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authorKevin Wolf <kwolf@redhat.com>2013-12-02 16:09:46 +0100
committerKevin Wolf <kwolf@redhat.com>2014-01-24 17:40:02 +0100
commit1b0288ae7fc695a8e652973f75e92464bbc13416 (patch)
treeea5c8c95ed48aa5de2f967e13187b03779970804 /block.c
parentd0c7f642f5eb2cb21d0c3acf766cb375eaaf4666 (diff)
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block: Introduce bdrv_co_do_preadv()
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>
Diffstat (limited to 'block.c')
-rw-r--r--block.c64
1 files changed, 58 insertions, 6 deletions
diff --git a/block.c b/block.c
index 701e95af..fa4feb0 100644
--- a/block.c
+++ b/block.c
@@ -2971,17 +2971,23 @@ 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;
}
@@ -2991,14 +2997,60 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
/* throttling disk I/O */
if (bs->io_limits_enabled) {
- bdrv_io_limits_intercept(bs, nb_sectors, false);
+ /* TODO Switch to byte granularity */
+ bdrv_io_limits_intercept(bs, bytes >> BDRV_SECTOR_BITS, false);
+ }
+
+ /* 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)
{