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

[MORITA Kazutaka]

This introduces a qemu-img create option for sheepdog which allows the
data to be preallocated (note that sheepdog always preallocates
metadata).  This is necessary to use Sheepdog volumes as a backend
storage for iSCSI target.  More information is available at
https://sourceforge.net/apps/trac/sheepdog/wiki/General%20Protocol%20Support

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

qemu-img create sheepdog:test -o preallocation=data 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 |   73 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 72 insertions(+), 1 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 0392ca8..38ca9aa 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1292,6 +1292,57 @@ static int do_sd_create(char *filename, int64_t vdi_size,
     return 0;
 }
 
+static int sd_prealloc(uint32_t vid, int64_t vdi_size)
+{
+    int fd, ret;
+    SheepdogInode *inode;
+    char *buf;
+    unsigned long idx, max_idx;
+
+    fd = connect_to_sdog(NULL, NULL);
+    if (fd < 0) {
+        return -EIO;
+    }
+
+    inode = qemu_malloc(sizeof(*inode));
+    buf = qemu_malloc(SD_DATA_OBJ_SIZE);
+
+    ret = read_object(fd, (char *)inode, vid_to_vdi_oid(vid),
+                      0, sizeof(*inode), 0);
+
+    max_idx = (vdi_size + SD_DATA_OBJ_SIZE - 1) / SD_DATA_OBJ_SIZE;
+
+    for (idx = 0; idx < max_idx; idx++) {
+        uint64_t oid;
+        oid = vid_to_data_oid(vid, idx);
+
+        if (inode->data_vdi_id[idx]) {
+            ret = read_object(fd, buf, vid_to_vdi_oid(inode->data_vdi_id[idx]),
+                              1, SD_DATA_OBJ_SIZE, 0);
+            if (ret)
+                goto out;
+        } else {
+            memset(buf, 0, SD_DATA_OBJ_SIZE);
+        }
+
+        ret = write_object(fd, buf, oid, 1, SD_DATA_OBJ_SIZE, 0, 1);
+        if (ret)
+            goto out;
+
+        inode->data_vdi_id[idx] = vid;
+        ret = write_object(fd, (char *)inode, vid_to_vdi_oid(vid),
+                           1, sizeof(*inode), 0, 0);
+        if (ret)
+            goto out;
+    }
+out:
+    free(inode);
+    free(buf);
+    closesocket(fd);
+
+    return ret;
+}
+
 static int sd_create(const char *filename, QEMUOptionParameter *options)
 {
     int ret;
@@ -1301,6 +1352,7 @@ 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;
 
     strstart(filename, "sheepdog:", (const char **)&filename);
 
@@ -1317,6 +1369,16 @@ 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, "data")) {
+                prealloc = 1;
+            } else {
+                error_report("Invalid preallocation mode: '%s'\n",
+                    options->value.s);
+                return -EINVAL;
+            }
         }
         options++;
     }
@@ -1354,7 +1416,11 @@ 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((char *)vdi, vdi_size, base_vid, &vid, 0, s.addr, s.port);
+    if (!prealloc || ret)
+        return ret;
+
+    return sd_prealloc(vid, vdi_size);
 }
 
 static void sd_close(BlockDriverState *bs)
@@ -1990,6 +2056,11 @@ 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, data)"
+    },
     { NULL }
 };
 
-- 
1.5.6.5