From 39ee3b773c08395007137198542c2012e11295f5 Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Mon, 2 Dec 2013 16:09:46 +0100

Subject: [PATCH 12/37] block: Introduce bdrv_co_do_preadv()

Message-id: <1392117622-28812-13-git-send-email-kwolf@redhat.com>

Patchwork-id: 57177

O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 12/37] block: Introduce bdrv_co_do_preadv()

Bugzilla: 748906

RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

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

RH-Acked-by: Max Reitz <mreitz@redhat.com>

Similar to bdrv_pread(), which aligns byte-aligned request to 512 byte

sectors, bdrv_co_do_preadv() takes a byte-aligned request and aligns it

to the alignment specified in bs->request_alignment.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-by: Max Reitz <mreitz@redhat.com>

Reviewed-by: Benoit Canet <benoit@irqsave.net>

(cherry picked from commit 1b0288ae7fc695a8e652973f75e92464bbc13416)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

---

 block.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------

 1 file changed, 58 insertions(+), 6 deletions(-)

---

 block.c |   64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----

 1 files changed, 58 insertions(+), 6 deletions(-)

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

index 1787ab0..ce3edb0 100644

--- a/block.c

+++ b/block.c

@@ -2809,17 +2809,23 @@ out:

 /*

  * Handle a read request in coroutine context

  */

-static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,

-    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,

+static int coroutine_fn bdrv_co_do_preadv(BlockDriverState *bs,

+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov,

     BdrvRequestFlags flags)

 {

     BlockDriver *drv = bs->drv;

+    /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */

+    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);

+    uint8_t *head_buf = NULL;

+    uint8_t *tail_buf = NULL;

+    QEMUIOVector local_qiov;

+    bool use_local_qiov = false;

     int ret;

     if (!drv) {

         return -ENOMEDIUM;

     }

-    if (bdrv_check_request(bs, sector_num, nb_sectors)) {

+    if (bdrv_check_byte_request(bs, offset, bytes)) {

         return -EIO;

     }

@@ -2829,14 +2835,60 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,

     /* throttling disk I/O */

     if (bs->io_limits_enabled) {

-        bdrv_io_limits_intercept(bs, false, nb_sectors);

+        /* TODO Switch to byte granularity */

+        bdrv_io_limits_intercept(bs, false, bytes >> BDRV_SECTOR_BITS);

+    }

+

+    /* Align read if necessary by padding qiov */

+    if (offset & (align - 1)) {

+        head_buf = qemu_blockalign(bs, align);

+        qemu_iovec_init(&local_qiov, qiov->niov + 2);

+        qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));

+        qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);

+        use_local_qiov = true;

+

+        bytes += offset & (align - 1);

+        offset = offset & ~(align - 1);

+    }

+

+    if ((offset + bytes) & (align - 1)) {

+        if (!use_local_qiov) {

+            qemu_iovec_init(&local_qiov, qiov->niov + 1);

+            qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);

+            use_local_qiov = true;

+        }

+        tail_buf = qemu_blockalign(bs, align);

+        qemu_iovec_add(&local_qiov, tail_buf,

+                       align - ((offset + bytes) & (align - 1)));

+

+        bytes = ROUND_UP(bytes, align);

+    }

+

+    ret = bdrv_aligned_preadv(bs, offset, bytes,

+                              use_local_qiov ? &local_qiov : qiov,

+                              flags);

+

+    if (use_local_qiov) {

+        qemu_iovec_destroy(&local_qiov);

+        qemu_vfree(head_buf);

+        qemu_vfree(tail_buf);

     }

-    ret = bdrv_aligned_preadv(bs, sector_num << BDRV_SECTOR_BITS,

-                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);

     return ret;

 }

+static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,

+    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,

+    BdrvRequestFlags flags)

+{

+    if (nb_sectors < 0 || nb_sectors > (UINT_MAX >> BDRV_SECTOR_BITS)) {

+        return -EINVAL;

+    }

+

+    return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,

+                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);

+}

+

 int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,

     int nb_sectors, QEMUIOVector *qiov)

 {

-- 

1.7.1