diff options
| -rw-r--r-- | block/io.c | 365 |
1 files changed, 200 insertions, 165 deletions
diff --git a/block/io.c b/block/io.c index f656fb2dce..04e69400d8 100644 --- a/block/io.c +++ b/block/io.c @@ -1415,28 +1415,177 @@ out: } /* - * Handle a read request in coroutine context + * Request padding + * + * |<---- align ----->| |<----- align ---->| + * |<- head ->|<------------- bytes ------------->|<-- tail -->| + * | | | | | | + * -*----------$-------*-------- ... --------*-----$------------*--- + * | | | | | | + * | offset | | end | + * ALIGN_DOWN(offset) ALIGN_UP(offset) ALIGN_DOWN(end) ALIGN_UP(end) + * [buf ... ) [tail_buf ) + * + * @buf is an aligned allocation needed to store @head and @tail paddings. @head + * is placed at the beginning of @buf and @tail at the @end. + * + * @tail_buf is a pointer to sub-buffer, corresponding to align-sized chunk + * around tail, if tail exists. + * + * @merge_reads is true for small requests, + * if @buf_len == @head + bytes + @tail. In this case it is possible that both + * head and tail exist but @buf_len == align and @tail_buf == @buf. + */ +typedef struct BdrvRequestPadding { + uint8_t *buf; + size_t buf_len; + uint8_t *tail_buf; + size_t head; + size_t tail; + bool merge_reads; + QEMUIOVector local_qiov; +} BdrvRequestPadding; + +static bool bdrv_init_padding(BlockDriverState *bs, + int64_t offset, int64_t bytes, + BdrvRequestPadding *pad) +{ + uint64_t align = bs->bl.request_alignment; + size_t sum; + + memset(pad, 0, sizeof(*pad)); + + pad->head = offset & (align - 1); + pad->tail = ((offset + bytes) & (align - 1)); + if (pad->tail) { + pad->tail = align - pad->tail; + } + + if ((!pad->head && !pad->tail) || !bytes) { + return false; + } + + sum = pad->head + bytes + pad->tail; + pad->buf_len = (sum > align && pad->head && pad->tail) ? 2 * align : align; + pad->buf = qemu_blockalign(bs, pad->buf_len); + pad->merge_reads = sum == pad->buf_len; + if (pad->tail) { + pad->tail_buf = pad->buf + pad->buf_len - align; + } + + return true; +} + +static int bdrv_padding_rmw_read(BdrvChild *child, + BdrvTrackedRequest *req, + BdrvRequestPadding *pad, + bool zero_middle) +{ + QEMUIOVector local_qiov; + BlockDriverState *bs = child->bs; + uint64_t align = bs->bl.request_alignment; + int ret; + + assert(req->serialising && pad->buf); + + if (pad->head || pad->merge_reads) { + uint64_t bytes = pad->merge_reads ? pad->buf_len : align; + + qemu_iovec_init_buf(&local_qiov, pad->buf, bytes); + + if (pad->head) { + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD); + } + if (pad->merge_reads && pad->tail) { + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); + } + ret = bdrv_aligned_preadv(child, req, req->overlap_offset, bytes, + align, &local_qiov, 0); + if (ret < 0) { + return ret; + } + if (pad->head) { + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD); + } + if (pad->merge_reads && pad->tail) { + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); + } + + if (pad->merge_reads) { + goto zero_mem; + } + } + + if (pad->tail) { + qemu_iovec_init_buf(&local_qiov, pad->tail_buf, align); + + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); + ret = bdrv_aligned_preadv( + child, req, + req->overlap_offset + req->overlap_bytes - align, + align, align, &local_qiov, 0); + if (ret < 0) { + return ret; + } + bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); + } + +zero_mem: + if (zero_middle) { + memset(pad->buf + pad->head, 0, pad->buf_len - pad->head - pad->tail); + } + + return 0; +} + +static void bdrv_padding_destroy(BdrvRequestPadding *pad) +{ + if (pad->buf) { + qemu_vfree(pad->buf); + qemu_iovec_destroy(&pad->local_qiov); + } +} + +/* + * bdrv_pad_request + * + * Exchange request parameters with padded request if needed. Don't include RMW + * read of padding, bdrv_padding_rmw_read() should be called separately if + * needed. + * + * All parameters except @bs are in-out: they represent original request at + * function call and padded (if padding needed) at function finish. + * + * Function always succeeds. */ +static bool bdrv_pad_request(BlockDriverState *bs, QEMUIOVector **qiov, + int64_t *offset, unsigned int *bytes, + BdrvRequestPadding *pad) +{ + if (!bdrv_init_padding(bs, *offset, *bytes, pad)) { + return false; + } + + qemu_iovec_init_extended(&pad->local_qiov, pad->buf, pad->head, + *qiov, 0, *bytes, + pad->buf + pad->buf_len - pad->tail, pad->tail); + *bytes += pad->head + pad->tail; + *offset -= pad->head; + *qiov = &pad->local_qiov; + + return true; +} + int coroutine_fn bdrv_co_preadv(BdrvChild *child, int64_t offset, unsigned int bytes, QEMUIOVector *qiov, BdrvRequestFlags flags) { BlockDriverState *bs = child->bs; - BlockDriver *drv = bs->drv; BdrvTrackedRequest req; - - uint64_t align = bs->bl.request_alignment; - uint8_t *head_buf = NULL; - uint8_t *tail_buf = NULL; - QEMUIOVector local_qiov; - bool use_local_qiov = false; + BdrvRequestPadding pad; int ret; - trace_bdrv_co_preadv(child->bs, offset, bytes, flags); - - if (!drv) { - return -ENOMEDIUM; - } + trace_bdrv_co_preadv(bs, offset, bytes, flags); ret = bdrv_check_byte_request(bs, offset, bytes); if (ret < 0) { @@ -1450,43 +1599,16 @@ int coroutine_fn bdrv_co_preadv(BdrvChild *child, flags |= BDRV_REQ_COPY_ON_READ; } - /* 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); - } + bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad); tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_READ); - ret = bdrv_aligned_preadv(child, &req, offset, bytes, align, - use_local_qiov ? &local_qiov : qiov, - flags); + ret = bdrv_aligned_preadv(child, &req, offset, bytes, + bs->bl.request_alignment, + qiov, flags); tracked_request_end(&req); bdrv_dec_in_flight(bs); - if (use_local_qiov) { - qemu_iovec_destroy(&local_qiov); - qemu_vfree(head_buf); - qemu_vfree(tail_buf); - } + bdrv_padding_destroy(&pad); return ret; } @@ -1782,44 +1904,34 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, BdrvTrackedRequest *req) { BlockDriverState *bs = child->bs; - uint8_t *buf = NULL; QEMUIOVector local_qiov; uint64_t align = bs->bl.request_alignment; - unsigned int head_padding_bytes, tail_padding_bytes; int ret = 0; + bool padding; + BdrvRequestPadding pad; - head_padding_bytes = offset & (align - 1); - tail_padding_bytes = (align - (offset + bytes)) & (align - 1); - - - assert(flags & BDRV_REQ_ZERO_WRITE); - if (head_padding_bytes || tail_padding_bytes) { - buf = qemu_blockalign(bs, align); - qemu_iovec_init_buf(&local_qiov, buf, align); - } - if (head_padding_bytes) { - uint64_t zero_bytes = MIN(bytes, align - head_padding_bytes); - - /* RMW the unaligned part before head. */ + padding = bdrv_init_padding(bs, offset, bytes, &pad); + if (padding) { mark_request_serialising(req, align); wait_serialising_requests(req); - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD); - ret = bdrv_aligned_preadv(child, req, offset & ~(align - 1), align, - align, &local_qiov, 0); - if (ret < 0) { - goto fail; - } - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD); - memset(buf + head_padding_bytes, 0, zero_bytes); - ret = bdrv_aligned_pwritev(child, req, offset & ~(align - 1), align, - align, &local_qiov, - flags & ~BDRV_REQ_ZERO_WRITE); - if (ret < 0) { - goto fail; + bdrv_padding_rmw_read(child, req, &pad, true); + + if (pad.head || pad.merge_reads) { + int64_t aligned_offset = offset & ~(align - 1); + int64_t write_bytes = pad.merge_reads ? pad.buf_len : align; + + qemu_iovec_init_buf(&local_qiov, pad.buf, write_bytes); + ret = bdrv_aligned_pwritev(child, req, aligned_offset, write_bytes, + align, &local_qiov, + flags & ~BDRV_REQ_ZERO_WRITE); + if (ret < 0 || pad.merge_reads) { + /* Error or all work is done */ + goto out; + } + offset += write_bytes - pad.head; + bytes -= write_bytes - pad.head; } - offset += zero_bytes; - bytes -= zero_bytes; } assert(!bytes || (offset & (align - 1)) == 0); @@ -1829,7 +1941,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, ret = bdrv_aligned_pwritev(child, req, offset, aligned_bytes, align, NULL, flags); if (ret < 0) { - goto fail; + goto out; } bytes -= aligned_bytes; offset += aligned_bytes; @@ -1837,26 +1949,17 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child, assert(!bytes || (offset & (align - 1)) == 0); if (bytes) { - assert(align == tail_padding_bytes + bytes); - /* RMW the unaligned part after tail. */ - mark_request_serialising(req, align); - wait_serialising_requests(req); - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); - ret = bdrv_aligned_preadv(child, req, offset, align, - align, &local_qiov, 0); - if (ret < 0) { - goto fail; - } - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); + assert(align == pad.tail + bytes); - memset(buf, 0, bytes); + qemu_iovec_init_buf(&local_qiov, pad.tail_buf, align); ret = bdrv_aligned_pwritev(child, req, offset, align, align, &local_qiov, flags & ~BDRV_REQ_ZERO_WRITE); } -fail: - qemu_vfree(buf); - return ret; +out: + bdrv_padding_destroy(&pad); + + return ret; } /* @@ -1869,10 +1972,7 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, BlockDriverState *bs = child->bs; BdrvTrackedRequest req; uint64_t align = bs->bl.request_alignment; - uint8_t *head_buf = NULL; - uint8_t *tail_buf = NULL; - QEMUIOVector local_qiov; - bool use_local_qiov = false; + BdrvRequestPadding pad; int ret; trace_bdrv_co_pwritev(child->bs, offset, bytes, flags); @@ -1899,86 +1999,21 @@ int coroutine_fn bdrv_co_pwritev(BdrvChild *child, goto out; } - if (offset & (align - 1)) { - QEMUIOVector head_qiov; - + if (bdrv_pad_request(bs, &qiov, &offset, &bytes, &pad)) { mark_request_serialising(&req, align); wait_serialising_requests(&req); - - head_buf = qemu_blockalign(bs, align); - qemu_iovec_init_buf(&head_qiov, head_buf, align); - - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_HEAD); - ret = bdrv_aligned_preadv(child, &req, offset & ~(align - 1), align, - align, &head_qiov, 0); - if (ret < 0) { - goto fail; - } - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_HEAD); - - 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); - - /* We have read the tail already if the request is smaller - * than one aligned block. - */ - if (bytes < align) { - qemu_iovec_add(&local_qiov, head_buf + bytes, align - bytes); - bytes = align; - } - } - - if ((offset + bytes) & (align - 1)) { - QEMUIOVector tail_qiov; - size_t tail_bytes; - bool waited; - - mark_request_serialising(&req, align); - waited = wait_serialising_requests(&req); - assert(!waited || !use_local_qiov); - - tail_buf = qemu_blockalign(bs, align); - qemu_iovec_init_buf(&tail_qiov, tail_buf, align); - - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_TAIL); - ret = bdrv_aligned_preadv(child, &req, (offset + bytes) & ~(align - 1), - align, align, &tail_qiov, 0); - if (ret < 0) { - goto fail; - } - bdrv_debug_event(bs, BLKDBG_PWRITEV_RMW_AFTER_TAIL); - - 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_bytes = (offset + bytes) & (align - 1); - qemu_iovec_add(&local_qiov, tail_buf + tail_bytes, align - tail_bytes); - - bytes = ROUND_UP(bytes, align); + bdrv_padding_rmw_read(child, &req, &pad, false); } ret = bdrv_aligned_pwritev(child, &req, offset, bytes, align, - use_local_qiov ? &local_qiov : qiov, - 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; } |