[Sheepdog] [PATCH v2] sheepdog: add full data preallocation support

[MORITA Kazutaka]

This introduces qemu-img create option for sheepdog which allows the
data to be fully preallocated (note that sheepdog always preallocates
metadata).

The option is disabled by default and you need to enable it like the
following:

qemu-img create sheepdog:test -o preallocation=full 1G

Signed-off-by: MORITA Kazutaka <morita.kazutaka at lab.ntt.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori at lab.ntt.co.jp>
---
 block/sheepdog.c |   71 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 68 insertions(+), 3 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 0392ca8..5b1eb57 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1292,6 +1292,49 @@ static int do_sd_create(char *filename, int64_t vdi_size,
     return 0;
 }
 
+static int sd_prealloc(const char *filename)
+{
+    BlockDriverState *bs = NULL;
+    uint32_t idx, max_idx;
+    int64_t vdi_size;
+    void *buf = qemu_mallocz(SD_DATA_OBJ_SIZE);
+    int ret;
+
+    ret = bdrv_file_open(&bs, filename, BDRV_O_RDWR);
+    if (ret < 0) {
+        goto out;
+    }
+
+    vdi_size = bdrv_getlength(bs);
+    if (vdi_size < 0) {
+        ret = vdi_size;
+        goto out;
+    }
+    max_idx = DIV_ROUND_UP(vdi_size, SD_DATA_OBJ_SIZE);
+
+    for (idx = 0; idx < max_idx; idx++) {
+        /*
+         * The created image can be a cloned image, so we need to read
+         * a data from the source image.
+         */
+        ret = bdrv_pread(bs, idx * SD_DATA_OBJ_SIZE, buf, SD_DATA_OBJ_SIZE);
+        if (ret < 0) {
+            goto out;
+        }
+        ret = bdrv_pwrite(bs, idx * SD_DATA_OBJ_SIZE, buf, SD_DATA_OBJ_SIZE);
+        if (ret < 0) {
+            goto out;
+        }
+    }
+out:
+    if (bs) {
+        bdrv_delete(bs);
+    }
+    qemu_free(buf);
+
+    return ret;
+}
+
 static int sd_create(const char *filename, QEMUOptionParameter *options)
 {
     int ret;
@@ -1301,13 +1344,15 @@ static int sd_create(const char *filename, QEMUOptionParameter *options)
     BDRVSheepdogState s;
     char vdi[SD_MAX_VDI_LEN], tag[SD_MAX_VDI_TAG_LEN];
     uint32_t snapid;
+    int prealloc = 0;
+    const char *vdiname;
 
-    strstart(filename, "sheepdog:", (const char **)&filename);
+    strstart(filename, "sheepdog:", &vdiname);
 
     memset(&s, 0, sizeof(s));
     memset(vdi, 0, sizeof(vdi));
     memset(tag, 0, sizeof(tag));
-    if (parse_vdiname(&s, filename, vdi, &snapid, tag) < 0) {
+    if (parse_vdiname(&s, vdiname, vdi, &snapid, tag) < 0) {
         error_report("invalid filename\n");
         return -EINVAL;
     }
@@ -1317,6 +1362,16 @@ static int sd_create(const char *filename, QEMUOptionParameter *options)
             vdi_size = options->value.n;
         } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
             backing_file = options->value.s;
+        } else if (!strcmp(options->name, BLOCK_OPT_PREALLOC)) {
+            if (!options->value.s || !strcmp(options->value.s, "off")) {
+                prealloc = 0;
+            } else if (!strcmp(options->value.s, "full")) {
+                prealloc = 1;
+            } else {
+                error_report("Invalid preallocation mode: '%s'",
+                             options->value.s);
+                return -EINVAL;
+            }
         }
         options++;
     }
@@ -1354,7 +1409,12 @@ static int sd_create(const char *filename, QEMUOptionParameter *options)
         bdrv_delete(bs);
     }
 
-    return do_sd_create((char *)vdi, vdi_size, base_vid, &vid, 0, s.addr, s.port);
+    ret = do_sd_create(vdi, vdi_size, base_vid, &vid, 0, s.addr, s.port);
+    if (!prealloc || ret) {
+        return ret;
+    }
+
+    return sd_prealloc(filename);
 }
 
 static void sd_close(BlockDriverState *bs)
@@ -1990,6 +2050,11 @@ static QEMUOptionParameter sd_create_options[] = {
         .type = OPT_STRING,
         .help = "File name of a base image"
     },
+    {
+        .name = BLOCK_OPT_PREALLOC,
+        .type = OPT_STRING,
+        .help = "Preallocation mode (allowed values: off, full)"
+    },
     { NULL }
 };
 
-- 
1.7.2.5