[PULL,08/37] iscsi: Switch to .bdrv_co_block_status()

Commit Message

Kevin Wolf March 2, 2018, 6:54 p.m. UTC

From: Eric Blake <[e-mail]>

We are gradually moving away from sector-based interfaces, towards
byte-based.  Update the iscsi driver accordingly.  In this case,
it is handy to teach iscsi_co_block_status() to handle a NULL map
and file parameter, even though the block layer passes non-NULL
values, because we also call the function directly.  For now, there
are no optimizations done based on the want_zero flag.

We can also make the simplification of asserting that the block
layer passed in aligned values.

Signed-off-by: Eric Blake <[e-mail]>
Reviewed-by: Fam Zheng <[e-mail]>
Signed-off-by: Kevin Wolf <[e-mail]>
---
 block/iscsi.c | 69 ++++++++++++++++++++++++++++-------------------------------
 1 file changed, 33 insertions(+), 36 deletions(-)

Comments

Peter Maydell May 8, 2018, 3:37 p.m. UTC | #1

On 2 March 2018 at 18:54, Kevin Wolf <[e-mail]> wrote:
> From: Eric Blake <[e-mail]>
>
> We are gradually moving away from sector-based interfaces, towards
> byte-based.  Update the iscsi driver accordingly.  In this case,
> it is handy to teach iscsi_co_block_status() to handle a NULL map
> and file parameter, even though the block layer passes non-NULL
> values, because we also call the function directly.  For now, there
> are no optimizations done based on the want_zero flag.
>

> -    *pnum = sector_lun2qemu(lbasd->num_blocks, iscsilun);
> +    *pnum = lbasd->num_blocks * iscsilun->block_size;

Hi; following this change Coverity complains (CID1390646) about
this multiplication, which is a 32-bit multiply whose result
is then put into a 64-bit result. Is it intended to be a
64-bit multiply ?

thanks
-- PMM

Eric Blake May 8, 2018, 4:38 p.m. UTC | #2

On 05/08/2018 10:37 AM, Peter Maydell wrote:
> On 2 March 2018 at 18:54, Kevin Wolf <[e-mail]> wrote:
>> From: Eric Blake <[e-mail]>
>>
>> We are gradually moving away from sector-based interfaces, towards
>> byte-based.  Update the iscsi driver accordingly.  In this case,
>> it is handy to teach iscsi_co_block_status() to handle a NULL map
>> and file parameter, even though the block layer passes non-NULL
>> values, because we also call the function directly.  For now, there
>> are no optimizations done based on the want_zero flag.
>>
> 
>> -    *pnum = sector_lun2qemu(lbasd->num_blocks, iscsilun);
>> +    *pnum = lbasd->num_blocks * iscsilun->block_size;
> 
> Hi; following this change Coverity complains (CID1390646) about
> this multiplication, which is a 32-bit multiply whose result
> is then put into a 64-bit result. Is it intended to be a
> 64-bit multiply ?

Hmm, good question.  Before this patch, the block layer definitely 
capped things below 2G so that the multiply would not overflow; but in 
rewriting it to be byte-based, it also removed that cap.  I'll send a 
patch to do a 64-bit multiply, just to be safe (even though I don't know 
for sure whether iscsi_get_lba_status_task can return more blocks than 
INT_MAX/block_size).

Patch

diff --git a/block/iscsi.c b/block/iscsi.c
index d2b0466775..c228ca21c8 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -653,36 +653,36 @@  out_unlock:
 
 
 
-static int64_t coroutine_fn iscsi_co_get_block_status(BlockDriverState *bs,
-                                                  int64_t sector_num,
-                                                  int nb_sectors, int *pnum,
-                                                  BlockDriverState **file)
+static int coroutine_fn iscsi_co_block_status(BlockDriverState *bs,
+                                              bool want_zero, int64_t offset,
+                                              int64_t bytes, int64_t *pnum,
+                                              int64_t *map,
+                                              BlockDriverState **file)
 {
     IscsiLun *iscsilun = bs->opaque;
     struct scsi_get_lba_status *lbas = NULL;
     struct scsi_lba_status_descriptor *lbasd = NULL;
     struct IscsiTask iTask;
     uint64_t lba;
-    int64_t ret;
+    int ret;
 
     iscsi_co_init_iscsitask(iscsilun, &iTask);
 
-    if (!is_sector_request_lun_aligned(sector_num, nb_sectors, iscsilun)) {
-        ret = -EINVAL;
-        goto out;
-    }
+    assert(QEMU_IS_ALIGNED(offset | bytes, iscsilun->block_size));
 
     /* default to all sectors allocated */
-    ret = BDRV_BLOCK_DATA;
-    ret |= (sector_num << BDRV_SECTOR_BITS) | BDRV_BLOCK_OFFSET_VALID;
-    *pnum = nb_sectors;
+    ret = BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID;
+    if (map) {
+        *map = offset;
+    }
+    *pnum = bytes;
 
     /* LUN does not support logical block provisioning */
     if (!iscsilun->lbpme) {
         goto out;
     }
 
-    lba = sector_qemu2lun(sector_num, iscsilun);
+    lba = offset / iscsilun->block_size;
 
     qemu_mutex_lock(&iscsilun->mutex);
 retry:
@@ -727,12 +727,12 @@  retry:
 
     lbasd = &lbas->descriptors[0];
 
-    if (sector_qemu2lun(sector_num, iscsilun) != lbasd->lba) {
+    if (lba != lbasd->lba) {
         ret = -EIO;
         goto out_unlock;
     }
 
-    *pnum = sector_lun2qemu(lbasd->num_blocks, iscsilun);
+    *pnum = lbasd->num_blocks * iscsilun->block_size;
 
     if (lbasd->provisioning == SCSI_PROVISIONING_TYPE_DEALLOCATED ||
         lbasd->provisioning == SCSI_PROVISIONING_TYPE_ANCHORED) {
@@ -743,15 +743,13 @@  retry:
     }
 
     if (ret & BDRV_BLOCK_ZERO) {
-        iscsi_allocmap_set_unallocated(iscsilun, sector_num * BDRV_SECTOR_SIZE,
-                                       *pnum * BDRV_SECTOR_SIZE);
+        iscsi_allocmap_set_unallocated(iscsilun, offset, *pnum);
     } else {
-        iscsi_allocmap_set_allocated(iscsilun, sector_num * BDRV_SECTOR_SIZE,
-                                     *pnum * BDRV_SECTOR_SIZE);
+        iscsi_allocmap_set_allocated(iscsilun, offset, *pnum);
     }
 
-    if (*pnum > nb_sectors) {
-        *pnum = nb_sectors;
+    if (*pnum > bytes) {
+        *pnum = bytes;
     }
 out_unlock:
     qemu_mutex_unlock(&iscsilun->mutex);
@@ -760,7 +758,7 @@  out:
     if (iTask.task != NULL) {
         scsi_free_scsi_task(iTask.task);
     }
-    if (ret > 0 && ret & BDRV_BLOCK_OFFSET_VALID) {
+    if (ret > 0 && ret & BDRV_BLOCK_OFFSET_VALID && file) {
         *file = bs;
     }
     return ret;
@@ -800,25 +798,24 @@  static int coroutine_fn iscsi_co_readv(BlockDriverState *bs,
                                  nb_sectors * BDRV_SECTOR_SIZE) &&
         !iscsi_allocmap_is_allocated(iscsilun, sector_num * BDRV_SECTOR_SIZE,
                                      nb_sectors * BDRV_SECTOR_SIZE)) {
-        int pnum;
-        BlockDriverState *file;
+        int64_t pnum;
         /* check the block status from the beginning of the cluster
          * containing the start sector */
-        int cluster_sectors = iscsilun->cluster_size >> BDRV_SECTOR_BITS;
-        int head;
-        int64_t ret;
-
-        assert(cluster_sectors);
-        head = sector_num % cluster_sectors;
-        ret = iscsi_co_get_block_status(bs, sector_num - head,
-                                        BDRV_REQUEST_MAX_SECTORS, &pnum,
-                                        &file);
+        int64_t head;
+        int ret;
+
+        assert(iscsilun->cluster_size);
+        head = (sector_num * BDRV_SECTOR_SIZE) % iscsilun->cluster_size;
+        ret = iscsi_co_block_status(bs, true,
+                                    sector_num * BDRV_SECTOR_SIZE - head,
+                                    BDRV_REQUEST_MAX_BYTES, &pnum, NULL, NULL);
         if (ret < 0) {
             return ret;
         }
         /* if the whole request falls into an unallocated area we can avoid
          * reading and directly return zeroes instead */
-        if (ret & BDRV_BLOCK_ZERO && pnum >= nb_sectors + head) {
+        if (ret & BDRV_BLOCK_ZERO &&
+            pnum >= nb_sectors * BDRV_SECTOR_SIZE + head) {
             qemu_iovec_memset(iov, 0, 0x00, iov->size);
             return 0;
         }
@@ -2218,7 +2215,7 @@  static BlockDriver bdrv_iscsi = {
     .bdrv_truncate   = iscsi_truncate,
     .bdrv_refresh_limits = iscsi_refresh_limits,
 
-    .bdrv_co_get_block_status = iscsi_co_get_block_status,
+    .bdrv_co_block_status  = iscsi_co_block_status,
     .bdrv_co_pdiscard      = iscsi_co_pdiscard,
     .bdrv_co_pwrite_zeroes = iscsi_co_pwrite_zeroes,
     .bdrv_co_readv         = iscsi_co_readv,
@@ -2253,7 +2250,7 @@  static BlockDriver bdrv_iser = {
     .bdrv_truncate   = iscsi_truncate,
     .bdrv_refresh_limits = iscsi_refresh_limits,
 
-    .bdrv_co_get_block_status = iscsi_co_get_block_status,
+    .bdrv_co_block_status  = iscsi_co_block_status,
     .bdrv_co_pdiscard      = iscsi_co_pdiscard,
     .bdrv_co_pwrite_zeroes = iscsi_co_pwrite_zeroes,
     .bdrv_co_readv         = iscsi_co_readv,