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[Qemu-devel] [PATCH 2/6] block: Prepare bdrv_aligned_preadv() for byte-a
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PATCH 2/6] block: Prepare bdrv_aligned_preadv() for byte-aligned requests |
Date: |
Wed, 8 Jun 2016 16:10:07 +0200 |
This patch makes bdrv_aligned_preadv() ready to accept byte-aligned
requests. Note that this doesn't mean that such requests are actually
made. The caller still ensures that all requests are aligned to at least
512 bytes.
Signed-off-by: Kevin Wolf <address@hidden>
---
block/io.c | 41 +++++++++++++++++------------------------
1 file changed, 17 insertions(+), 24 deletions(-)
diff --git a/block/io.c b/block/io.c
index 3b34f20..2fd88cb 100644
--- a/block/io.c
+++ b/block/io.c
@@ -959,11 +959,6 @@ static int coroutine_fn
bdrv_aligned_preadv(BlockDriverState *bs,
{
int ret;
- int64_t sector_num = offset >> BDRV_SECTOR_BITS;
- unsigned int nb_sectors = bytes >> BDRV_SECTOR_BITS;
-
- assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
- assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
assert(!qiov || bytes == qiov->size);
assert((bs->open_flags & BDRV_O_NO_IO) == 0);
@@ -982,9 +977,12 @@ static int coroutine_fn
bdrv_aligned_preadv(BlockDriverState *bs,
}
if (flags & BDRV_REQ_COPY_ON_READ) {
+ int64_t start_sector = offset >> BDRV_SECTOR_BITS;
+ int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
+ unsigned int nb_sectors = end_sector - start_sector;
int pnum;
- ret = bdrv_is_allocated(bs, sector_num, nb_sectors, &pnum);
+ ret = bdrv_is_allocated(bs, start_sector, nb_sectors, &pnum);
if (ret < 0) {
goto out;
}
@@ -1000,28 +998,24 @@ static int coroutine_fn
bdrv_aligned_preadv(BlockDriverState *bs,
ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
} else {
/* Read zeros after EOF */
- int64_t total_sectors, max_nb_sectors;
+ int64_t total_bytes, max_bytes;
- total_sectors = bdrv_nb_sectors(bs);
- if (total_sectors < 0) {
- ret = total_sectors;
+ total_bytes = bdrv_getlength(bs);
+ if (total_bytes < 0) {
+ ret = total_bytes;
goto out;
}
- max_nb_sectors = ROUND_UP(MAX(0, total_sectors - sector_num),
- align >> BDRV_SECTOR_BITS);
- if (nb_sectors < max_nb_sectors) {
+ max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
+ if (bytes < max_bytes) {
ret = bdrv_driver_preadv(bs, offset, bytes, qiov, 0);
- } else if (max_nb_sectors > 0) {
+ } else if (max_bytes > 0) {
QEMUIOVector local_qiov;
qemu_iovec_init(&local_qiov, qiov->niov);
- qemu_iovec_concat(&local_qiov, qiov, 0,
- max_nb_sectors * BDRV_SECTOR_SIZE);
+ qemu_iovec_concat(&local_qiov, qiov, 0, max_bytes);
- ret = bdrv_driver_preadv(bs, offset,
- max_nb_sectors * BDRV_SECTOR_SIZE,
- &local_qiov, 0);
+ ret = bdrv_driver_preadv(bs, offset, max_bytes, &local_qiov, 0);
qemu_iovec_destroy(&local_qiov);
} else {
@@ -1029,11 +1023,10 @@ static int coroutine_fn
bdrv_aligned_preadv(BlockDriverState *bs,
}
/* Reading beyond end of file is supposed to produce zeroes */
- if (ret == 0 && total_sectors < sector_num + nb_sectors) {
- uint64_t offset = MAX(0, total_sectors - sector_num);
- uint64_t bytes = (sector_num + nb_sectors - offset) *
- BDRV_SECTOR_SIZE;
- qemu_iovec_memset(qiov, offset * BDRV_SECTOR_SIZE, 0, bytes);
+ if (ret == 0 && total_bytes < offset + bytes) {
+ uint64_t zero_offset = MAX(0, total_bytes - offset);
+ uint64_t zero_bytes = offset + bytes - zero_offset;
+ qemu_iovec_memset(qiov, zero_offset, 0, zero_bytes);
}
}
--
1.8.3.1