block: Convert bdrv_co_discard() to byte-based

Another step towards byte-based interfaces everywhere.  Replace
the sector-based bdrv_co_discard() with a new byte-based
bdrv_co_pdiscard(), which silently ignores any unaligned head
or tail.  Driver callbacks will be converted in followup patches.

By calculating the alignment outside of the loop, and clamping
the max discard to an aligned value, we can simplify the actions
done within the loop.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1468624988-423-2-git-send-email-eblake@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/blkreplay.c

@@ -118,7 +118,8 @@ static int coroutine_fn blkreplay_co_discard(BlockDriverState *bs,
     int64_t sector_num, int nb_sectors)
 {
     uint64_t reqid = request_id++;
-    int ret = bdrv_co_discard(bs->file->bs, sector_num, nb_sectors);
+    int ret = bdrv_co_pdiscard(bs->file->bs, sector_num << BDRV_SECTOR_BITS,
+                               nb_sectors << BDRV_SECTOR_BITS);
     block_request_create(reqid, bs, qemu_coroutine_self());
     qemu_coroutine_yield();
 

block/block-backend.c

@@ -1113,7 +1113,8 @@ int blk_co_discard(BlockBackend *blk, int64_t sector_num, int nb_sectors)
         return ret;
     }
 
-    return bdrv_co_discard(blk_bs(blk), sector_num, nb_sectors);
+    return bdrv_co_pdiscard(blk_bs(blk), sector_num << BDRV_SECTOR_BITS,
+                            nb_sectors << BDRV_SECTOR_BITS);
 }
 
 int blk_co_flush(BlockBackend *blk)

block/io.c

@@ -2199,7 +2199,8 @@ static void coroutine_fn bdrv_aio_discard_co_entry(void *opaque)
     BlockAIOCBCoroutine *acb = opaque;
     BlockDriverState *bs = acb->common.bs;
 
-    acb->req.error = bdrv_co_discard(bs, acb->req.sector, acb->req.nb_sectors);
+    acb->req.error = bdrv_co_pdiscard(bs, acb->req.sector << BDRV_SECTOR_BITS,
+                                      acb->req.nb_sectors << BDRV_SECTOR_BITS);
     bdrv_co_complete(acb);
 }
 
@@ -2398,20 +2399,22 @@ static void coroutine_fn bdrv_discard_co_entry(void *opaque)
 {
     DiscardCo *rwco = opaque;
 
-    rwco->ret = bdrv_co_discard(rwco->bs, rwco->sector_num, rwco->nb_sectors);
+    rwco->ret = bdrv_co_pdiscard(rwco->bs, rwco->sector_num << BDRV_SECTOR_BITS,
+                                 rwco->nb_sectors << BDRV_SECTOR_BITS);
 }
 
-int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
+int coroutine_fn bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset,
-                                 int nb_sectors)
+                                  int count)
 {
     BdrvTrackedRequest req;
-    int max_discard, ret;
+    int max_pdiscard, ret;
+    int head, align;
 
     if (!bs->drv) {
         return -ENOMEDIUM;
     }
 
-    ret = bdrv_check_request(bs, sector_num, nb_sectors);
+    ret = bdrv_check_byte_request(bs, offset, count);
     if (ret < 0) {
         return ret;
     } else if (bs->read_only) {
@@ -2428,45 +2431,45 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
         return 0;
     }
 
-    tracked_request_begin(&req, bs, sector_num << BDRV_SECTOR_BITS,
+    /* Discard is advisory, so ignore any unaligned head or tail */
-                          nb_sectors << BDRV_SECTOR_BITS, BDRV_TRACKED_DISCARD);
+    align = MAX(BDRV_SECTOR_SIZE,
+                MAX(bs->bl.pdiscard_alignment, bs->bl.request_alignment));
+    assert(is_power_of_2(align));
+    head = MIN(count, -offset & (align - 1));
+    if (head) {
+        count -= head;
+        offset += head;
+    }
+    count = QEMU_ALIGN_DOWN(count, align);
+    if (!count) {
+        return 0;
+    }
+
+    tracked_request_begin(&req, bs, offset, count, BDRV_TRACKED_DISCARD);
 
     ret = notifier_with_return_list_notify(&bs->before_write_notifiers, &req);
     if (ret < 0) {
         goto out;
     }
 
-    max_discard = MIN_NON_ZERO(bs->bl.max_pdiscard >> BDRV_SECTOR_BITS,
+    max_pdiscard = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_pdiscard, INT_MAX),
-                               BDRV_REQUEST_MAX_SECTORS);
+                                   align);
-    while (nb_sectors > 0) {
+
+    while (count > 0) {
         int ret;
-        int num = nb_sectors;
+        int num = MIN(count, max_pdiscard);
-        int discard_alignment = bs->bl.pdiscard_alignment >> BDRV_SECTOR_BITS;
-
-        /* align request */
-        if (discard_alignment &&
-            num >= discard_alignment &&
-            sector_num % discard_alignment) {
-            if (num > discard_alignment) {
-                num = discard_alignment;
-            }
-            num -= sector_num % discard_alignment;
-        }
-
-        /* limit request size */
-        if (num > max_discard) {
-            num = max_discard;
-        }
 
         if (bs->drv->bdrv_co_discard) {
-            ret = bs->drv->bdrv_co_discard(bs, sector_num, num);
+            ret = bs->drv->bdrv_co_discard(bs, offset >> BDRV_SECTOR_BITS,
+                                           num >> BDRV_SECTOR_BITS);
         } else {
             BlockAIOCB *acb;
             CoroutineIOCompletion co = {
                 .coroutine = qemu_coroutine_self(),
             };
 
-            acb = bs->drv->bdrv_aio_discard(bs, sector_num, nb_sectors,
+            acb = bs->drv->bdrv_aio_discard(bs, offset >> BDRV_SECTOR_BITS,
+                                            num >> BDRV_SECTOR_BITS,
                                             bdrv_co_io_em_complete, &co);
             if (acb == NULL) {
                 ret = -EIO;
@@ -2480,8 +2483,8 @@ int coroutine_fn bdrv_co_discard(BlockDriverState *bs, int64_t sector_num,
             goto out;
         }
 
-        sector_num += num;
+        offset += num;
-        nb_sectors -= num;
+        count -= num;
     }
     ret = 0;
 out:

block/raw_bsd.c

@@ -137,7 +137,8 @@ static int coroutine_fn raw_co_pwrite_zeroes(BlockDriverState *bs,
 static int coroutine_fn raw_co_discard(BlockDriverState *bs,
                                        int64_t sector_num, int nb_sectors)
 {
-    return bdrv_co_discard(bs->file->bs, sector_num, nb_sectors);
+    return bdrv_co_pdiscard(bs->file->bs, sector_num << BDRV_SECTOR_BITS,
+                            nb_sectors << BDRV_SECTOR_BITS);
 }
 
 static int64_t raw_getlength(BlockDriverState *bs)

include/block/block.h

@@ -342,7 +342,7 @@ void coroutine_fn bdrv_co_drain(BlockDriverState *bs);
 void bdrv_drain_all(void);
 
 int bdrv_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
-int bdrv_co_discard(BlockDriverState *bs, int64_t sector_num, int nb_sectors);
+int bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset, int count);
 int bdrv_has_zero_init_1(BlockDriverState *bs);
 int bdrv_has_zero_init(BlockDriverState *bs);
 bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs);