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From 2e2ad02f2cecf419eaad0df982ceb5b41170cc7e Mon Sep 17 00:00:00 2001
From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Date: Tue, 4 Jun 2019 19:15:05 +0300
Subject: [PATCH] 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>
(cherry picked from commit 7a3f542fbdfd799be4fa6f8b96dc8c1e6933fce4)
*prereq for 292d06b9
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
block/io.c | 365 +++++++++++++++++++++++++++++------------------------
1 file changed, 200 insertions(+), 165 deletions(-)
diff --git a/block/io.c b/block/io.c
index dccf687acc..07d2d825c3 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1408,28 +1408,177 @@ 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) {
@@ -1443,43 +1592,16 @@ 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;
}
@@ -1775,44 +1897,34 @@ 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);
@@ -1822,7 +1934,7 @@ 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;
@@ -1830,26 +1942,17 @@ 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;
}
/*
@@ -1862,10 +1965,7 @@ 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);
@@ -1892,86 +1992,21 @@ 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;
}
--
2.23.0
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