block: vhdx write support

This adds support for writing to VHDX image files, using coroutines.
Writes into the BAT table goes through the VHDX log.  Currently, BAT
table writes occur when expanding a dynamic VHDX file, and allocating a
new BAT entry.
Signed-off-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

block/vhdx.c

@@ -914,7 +914,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
         if (payblocks--) {
             /* payload bat entries */
             if ((s->bat[i] & VHDX_BAT_STATE_BIT_MASK) ==
-                    PAYLOAD_BLOCK_FULL_PRESENT) {
+                    PAYLOAD_BLOCK_FULLY_PRESENT) {
                 ret = vhdx_region_check(s, s->bat[i] & VHDX_BAT_FILE_OFF_MASK,
                                         s->block_size);
                 if (ret < 0) {
@@ -935,7 +935,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
         }
     }
 
-    /* TODO: differencing files, write */
+    /* TODO: differencing files */
 
     /* Disable migration when VHDX images are used */
     error_set(&s->migration_blocker,
@@ -1040,7 +1040,7 @@ static coroutine_fn int vhdx_co_readv(BlockDriverState *bs, int64_t sector_num,
                 /* return zero */
                 qemu_iovec_memset(&hd_qiov, 0, 0, sinfo.bytes_avail);
                 break;
-            case PAYLOAD_BLOCK_FULL_PRESENT:
+            case PAYLOAD_BLOCK_FULLY_PRESENT:
                 qemu_co_mutex_unlock(&s->lock);
                 ret = bdrv_co_readv(bs->file,
                                     sinfo.file_offset >> BDRV_SECTOR_BITS,
@@ -1070,7 +1070,43 @@ exit:
     return ret;
 }
 
+/*
+ * Allocate a new payload block at the end of the file.
+ *
+ * Allocation will happen at 1MB alignment inside the file
+ *
+ * Returns the file offset start of the new payload block
+ */
+static int vhdx_allocate_block(BlockDriverState *bs, BDRVVHDXState *s,
+                                    uint64_t *new_offset)
+{
+    *new_offset = bdrv_getlength(bs->file);
+
+    /* per the spec, the address for a block is in units of 1MB */
+    *new_offset = ROUND_UP(*new_offset, 1024 * 1024);
+
+    return bdrv_truncate(bs->file, *new_offset + s->block_size);
+}
+
+/*
+ * Update the BAT table entry with the new file offset, and the new entry
+ * state */
+static void vhdx_update_bat_table_entry(BlockDriverState *bs, BDRVVHDXState *s,
+                                       VHDXSectorInfo *sinfo,
+                                       uint64_t *bat_entry_le,
+                                       uint64_t *bat_offset, int state)
+{
+    /* The BAT entry is a uint64, with 44 bits for the file offset in units of
+     * 1MB, and 3 bits for the block state. */
+    s->bat[sinfo->bat_idx]  = ((sinfo->file_offset>>20) <<
+                               VHDX_BAT_FILE_OFF_BITS);
 
+    s->bat[sinfo->bat_idx] |= state & VHDX_BAT_STATE_BIT_MASK;
+
+    *bat_entry_le = cpu_to_le64(s->bat[sinfo->bat_idx]);
+    *bat_offset = s->bat_offset + sinfo->bat_idx * sizeof(VHDXBatEntry);
+
+}
 
 /* Per the spec, on the first write of guest-visible data to the file the
  * data write guid must be updated in the header */
@@ -1087,7 +1123,175 @@ int vhdx_user_visible_write(BlockDriverState *bs, BDRVVHDXState *s)
 static coroutine_fn int vhdx_co_writev(BlockDriverState *bs, int64_t sector_num,
                                       int nb_sectors, QEMUIOVector *qiov)
 {
-    return -ENOTSUP;
+    int ret = -ENOTSUP;
+    BDRVVHDXState *s = bs->opaque;
+    VHDXSectorInfo sinfo;
+    uint64_t bytes_done = 0;
+    uint64_t bat_entry = 0;
+    uint64_t bat_entry_offset = 0;
+    QEMUIOVector hd_qiov;
+    struct iovec iov1 = { 0 };
+    struct iovec iov2 = { 0 };
+    int sectors_to_write;
+    int bat_state;
+    uint64_t bat_prior_offset = 0;
+    bool bat_update = false;
+
+    qemu_iovec_init(&hd_qiov, qiov->niov);
+
+    qemu_co_mutex_lock(&s->lock);
+
+    ret = vhdx_user_visible_write(bs, s);
+    if (ret < 0) {
+        goto exit;
+    }
+
+    while (nb_sectors > 0) {
+        bool use_zero_buffers = false;
+        bat_update = false;
+        if (s->params.data_bits & VHDX_PARAMS_HAS_PARENT) {
+            /* not supported yet */
+            ret = -ENOTSUP;
+            goto exit;
+        } else {
+            vhdx_block_translate(s, sector_num, nb_sectors, &sinfo);
+            sectors_to_write = sinfo.sectors_avail;
+
+            qemu_iovec_reset(&hd_qiov);
+            /* check the payload block state */
+            bat_state = s->bat[sinfo.bat_idx] & VHDX_BAT_STATE_BIT_MASK;
+            switch (bat_state) {
+            case PAYLOAD_BLOCK_ZERO:
+                /* in this case, we need to preserve zero writes for
+                 * data that is not part of this write, so we must pad
+                 * the rest of the buffer to zeroes */
+
+                /* if we are on a posix system with ftruncate() that extends
+                 * a file, then it is zero-filled for us.  On Win32, the raw
+                 * layer uses SetFilePointer and SetFileEnd, which does not
+                 * zero fill AFAIK */
+
+                /* Queue another write of zero buffers if the underlying file
+                 * does not zero-fill on file extension */
+
+                if (bdrv_has_zero_init(bs->file) == 0) {
+                    use_zero_buffers = true;
+
+                    /* zero fill the front, if any */
+                    if (sinfo.block_offset) {
+                        iov1.iov_len = sinfo.block_offset;
+                        iov1.iov_base = qemu_blockalign(bs, iov1.iov_len);
+                        memset(iov1.iov_base, 0, iov1.iov_len);
+                        qemu_iovec_concat_iov(&hd_qiov, &iov1, 1, 0,
+                                              sinfo.block_offset);
+                        sectors_to_write += iov1.iov_len >> BDRV_SECTOR_BITS;
+                    }
+
+                    /* our actual data */
+                    qemu_iovec_concat(&hd_qiov, qiov,  bytes_done,
+                                      sinfo.bytes_avail);
+
+                    /* zero fill the back, if any */
+                    if ((sinfo.bytes_avail - sinfo.block_offset) <
+                         s->block_size) {
+                        iov2.iov_len = s->block_size -
+                                      (sinfo.bytes_avail + sinfo.block_offset);
+                        iov2.iov_base = qemu_blockalign(bs, iov2.iov_len);
+                        memset(iov2.iov_base, 0, iov2.iov_len);
+                        qemu_iovec_concat_iov(&hd_qiov, &iov2, 1, 0,
+                                              sinfo.block_offset);
+                        sectors_to_write += iov2.iov_len >> BDRV_SECTOR_BITS;
+                    }
+                }
+
+                /* fall through */
+            case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
+            case PAYLOAD_BLOCK_UNMAPPED:    /* fall through */
+            case PAYLOAD_BLOCK_UNDEFINED:   /* fall through */
+                bat_prior_offset = sinfo.file_offset;
+                ret = vhdx_allocate_block(bs, s, &sinfo.file_offset);
+                if (ret < 0) {
+                    goto exit;
+                }
+                /* once we support differencing files, this may also be
+                 * partially present */
+                /* update block state to the newly specified state */
+                vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
+                                            &bat_entry_offset,
+                                            PAYLOAD_BLOCK_FULLY_PRESENT);
+                bat_update = true;
+                /* since we just allocated a block, file_offset is the
+                 * beginning of the payload block. It needs to be the
+                 * write address, which includes the offset into the block */
+                if (!use_zero_buffers) {
+                    sinfo.file_offset += sinfo.block_offset;
+                }
+                /* fall through */
+            case PAYLOAD_BLOCK_FULLY_PRESENT:
+                /* if the file offset address is in the header zone,
+                 * there is a problem */
+                if (sinfo.file_offset < (1024 * 1024)) {
+                    ret = -EFAULT;
+                    goto error_bat_restore;
+                }
+
+                if (!use_zero_buffers) {
+                    qemu_iovec_concat(&hd_qiov, qiov,  bytes_done,
+                                      sinfo.bytes_avail);
+                }
+                /* block exists, so we can just overwrite it */
+                qemu_co_mutex_unlock(&s->lock);
+                ret = bdrv_co_writev(bs->file,
+                                    sinfo.file_offset >> BDRV_SECTOR_BITS,
+                                    sectors_to_write, &hd_qiov);
+                qemu_co_mutex_lock(&s->lock);
+                if (ret < 0) {
+                    goto error_bat_restore;
+                }
+                break;
+            case PAYLOAD_BLOCK_PARTIALLY_PRESENT:
+                /* we don't yet support difference files, fall through
+                 * to error */
+            default:
+                ret = -EIO;
+                goto exit;
+                break;
+            }
+
+            if (bat_update) {
+                /* this will update the BAT entry into the log journal, and
+                 * then flush the log journal out to disk */
+                ret =  vhdx_log_write_and_flush(bs, s, &bat_entry,
+                                                sizeof(VHDXBatEntry),
+                                                bat_entry_offset);
+                if (ret < 0) {
+                    goto exit;
+                }
+            }
+
+            nb_sectors -= sinfo.sectors_avail;
+            sector_num += sinfo.sectors_avail;
+            bytes_done += sinfo.bytes_avail;
+
+        }
+    }
+
+    goto exit;
+
+error_bat_restore:
+    if (bat_update) {
+        /* keep metadata in sync, and restore the bat entry state
+         * if error. */
+        sinfo.file_offset = bat_prior_offset;
+        vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
+                                    &bat_entry_offset, bat_state);
+    }
+exit:
+    qemu_vfree(iov1.iov_base);
+    qemu_vfree(iov2.iov_base);
+    qemu_co_mutex_unlock(&s->lock);
+    qemu_iovec_destroy(&hd_qiov);
+    return ret;
 }
 
 

block/vhdx.h

@@ -217,7 +217,7 @@ typedef struct QEMU_PACKED VHDXLogDataSector {
 #define PAYLOAD_BLOCK_UNDEFINED         1
 #define PAYLOAD_BLOCK_ZERO              2
 #define PAYLOAD_BLOCK_UNMAPPED          5
-#define PAYLOAD_BLOCK_FULL_PRESENT      6
+#define PAYLOAD_BLOCK_FULLY_PRESENT     6
 #define PAYLOAD_BLOCK_PARTIALLY_PRESENT 7
 
 #define SB_BLOCK_NOT_PRESENT    0