[Qemu-devel] [PATCH] SCSI: splite write_zero in unit of at most INT_MAX bytes

[Ming Lei]

Currently block can not handle big write well when write
size is bigger than INT_MAX, so split the write zero into
smaller size of chunks to meet block's requirement.

This patch fixes one WRITE SAME 16 failure in linux VM side.

Cc: Max Reitz <address@hidden>
Signed-off-by: Ming Lei <address@hidden>
---
 hw/scsi/scsi-disk.c |   67 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 57 insertions(+), 10 deletions(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 2f75d7d..a843f9b 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -42,6 +42,9 @@ do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)
 #include <scsi/sg.h>
 #endif
 
+/* bytes in one single write should be held in one 'int' variable */
+#define SCSI_WRITE_ZERO_MAX         (INT_MAX)
+
 #define SCSI_WRITE_SAME_MAX         524288
 #define SCSI_DMA_BUF_SIZE           131072
 #define SCSI_MAX_INQUIRY_LEN        256
@@ -1618,10 +1621,53 @@ typedef struct WriteSameCBData {
     SCSIDiskReq *r;
     int64_t sector;
     int nb_sectors;
+    int curr_sectors;
+    int flags;
     QEMUIOVector qiov;
     struct iovec iov;
 } WriteSameCBData;
 
+static void scsi_write_zero_complete(void *opaque, int ret)
+{
+    WriteSameCBData *data = opaque;
+    SCSIDiskReq *r = data->r;
+    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+
+    assert(r->req.aiocb != NULL);
+    r->req.aiocb = NULL;
+    block_acct_done(blk_get_stats(s->qdev.conf.blk), &r->acct);
+    if (r->req.io_canceled) {
+        scsi_req_cancel_complete(&r->req);
+        goto done;
+    }
+
+    if (ret < 0) {
+        if (scsi_handle_rw_error(r, -ret)) {
+            goto done;
+        }
+    }
+
+    data->nb_sectors -= data->curr_sectors;
+    data->sector += data->curr_sectors;
+    data->curr_sectors = MIN(data->nb_sectors, SCSI_WRITE_ZERO_MAX / 512);
+    if (data->nb_sectors) {
+        block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
+                         data->curr_sectors * s->qdev.blocksize,
+                         BLOCK_ACCT_WRITE);
+        r->req.aiocb = blk_aio_write_zeroes(s->qdev.conf.blk,
+                                data->sector,
+                                data->curr_sectors,
+                                data->flags, scsi_write_zero_complete, data);
+        return;
+    }
+
+    scsi_req_complete(&r->req, GOOD);
+
+done:
+    scsi_req_unref(&r->req);
+    g_free(data);
+}
+
 static void scsi_write_same_complete(void *opaque, int ret)
 {
     WriteSameCBData *data = opaque;
@@ -1686,25 +1732,26 @@ static void scsi_disk_emulate_write_same(SCSIDiskReq 
*r, uint8_t *inbuf)
         return;
     }
 
+    data = g_new0(WriteSameCBData, 1);
+    data->r = r;
+    data->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
+    data->nb_sectors = nb_sectors * (s->qdev.blocksize / 512);
+    data->curr_sectors = MIN(data->nb_sectors, SCSI_WRITE_ZERO_MAX / 512);
     if (buffer_is_zero(inbuf, s->qdev.blocksize)) {
-        int flags = (req->cmd.buf[1] & 0x8) ? BDRV_REQ_MAY_UNMAP : 0;
+        data->flags = (req->cmd.buf[1] & 0x8) ? BDRV_REQ_MAY_UNMAP : 0;
 
         /* The request is used as the AIO opaque value, so add a ref.  */
         scsi_req_ref(&r->req);
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
-                         nb_sectors * s->qdev.blocksize,
-                        BLOCK_ACCT_WRITE);
+                         data->curr_sectors * s->qdev.blocksize,
+                         BLOCK_ACCT_WRITE);
         r->req.aiocb = blk_aio_write_zeroes(s->qdev.conf.blk,
-                                r->req.cmd.lba * (s->qdev.blocksize / 512),
-                                nb_sectors * (s->qdev.blocksize / 512),
-                                flags, scsi_aio_complete, r);
+                                data->sector,
+                                data->curr_sectors,
+                                data->flags, scsi_write_zero_complete, data);
         return;
     }
 
-    data = g_new0(WriteSameCBData, 1);
-    data->r = r;
-    data->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
-    data->nb_sectors = nb_sectors * (s->qdev.blocksize / 512);
     data->iov.iov_len = MIN(data->nb_sectors * 512, SCSI_WRITE_SAME_MAX);
     data->iov.iov_base = buf = blk_blockalign(s->qdev.conf.blk,
                                               data->iov.iov_len);
-- 
1.7.9.5