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block/io: refactor padding
We have similar padding code in bdrv_co_pwritev, bdrv_co_do_pwrite_zeroes and bdrv_co_preadv. Let's combine and unify it. [Squashed in Vladimir's qemu-iotests 077 fix --Stefan] Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20190604161514.262241-4-vsementsov@virtuozzo.com Message-Id: <20190604161514.262241-4-vsementsov@virtuozzo.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy
Stefan Hajnoczi
parent
f76889e7b9
commit
7a3f542fbd
365
block/io.c
365
block/io.c
@ -1415,28 +1415,177 @@ out:
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}
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/*
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* Handle a read request in coroutine context
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* Request padding
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*
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* |<---- align ----->| |<----- align ---->|
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* |<- head ->|<------------- bytes ------------->|<-- tail -->|
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* | | | | | |
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* -*----------$-------*-------- ... --------*-----$------------*---
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* | | | | | |
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* | offset | | end |
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* ALIGN_DOWN(offset) ALIGN_UP(offset) ALIGN_DOWN(end) ALIGN_UP(end)
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* [buf ... ) [tail_buf )
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*
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* @buf is an aligned allocation needed to store @head and @tail paddings. @head
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* is placed at the beginning of @buf and @tail at the @end.
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*
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* @tail_buf is a pointer to sub-buffer, corresponding to align-sized chunk
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* around tail, if tail exists.
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*
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* @merge_reads is true for small requests,
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* if @buf_len == @head + bytes + @tail. In this case it is possible that both
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* head and tail exist but @buf_len == align and @tail_buf == @buf.
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*/
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typedef struct BdrvRequestPadding {
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uint8_t *buf;
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size_t buf_len;
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uint8_t *tail_buf;
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size_t head;
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size_t tail;
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bool merge_reads;
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QEMUIOVector local_qiov;
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} BdrvRequestPadding;
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static bool bdrv_init_padding(BlockDriverState *bs,
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int64_t offset, int64_t bytes,
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BdrvRequestPadding *pad)
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{
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uint64_t align = bs->bl.request_alignment;
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size_t sum;
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memset(pad, 0, sizeof(*pad));
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pad->head = offset & (align - 1);
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pad->tail = ((offset + bytes) & (align - 1));
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if (pad->tail) {
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pad->tail = align - pad->tail;
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}
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if ((!pad->head && !pad->tail) || !bytes) {
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return false;
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}
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sum = pad->head + bytes + pad->tail;
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pad->buf_len = (sum > align && pad->head && pad->tail) ? 2 * align : align;
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pad->buf = qemu_blockalign(bs, pad->buf_len);
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pad->merge_reads = sum == pad->buf_len;
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if (pad->tail) {
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pad->tail_buf = pad->buf + pad->buf_len - align;
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}
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return true;
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}
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static int bdrv_padding_rmw_read(BdrvChild *child,
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BdrvTrackedRequest *req,
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BdrvRequestPadding *pad,
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bool zero_middle)
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{
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QEMUIOVector local_qiov;
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BlockDriverState *bs = child->bs;
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uint64_t align = bs->bl.request_alignment;
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int ret;
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assert(req->serialising && pad->buf);
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if (pad->head || pad->merge_reads) {
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uint64_t bytes = pad->merge_reads ? pad->buf_len : align;
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qemu_iovec_init_buf(&local_qiov, pad->buf, bytes);
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if (pad->head) {
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
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}
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if (pad->merge_reads && pad->tail) {
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
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}
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ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes,
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align, &local_qiov, 0);
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if (ret < 0) {
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return ret;
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}
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if (pad->head) {
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
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}
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if (pad->merge_reads && pad->tail) {
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
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}
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if (pad->merge_reads) {
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goto zero_mem;
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}
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}
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if (pad->tail) {
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qemu_iovec_init_buf(&local_qiov, pad->tail_buf, align);
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
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ret = bdrv_aligned_preadv(
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child, req,
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req->overlap_offset + req->overlap_bytes - align,
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align, align, &local_qiov, 0);
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if (ret < 0) {
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return ret;
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}
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
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}
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zero_mem:
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if (zero_middle) {
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memset(pad->buf + pad->head, 0, pad->buf_len - pad->head - pad->tail);
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}
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return 0;
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}
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static void bdrv_padding_destroy(BdrvRequestPadding *pad)
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{
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if (pad->buf) {
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qemu_vfree(pad->buf);
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qemu_iovec_destroy(&pad->local_qiov);
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}
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}
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/*
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* bdrv_pad_request
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*
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* Exchange request parameters with padded request if needed. Don't include RMW
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* read of padding, bdrv_padding_rmw_read() should be called separately if
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* needed.
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*
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* All parameters except @bs are in-out: they represent original request at
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* function call and padded (if padding needed) at function finish.
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*
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* Function always succeeds.
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*/
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static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov,
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int64_t *offset, unsigned int *bytes,
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BdrvRequestPadding *pad)
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{
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if (!bdrv_init_padding(bs, *offset, *bytes, pad)) {
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return false;
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}
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qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head,
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*qiov, 0, *bytes,
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pad->buf + pad->buf_len - pad->tail, pad->tail);
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*bytes += pad->head + pad->tail;
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*offset -= pad->head;
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*qiov = &pad->local_qiov;
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return true;
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}
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int coroutine_fn bdrv_co_preadv(BdrvChild *child,
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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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BlockDriverState *bs = child->bs;
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BlockDriver *drv = bs->drv;
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BdrvTrackedRequest req;
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uint64_t align = bs->bl.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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BdrvRequestPadding pad;
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int ret;
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trace_bdrv_co_preadv(child->bs, offset, bytes, flags);
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if (!drv) {
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return -ENOMEDIUM;
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}
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trace_bdrv_co_preadv(bs, offset, bytes, flags);
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ret = bdrv_check_byte_request(bs, offset, bytes);
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if (ret < 0) {
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@ -1450,43 +1599,16 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child,
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flags |= BDRV_REQ_COPY_ON_READ;
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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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bytes += offset & (align - 1);
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offset = offset & ~(align - 1);
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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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bytes = ROUND_UP(bytes, align);
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}
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bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad);
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tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ);
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ret = bdrv_aligned_preadv(child, &req, offset, bytes, align,
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use_local_qiov ? &local_qiov : qiov,
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flags);
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ret = bdrv_aligned_preadv(child, &req, offset, bytes,
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bs->bl.request_alignment,
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qiov, flags);
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tracked_request_end(&req);
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bdrv_dec_in_flight(bs);
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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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bdrv_padding_destroy(&pad);
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return ret;
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}
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@ -1782,44 +1904,34 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
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BdrvTrackedRequest *req)
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{
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BlockDriverState *bs = child->bs;
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uint8_t *buf = NULL;
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QEMUIOVector local_qiov;
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uint64_t align = bs->bl.request_alignment;
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unsigned int head_padding_bytes, tail_padding_bytes;
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int ret = 0;
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bool padding;
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BdrvRequestPadding pad;
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head_padding_bytes = offset & (align - 1);
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tail_padding_bytes = (align - (offset + bytes)) & (align - 1);
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assert(flags & BDRV_REQ_ZERO_WRITE);
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if (head_padding_bytes || tail_padding_bytes) {
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buf = qemu_blockalign(bs, align);
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qemu_iovec_init_buf(&local_qiov, buf, align);
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}
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if (head_padding_bytes) {
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uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes);
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/* RMW the unaligned part before head. */
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padding = bdrv_init_padding(bs, offset, bytes, &pad);
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if (padding) {
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mark_request_serialising(req, align);
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wait_serialising_requests(req);
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
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ret = bdrv_aligned_preadv(child, req, offset & ~(align - 1), align,
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align, &local_qiov, 0);
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if (ret < 0) {
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goto fail;
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}
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
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memset(buf + head_padding_bytes, 0, zero_bytes);
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ret = bdrv_aligned_pwritev(child, req, offset & ~(align - 1), align,
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align, &local_qiov,
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flags & ~BDRV_REQ_ZERO_WRITE);
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if (ret < 0) {
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goto fail;
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bdrv_padding_rmw_read(child, req, &pad, true);
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if (pad.head || pad.merge_reads) {
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int64_t aligned_offset = offset & ~(align - 1);
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int64_t write_bytes = pad.merge_reads ? pad.buf_len : align;
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qemu_iovec_init_buf(&local_qiov, pad.buf, write_bytes);
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ret = bdrv_aligned_pwritev(child, req, aligned_offset, write_bytes,
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align, &local_qiov,
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flags & ~BDRV_REQ_ZERO_WRITE);
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if (ret < 0 || pad.merge_reads) {
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/* Error or all work is done */
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goto out;
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}
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offset += write_bytes - pad.head;
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bytes -= write_bytes - pad.head;
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}
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offset += zero_bytes;
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bytes -= zero_bytes;
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}
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assert(!bytes || (offset & (align - 1)) == 0);
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@ -1829,7 +1941,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
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ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align,
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NULL, flags);
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if (ret < 0) {
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goto fail;
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goto out;
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}
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bytes -= aligned_bytes;
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offset += aligned_bytes;
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@ -1837,26 +1949,17 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
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assert(!bytes || (offset & (align - 1)) == 0);
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if (bytes) {
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assert(align == tail_padding_bytes + bytes);
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/* RMW the unaligned part after tail. */
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mark_request_serialising(req, align);
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wait_serialising_requests(req);
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
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ret = bdrv_aligned_preadv(child, req, offset, align,
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align, &local_qiov, 0);
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if (ret < 0) {
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goto fail;
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}
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
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assert(align == pad.tail + bytes);
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memset(buf, 0, bytes);
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qemu_iovec_init_buf(&local_qiov, pad.tail_buf, align);
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ret = bdrv_aligned_pwritev(child, req, offset, align, align,
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&local_qiov, flags & ~BDRV_REQ_ZERO_WRITE);
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}
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fail:
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qemu_vfree(buf);
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return ret;
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out:
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bdrv_padding_destroy(&pad);
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return ret;
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}
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/*
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@ -1869,10 +1972,7 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
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BlockDriverState *bs = child->bs;
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BdrvTrackedRequest req;
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uint64_t align = bs->bl.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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BdrvRequestPadding pad;
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int ret;
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trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
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@ -1899,86 +1999,21 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child,
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goto out;
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}
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if (offset & (align - 1)) {
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QEMUIOVector head_qiov;
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if (bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad)) {
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mark_request_serialising(&req, align);
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wait_serialising_requests(&req);
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head_buf = qemu_blockalign(bs, align);
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qemu_iovec_init_buf(&head_qiov, head_buf, align);
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD);
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ret = bdrv_aligned_preadv(child, &req, offset & ~(align - 1), align,
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align, &head_qiov, 0);
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if (ret < 0) {
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goto fail;
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}
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD);
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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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bytes += offset & (align - 1);
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offset = offset & ~(align - 1);
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/* We have read the tail already if the request is smaller
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* than one aligned block.
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*/
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if (bytes < align) {
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qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes);
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bytes = align;
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}
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}
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if ((offset + bytes) & (align - 1)) {
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QEMUIOVector tail_qiov;
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size_t tail_bytes;
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bool waited;
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mark_request_serialising(&req, align);
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waited = wait_serialising_requests(&req);
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assert(!waited || !use_local_qiov);
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tail_buf = qemu_blockalign(bs, align);
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qemu_iovec_init_buf(&tail_qiov, tail_buf, align);
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL);
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ret = bdrv_aligned_preadv(child, &req, (offset + bytes) & ~(align - 1),
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align, align, &tail_qiov, 0);
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if (ret < 0) {
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goto fail;
|
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}
|
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bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL);
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|
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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_bytes = (offset + bytes) & (align - 1);
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qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes);
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bytes = ROUND_UP(bytes, align);
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bdrv_padding_rmw_read(child, &req, &pad, false);
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}
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|
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ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align,
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use_local_qiov ? &local_qiov : qiov,
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flags);
|
||||
qiov, flags);
|
||||
|
||||
fail:
|
||||
bdrv_padding_destroy(&pad);
|
||||
|
||||
if (use_local_qiov) {
|
||||
qemu_iovec_destroy(&local_qiov);
|
||||
}
|
||||
qemu_vfree(head_buf);
|
||||
qemu_vfree(tail_buf);
|
||||
out:
|
||||
tracked_request_end(&req);
|
||||
bdrv_dec_in_flight(bs);
|
||||
|
||||
return ret;
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user