Re: [Qemu-block] [PATCH v2 1/6] mirror: Discard target sectors if not allocated at source side

[wangxiaolong]

I just wander if bdrv_is_allocated_above works as it is considered,

migrate image in format of qcow2 run into such backtrace:

#0  0x00007f9e73822c6d in lseek64 () at ../sysdeps/unix/syscall-template.S:82

#1  0x00007f9e765f08e4 in find_allocation (bs=<value optimized out>,

    sector_num=<value optimized out>, nb_sectors=20480, pnum=0x7f9e7bab00fc)

    at block/raw-posix.c:1285

#2  raw_co_get_block_status (bs=<value optimized out>,

    sector_num=<value optimized out>, nb_sectors=20480, pnum=0x7f9e7bab00fc)

    at block/raw-posix.c:1381

#3  0x00007f9e765cfe61 in bdrv_co_get_block_status (bs=0x7f9e790e4300, sector_num=

    22470528, nb_sectors=20480, pnum=0x7f9e7bab00fc) at block.c:3593

#4  0x00007f9e765cffa8 in bdrv_co_get_block_status (bs=0x7f9e790e00a0, sector_num=

    22466560, nb_sectors=<value optimized out>, pnum=0x7f9e7bab00fc)

    at block.c:3620

#5  0x00007f9e765cfff7 in bdrv_get_block_status_co_entry (opaque=0x7f9e7bab0080)

    at block.c:3639

#6  0x00007f9e765d0088 in bdrv_get_block_status (bs=<value optimized out>,

    sector_num=<value optimized out>, nb_sectors=<value optimized out>,

    pnum=<value optimized out>) at block.c:3663

#7  0x00007f9e765d00a9 in bdrv_is_allocated (bs=0x7f9e790e00a0,

    sector_num=<value optimized out>, nb_sectors=<value optimized out>,

    pnum=<value optimized out>) at block.c:3677

#8  0x00007f9e765d0166 in bdrv_is_allocated_above (top=0x7f9e790e00a0, base=0x0,

    sector_num=22466560, nb_sectors=20480, pnum=0x7f9e7bab020c) at block.c:3709

#9  0x00007f9e765dcf9e in mirror_iteration (opaque=0x7f9e79486110)

    at block/mirror.c:305

#10 mirror_run (opaque=0x7f9e79486110) at block/mirror.c:430

#11 0x00007f9e766120eb in coroutine_trampoline (i0=<value optimized out>,

    i1=<value optimized out>) at coroutine-ucontext.c:118

#12 0x00007f9e734c4b70 in ?? () from /lib64/libc.so.6

#13 0x00007ffffa897850 in ?? ()

#14 0x0000000000000000 in ?? ()

it is too slow to tolerate…...

 Original Message 

Sender: Fam Zheng<f...@redhat.com>

Recipient: qemu-devel<qemu-de...@nongnu.org>

Cc: Kevin Wolf<kw...@redhat.com>; Stefan Hajnoczi<stefa...@redhat.com>; qemu-block<qemu-block@nongnu.org>; pbonzini<pbonz...@redhat.com>; jsnow<js...@redhat.com>; wangxiaolong<wangxiaol...@ucloud.cn>

Date: Wednesday, May 6, 2015 12:52

Subject: [PATCH v2 1/6] mirror: Discard target sectors if not allocated at source side

If guest discards a source cluster during mirror, we would want to
discard target side as well.

Signed-off-by: Fam Zheng <f...@redhat.com>
---
 block/mirror.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 58f391a..37a5b61 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -163,6 +163,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
     int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
     uint64_t delay_ns = 0;
     MirrorOp *op;
+    int pnum;
 
     s->sector_num = hbitmap_iter_next(&s->hbi);
     if (s->sector_num < 0) {
@@ -289,8 +290,15 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
     s->in_flight++;
     s->sectors_in_flight += nb_sectors;
     trace_mirror_one_iteration(s, sector_num, nb_sectors);
-    bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
-                   mirror_read_complete, op);
+
+    if (!bdrv_is_allocated_above(source, NULL, sector_num,
+                                 nb_sectors, &pnum)) {
+        bdrv_aio_discard(s->target, sector_num, nb_sectors,
+                         mirror_write_complete, op);
+    } else {
+        bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
+                       mirror_read_complete, op);
+    }
     return delay_ns;
 }
 
-- 
1.9.3