bs->opaque;
 
diff --git a/block/rbd.c b/block/rbd.c
index e637639a07..f2d52091c7 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1108,6 +1108,7 @@ static int coroutine_fn qemu_rbd_co_truncate(BlockDriverState *bs,
                                              int64_t offset,
                                              bool exact,
                                              PreallocMode prealloc,
+                                             BdrvRequestFlags flags,
                                              Error **errp)
 {
     int r;
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 59f7ebb171..ef0a6e743e 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2288,7 +2288,7 @@ static int64_t sd_getlength(BlockDriverState *bs)
 
 static int coroutine_fn sd_co_truncate(BlockDriverState *bs, int64_t offset,
                                        bool exact, PreallocMode prealloc,
-                                       Error **errp)
+                                       BdrvRequestFlags flags, Error **errp)
 {
     BDRVSheepdogState *s = bs->opaque;
     int ret, fd;
@@ -2604,7 +2604,7 @@ static coroutine_fn int sd_co_writev(BlockDriverState *bs, int64_t sector_num,
 
     assert(!flags);
     if (offset > s->inode.vdi_size) {
-        ret = sd_co_truncate(bs, offset, false, PREALLOC_MODE_OFF, NULL);
+        ret = sd_co_truncate(bs, offset, false, PREALLOC_MODE_OFF, 0, NULL);
         if (ret < 0) {
             return ret;
         }
diff --git a/block/ssh.c b/block/ssh.c
index 84e92821c0..9eb33df859 100644
--- a/block/ssh.c
+++ b/block/ssh.c
@@ -1298,7 +1298,7 @@ static int64_t ssh_getlength(BlockDriverState *bs)
 
 static int coroutine_fn ssh_co_truncate(BlockDriverState *bs, int64_t offset,
                                         bool exact, PreallocMode prealloc,
-                                        Error **errp)
+                                        BdrvRequestFlags flags, Error **errp)
 {
     BDRVSSHState *s = bs->opaque;
 
diff --git a/tests/test-block-iothread.c b/tests/test-block-iothread.c
index 0c861809f0..2f3b76323d 100644
--- a/tests/test-block-iothread.c
+++ b/tests/test-block-iothread.c
@@ -46,7 +46,8 @@ static int coroutine_fn bdrv_test_co_pdiscard(BlockDriverState *bs,
 
 static int coroutine_fn
 bdrv_test_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
-                      PreallocMode prealloc, Error **errp)
+                      PreallocMode prealloc, BdrvRequestFlags flags,
+                      Error **errp)
 {
     return 0;
 }
-- 
2.25.3

[PATCH v5 2/9] block: Add flags to bdrv(_co)_truncate()

[Kevin Wolf]

Now that block drivers can support flags for .bdrv_co_truncate, expose
the parameter in the node level interfaces bdrv_co_truncate() and
bdrv_truncate().

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 include/block/block.h       |  5 +++--
 block/block-backend.c       |  2 +-
 block/crypto.c              |  2 +-
 block/io.c                  | 12 +++++++-----
 block/parallels.c           |  6 +++---
 block/qcow.c                |  4 ++--
 block/qcow2-refcount.c      |  2 +-
 block/qcow2.c               | 15 +++++++++------
 block/raw-format.c          |  2 +-
 block/vhdx-log.c            |  2 +-
 block/vhdx.c                |  2 +-
 block/vmdk.c                |  2 +-
 tests/test-block-iothread.c |  6 +++---
 13 files changed, 34 insertions(+), 28 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index b05995fe9c..8b62429aa4 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -339,9 +339,10 @@ BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
 void bdrv_refresh_filename(BlockDriverState *bs);
 
 int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
-                                  PreallocMode prealloc, Error **errp);
+                                  PreallocMode prealloc, BdrvRequestFlags flags,
+                                  Error **errp);
 int bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
-                  PreallocMode prealloc, Error **errp);
+                  PreallocMode prealloc, BdrvRequestFlags flags, Error **errp);
 
 int64_t bdrv_nb_sectors(BlockDriverState *bs);
 int64_t bdrv_getlength(BlockDriverState *bs);
diff --git a/block/block-backend.c b/block/block-backend.c
index 38ae413826..8be20060d3 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2144,7 +2144,7 @@ int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
         return -ENOMEDIUM;
     }
 
-    return bdrv_truncate(blk->root, offset, exact, prealloc, errp);
+    return bdrv_truncate(blk->root, offset, exact, prealloc, 0, errp);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
diff --git a/block/crypto.c b/block/crypto.c
index 3721a8495c..ab33545c92 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -313,7 +313,7 @@ block_crypto_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
 
     offset += payload_offset;
 
-    return bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
+    return bdrv_co_truncate(bs->file, offset, exact, prealloc, 0, errp);
 }
 
 static void block_crypto_close(BlockDriverState *bs)
diff --git a/block/io.c b/block/io.c
index 04ac5cf023..795075954e 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3339,12 +3339,12 @@ static void bdrv_parent_cb_resize(BlockDriverState *bs)
  * 'offset' bytes in length.
  */
 int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
-                                  PreallocMode prealloc, Error **errp)
+                                  PreallocMode prealloc, BdrvRequestFlags flags,
+                                  Error **errp)
 {
     BlockDriverState *bs = child->bs;
     BlockDriver *drv = bs->drv;
     BdrvTrackedRequest req;
-    BdrvRequestFlags flags = 0;
     int64_t old_size, new_bytes;
     int ret;
 
@@ -3402,7 +3402,7 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
         }
         ret = drv->bdrv_co_truncate(bs, offset, exact, prealloc, flags, errp);
     } else if (bs->file && drv->is_filter) {
-        ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
+        ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
     } else {
         error_setg(errp, "Image format driver does not support resize");
         ret = -ENOTSUP;
@@ -3435,6 +3435,7 @@ typedef struct TruncateCo {
     int64_t offset;
     bool exact;
     PreallocMode prealloc;
+    BdrvRequestFlags flags;
     Error **errp;
     int ret;
 } TruncateCo;
@@ -3443,12 +3444,12 @@ static void coroutine_fn bdrv_truncate_co_entry(void *opaque)
 {
     TruncateCo *tco = opaque;
     tco->ret = bdrv_co_truncate(tco->child, tco->offset, tco->exact,
-                                tco->prealloc, tco->errp);
+                                tco->prealloc, tco->flags, tco->errp);
     aio_wait_kick();
 }
 
 int bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
-                  PreallocMode prealloc, Error **errp)
+                  PreallocMode prealloc, BdrvRequestFlags flags, Error **errp)
 {
     Coroutine *co;
     TruncateCo tco = {
@@ -3456,6 +3457,7 @@ int bdrv_truncate(BdrvChild *child, int64_t offset, bool exact,
         .offset     = offset,
         .exact      = exact,
         .prealloc   = prealloc,
+        .flags      = flags,
         .errp       = errp,
         .ret        = NOT_DONE,
     };
diff --git a/block/parallels.c b/block/parallels.c
index 6d4ed77f16..2be92cf417 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -203,7 +203,7 @@ static int64_t allocate_clusters(BlockDriverState *bs, int64_t sector_num,
         } else {
             ret = bdrv_truncate(bs->file,
                                 (s->data_end + space) << BDRV_SECTOR_BITS,
-                                false, PREALLOC_MODE_OFF, NULL);
+                                false, PREALLOC_MODE_OFF, 0, NULL);
         }
         if (ret < 0) {
             return ret;
@@ -493,7 +493,7 @@ static int coroutine_fn parallels_co_check(BlockDriverState *bs,
              * That means we have to pass exact=true.
              */
             ret = bdrv_truncate(bs->file, res->image_end_offset, true,
-                                PREALLOC_MODE_OFF, &local_err);
+                                PREALLOC_MODE_OFF, 0, &local_err);
             if (ret < 0) {
                 error_report_err(local_err);
                 res->check_errors++;
@@ -889,7 +889,7 @@ static void parallels_close(BlockDriverState *bs)
 
         /* errors are ignored, so we might as well pass exact=true */
         bdrv_truncate(bs->file, s->data_end << BDRV_SECTOR_BITS, true,
-                      PREALLOC_MODE_OFF, NULL);
+                      PREALLOC_MODE_OFF, 0, NULL);
     }
 
     g_free(s->bat_dirty_bmap);
diff --git a/block/qcow.c b/block/qcow.c
index 8973e4e565..6b5f2269f0 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -480,7 +480,7 @@ static int get_cluster_offset(BlockDriverState *bs,
                     return -E2BIG;
                 }
                 ret = bdrv_truncate(bs->file, cluster_offset + s->cluster_size,
-                                    false, PREALLOC_MODE_OFF, NULL);
+                                    false, PREALLOC_MODE_OFF, 0, NULL);
                 if (ret < 0) {
                     return ret;
                 }
@@ -1035,7 +1035,7 @@ static int qcow_make_empty(BlockDriverState *bs)
             l1_length) < 0)
         return -1;
     ret = bdrv_truncate(bs->file, s->l1_table_offset + l1_length, false,
-                        PREALLOC_MODE_OFF, NULL);
+                        PREALLOC_MODE_OFF, 0, NULL);
     if (ret < 0)
         return ret;
 
diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 7ef1c0e42a..d9650b9b6c 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -2018,7 +2018,7 @@ static int check_refblocks(BlockDriverState *bs, BdrvCheckResult *res,
                 }
 
                 ret = bdrv_truncate(bs->file, offset + s->cluster_size, false,
-                                    PREALLOC_MODE_OFF, &local_err);
+                                    PREALLOC_MODE_OFF, 0, &local_err);
                 if (ret < 0) {
                     error_report_err(local_err);
                     goto resize_fail;
diff --git a/block/qcow2.c b/block/qcow2.c
index 0b406b22fb..c5b0711357 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3095,7 +3095,7 @@ static int coroutine_fn preallocate_co(BlockDriverState *bs, uint64_t offset,
             mode = PREALLOC_MODE_OFF;
         }
         ret = bdrv_co_truncate(s->data_file, host_offset + cur_bytes, false,
-                               mode, errp);
+                               mode, 0, errp);
         if (ret < 0) {
             return ret;
         }
@@ -4061,7 +4061,7 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
              * always fulfilled, so there is no need to pass it on.)
              */
             bdrv_co_truncate(bs->file, (last_cluster + 1) * s->cluster_size,
-                             false, PREALLOC_MODE_OFF, &local_err);
+                             false, PREALLOC_MODE_OFF, 0, &local_err);
             if (local_err) {
                 warn_reportf_err(local_err,
                                  "Failed to truncate the tail of the image: ");
@@ -4083,7 +4083,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
              * file should be resized to the exact target size, too,
              * so we pass @exact here.
              */
-            ret = bdrv_co_truncate(s->data_file, offset, exact, prealloc, errp);
+            ret = bdrv_co_truncate(s->data_file, offset, exact, prealloc, 0,
+                                   errp);
             if (ret < 0) {
                 goto fail;
             }
@@ -4169,7 +4170,8 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         new_file_size = allocation_start +
                         nb_new_data_clusters * s->cluster_size;
         /* Image file grows, so @exact does not matter */
-        ret = bdrv_co_truncate(bs->file, new_file_size, false, prealloc, errp);
+        ret = bdrv_co_truncate(bs->file, new_file_size, false, prealloc, 0,
+                               errp);
         if (ret < 0) {
             error_prepend(errp, "Failed to resize underlying file: ");
             qcow2_free_clusters(bs, allocation_start,
@@ -4348,7 +4350,8 @@ qcow2_co_pwritev_compressed_part(BlockDriverState *bs,
         if (len < 0) {
             return len;
         }
-        return bdrv_co_truncate(bs->file, len, false, PREALLOC_MODE_OFF, NULL);
+        return bdrv_co_truncate(bs->file, len, false, PREALLOC_MODE_OFF, 0,
+                                NULL);
     }
 
     if (offset_into_cluster(s, offset)) {
@@ -4563,7 +4566,7 @@ static int make_completely_empty(BlockDriverState *bs)
     }
 
     ret = bdrv_truncate(bs->file, (3 + l1_clusters) * s->cluster_size, false,
-                        PREALLOC_MODE_OFF, &local_err);
+                        PREALLOC_MODE_OFF, 0, &local_err);
     if (ret < 0) {
         error_report_err(local_err);
         goto fail;
diff --git a/block/raw-format.c b/block/raw-format.c
index 9331368f43..3465c9a865 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -387,7 +387,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
 
     s->size = offset;
     offset += s->offset;
-    return bdrv_co_truncate(bs->file, offset, exact, prealloc, errp);
+    return bdrv_co_truncate(bs->file, offset, exact, prealloc, 0, errp);
 }
 
 static void raw_eject(BlockDriverState *bs, bool eject_flag)
diff --git a/block/vhdx-log.c b/block/vhdx-log.c
index 13a49c2a33..404fb5f3cb 100644
--- a/block/vhdx-log.c
+++ b/block/vhdx-log.c
@@ -558,7 +558,7 @@ static int vhdx_log_flush(BlockDriverState *bs, BDRVVHDXState *s,
                     goto exit;
                 }
                 ret = bdrv_truncate(bs->file, new_file_size, false,
-                                    PREALLOC_MODE_OFF, NULL);
+                                    PREALLOC_MODE_OFF, 0, NULL);
                 if (ret < 0) {
                     goto exit;
                 }
diff --git a/block/vhdx.c b/block/vhdx.c
index 33e57cd656..5dfbb2029a 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1264,7 +1264,7 @@ static int vhdx_allocate_block(BlockDriverState *bs, BDRVVHDXState *s,
     }
 
     return bdrv_truncate(bs->file, *new_offset + s->block_size, false,
-                         PREALLOC_MODE_OFF, NULL);
+                         PREALLOC_MODE_OFF, 0, NULL);
 }
 
 /*
diff --git a/block/vmdk.c b/block/vmdk.c
index 218d9c9800..5de99fe813 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -2077,7 +2077,7 @@ vmdk_co_pwritev_compressed(BlockDriverState *bs, uint64_t offset,
             }
             length = QEMU_ALIGN_UP(length, BDRV_SECTOR_SIZE);
             ret = bdrv_truncate(s->extents[i].file, length, false,
-                                PREALLOC_MODE_OFF, NULL);
+                                PREALLOC_MODE_OFF, 0, NULL);
             if (ret < 0) {
                 return ret;
             }
diff --git a/tests/test-block-iothread.c b/tests/test-block-iothread.c
index 2f3b76323d..71e9bce3b1 100644
--- a/tests/test-block-iothread.c
+++ b/tests/test-block-iothread.c
@@ -186,18 +186,18 @@ static void test_sync_op_truncate(BdrvChild *c)
     int ret;
 
     /* Normal success path */
-    ret = bdrv_truncate(c, 65536, false, PREALLOC_MODE_OFF, NULL);
+    ret = bdrv_truncate(c, 65536, false, PREALLOC_MODE_OFF, 0, NULL);
     g_assert_cmpint(ret, ==, 0);
 
     /* Early error: Negative offset */
-    ret = bdrv_truncate(c, -2, false, PREALLOC_MODE_OFF, NULL);
+    ret = bdrv_truncate(c, -2, false, PREALLOC_MODE_OFF, 0, NULL);
     g_assert_cmpint(ret, ==, -EINVAL);
 
     /* Error: Read-only image */
     c->bs->read_only = true;
     c->bs->open_flags &= ~BDRV_O_RDWR;
 
-    ret = bdrv_truncate(c, 65536, false, PREALLOC_MODE_OFF, NULL);
+    ret = bdrv_truncate(c, 65536, false, PREALLOC_MODE_OFF, 0, NULL);
     g_assert_cmpint(ret, ==, -EACCES);
 
     c->bs->read_only = false;
-- 
2.25.3

[PATCH v5 3/9] block-backend: Add flags to blk_truncate()

[Kevin Wolf]

Now that node level interface bdrv_truncate() supports passing request
flags to the block driver, expose this on the BlockBackend level, too.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 include/sysemu/block-backend.h | 2 +-
 block.c                        | 3 ++-
 block/block-backend.c          | 4 ++--
 block/commit.c                 | 4 ++--
 block/crypto.c                 | 2 +-
 block/mirror.c                 | 2 +-
 block/qcow2.c                  | 4 ++--
 block/qed.c                    | 2 +-
 block/vdi.c                    | 2 +-
 block/vhdx.c                   | 4 ++--
 block/vmdk.c                   | 6 +++---
 block/vpc.c                    | 2 +-
 blockdev.c                     | 2 +-
 qemu-img.c                     | 2 +-
 qemu-io-cmds.c                 | 2 +-
 15 files changed, 22 insertions(+), 21 deletions(-)

diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 9bbdbd63d7..34de7faa81 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -237,7 +237,7 @@ int coroutine_fn blk_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
 int blk_pwrite_compressed(BlockBackend *blk, int64_t offset, const void *buf,
                           int bytes);
 int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
-                 PreallocMode prealloc, Error **errp);
+                 PreallocMode prealloc, BdrvRequestFlags flags, Error **errp);
 int blk_pdiscard(BlockBackend *blk, int64_t offset, int bytes);
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
                      int64_t pos, int size);
diff --git a/block.c b/block.c
index 2e3905c99e..03cc5813a2 100644
--- a/block.c
+++ b/block.c
@@ -548,7 +548,8 @@ static int64_t create_file_fallback_truncate(BlockBackend *blk,
     int64_t size;
     int ret;
 
-    ret = blk_truncate(blk, minimum_size, false, PREALLOC_MODE_OFF, &local_err);
+    ret = blk_truncate(blk, minimum_size, false, PREALLOC_MODE_OFF, 0,
+                       &local_err);
     if (ret < 0 && ret != -ENOTSUP) {
         error_propagate(errp, local_err);
         return ret;
diff --git a/block/block-backend.c b/block/block-backend.c
index 8be20060d3..17ed6d8c5b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2137,14 +2137,14 @@ int blk_pwrite_compressed(BlockBackend *blk, int64_t offset, const void *buf,
 }
 
 int blk_truncate(BlockBackend *blk, int64_t offset, bool exact,
-                 PreallocMode prealloc, Error **errp)
+                 PreallocMode prealloc, BdrvRequestFlags flags, Error **errp)
 {
     if (!blk_is_available(blk)) {
         error_setg(errp, "No medium inserted");
         return -ENOMEDIUM;
     }
 
-    return bdrv_truncate(blk->root, offset, exact, prealloc, 0, errp);
+    return bdrv_truncate(blk->root, offset, exact, prealloc, flags, errp);
 }
 
 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
diff --git a/block/commit.c b/block/commit.c
index 8e672799af..87f6096d90 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -133,7 +133,7 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
     }
 
     if (base_len < len) {
-        ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, NULL);
+        ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL);
         if (ret) {
             goto out;
         }
@@ -458,7 +458,7 @@ int bdrv_commit(BlockDriverState *bs)
      * grow the backing file image if possible.  If not possible,
      * we must return an error */
     if (length > backing_length) {
-        ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF,
+        ret = blk_truncate(backing, length, false, PREALLOC_MODE_OFF, 0,
                            &local_err);
         if (ret < 0) {
             error_report_err(local_err);
diff --git a/block/crypto.c b/block/crypto.c
index ab33545c92..e02f343590 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -115,7 +115,7 @@ static ssize_t block_crypto_init_func(QCryptoBlock *block,
      * which will be used by the crypto header
      */
     return blk_truncate(data->blk, data->size + headerlen, false,
-                        data->prealloc, errp);
+                        data->prealloc, 0, errp);
 }
 
 
diff --git a/block/mirror.c b/block/mirror.c
index c26fd9260d..aca95c9bc9 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -900,7 +900,7 @@ static int coroutine_fn mirror_run(Job *job, Error **errp)
 
         if (s->bdev_length > base_length) {
             ret = blk_truncate(s->target, s->bdev_length, false,
-                               PREALLOC_MODE_OFF, NULL);
+                               PREALLOC_MODE_OFF, 0, NULL);
             if (ret < 0) {
                 goto immediate_exit;
             }
diff --git a/block/qcow2.c b/block/qcow2.c
index c5b0711357..9cfbdfc939 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3511,7 +3511,7 @@ qcow2_co_create(BlockdevCreateOptions *create_options, Error **errp)
 
     /* Okay, now that we have a valid image, let's give it the right size */
     ret = blk_truncate(blk, qcow2_opts->size, false, qcow2_opts->preallocation,
-                       errp);
+                       0, errp);
     if (ret < 0) {
         error_prepend(errp, "Could not resize image: ");
         goto out;
@@ -5374,7 +5374,7 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
          * Amending image options should ensure that the image has
          * exactly the given new values, so pass exact=true here.
          */
-        ret = blk_truncate(blk, new_size, true, PREALLOC_MODE_OFF, errp);
+        ret = blk_truncate(blk, new_size, true, PREALLOC_MODE_OFF, 0, errp);
         blk_unref(blk);
         if (ret < 0) {
             return ret;
diff --git a/block/qed.c b/block/qed.c
index fb6100bd20..b0fdb8f565 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -677,7 +677,7 @@ static int coroutine_fn bdrv_qed_co_create(BlockdevCreateOptions *opts,
      * The QED format associates file length with allocation status,
      * so a new file (which is empty) must have a length of 0.
      */
-    ret = blk_truncate(blk, 0, true, PREALLOC_MODE_OFF, errp);
+    ret = blk_truncate(blk, 0, true, PREALLOC_MODE_OFF, 0, errp);
     if (ret < 0) {
         goto out;
     }
diff --git a/block/vdi.c b/block/vdi.c
index e1a11f2aa0..0c7835ae70 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -875,7 +875,7 @@ static int coroutine_fn vdi_co_do_create(BlockdevCreateOptions *create_options,
 
     if (image_type == VDI_TYPE_STATIC) {
         ret = blk_truncate(blk, offset + blocks * block_size, false,
-                           PREALLOC_MODE_OFF, errp);
+                           PREALLOC_MODE_OFF, 0, errp);
         if (ret < 0) {
             error_prepend(errp, "Failed to statically allocate file");
             goto exit;
diff --git a/block/vhdx.c b/block/vhdx.c
index 5dfbb2029a..21497f7318 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1703,13 +1703,13 @@ static int vhdx_create_bat(BlockBackend *blk, BDRVVHDXState *s,
         /* All zeroes, so we can just extend the file - the end of the BAT
          * is the furthest thing we have written yet */
         ret = blk_truncate(blk, data_file_offset, false, PREALLOC_MODE_OFF,
-                           errp);
+                           0, errp);
         if (ret < 0) {
             goto exit;
         }
     } else if (type == VHDX_TYPE_FIXED) {
         ret = blk_truncate(blk, data_file_offset + image_size, false,
-                           PREALLOC_MODE_OFF, errp);
+                           PREALLOC_MODE_OFF, 0, errp);
         if (ret < 0) {
             goto exit;
         }
diff --git a/block/vmdk.c b/block/vmdk.c
index 5de99fe813..8ec18f35a5 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -2118,7 +2118,7 @@ static int vmdk_init_extent(BlockBackend *blk,
     int gd_buf_size;
 
     if (flat) {
-        ret = blk_truncate(blk, filesize, false, PREALLOC_MODE_OFF, errp);
+        ret = blk_truncate(blk, filesize, false, PREALLOC_MODE_OFF, 0, errp);
         goto exit;
     }
     magic = cpu_to_be32(VMDK4_MAGIC);
@@ -2182,7 +2182,7 @@ static int vmdk_init_extent(BlockBackend *blk,
     }
 
     ret = blk_truncate(blk, le64_to_cpu(header.grain_offset) << 9, false,
-                       PREALLOC_MODE_OFF, errp);
+                       PREALLOC_MODE_OFF, 0, errp);
     if (ret < 0) {
         goto exit;
     }
@@ -2523,7 +2523,7 @@ static int coroutine_fn vmdk_co_do_create(int64_t size,
     /* bdrv_pwrite write padding zeros to align to sector, we don't need that
      * for description file */
     if (desc_offset == 0) {
-        ret = blk_truncate(blk, desc_len, false, PREALLOC_MODE_OFF, errp);
+        ret = blk_truncate(blk, desc_len, false, PREALLOC_MODE_OFF, 0, errp);
         if (ret < 0) {
             goto exit;
         }
diff --git a/block/vpc.c b/block/vpc.c
index d8141b52da..2d1eade146 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -898,7 +898,7 @@ static int create_fixed_disk(BlockBackend *blk, uint8_t *buf,
     /* Add footer to total size */
     total_size += HEADER_SIZE;
 
-    ret = blk_truncate(blk, total_size, false, PREALLOC_MODE_OFF, errp);
+    ret = blk_truncate(blk, total_size, false, PREALLOC_MODE_OFF, 0, errp);
     if (ret < 0) {
         return ret;
     }
diff --git a/blockdev.c b/blockdev.c
index 5faddaa705..fbe3a06dbf 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2741,7 +2741,7 @@ void qmp_block_resize(bool has_device, const char *device,
     }
 
     bdrv_drained_begin(bs);
-    ret = blk_truncate(blk, size, false, PREALLOC_MODE_OFF, errp);
+    ret = blk_truncate(blk, size, false, PREALLOC_MODE_OFF, 0, errp);
     bdrv_drained_end(bs);
 
 out:
diff --git a/qemu-img.c b/qemu-img.c
index 821cbf610e..7f52742ef2 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -3866,7 +3866,7 @@ static int img_resize(int argc, char **argv)
      * resizing, so pass @exact=true.  It is of no use to report
      * success when the image has not actually been resized.
      */
-    ret = blk_truncate(blk, total_size, true, prealloc, &err);
+    ret = blk_truncate(blk, total_size, true, prealloc, 0, &err);
     if (!ret) {
         qprintf(quiet, "Image resized.\n");
     } else {
diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 1b7e700020..851f07e8f8 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1715,7 +1715,7 @@ static int truncate_f(BlockBackend *blk, int argc, char **argv)
      * exact=true.  It is better to err on the "emit more errors" side
      * than to be overly permissive.
      */
-    ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, &local_err);
+    ret = blk_truncate(blk, offset, true, PREALLOC_MODE_OFF, 0, &local_err);
     if (ret < 0) {
         error_report_err(local_err);
         return ret;
-- 
2.25.3

[PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
undo any previous preallocation, but just adds the zero flag to all
relevant L2 entries. If an external data file is in use, a write_zeroes
request to the data file is made instead.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index 9cfbdfc939..bd632405d1 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1726,6 +1726,7 @@ static int coroutine_fn qcow2_do_open(BlockDriverState *bs, QDict *options,
 
     bs->supported_zero_flags = header.version >= 3 ?
                                BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK : 0;
+    bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
 
     /* Repair image if dirty */
     if (!(flags & (BDRV_O_CHECK | BDRV_O_INACTIVE)) && !bs->read_only &&
@@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
         g_assert_not_reached();
     }
 
+    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
+        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
+        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
+
+        /* Use zero clusters as much as we can */
+        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
+        if (ret < 0) {
+            error_setg_errno(errp, -ret, "Failed to zero out the new area");
+            goto fail;
+        }
+
+        /* Write explicit zeros for the unaligned head */
+        if (zero_start > old_length) {
+            uint8_t *buf = qemu_blockalign0(bs, s->cluster_size);
+            QEMUIOVector qiov;
+            qemu_iovec_init_buf(&qiov, buf, zero_start - old_length);
+
+            qemu_co_mutex_unlock(&s->lock);
+            ret = qcow2_co_pwritev_part(bs, old_length, qiov.size, &qiov, 0, 0);
+            qemu_co_mutex_lock(&s->lock);
+
+            qemu_vfree(buf);
+            if (ret < 0) {
+                error_setg_errno(errp, -ret, "Failed to zero out the new area");
+                goto fail;
+            }
+        }
+    }
+
     if (prealloc != PREALLOC_MODE_OFF) {
         /* Flush metadata before actually changing the image size */
         ret = qcow2_write_caches(bs);
-- 
2.25.3

[PATCH v5 5/9] raw-format: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

The raw format driver can simply forward the flag and let its bs->file
child take care of actually providing the zeros.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/raw-format.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/raw-format.c b/block/raw-format.c
index 3465c9a865..351f2d91c6 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -387,7 +387,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
 
     s->size = offset;
     offset += s->offset;
-    return bdrv_co_truncate(bs->file, offset, exact, prealloc, 0, errp);
+    return bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
 }
 
 static void raw_eject(BlockDriverState *bs, bool eject_flag)
@@ -445,6 +445,8 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
     bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
         ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
             bs->file->bs->supported_zero_flags);
+    bs->supported_truncate_flags = bs->file->bs->supported_truncate_flags &
+                                   BDRV_REQ_ZERO_WRITE;
 
     if (bs->probed && !bdrv_is_read_only(bs)) {
         bdrv_refresh_filename(bs->file->bs);
-- 
2.25.3

[PATCH v5 6/9] file-posix: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

For regular files, we always get BDRV_REQ_ZERO_WRITE behaviour from the
OS, so we can advertise the flag and just ignore it.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 block/file-posix.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/file-posix.c b/block/file-posix.c
index 53f475ed61..1dca220a81 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -702,6 +702,10 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
 #endif
 
     bs->supported_zero_flags = BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK;
+    if (S_ISREG(st.st_mode)) {
+        /* When extending regular files, we get zeros from the OS */
+        bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
+    }
     ret = 0;
 fail:
     if (filename && (bdrv_flags & BDRV_O_TEMPORARY)) {
-- 
2.25.3

[PATCH v5 7/9] block: truncate: Don't make backing file data visible

[Kevin Wolf]

When extending the size of an image that has a backing file larger than
its old size, make sure that the backing file data doesn't become
visible in the guest, but the added area is properly zeroed out.

Consider the following scenario where the overlay is shorter than its
backing file:

    base.qcow2:     AAAAAAAA
    overlay.qcow2:  BBBB

When resizing (extending) overlay.qcow2, the new blocks should not stay
unallocated and make the additional As from base.qcow2 visible like
before this patch, but zeros should be read.

A similar case happens with the various variants of a commit job when an
intermediate file is short (- for unallocated):

    base.qcow2:     A-A-AAAA
    mid.qcow2:      BB-B
    top.qcow2:      C--C--C-

After commit top.qcow2 to mid.qcow2, the following happens:

    mid.qcow2:      CB-C00C0 (correct result)
    mid.qcow2:      CB-C--C- (before this fix)

Without the fix, blocks that previously read as zeros on top.qcow2
suddenly turn into A.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
---
 block/io.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/block/io.c b/block/io.c
index 795075954e..8fbb607515 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3394,6 +3394,20 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
         goto out;
     }
 
+    /*
+     * If the image has a backing file that is large enough that it would
+     * provide data for the new area, we cannot leave it unallocated because
+     * then the backing file content would become visible. Instead, zero-fill
+     * the new area.
+     *
+     * Note that if the image has a backing file, but was opened without the
+     * backing file, taking care of keeping things consistent with that backing
+     * file is the user's responsibility.
+     */
+    if (new_bytes && bs->backing) {
+        flags |= BDRV_REQ_ZERO_WRITE;
+    }
+
     if (drv->bdrv_co_truncate) {
         if (flags & ~bs->supported_truncate_flags) {
             error_setg(errp, "Block driver does not support requested flags");
-- 
2.25.3

[PATCH v5 8/9] iotests: Filter testfiles out in filter_img_info()

[Kevin Wolf]

We want to keep TEST_IMG for the full path of the main test image, but
filter_testfiles() must be called for other test images before replacing
other things like the image format because the test directory path could
contain the format as a substring.

Insert a filter_testfiles() call between both.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/qemu-iotests/iotests.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 7bc4934cd2..5f8c263d59 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -338,8 +338,9 @@ def filter_img_info(output, filename):
     for line in output.split('\n'):
         if 'disk size' in line or 'actual-size' in line:
             continue
-        line = line.replace(filename, 'TEST_IMG') \
-                   .replace(imgfmt, 'IMGFMT')
+        line = line.replace(filename, 'TEST_IMG')
+        line = filter_testfiles(line)
+        line = line.replace(imgfmt, 'IMGFMT')
         line = re.sub('iters: [0-9]+', 'iters: XXX', line)
         line = re.sub('uuid: [-a-f0-9]+', 'uuid: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX', line)
         line = re.sub('cid: [0-9]+', 'cid: XXXXXXXXXX', line)
-- 
2.25.3

[PATCH v5 9/9] iotests: Test committing to short backing file

[Kevin Wolf]

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 tests/qemu-iotests/274     | 157 ++++++++++++++++++++++
 tests/qemu-iotests/274.out | 260 +++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/group   |   1 +
 3 files changed, 418 insertions(+)
 create mode 100755 tests/qemu-iotests/274
 create mode 100644 tests/qemu-iotests/274.out

diff --git a/tests/qemu-iotests/274 b/tests/qemu-iotests/274
new file mode 100755
index 0000000000..8bf7ff3122
--- /dev/null
+++ b/tests/qemu-iotests/274
@@ -0,0 +1,157 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2019 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Creator/Owner: Kevin Wolf <kwolf@redhat.com>
+#
+# Some tests for short backing files and short overlays
+
+import iotests
+import os
+
+iotests.verify_image_format(supported_fmts=['qcow2'])
+iotests.verify_platform(['linux'])
+
+size_short = 1 * 1024 * 1024
+size_long = 2 * 1024 * 1024
+size_diff = size_long - size_short
+
+def create_chain():
+    iotests.qemu_img_log('create', '-f', iotests.imgfmt, base,
+                         str(size_long))
+    iotests.qemu_img_log('create', '-f', iotests.imgfmt, '-b', base, mid,
+                         str(size_short))
+    iotests.qemu_img_log('create', '-f', iotests.imgfmt, '-b', mid, top,
+                         str(size_long))
+
+    iotests.qemu_io_log('-c', 'write -P 1 0 %d' % size_long, base)
+
+def create_vm():
+    vm = iotests.VM()
+    vm.add_blockdev('file,filename=%s,node-name=base-file' % (base))
+    vm.add_blockdev('%s,file=base-file,node-name=base' % (iotests.imgfmt))
+    vm.add_blockdev('file,filename=%s,node-name=mid-file' % (mid))
+    vm.add_blockdev('%s,file=mid-file,node-name=mid,backing=base' % (iotests.imgfmt))
+    vm.add_drive(top, 'backing=mid,node-name=top')
+    return vm
+
+with iotests.FilePath('base') as base, \
+     iotests.FilePath('mid') as mid, \
+     iotests.FilePath('top') as top:
+
+    iotests.log('== Commit tests ==')
+
+    create_chain()
+
+    iotests.log('=== Check visible data ===')
+
+    iotests.qemu_io_log('-c', 'read -P 1 0 %d' % size_short, top)
+    iotests.qemu_io_log('-c', 'read -P 0 %d %d' % (size_short, size_diff), top)
+
+    iotests.log('=== Checking allocation status ===')
+
+    iotests.qemu_io_log('-c', 'alloc 0 %d' % size_short,
+                        '-c', 'alloc %d %d' % (size_short, size_diff),
+                        base)
+
+    iotests.qemu_io_log('-c', 'alloc 0 %d' % size_short,
+                        '-c', 'alloc %d %d' % (size_short, size_diff),
+                        mid)
+
+    iotests.qemu_io_log('-c', 'alloc 0 %d' % size_short,
+                        '-c', 'alloc %d %d' % (size_short, size_diff),
+                        top)
+
+    iotests.log('=== Checking map ===')
+
+    iotests.qemu_img_log('map', '--output=json', base)
+    iotests.qemu_img_log('map', '--output=human', base)
+    iotests.qemu_img_log('map', '--output=json', mid)
+    iotests.qemu_img_log('map', '--output=human', mid)
+    iotests.qemu_img_log('map', '--output=json', top)
+    iotests.qemu_img_log('map', '--output=human', top)
+
+    iotests.log('=== Testing qemu-img commit (top -> mid) ===')
+
+    iotests.qemu_img_log('commit', top)
+    iotests.img_info_log(mid)
+    iotests.qemu_io_log('-c', 'read -P 1 0 %d' % size_short, mid)
+    iotests.qemu_io_log('-c', 'read -P 0 %d %d' % (size_short, size_diff), mid)
+
+    iotests.log('=== Testing HMP commit (top -> mid) ===')
+
+    create_chain()
+    with create_vm() as vm:
+        vm.launch()
+        vm.qmp_log('human-monitor-command', command_line='commit drive0')
+
+    iotests.img_info_log(mid)
+    iotests.qemu_io_log('-c', 'read -P 1 0 %d' % size_short, mid)
+    iotests.qemu_io_log('-c', 'read -P 0 %d %d' % (size_short, size_diff), mid)
+
+    iotests.log('=== Testing QMP active commit (top -> mid) ===')
+
+    create_chain()
+    with create_vm() as vm:
+        vm.launch()
+        vm.qmp_log('block-commit', device='top', base_node='mid',
+                   job_id='job0', auto_dismiss=False)
+        vm.run_job('job0', wait=5)
+
+    iotests.img_info_log(mid)
+    iotests.qemu_io_log('-c', 'read -P 1 0 %d' % size_short, mid)
+    iotests.qemu_io_log('-c', 'read -P 0 %d %d' % (size_short, size_diff), mid)
+
+
+    iotests.log('== Resize tests ==')
+
+    # Use different sizes for different allocation modes:
+    #
+    # We want to have at least one test where 32 bit truncation in the size of
+    # the overlapping area becomes visible. This is covered by the
+    # prealloc='off' case (1G to 6G is an overlap of 5G).
+    #
+    # However, we can only do this for modes that don't preallocate data
+    # because otherwise we might run out of space on the test host.
+    #
+    # We also want to test some unaligned combinations.
+    for (prealloc, base_size, top_size_old, top_size_new, off)  in [
+            ('off',       '6G',    '1G',   '8G',   '5G'),
+            ('metadata', '32G',   '30G',  '33G',  '31G'),
+            ('falloc',   '10M',    '5M',  '15M',   '9M'),
+            ('full',     '16M',    '8M',  '12M',  '11M'),
+            ('off',      '384k', '253k', '512k', '253k'),
+            ('off',      '400k', '256k', '512k', '336k'),
+            ('off',      '512k', '256k', '500k', '436k')]:
+
+        iotests.log('=== preallocation=%s ===' % prealloc)
+        iotests.qemu_img_log('create', '-f', iotests.imgfmt, base, base_size)
+        iotests.qemu_img_log('create', '-f', iotests.imgfmt, '-b', base, top,
+                             top_size_old)
+        iotests.qemu_io_log('-c', 'write -P 1 %s 64k' % off, base)
+
+        # After this, 0 to base_size should be allocated/zeroed
+        # base_size to top_size_new should be unallocated with
+        # preallocation=off and allocated with preallocation enabled
+        iotests.qemu_img_log('resize', '-f', iotests.imgfmt,
+                             '--preallocation', prealloc, top, top_size_new)
+        iotests.qemu_io_log('-c', 'read -P 0 %s 64k' % off, top)
+
+        # Metadata preallocation doesn't have a defined result on the file
+        # system level with respect to holes, so skip it here
+        iotests.qemu_io_log('-c', 'map', top)
+        if prealloc != 'metadata':
+            iotests.qemu_img_log('map', '--output=json', top)
diff --git a/tests/qemu-iotests/274.out b/tests/qemu-iotests/274.out
new file mode 100644
index 0000000000..179bd7ccaf
--- /dev/null
+++ b/tests/qemu-iotests/274.out
@@ -0,0 +1,260 @@
+== Commit tests ==
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=2097152 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-mid', fmt=qcow2 size=1048576 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=2097152 backing_file=TEST_DIR/PID-mid cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 2097152/2097152 bytes at offset 0
+2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Check visible data ===
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+read 1048576/1048576 bytes at offset 1048576
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Checking allocation status ===
+1048576/1048576 bytes allocated at offset 0 bytes
+1048576/1048576 bytes allocated at offset 1 MiB
+
+0/1048576 bytes allocated at offset 0 bytes
+0/0 bytes allocated at offset 1 MiB
+
+0/1048576 bytes allocated at offset 0 bytes
+0/1048576 bytes allocated at offset 1 MiB
+
+=== Checking map ===
+[{ "start": 0, "length": 2097152, "depth": 0, "zero": false, "data": true, "offset": 327680}]
+
+Offset          Length          Mapped to       File
+0               0x200000        0x50000         TEST_DIR/PID-base
+
+[{ "start": 0, "length": 1048576, "depth": 1, "zero": false, "data": true, "offset": 327680}]
+
+Offset          Length          Mapped to       File
+0               0x100000        0x50000         TEST_DIR/PID-base
+
+[{ "start": 0, "length": 1048576, "depth": 2, "zero": false, "data": true, "offset": 327680},
+{ "start": 1048576, "length": 1048576, "depth": 0, "zero": true, "data": false}]
+
+Offset          Length          Mapped to       File
+0               0x100000        0x50000         TEST_DIR/PID-base
+
+=== Testing qemu-img commit (top -> mid) ===
+Image committed.
+
+image: TEST_IMG
+file format: IMGFMT
+virtual size: 2 MiB (2097152 bytes)
+cluster_size: 65536
+backing file: TEST_DIR/PID-base
+Format specific information:
+    compat: 1.1
+    lazy refcounts: false
+    refcount bits: 16
+    corrupt: false
+
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+read 1048576/1048576 bytes at offset 1048576
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Testing HMP commit (top -> mid) ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=2097152 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-mid', fmt=qcow2 size=1048576 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=2097152 backing_file=TEST_DIR/PID-mid cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 2097152/2097152 bytes at offset 0
+2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+{"execute": "human-monitor-command", "arguments": {"command-line": "commit drive0"}}
+{"return": ""}
+image: TEST_IMG
+file format: IMGFMT
+virtual size: 2 MiB (2097152 bytes)
+cluster_size: 65536
+backing file: TEST_DIR/PID-base
+Format specific information:
+    compat: 1.1
+    lazy refcounts: false
+    refcount bits: 16
+    corrupt: false
+
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+read 1048576/1048576 bytes at offset 1048576
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Testing QMP active commit (top -> mid) ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=2097152 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-mid', fmt=qcow2 size=1048576 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=2097152 backing_file=TEST_DIR/PID-mid cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 2097152/2097152 bytes at offset 0
+2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+{"execute": "block-commit", "arguments": {"auto-dismiss": false, "base-node": "mid", "device": "top", "job-id": "job0"}}
+{"return": {}}
+{"execute": "job-complete", "arguments": {"id": "job0"}}
+{"return": {}}
+{"data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}, "event": "BLOCK_JOB_READY", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"data": {"device": "job0", "len": 0, "offset": 0, "speed": 0, "type": "commit"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"execute": "job-dismiss", "arguments": {"id": "job0"}}
+{"return": {}}
+image: TEST_IMG
+file format: IMGFMT
+virtual size: 2 MiB (2097152 bytes)
+cluster_size: 65536
+backing file: TEST_DIR/PID-base
+Format specific information:
+    compat: 1.1
+    lazy refcounts: false
+    refcount bits: 16
+    corrupt: false
+
+read 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+read 1048576/1048576 bytes at offset 1048576
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== Resize tests ==
+=== preallocation=off ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=6442450944 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=1073741824 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 5368709120
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 5368709120
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+1 GiB (0x40000000) bytes not allocated at offset 0 bytes (0x0)
+7 GiB (0x1c0000000) bytes     allocated at offset 1 GiB (0x40000000)
+
+[{ "start": 0, "length": 1073741824, "depth": 1, "zero": true, "data": false},
+{ "start": 1073741824, "length": 7516192768, "depth": 0, "zero": true, "data": false}]
+
+=== preallocation=metadata ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=34359738368 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=32212254720 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 33285996544
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 33285996544
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+30 GiB (0x780000000) bytes not allocated at offset 0 bytes (0x0)
+3 GiB (0xc0000000) bytes     allocated at offset 30 GiB (0x780000000)
+
+=== preallocation=falloc ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=10485760 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=5242880 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 9437184
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 9437184
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+5 MiB (0x500000) bytes not allocated at offset 0 bytes (0x0)
+10 MiB (0xa00000) bytes     allocated at offset 5 MiB (0x500000)
+
+[{ "start": 0, "length": 5242880, "depth": 1, "zero": true, "data": false},
+{ "start": 5242880, "length": 10485760, "depth": 0, "zero": true, "data": false, "offset": 327680}]
+
+=== preallocation=full ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=16777216 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=8388608 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 11534336
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 11534336
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+8 MiB (0x800000) bytes not allocated at offset 0 bytes (0x0)
+4 MiB (0x400000) bytes     allocated at offset 8 MiB (0x800000)
+
+[{ "start": 0, "length": 8388608, "depth": 1, "zero": true, "data": false},
+{ "start": 8388608, "length": 4194304, "depth": 0, "zero": true, "data": false, "offset": 327680}]
+
+=== preallocation=off ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=393216 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=259072 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 259072
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 259072
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+192 KiB (0x30000) bytes not allocated at offset 0 bytes (0x0)
+320 KiB (0x50000) bytes     allocated at offset 192 KiB (0x30000)
+
+[{ "start": 0, "length": 196608, "depth": 1, "zero": true, "data": false},
+{ "start": 196608, "length": 65536, "depth": 0, "zero": false, "data": true, "offset": 327680},
+{ "start": 262144, "length": 262144, "depth": 0, "zero": true, "data": false}]
+
+=== preallocation=off ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=409600 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=262144 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 344064
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 344064
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+256 KiB (0x40000) bytes not allocated at offset 0 bytes (0x0)
+256 KiB (0x40000) bytes     allocated at offset 256 KiB (0x40000)
+
+[{ "start": 0, "length": 262144, "depth": 1, "zero": true, "data": false},
+{ "start": 262144, "length": 262144, "depth": 0, "zero": true, "data": false}]
+
+=== preallocation=off ===
+Formatting 'TEST_DIR/PID-base', fmt=qcow2 size=524288 cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+Formatting 'TEST_DIR/PID-top', fmt=qcow2 size=262144 backing_file=TEST_DIR/PID-base cluster_size=65536 lazy_refcounts=off refcount_bits=16
+
+wrote 65536/65536 bytes at offset 446464
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+Image resized.
+
+read 65536/65536 bytes at offset 446464
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+256 KiB (0x40000) bytes not allocated at offset 0 bytes (0x0)
+244 KiB (0x3d000) bytes     allocated at offset 256 KiB (0x40000)
+
+[{ "start": 0, "length": 262144, "depth": 1, "zero": true, "data": false},
+{ "start": 262144, "length": 249856, "depth": 0, "zero": true, "data": false}]
+
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 435dccd5af..1710470e70 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -286,6 +286,7 @@
 270 rw backing quick
 272 rw
 273 backing quick
+274 rw backing
 277 rw quick
 279 rw backing quick
 280 rw migration quick
-- 
2.25.3

Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Eric Blake]

On 4/22/20 10:21 AM, Kevin Wolf wrote:
> If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
> qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
> undo any previous preallocation, but just adds the zero flag to all
> relevant L2 entries. If an external data file is in use, a write_zeroes
> request to the data file is made instead.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/qcow2.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
> 

> @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
>           g_assert_not_reached();
>       }
>   
> +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
> +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
> +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);

This rounds up beyond the new size...

> +
> +        /* Use zero clusters as much as we can */
> +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);

and then requests that the extra be zeroed.  Does that always work, even 
when it results in pdrv_co_pwrite_zeroes beyond the end of s->data_file? 
  If so,

Reviewed-by: Eric Blake <eblake@redhat.com>

otherwise, you may have to treat the tail specially, the same way you 
treated an unaligned head.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v5 5/9] raw-format: Support BDRV_REQ_ZERO_WRITE for truncate

[Eric Blake]

On 4/22/20 10:21 AM, Kevin Wolf wrote:
> The raw format driver can simply forward the flag and let its bs->file
> child take care of actually providing the zeros.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>   block/raw-format.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

> diff --git a/block/raw-format.c b/block/raw-format.c
> index 3465c9a865..351f2d91c6 100644
> --- a/block/raw-format.c
> +++ b/block/raw-format.c
> @@ -387,7 +387,7 @@ static int coroutine_fn raw_co_truncate(BlockDriverState *bs, int64_t offset,
>   
>       s->size = offset;
>       offset += s->offset;
> -    return bdrv_co_truncate(bs->file, offset, exact, prealloc, 0, errp);
> +    return bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
>   }
>   
>   static void raw_eject(BlockDriverState *bs, bool eject_flag)
> @@ -445,6 +445,8 @@ static int raw_open(BlockDriverState *bs, QDict *options, int flags,
>       bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
>           ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
>               bs->file->bs->supported_zero_flags);
> +    bs->supported_truncate_flags = bs->file->bs->supported_truncate_flags &
> +                                   BDRV_REQ_ZERO_WRITE;
>   
>       if (bs->probed && !bdrv_is_read_only(bs)) {
>           bdrv_refresh_filename(bs->file->bs);
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

Am 22.04.2020 um 17:33 hat Eric Blake geschrieben:
> On 4/22/20 10:21 AM, Kevin Wolf wrote:
> > If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
> > qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
> > undo any previous preallocation, but just adds the zero flag to all
> > relevant L2 entries. If an external data file is in use, a write_zeroes
> > request to the data file is made instead.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >   block/qcow2.c | 30 ++++++++++++++++++++++++++++++
> >   1 file changed, 30 insertions(+)
> > 
> 
> > @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
> >           g_assert_not_reached();
> >       }
> > +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
> > +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
> > +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
> 
> This rounds up beyond the new size...
> 
> > +
> > +        /* Use zero clusters as much as we can */
> > +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
> 
> and then requests that the extra be zeroed.  Does that always work, even
> when it results in pdrv_co_pwrite_zeroes beyond the end of s->data_file?

You mean the data_file_is_raw() path in qcow2_cluster_zeroize()? It's
currently not a code path that is run because we only set
BDRV_REQ_ZERO_WRITE for truncate if the image has a backing file, and
data_file_is_raw() doesn't work with backing files.

But hypothetically, if someone called truncate with BDRV_REQ_ZERO_WRITE
for such a file, I think it would fail.

> If so,
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> otherwise, you may have to treat the tail specially, the same way you
> treated an unaligned head.

Actually, do I even need to round the tail?

    /* Caller must pass aligned values, except at image end */
    assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
    assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
           end_offset == bs->total_sectors << BDRV_SECTOR_BITS);

So qcow2_cluster_zeroize() seems to accept the unaligned tail. It would
still set the zero flag for the partial last cluster and for the
external data file, bdrv_co_pwrite_zeroes() would have the correct size.

Kevin

Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Eric Blake]

On 4/22/20 10:58 AM, Kevin Wolf wrote:

>>> @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
>>>            g_assert_not_reached();
>>>        }
>>> +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
>>> +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
>>> +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
>>
>> This rounds up beyond the new size...
>>
>>> +
>>> +        /* Use zero clusters as much as we can */
>>> +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
>>
>> and then requests that the extra be zeroed.  Does that always work, even
>> when it results in pdrv_co_pwrite_zeroes beyond the end of s->data_file?
> 
> You mean the data_file_is_raw() path in qcow2_cluster_zeroize()? It's
> currently not a code path that is run because we only set
> BDRV_REQ_ZERO_WRITE for truncate if the image has a backing file, and
> data_file_is_raw() doesn't work with backing files.

Good point.

> 
> But hypothetically, if someone called truncate with BDRV_REQ_ZERO_WRITE
> for such a file, I think it would fail.
> 
>> If so,
>>
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>>
>> otherwise, you may have to treat the tail specially, the same way you
>> treated an unaligned head.
> 
> Actually, do I even need to round the tail?
> 
>      /* Caller must pass aligned values, except at image end */
>      assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
>      assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
>             end_offset == bs->total_sectors << BDRV_SECTOR_BITS);
> 
> So qcow2_cluster_zeroize() seems to accept the unaligned tail. It would
> still set the zero flag for the partial last cluster and for the
> external data file, bdrv_co_pwrite_zeroes() would have the correct size.

Then I'm in favor of NOT rounding the tail.  That's an easy enough 
change and we've now justified that it does what we want, so R-b stands 
with that one-line tweak.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org

Re: [PATCH v5 1/9] block: Add flags to BlockDriver.bdrv_co_truncate()

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> This adds a new BdrvRequestFlags parameter to the .bdrv_co_truncate()
> driver callbacks, and a supported_truncate_flags field in
> BlockDriverState that allows drivers to advertise support for request
> flags in the context of truncate.
> 
> For now, we always pass 0 and no drivers declare support for any flag.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  include/block/block_int.h   | 10 +++++++++-
>  block/crypto.c              |  3 ++-
>  block/file-posix.c          |  2 +-
>  block/file-win32.c          |  2 +-
>  block/gluster.c             |  1 +
>  block/io.c                  |  8 +++++++-
>  block/iscsi.c               |  2 +-
>  block/nfs.c                 |  3 ++-
>  block/qcow2.c               |  2 +-
>  block/qed.c                 |  1 +
>  block/raw-format.c          |  2 +-
>  block/rbd.c                 |  1 +
>  block/sheepdog.c            |  4 ++--
>  block/ssh.c                 |  2 +-
>  tests/test-block-iothread.c |  3 ++-
>  15 files changed, 33 insertions(+), 13 deletions(-)

(I know I haven’t complained before, so *shrug*, but I wonder now
whether it actually makes sense to have the same BdrvRequestFlags for
all request types.  Or why we have the same flags type for read, write,
and zero-write already.)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 2/9] block: Add flags to bdrv(_co)_truncate()

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> Now that block drivers can support flags for .bdrv_co_truncate, expose
> the parameter in the node level interfaces bdrv_co_truncate() and
> bdrv_truncate().
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  include/block/block.h       |  5 +++--
>  block/block-backend.c       |  2 +-
>  block/crypto.c              |  2 +-
>  block/io.c                  | 12 +++++++-----
>  block/parallels.c           |  6 +++---
>  block/qcow.c                |  4 ++--
>  block/qcow2-refcount.c      |  2 +-
>  block/qcow2.c               | 15 +++++++++------
>  block/raw-format.c          |  2 +-
>  block/vhdx-log.c            |  2 +-
>  block/vhdx.c                |  2 +-
>  block/vmdk.c                |  2 +-
>  tests/test-block-iothread.c |  6 +++---
>  13 files changed, 34 insertions(+), 28 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 3/9] block-backend: Add flags to blk_truncate()

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> Now that node level interface bdrv_truncate() supports passing request
> flags to the block driver, expose this on the BlockBackend level, too.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  include/sysemu/block-backend.h | 2 +-
>  block.c                        | 3 ++-
>  block/block-backend.c          | 4 ++--
>  block/commit.c                 | 4 ++--
>  block/crypto.c                 | 2 +-
>  block/mirror.c                 | 2 +-
>  block/qcow2.c                  | 4 ++--
>  block/qed.c                    | 2 +-
>  block/vdi.c                    | 2 +-
>  block/vhdx.c                   | 4 ++--
>  block/vmdk.c                   | 6 +++---
>  block/vpc.c                    | 2 +-
>  blockdev.c                     | 2 +-
>  qemu-img.c                     | 2 +-
>  qemu-io-cmds.c                 | 2 +-
>  15 files changed, 22 insertions(+), 21 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
> qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
> undo any previous preallocation, but just adds the zero flag to all
> relevant L2 entries. If an external data file is in use, a write_zeroes
> request to the data file is made instead.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/qcow2.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/block/qcow2.c b/block/qcow2.c
> index 9cfbdfc939..bd632405d1 100644
> --- a/block/qcow2.c
> +++ b/block/qcow2.c

[...]

> @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
>          g_assert_not_reached();
>      }
>  
> +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
> +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
> +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
> +
> +        /* Use zero clusters as much as we can */
> +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);

It’s kind of a pity that this changes the cluster mappings that were
established when using falloc/full preallocation already (i.e., they
become preallocated zero clusters then, so when writing to them, we need
COW again).

But falloc/full preallocation do not guarantee that the new data is
zero, so I suppose this is the only thing we can reasonably do.

I personally don’t really care about whether zero_end is aligned or not,
so either way:

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 5/9] raw-format: Support BDRV_REQ_ZERO_WRITE for truncate

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> The raw format driver can simply forward the flag and let its bs->file
> child take care of actually providing the zeros.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/raw-format.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 6/9] file-posix: Support BDRV_REQ_ZERO_WRITE for truncate

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> For regular files, we always get BDRV_REQ_ZERO_WRITE behaviour from the
> OS, so we can advertise the flag and just ignore it.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  block/file-posix.c | 4 ++++
>  1 file changed, 4 insertions(+)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 7/9] block: truncate: Don't make backing file data visible

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> When extending the size of an image that has a backing file larger than
> its old size, make sure that the backing file data doesn't become
> visible in the guest, but the added area is properly zeroed out.
> 
> Consider the following scenario where the overlay is shorter than its
> backing file:
> 
>     base.qcow2:     AAAAAAAA
>     overlay.qcow2:  BBBB
> 
> When resizing (extending) overlay.qcow2, the new blocks should not stay
> unallocated and make the additional As from base.qcow2 visible like
> before this patch, but zeros should be read.
> 
> A similar case happens with the various variants of a commit job when an
> intermediate file is short (- for unallocated):
> 
>     base.qcow2:     A-A-AAAA
>     mid.qcow2:      BB-B
>     top.qcow2:      C--C--C-
> 
> After commit top.qcow2 to mid.qcow2, the following happens:
> 
>     mid.qcow2:      CB-C00C0 (correct result)
>     mid.qcow2:      CB-C--C- (before this fix)
> 
> Without the fix, blocks that previously read as zeros on top.qcow2
> suddenly turn into A.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> Reviewed-by: Alberto Garcia <berto@igalia.com>
> ---
>  block/io.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/block/io.c b/block/io.c
> index 795075954e..8fbb607515 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -3394,6 +3394,20 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
>          goto out;
>      }
>  
> +    /*
> +     * If the image has a backing file that is large enough that it would
> +     * provide data for the new area, we cannot leave it unallocated because
> +     * then the backing file content would become visible. Instead, zero-fill
> +     * the new area.
> +     *
> +     * Note that if the image has a backing file, but was opened without the
> +     * backing file, taking care of keeping things consistent with that backing
> +     * file is the user's responsibility.
> +     */
> +    if (new_bytes && bs->backing) {
> +        flags |= BDRV_REQ_ZERO_WRITE;
> +    }

This breaks growing any non-qcow2 image with any backing file.  Do we
care about that?

The comment says something about “a backing file that is large enough
that it would provide data for the new area”, but that condition doesn’t
appear in the code.  Should it?  (If it did, I think the number of cases
this change broke would be much smaller.)

If it was deliberate to not have that condition here, and if we decide
that we don’t care about non-qcow2 formats here, then I think at least
the error message deserves some improvement over “qemu-img: Block driver
does not support requested flags”.

Max


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Re: [PATCH v5 8/9] iotests: Filter testfiles out in filter_img_info()

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> We want to keep TEST_IMG for the full path of the main test image, but
> filter_testfiles() must be called for other test images before replacing
> other things like the image format because the test directory path could
> contain the format as a substring.
> 
> Insert a filter_testfiles() call between both.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  tests/qemu-iotests/iotests.py | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 9/9] iotests: Test committing to short backing file

[Max Reitz]

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On 22.04.20 17:21, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  tests/qemu-iotests/274     | 157 ++++++++++++++++++++++
>  tests/qemu-iotests/274.out | 260 +++++++++++++++++++++++++++++++++++++
>  tests/qemu-iotests/group   |   1 +
>  3 files changed, 418 insertions(+)
>  create mode 100755 tests/qemu-iotests/274
>  create mode 100644 tests/qemu-iotests/274.out

Reviewed-by: Max Reitz <mreitz@redhat.com>


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Re: [PATCH v5 1/9] block: Add flags to BlockDriver.bdrv_co_truncate()

[Kevin Wolf]

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Am 23.04.2020 um 11:41 hat Max Reitz geschrieben:
> On 22.04.20 17:21, Kevin Wolf wrote:
> > This adds a new BdrvRequestFlags parameter to the .bdrv_co_truncate()
> > driver callbacks, and a supported_truncate_flags field in
> > BlockDriverState that allows drivers to advertise support for request
> > flags in the context of truncate.
> > 
> > For now, we always pass 0 and no drivers declare support for any flag.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> > Reviewed-by: Alberto Garcia <berto@igalia.com>
> > ---
> >  include/block/block_int.h   | 10 +++++++++-
> >  block/crypto.c              |  3 ++-
> >  block/file-posix.c          |  2 +-
> >  block/file-win32.c          |  2 +-
> >  block/gluster.c             |  1 +
> >  block/io.c                  |  8 +++++++-
> >  block/iscsi.c               |  2 +-
> >  block/nfs.c                 |  3 ++-
> >  block/qcow2.c               |  2 +-
> >  block/qed.c                 |  1 +
> >  block/raw-format.c          |  2 +-
> >  block/rbd.c                 |  1 +
> >  block/sheepdog.c            |  4 ++--
> >  block/ssh.c                 |  2 +-
> >  tests/test-block-iothread.c |  3 ++-
> >  15 files changed, 33 insertions(+), 13 deletions(-)
> 
> (I know I haven’t complained before, so *shrug*, but I wonder now
> whether it actually makes sense to have the same BdrvRequestFlags for
> all request types.  Or why we have the same flags type for read, write,
> and zero-write already.)

Yeah, nothing this series introduces. I wonder, too, but as long as we
have enough bits to cover flags for all request types, and because we
have overlaps between the request types, it might be easier to have only
one set of flags. So it might be accidental, but I actually feel the
current state isn't bad.

Kevin

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Re: [PATCH v5 7/9] block: truncate: Don't make backing file data visible

[Kevin Wolf]

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Am 23.04.2020 um 13:14 hat Max Reitz geschrieben:
> On 22.04.20 17:21, Kevin Wolf wrote:
> > When extending the size of an image that has a backing file larger than
> > its old size, make sure that the backing file data doesn't become
> > visible in the guest, but the added area is properly zeroed out.
> > 
> > Consider the following scenario where the overlay is shorter than its
> > backing file:
> > 
> >     base.qcow2:     AAAAAAAA
> >     overlay.qcow2:  BBBB
> > 
> > When resizing (extending) overlay.qcow2, the new blocks should not stay
> > unallocated and make the additional As from base.qcow2 visible like
> > before this patch, but zeros should be read.
> > 
> > A similar case happens with the various variants of a commit job when an
> > intermediate file is short (- for unallocated):
> > 
> >     base.qcow2:     A-A-AAAA
> >     mid.qcow2:      BB-B
> >     top.qcow2:      C--C--C-
> > 
> > After commit top.qcow2 to mid.qcow2, the following happens:
> > 
> >     mid.qcow2:      CB-C00C0 (correct result)
> >     mid.qcow2:      CB-C--C- (before this fix)
> > 
> > Without the fix, blocks that previously read as zeros on top.qcow2
> > suddenly turn into A.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > Reviewed-by: Alberto Garcia <berto@igalia.com>
> > ---
> >  block/io.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> > 
> > diff --git a/block/io.c b/block/io.c
> > index 795075954e..8fbb607515 100644
> > --- a/block/io.c
> > +++ b/block/io.c
> > @@ -3394,6 +3394,20 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
> >          goto out;
> >      }
> >  
> > +    /*
> > +     * If the image has a backing file that is large enough that it would
> > +     * provide data for the new area, we cannot leave it unallocated because
> > +     * then the backing file content would become visible. Instead, zero-fill
> > +     * the new area.
> > +     *
> > +     * Note that if the image has a backing file, but was opened without the
> > +     * backing file, taking care of keeping things consistent with that backing
> > +     * file is the user's responsibility.
> > +     */
> > +    if (new_bytes && bs->backing) {
> > +        flags |= BDRV_REQ_ZERO_WRITE;
> > +    }
> 
> This breaks growing any non-qcow2 image with any backing file.  Do we
> care about that?
> 
> The comment says something about “a backing file that is large enough
> that it would provide data for the new area”, but that condition doesn’t
> appear in the code.  Should it?  (If it did, I think the number of cases
> this change broke would be much smaller.)
> 
> If it was deliberate to not have that condition here, and if we decide
> that we don’t care about non-qcow2 formats here, then I think at least
> the error message deserves some improvement over “qemu-img: Block driver
> does not support requested flags”.

This was not deliberate. v3 had the check and I'm not sure why I removed
it. Probably because the new approach felt so much simpler and I was
glad that I could throw away complicated code that I threw away more
than I should have...

Kevin

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Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

Am 22.04.2020 um 18:14 hat Eric Blake geschrieben:
> On 4/22/20 10:58 AM, Kevin Wolf wrote:
> 
> > > > @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
> > > >            g_assert_not_reached();
> > > >        }
> > > > +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
> > > > +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
> > > > +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
> > > 
> > > This rounds up beyond the new size...
> > > 
> > > > +
> > > > +        /* Use zero clusters as much as we can */
> > > > +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
> > > 
> > > and then requests that the extra be zeroed.  Does that always work, even
> > > when it results in pdrv_co_pwrite_zeroes beyond the end of s->data_file?
> > 
> > You mean the data_file_is_raw() path in qcow2_cluster_zeroize()? It's
> > currently not a code path that is run because we only set
> > BDRV_REQ_ZERO_WRITE for truncate if the image has a backing file, and
> > data_file_is_raw() doesn't work with backing files.
> 
> Good point.
> 
> > 
> > But hypothetically, if someone called truncate with BDRV_REQ_ZERO_WRITE
> > for such a file, I think it would fail.
> > 
> > > If so,
> > > 
> > > Reviewed-by: Eric Blake <eblake@redhat.com>
> > > 
> > > otherwise, you may have to treat the tail specially, the same way you
> > > treated an unaligned head.
> > 
> > Actually, do I even need to round the tail?
> > 
> >      /* Caller must pass aligned values, except at image end */
> >      assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
> >      assert(QEMU_IS_ALIGNED(end_offset, s->cluster_size) ||
> >             end_offset == bs->total_sectors << BDRV_SECTOR_BITS);
> > 
> > So qcow2_cluster_zeroize() seems to accept the unaligned tail. It would
> > still set the zero flag for the partial last cluster and for the
> > external data file, bdrv_co_pwrite_zeroes() would have the correct size.
> 
> Then I'm in favor of NOT rounding the tail.  That's an easy enough change
> and we've now justified that it does what we want, so R-b stands with that
> one-line tweak.

Would have been too easy... bs->total_sectors isn't updated yet, so the
assertion does fail.

I can make the assertion check end_offset >= ... instead. That should
still check what we wanted to check here and allow the unaligned
extension.

This feels like the better option to me compared to updating
bs->total_sectors earlier and then undoing that change in every error
path.

Kevin

Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Kevin Wolf]

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Am 23.04.2020 um 12:53 hat Max Reitz geschrieben:
> On 22.04.20 17:21, Kevin Wolf wrote:
> > If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
> > qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
> > undo any previous preallocation, but just adds the zero flag to all
> > relevant L2 entries. If an external data file is in use, a write_zeroes
> > request to the data file is made instead.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> >  block/qcow2.c | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> > 
> > diff --git a/block/qcow2.c b/block/qcow2.c
> > index 9cfbdfc939..bd632405d1 100644
> > --- a/block/qcow2.c
> > +++ b/block/qcow2.c
> 
> [...]
> 
> > @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
> >          g_assert_not_reached();
> >      }
> >  
> > +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
> > +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
> > +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
> > +
> > +        /* Use zero clusters as much as we can */
> > +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
> 
> It’s kind of a pity that this changes the cluster mappings that were
> established when using falloc/full preallocation already (i.e., they
> become preallocated zero clusters then, so when writing to them, we need
> COW again).
> 
> But falloc/full preallocation do not guarantee that the new data is
> zero, so I suppose this is the only thing we can reasonably do.

If we really want, I guess we could make full preallocation first try
passing BDRV_REQ_ZERO_WRITE to the protocol layer and if that succeeds,
we could skip setting the zero cluster flag at the qcow2 level.

Feels like a separate patch, though.

Kevin

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Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Max Reitz]

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On 23.04.20 15:25, Kevin Wolf wrote:
> Am 23.04.2020 um 12:53 hat Max Reitz geschrieben:
>> On 22.04.20 17:21, Kevin Wolf wrote:
>>> If BDRV_REQ_ZERO_WRITE is set and we're extending the image, calling
>>> qcow2_cluster_zeroize() with flags=0 does the right thing: It doesn't
>>> undo any previous preallocation, but just adds the zero flag to all
>>> relevant L2 entries. If an external data file is in use, a write_zeroes
>>> request to the data file is made instead.
>>>
>>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>>> ---
>>>  block/qcow2.c | 30 ++++++++++++++++++++++++++++++
>>>  1 file changed, 30 insertions(+)
>>>
>>> diff --git a/block/qcow2.c b/block/qcow2.c
>>> index 9cfbdfc939..bd632405d1 100644
>>> --- a/block/qcow2.c
>>> +++ b/block/qcow2.c
>>
>> [...]
>>
>>> @@ -4214,6 +4215,35 @@ static int coroutine_fn qcow2_co_truncate(BlockDriverState *bs, int64_t offset,
>>>          g_assert_not_reached();
>>>      }
>>>  
>>> +    if ((flags & BDRV_REQ_ZERO_WRITE) && offset > old_length) {
>>> +        uint64_t zero_start = QEMU_ALIGN_UP(old_length, s->cluster_size);
>>> +        uint64_t zero_end = QEMU_ALIGN_UP(offset, s->cluster_size);
>>> +
>>> +        /* Use zero clusters as much as we can */
>>> +        ret = qcow2_cluster_zeroize(bs, zero_start, zero_end - zero_start, 0);
>>
>> It’s kind of a pity that this changes the cluster mappings that were
>> established when using falloc/full preallocation already (i.e., they
>> become preallocated zero clusters then, so when writing to them, we need
>> COW again).
>>
>> But falloc/full preallocation do not guarantee that the new data is
>> zero, so I suppose this is the only thing we can reasonably do.
> 
> If we really want, I guess we could make full preallocation first try
> passing BDRV_REQ_ZERO_WRITE to the protocol layer and if that succeeds,
> we could skip setting the zero cluster flag at the qcow2 level.

That might be nice.

> Feels like a separate patch, though.

Definitely, yes.

Max


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Re: [PATCH v5 4/9] qcow2: Support BDRV_REQ_ZERO_WRITE for truncate

[Eric Blake]

On 4/23/20 8:23 AM, Kevin Wolf wrote:

>>>
>>> So qcow2_cluster_zeroize() seems to accept the unaligned tail. It would
>>> still set the zero flag for the partial last cluster and for the
>>> external data file, bdrv_co_pwrite_zeroes() would have the correct size.
>>
>> Then I'm in favor of NOT rounding the tail.  That's an easy enough change
>> and we've now justified that it does what we want, so R-b stands with that
>> one-line tweak.
> 
> Would have been too easy... bs->total_sectors isn't updated yet, so the
> assertion does fail.
> 
> I can make the assertion check end_offset >= ... instead. That should
> still check what we wanted to check here and allow the unaligned
> extension.

Yes, that works for me.

> 
> This feels like the better option to me compared to updating
> bs->total_sectors earlier and then undoing that change in every error
> path.

Indeed.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org