From 69e802baf506bd21a2f444cfebe4ac7f5b5d07a8 Mon Sep 17 00:00:00 2001

Message-Id: <69e802baf506bd21a2f444cfebe4ac7f5b5d07a8.1389014116.git.minovotn@redhat.com>

In-Reply-To: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>

References: <c8cc35838d42aa286242772d97e3a9be7bb786ba.1389014116.git.minovotn@redhat.com>

From: Paolo Bonzini <pbonzini@redhat.com>

Date: Mon, 9 Dec 2013 14:09:02 +0100

Subject: [PATCH 14/50] block: honour BlockLimits in bdrv_co_do_write_zeroes

RH-Author: Paolo Bonzini <pbonzini@redhat.com>

Message-id: <1386598178-11845-17-git-send-email-pbonzini@redhat.com>

Patchwork-id: 56052

O-Subject: [RHEL 7.0 qemu-kvm PATCH 16/52] block: honour BlockLimits in bdrv_co_do_write_zeroes

Bugzilla: 1007815

RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

RH-Acked-by: Fam Zheng <famz@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

From: Peter Lieven <pl@kamp.de>

Reviewed-by: Eric Blake <eblake@redhat.com>

Signed-off-by: Peter Lieven <pl@kamp.de>

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

(cherry picked from commit c31cb70728d2c0c8900b35a66784baa446fd5147)

---

 block.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++----------------

 1 file changed, 49 insertions(+), 16 deletions(-)

Signed-off-by: Michal Novotny <minovotn@redhat.com>

---

 block.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++----------------

 1 file changed, 49 insertions(+), 16 deletions(-)

diff --git a/block.c b/block.c

index 2fae459..2ed9aa9 100644

--- a/block.c

+++ b/block.c

@@ -2724,32 +2724,65 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,

                             BDRV_REQ_COPY_ON_READ);

 }

+/* if no limit is specified in the BlockLimits use a default

+ * of 32768 512-byte sectors (16 MiB) per request.

+ */

+#define MAX_WRITE_ZEROES_DEFAULT 32768

+

 static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,

     int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)

 {

     BlockDriver *drv = bs->drv;

     QEMUIOVector qiov;

-    struct iovec iov;

-    int ret;

+    struct iovec iov = {0};

+    int ret = 0;

-    /* TODO Emulate only part of misaligned requests instead of letting block

-     * drivers return -ENOTSUP and emulate everything */

+    int max_write_zeroes = bs->bl.max_write_zeroes ?

+                           bs->bl.max_write_zeroes : MAX_WRITE_ZEROES_DEFAULT;

-    /* First try the efficient write zeroes operation */

-    if (drv->bdrv_co_write_zeroes) {

-        ret = drv->bdrv_co_write_zeroes(bs, sector_num, nb_sectors, flags);

-        if (ret != -ENOTSUP) {

-            return ret;

+    while (nb_sectors > 0 && !ret) {

+        int num = nb_sectors;

+

+        /* align request */

+        if (bs->bl.write_zeroes_alignment &&

+            num >= bs->bl.write_zeroes_alignment &&

+            sector_num % bs->bl.write_zeroes_alignment) {

+            if (num > bs->bl.write_zeroes_alignment) {

+                num = bs->bl.write_zeroes_alignment;

+            }

+            num -= sector_num % bs->bl.write_zeroes_alignment;

         }

-    }

-    /* Fall back to bounce buffer if write zeroes is unsupported */

-    iov.iov_len  = nb_sectors * BDRV_SECTOR_SIZE;

-    iov.iov_base = qemu_blockalign(bs, iov.iov_len);

-    memset(iov.iov_base, 0, iov.iov_len);

-    qemu_iovec_init_external(&qiov, &iov, 1);

+        /* limit request size */

+        if (num > max_write_zeroes) {

+            num = max_write_zeroes;

+        }

+

+        ret = -ENOTSUP;

+        /* First try the efficient write zeroes operation */

+        if (drv->bdrv_co_write_zeroes) {

+            ret = drv->bdrv_co_write_zeroes(bs, sector_num, num, flags);

+        }

+

+        if (ret == -ENOTSUP) {

+            /* Fall back to bounce buffer if write zeroes is unsupported */

+            iov.iov_len = num * BDRV_SECTOR_SIZE;

+            if (iov.iov_base == NULL) {

+                /* allocate bounce buffer only once and ensure that it

+                 * is big enough for this and all future requests.

+                 */

+                size_t bufsize = num <= nb_sectors ? num : max_write_zeroes;

+                iov.iov_base = qemu_blockalign(bs, bufsize * BDRV_SECTOR_SIZE);

+                memset(iov.iov_base, 0, bufsize * BDRV_SECTOR_SIZE);

+            }

+            qemu_iovec_init_external(&qiov, &iov, 1);

-    ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, &qiov);

+            ret = drv->bdrv_co_writev(bs, sector_num, num, &qiov);

+        }

+

+        sector_num += num;

+        nb_sectors -= num;

+    }

     qemu_vfree(iov.iov_base);

     return ret;

-- 

1.7.11.7