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From 39ee3b773c08395007137198542c2012e11295f5 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Mon, 2 Dec 2013 16:09:46 +0100
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Subject: [PATCH 12/37] block: Introduce bdrv_co_do_preadv()
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Message-id: <1392117622-28812-13-git-send-email-kwolf@redhat.com>
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Patchwork-id: 57177
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O-Subject: [RHEL-7.0 qemu-kvm PATCH v2 12/37] block: Introduce bdrv_co_do_preadv()
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Bugzilla: 748906
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Max Reitz <mreitz@redhat.com>
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Similar to bdrv_pread(), which aligns byte-aligned request to 512 byte
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sectors, bdrv_co_do_preadv() takes a byte-aligned request and aligns it
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to the alignment specified in bs->request_alignment.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Max Reitz <mreitz@redhat.com>
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Reviewed-by: Benoit Canet <benoit@irqsave.net>
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(cherry picked from commit 1b0288ae7fc695a8e652973f75e92464bbc13416)
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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---
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 block.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
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 1 file changed, 58 insertions(+), 6 deletions(-)
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---
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 block.c |   64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
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 1 files changed, 58 insertions(+), 6 deletions(-)
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diff --git a/block.c b/block.c
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index 1787ab0..ce3edb0 100644
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--- a/block.c
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+++ b/block.c
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@@ -2809,17 +2809,23 @@ out:
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 /*
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  * Handle a read request in coroutine context
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  */
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-static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
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-    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
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+static int coroutine_fn bdrv_co_do_preadv(BlockDriverState *bs,
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+    int64_t offset, unsigned int bytes, QEMUIOVector *qiov,
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     BdrvRequestFlags flags)
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 {
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     BlockDriver *drv = bs->drv;
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+    /* TODO Lift BDRV_SECTOR_SIZE restriction in BlockDriver interface */
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+    uint64_t align = MAX(BDRV_SECTOR_SIZE, bs->request_alignment);
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+    uint8_t *head_buf = NULL;
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+    uint8_t *tail_buf = NULL;
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+    QEMUIOVector local_qiov;
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+    bool use_local_qiov = false;
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     int ret;
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     if (!drv) {
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         return -ENOMEDIUM;
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     }
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-    if (bdrv_check_request(bs, sector_num, nb_sectors)) {
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+    if (bdrv_check_byte_request(bs, offset, bytes)) {
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         return -EIO;
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     }
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@@ -2829,14 +2835,60 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
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     /* throttling disk I/O */
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     if (bs->io_limits_enabled) {
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-        bdrv_io_limits_intercept(bs, false, nb_sectors);
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+        /* TODO Switch to byte granularity */
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+        bdrv_io_limits_intercept(bs, false, bytes >> BDRV_SECTOR_BITS);
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+    }
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+
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+    /* Align read if necessary by padding qiov */
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+    if (offset & (align - 1)) {
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+        head_buf = qemu_blockalign(bs, align);
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+        qemu_iovec_init(&local_qiov, qiov->niov + 2);
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+        qemu_iovec_add(&local_qiov, head_buf, offset & (align - 1));
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+        qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
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+        use_local_qiov = true;
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+
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+        bytes += offset & (align - 1);
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+        offset = offset & ~(align - 1);
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+    }
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+
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+    if ((offset + bytes) & (align - 1)) {
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+        if (!use_local_qiov) {
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+            qemu_iovec_init(&local_qiov, qiov->niov + 1);
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+            qemu_iovec_concat(&local_qiov, qiov, 0, qiov->size);
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+            use_local_qiov = true;
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+        }
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+        tail_buf = qemu_blockalign(bs, align);
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+        qemu_iovec_add(&local_qiov, tail_buf,
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+                       align - ((offset + bytes) & (align - 1)));
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+
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+        bytes = ROUND_UP(bytes, align);
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+    }
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+
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+    ret = bdrv_aligned_preadv(bs, offset, bytes,
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+                              use_local_qiov ? &local_qiov : qiov,
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+                              flags);
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+
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+    if (use_local_qiov) {
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+        qemu_iovec_destroy(&local_qiov);
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+        qemu_vfree(head_buf);
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+        qemu_vfree(tail_buf);
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     }
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-    ret = bdrv_aligned_preadv(bs, sector_num << BDRV_SECTOR_BITS,
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-                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
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     return ret;
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 }
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+static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
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+    int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
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+    BdrvRequestFlags flags)
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+{
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+    if (nb_sectors < 0 || nb_sectors > (UINT_MAX >> BDRV_SECTOR_BITS)) {
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+        return -EINVAL;
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+    }
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+
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+    return bdrv_co_do_preadv(bs, sector_num << BDRV_SECTOR_BITS,
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+                             nb_sectors << BDRV_SECTOR_BITS, qiov, flags);
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+}
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+
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 int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
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     int nb_sectors, QEMUIOVector *qiov)
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 {
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-- 
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1.7.1
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