[Qemu-devel] [PATCH 02/13] block: Track write zero limits in bytes

[Eric Blake <eblake@redhat.com>]

Another step towards removing sector-based interfaces: convert
the maximum write and minimum alignment values from sectorss to
bytes.  Alignment is changed to 'int', since it makes no sense
to have an alignment larger than the maximum write.  Add an
assert that no one was trying to use sectors to get a write
zeroes larger than 2G.  Rename the variables to let the compiler
check that all users are converted to the new semantics.

Signed-off-by: Eric Blake <eblake@redhat.com>
---
 include/block/block_int.h |  8 ++++----
 block/io.c                | 27 +++++++++++++++------------
 block/iscsi.c             |  6 ++----
 block/qcow2.c             |  2 +-
 block/qed.c               |  2 +-
 block/vmdk.c              |  6 +++---
 6 files changed, 26 insertions(+), 25 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index b6f4755..4282ffd 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -328,11 +328,11 @@ typedef struct BlockLimits {
     /* optimal alignment for discard requests in sectors */
     int64_t discard_alignment;

-    /* maximum number of sectors that can zeroized at once */
-    int max_write_zeroes;
+    /* maximum number of bytes that can zeroized at once */
+    int max_pwrite_zeroes;

-    /* optimal alignment for write zeroes requests in sectors */
-    int64_t write_zeroes_alignment;
+    /* optimal alignment for write zeroes requests in bytes */
+    int pwrite_zeroes_alignment;

     /* optimal transfer length in sectors */
     int opt_transfer_length;
diff --git a/block/io.c b/block/io.c
index 2a2ff84..41b4e9d 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1120,32 +1120,35 @@ static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
     int ret = 0;
     bool need_flush = false;

-    int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_write_zeroes,
-                                        BDRV_REQUEST_MAX_SECTORS);
+    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;

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

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

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

         ret = -ENOTSUP;
diff --git a/block/iscsi.c b/block/iscsi.c
index 10f3906..0acc3dc 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -1706,12 +1706,10 @@ static void iscsi_refresh_limits(BlockDriverState *bs, Error **errp)
     }

     if (iscsilun->bl.max_ws_len < 0xffffffff) {
-        bs->bl.max_write_zeroes =
-            sector_limits_lun2qemu(iscsilun->bl.max_ws_len, iscsilun);
+        bs->bl.max_pwrite_zeroes = iscsilun->bl.max_ws_len;
     }
     if (iscsilun->lbp.lbpws) {
-        bs->bl.write_zeroes_alignment =
-            sector_limits_lun2qemu(iscsilun->bl.opt_unmap_gran, iscsilun);
+        bs->bl.pwrite_zeroes_alignment = iscsilun->bl.opt_unmap_gran;
     }
     bs->bl.opt_transfer_length =
         sector_limits_lun2qemu(iscsilun->bl.opt_xfer_len, iscsilun);
diff --git a/block/qcow2.c b/block/qcow2.c
index c9306a7..745b66f 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1193,7 +1193,7 @@ static void qcow2_refresh_limits(BlockDriverState *bs, Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;

-    bs->bl.write_zeroes_alignment = s->cluster_sectors;
+    bs->bl.pwrite_zeroes_alignment = s->cluster_sectors << BDRV_SECTOR_BITS;
 }

 static int qcow2_set_key(BlockDriverState *bs, const char *key)
diff --git a/block/qed.c b/block/qed.c
index b591d4a..0ab5b40 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -518,7 +518,7 @@ static void bdrv_qed_refresh_limits(BlockDriverState *bs, Error **errp)
 {
     BDRVQEDState *s = bs->opaque;

-    bs->bl.write_zeroes_alignment = s->header.cluster_size >> BDRV_SECTOR_BITS;
+    bs->bl.pwrite_zeroes_alignment = s->header.cluster_size;
 }

 /* We have nothing to do for QED reopen, stubs just return
diff --git a/block/vmdk.c b/block/vmdk.c
index 372e5ed..8494d63 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -998,9 +998,9 @@ static void vmdk_refresh_limits(BlockDriverState *bs, Error **errp)

     for (i = 0; i < s->num_extents; i++) {
         if (!s->extents[i].flat) {
-            bs->bl.write_zeroes_alignment =
-                MAX(bs->bl.write_zeroes_alignment,
-                    s->extents[i].cluster_sectors);
+            bs->bl.pwrite_zeroes_alignment =
+                MAX(bs->bl.pwrite_zeroes_alignment,
+                    s->extents[i].cluster_sectors << BDRV_SECTOR_BITS);
         }
     }
 }
-- 
2.5.5