Patchwork [v2] sheepdog: implement SD_OP_FLUSH_VDI operation

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Submitter namei.unix@gmail.com
Date April 3, 2012, 5:15 a.m.
Message ID <1333430140-21372-1-git-send-email-namei.unix@gmail.com>
Download mbox | patch
Permalink /patch/150321/
State New
Headers show

Comments

namei.unix@gmail.com - April 3, 2012, 5:15 a.m.
From: Liu Yuan <tailai.ly@taobao.com>

Flush operation is supposed to flush the write-back cache of
sheepdog cluster.

By issuing flush operation, we can assure the Guest of data
reaching the sheepdog cluster storage.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Michael Tokarev <mjt@tls.msk.ru>
Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
---
 v1 -> v2:
 address Michael Tokarev comments. Thanks !
  - use per-device flag
  - use bs->fd instead of 'connect_to_sdog()'
 block/sheepdog.c |   81 ++++++++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 67 insertions(+), 14 deletions(-)
Stefan Hajnoczi - April 3, 2012, 7:23 a.m.
On Tue, Apr 03, 2012 at 01:15:40PM +0800, Liu Yuan wrote:
> +static int coroutine_fn sd_co_flush_to_disk(BlockDriverState *bs)
> +{
> +    BDRVSheepdogState *s = bs->opaque;
> +    SheepdogObjReq hdr = { 0 };
> +    SheepdogObjRsp *rsp = (SheepdogObjRsp *)&hdr;
> +    SheepdogInode *inode = &s->inode;
> +    int ret;
> +    unsigned int wlen = 0, rlen = 0;
> +
> +    if (!s->cache_enabled)
> +        return 0;
> +
> +    hdr.opcode = SD_OP_FLUSH_VDI;
> +    hdr.oid = vid_to_vdi_oid(inode->vdi_id);
> +
> +    ret = do_req(s->fd, (SheepdogReq *)&hdr, NULL, &wlen, &rlen);
> +    if (ret) {
> +        error_report("failed to send a request to the sheep");
> +        return -1;
> +    }
> +
> +    if (rsp->result != SD_RES_SUCCESS) {
> +        error_report("%s", sd_strerror(rsp->result));
> +        return -1;
> +    }
> +
> +    return 0;
> +}

.bdrv_co_flush_to_disk() is a coroutine_fn so that it can yield while
waiting for socket I/O.  Using do_req() defeats its purpose and will
pause both the guest and QEMU's own monitor/VNC/etc while waiting for
the sheepdog server to communicate with us.

You should use coroutine send/recv functions - they yield if the socket
returns EAGAIN/EWOULDBLOCK.

Also please return negative errno values instead of -1 (which is
-EPERM).

Stefan

Patch

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 00276f6f..dbac629 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -32,9 +32,11 @@ 
 #define SD_OP_RELEASE_VDI    0x13
 #define SD_OP_GET_VDI_INFO   0x14
 #define SD_OP_READ_VDIS      0x15
+#define SD_OP_FLUSH_VDI      0x16
 
 #define SD_FLAG_CMD_WRITE    0x01
 #define SD_FLAG_CMD_COW      0x02
+#define SD_FLAG_CMD_CACHE    0x04
 
 #define SD_RES_SUCCESS       0x00 /* Success */
 #define SD_RES_UNKNOWN       0x01 /* Unknown error */
@@ -293,6 +295,7 @@  typedef struct BDRVSheepdogState {
 
     char name[SD_MAX_VDI_LEN];
     int is_snapshot;
+    uint8_t cache_enabled;
 
     char *addr;
     char *port;
@@ -900,6 +903,10 @@  static int coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
         hdr.flags = SD_FLAG_CMD_WRITE | flags;
     }
 
+    if (s->cache_enabled) {
+        hdr.flags |= SD_FLAG_CMD_CACHE;
+    }
+
     hdr.oid = oid;
     hdr.cow_oid = old_oid;
     hdr.copies = s->inode.nr_copies;
@@ -942,7 +949,7 @@  static int coroutine_fn add_aio_request(BDRVSheepdogState *s, AIOReq *aio_req,
 
 static int read_write_object(int fd, char *buf, uint64_t oid, int copies,
                              unsigned int datalen, uint64_t offset,
-                             int write, int create)
+                             int write, int create, uint8_t cache)
 {
     SheepdogObjReq hdr;
     SheepdogObjRsp *rsp = (SheepdogObjRsp *)&hdr;
@@ -965,6 +972,11 @@  static int read_write_object(int fd, char *buf, uint64_t oid, int copies,
         rlen = datalen;
         hdr.opcode = SD_OP_READ_OBJ;
     }
+
+    if (cache) {
+        hdr.flags |= SD_FLAG_CMD_CACHE;
+    }
+
     hdr.oid = oid;
     hdr.data_length = datalen;
     hdr.offset = offset;
@@ -986,15 +998,18 @@  static int read_write_object(int fd, char *buf, uint64_t oid, int copies,
 }
 
 static int read_object(int fd, char *buf, uint64_t oid, int copies,
-                       unsigned int datalen, uint64_t offset)
+                       unsigned int datalen, uint64_t offset, uint8_t cache)
 {
-    return read_write_object(fd, buf, oid, copies, datalen, offset, 0, 0);
+    return read_write_object(fd, buf, oid, copies, datalen, offset, 0, 0,
+                             cache);
 }
 
 static int write_object(int fd, char *buf, uint64_t oid, int copies,
-                        unsigned int datalen, uint64_t offset, int create)
+                        unsigned int datalen, uint64_t offset, int create,
+                        uint8_t cache)
 {
-    return read_write_object(fd, buf, oid, copies, datalen, offset, 1, create);
+    return read_write_object(fd, buf, oid, copies, datalen, offset, 1, create,
+                             cache);
 }
 
 static int sd_open(BlockDriverState *bs, const char *filename, int flags)
@@ -1011,6 +1026,10 @@  static int sd_open(BlockDriverState *bs, const char *filename, int flags)
     QLIST_INIT(&s->outstanding_aio_head);
     s->fd = -1;
 
+    if (flags & BDRV_O_CACHE_WB) {
+        s->cache_enabled = 1;
+    }
+
     memset(vdi, 0, sizeof(vdi));
     memset(tag, 0, sizeof(tag));
     if (parse_vdiname(s, filename, vdi, &snapid, tag) < 0) {
@@ -1038,7 +1057,8 @@  static int sd_open(BlockDriverState *bs, const char *filename, int flags)
     }
 
     buf = g_malloc(SD_INODE_SIZE);
-    ret = read_object(fd, buf, vid_to_vdi_oid(vid), 0, SD_INODE_SIZE, 0);
+    ret = read_object(fd, buf, vid_to_vdi_oid(vid), 0, SD_INODE_SIZE, 0,
+                      s->cache_enabled);
 
     closesocket(fd);
 
@@ -1305,7 +1325,7 @@  static int sd_truncate(BlockDriverState *bs, int64_t offset)
     datalen = SD_INODE_SIZE - sizeof(s->inode.data_vdi_id);
     s->inode.vdi_size = offset;
     ret = write_object(fd, (char *)&s->inode, vid_to_vdi_oid(s->inode.vdi_id),
-                       s->inode.nr_copies, datalen, 0, 0);
+                       s->inode.nr_copies, datalen, 0, 0, s->cache_enabled);
     close(fd);
 
     if (ret < 0) {
@@ -1387,7 +1407,7 @@  static int sd_create_branch(BDRVSheepdogState *s)
     }
 
     ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
-                      SD_INODE_SIZE, 0);
+                      SD_INODE_SIZE, 0, s->cache_enabled);
 
     closesocket(fd);
 
@@ -1575,6 +1595,35 @@  static coroutine_fn int sd_co_readv(BlockDriverState *bs, int64_t sector_num,
     return acb->ret;
 }
 
+static int coroutine_fn sd_co_flush_to_disk(BlockDriverState *bs)
+{
+    BDRVSheepdogState *s = bs->opaque;
+    SheepdogObjReq hdr = { 0 };
+    SheepdogObjRsp *rsp = (SheepdogObjRsp *)&hdr;
+    SheepdogInode *inode = &s->inode;
+    int ret;
+    unsigned int wlen = 0, rlen = 0;
+
+    if (!s->cache_enabled)
+        return 0;
+
+    hdr.opcode = SD_OP_FLUSH_VDI;
+    hdr.oid = vid_to_vdi_oid(inode->vdi_id);
+
+    ret = do_req(s->fd, (SheepdogReq *)&hdr, NULL, &wlen, &rlen);
+    if (ret) {
+        error_report("failed to send a request to the sheep");
+        return -1;
+    }
+
+    if (rsp->result != SD_RES_SUCCESS) {
+        error_report("%s", sd_strerror(rsp->result));
+        return -1;
+    }
+
+    return 0;
+}
+
 static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
 {
     BDRVSheepdogState *s = bs->opaque;
@@ -1610,7 +1659,7 @@  static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
     }
 
     ret = write_object(fd, (char *)&s->inode, vid_to_vdi_oid(s->inode.vdi_id),
-                       s->inode.nr_copies, datalen, 0, 0);
+                       s->inode.nr_copies, datalen, 0, 0, s->cache_enabled);
     if (ret < 0) {
         error_report("failed to write snapshot's inode.");
         ret = -EIO;
@@ -1629,7 +1678,7 @@  static int sd_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
     inode = (SheepdogInode *)g_malloc(datalen);
 
     ret = read_object(fd, (char *)inode, vid_to_vdi_oid(new_vid),
-                      s->inode.nr_copies, datalen, 0);
+                      s->inode.nr_copies, datalen, 0, s->cache_enabled);
 
     if (ret < 0) {
         error_report("failed to read new inode info. %s", strerror(errno));
@@ -1684,7 +1733,7 @@  static int sd_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
 
     buf = g_malloc(SD_INODE_SIZE);
     ret = read_object(fd, buf, vid_to_vdi_oid(vid), s->inode.nr_copies,
-                      SD_INODE_SIZE, 0);
+                      SD_INODE_SIZE, 0, s->cache_enabled);
 
     closesocket(fd);
 
@@ -1779,7 +1828,8 @@  static int sd_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
 
         /* we don't need to read entire object */
         ret = read_object(fd, (char *)&inode, vid_to_vdi_oid(vid),
-                          0, SD_INODE_SIZE - sizeof(inode.data_vdi_id), 0);
+                          0, SD_INODE_SIZE - sizeof(inode.data_vdi_id), 0,
+                          s->cache_enabled);
 
         if (ret) {
             continue;
@@ -1835,10 +1885,12 @@  static int do_load_save_vmstate(BDRVSheepdogState *s, uint8_t *data,
         create = (offset == 0);
         if (load) {
             ret = read_object(fd, (char *)data, vmstate_oid,
-                              s->inode.nr_copies, data_len, offset);
+                              s->inode.nr_copies, data_len, offset,
+                              s->cache_enabled);
         } else {
             ret = write_object(fd, (char *)data, vmstate_oid,
-                               s->inode.nr_copies, data_len, offset, create);
+                               s->inode.nr_copies, data_len, offset, create,
+                               s->cache_enabled);
         }
 
         if (ret < 0) {
@@ -1904,6 +1956,7 @@  BlockDriver bdrv_sheepdog = {
 
     .bdrv_co_readv  = sd_co_readv,
     .bdrv_co_writev = sd_co_writev,
+    .bdrv_co_flush_to_disk  = sd_co_flush_to_disk,
 
     .bdrv_snapshot_create   = sd_snapshot_create,
     .bdrv_snapshot_goto     = sd_snapshot_goto,