[Qemu-devel] [PATCH 03/13] block: Add .bdrv_co_pwrite_zeroes()

[Eric Blake]

Update bdrv_co_do_write_zeroes() to be byte-based, and select
between the new byte-based bdrv_co_pwrite_zeroes() or the old
bdrv_co_write_zeroes().  The next patches will convert drivers,
then remove the old interface.

Signed-off-by: Eric Blake <address@hidden>
---
 include/block/block_int.h |  4 ++-
 block/io.c                | 81 +++++++++++++++++++++++++----------------------
 2 files changed, 47 insertions(+), 38 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 4282ffd..fa7e3f9 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -165,6 +165,8 @@ struct BlockDriver {
      */
     int coroutine_fn (*bdrv_co_write_zeroes)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors, BdrvRequestFlags flags);
+    int coroutine_fn (*bdrv_co_pwrite_zeroes)(BlockDriverState *bs,
+        int64_t offset, int count, BdrvRequestFlags flags);
     int coroutine_fn (*bdrv_co_discard)(BlockDriverState *bs,
         int64_t sector_num, int nb_sectors);
     int64_t coroutine_fn (*bdrv_co_get_block_status)(BlockDriverState *bs,
@@ -454,7 +456,7 @@ struct BlockDriverState {
     unsigned int request_alignment;
     /* Flags honored during pwrite (so far: BDRV_REQ_FUA) */
     unsigned int supported_write_flags;
-    /* Flags honored during write_zeroes (so far: BDRV_REQ_FUA,
+    /* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
      * BDRV_REQ_MAY_UNMAP) */
     unsigned int supported_zero_flags;

diff --git a/block/io.c b/block/io.c
index 41b4e9d..c1d700b 100644
--- a/block/io.c
+++ b/block/io.c
@@ -42,8 +42,8 @@ static BlockAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
                                          void *opaque,
                                          bool is_write);
 static void coroutine_fn bdrv_co_do_rw(void *opaque);
-static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
-    int64_t sector_num, int nb_sectors, BdrvRequestFlags flags);
+static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
+    int64_t offset, int count, BdrvRequestFlags flags);

 static void bdrv_parent_drained_begin(BlockDriverState *bs)
 {
@@ -876,10 +876,12 @@ static int coroutine_fn 
bdrv_co_do_copy_on_readv(BlockDriverState *bs,
         goto err;
     }

-    if (drv->bdrv_co_write_zeroes &&
+    if ((drv->bdrv_co_write_zeroes || drv->bdrv_co_pwrite_zeroes) &&
         buffer_is_zero(bounce_buffer, iov.iov_len)) {
-        ret = bdrv_co_do_write_zeroes(bs, cluster_sector_num,
-                                      cluster_nb_sectors, 0);
+        ret = bdrv_co_do_pwrite_zeroes(bs,
+                                       cluster_sector_num * BDRV_SECTOR_SIZE,
+                                       cluster_nb_sectors * BDRV_SECTOR_SIZE,
+                                       0);
     } else {
         /* This does not change the data on the disk, it is not necessary
          * to flush even in cache=writethrough mode.
@@ -1111,8 +1113,8 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState 
*bs,

 #define MAX_WRITE_ZEROES_BOUNCE_BUFFER 32768

-static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
-    int64_t sector_num, int nb_sectors, BdrvRequestFlags flags)
+static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
+    int64_t offset, int count, BdrvRequestFlags flags)
 {
     BlockDriver *drv = bs->drv;
     QEMUIOVector qiov;
@@ -1121,40 +1123,45 @@ static int coroutine_fn 
bdrv_co_do_write_zeroes(BlockDriverState *bs,
     bool need_flush = false;

     int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_pwrite_zeroes, INT_MAX);
-    int max_write_zeroes_sectors = max_write_zeroes >> BDRV_SECTOR_BITS;
-    int write_zeroes_sector_align =
-        bs->bl.pwrite_zeroes_alignment >> BDRV_SECTOR_BITS;
+    int alignment = MAX(bs->bl.pwrite_zeroes_alignment, BDRV_SECTOR_SIZE);

-    assert(nb_sectors <= BDRV_REQUEST_MAX_SECTORS);
-    while (nb_sectors > 0 && !ret) {
-        int num = nb_sectors;
+    while (count > 0 && !ret) {
+        int num = count;

         /* Align request.  Block drivers can expect the "bulk" of the request
          * to be aligned.
          */
-        if (write_zeroes_sector_align
-            && num > write_zeroes_sector_align) {
-            if (sector_num % write_zeroes_sector_align != 0) {
+        if (count > alignment) {
+            if (offset % alignment) {
                 /* Make a small request up to the first aligned sector.  */
-                num = write_zeroes_sector_align;
-                num -= sector_num % write_zeroes_sector_align;
-            } else if ((sector_num + num) % write_zeroes_sector_align != 0) {
+                num = alignment - (offset % alignment);
+            } else if ((offset + count) % alignment) {
                 /* Shorten the request to the last aligned sector.  num cannot
-                 * underflow because num > write_zeroes_sector_align.
+                 * underflow because num > alignment.
                  */
-                num -= (sector_num + num) % write_zeroes_sector_align;
+                num -= (offset + num) % alignment;
             }
         }

         /* limit request size */
-        if (num > max_write_zeroes_sectors) {
-            num = max_write_zeroes_sectors;
+        if (num > max_write_zeroes) {
+            num = max_write_zeroes;
         }

         ret = -ENOTSUP;
         /* First try the efficient write zeroes operation */
-        if (drv->bdrv_co_write_zeroes) {
-            ret = drv->bdrv_co_write_zeroes(bs, sector_num, num,
+        if (drv->bdrv_co_pwrite_zeroes) {
+            ret = drv->bdrv_co_pwrite_zeroes(bs, offset, num,
+                                             flags & bs->supported_zero_flags);
+            if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) &&
+                !(bs->supported_zero_flags & BDRV_REQ_FUA)) {
+                need_flush = true;
+            }
+        } else if (drv->bdrv_co_write_zeroes) {
+            assert(offset % BDRV_SECTOR_SIZE == 0);
+            assert(count % BDRV_SECTOR_SIZE == 0);
+            ret = drv->bdrv_co_write_zeroes(bs, offset >> BDRV_SECTOR_BITS,
+                                            num >> BDRV_SECTOR_BITS,
                                             flags & bs->supported_zero_flags);
             if (ret != -ENOTSUP && (flags & BDRV_REQ_FUA) &&
                 !(bs->supported_zero_flags & BDRV_REQ_FUA)) {
@@ -1177,33 +1184,31 @@ static int coroutine_fn 
bdrv_co_do_write_zeroes(BlockDriverState *bs,
                 write_flags &= ~BDRV_REQ_FUA;
                 need_flush = true;
             }
-            num = MIN(num, max_xfer_len);
-            iov.iov_len = num * BDRV_SECTOR_SIZE;
+            num = MIN(num, max_xfer_len << BDRV_SECTOR_BITS);
+            iov.iov_len = num;
             if (iov.iov_base == NULL) {
-                iov.iov_base = qemu_try_blockalign(bs, num * BDRV_SECTOR_SIZE);
+                iov.iov_base = qemu_try_blockalign(bs, num);
                 if (iov.iov_base == NULL) {
                     ret = -ENOMEM;
                     goto fail;
                 }
-                memset(iov.iov_base, 0, num * BDRV_SECTOR_SIZE);
+                memset(iov.iov_base, 0, num);
             }
             qemu_iovec_init_external(&qiov, &iov, 1);

-            ret = bdrv_driver_pwritev(bs, sector_num * BDRV_SECTOR_SIZE,
-                                      num * BDRV_SECTOR_SIZE, &qiov,
-                                      write_flags);
+            ret = bdrv_driver_pwritev(bs, offset, num, &qiov, write_flags);

             /* Keep bounce buffer around if it is big enough for all
              * all future requests.
              */
-            if (num < max_xfer_len) {
+            if (num < max_xfer_len << BDRV_SECTOR_BITS) {
                 qemu_vfree(iov.iov_base);
                 iov.iov_base = NULL;
             }
         }

-        sector_num += num;
-        nb_sectors -= num;
+        offset += num;
+        count -= num;
     }

 fail:
@@ -1241,7 +1246,8 @@ static int coroutine_fn 
bdrv_aligned_pwritev(BlockDriverState *bs,
     ret = notifier_with_return_list_notify(&bs->before_write_notifiers, req);

     if (!ret && bs->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF &&
-        !(flags & BDRV_REQ_ZERO_WRITE) && drv->bdrv_co_write_zeroes &&
+        !(flags & BDRV_REQ_ZERO_WRITE) &&
+        (drv->bdrv_co_pwrite_zeroes || drv->bdrv_co_write_zeroes) &&
         qemu_iovec_is_zero(qiov)) {
         flags |= BDRV_REQ_ZERO_WRITE;
         if (bs->detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP) {
@@ -1253,7 +1259,8 @@ static int coroutine_fn 
bdrv_aligned_pwritev(BlockDriverState *bs,
         /* Do nothing, write notifier decided to fail this request */
     } else if (flags & BDRV_REQ_ZERO_WRITE) {
         bdrv_debug_event(bs, BLKDBG_PWRITEV_ZERO);
-        ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors, flags);
+        ret = bdrv_co_do_pwrite_zeroes(bs, sector_num << BDRV_SECTOR_BITS,
+                                       nb_sectors << BDRV_SECTOR_BITS, flags);
     } else {
         bdrv_debug_event(bs, BLKDBG_PWRITEV);
         ret = bdrv_driver_pwritev(bs, offset, bytes, qiov, flags);
-- 
2.5.5