[PATCH v12 10/14] block: include supported_read_flags into BDS structure

[Andrey Shinkevich via]

Add the new member supported_read_flags to the BlockDriverState
structure. It will control the flags set for copy-on-read operations.
Make the block generic layer evaluate supported read flags before they
go to a block driver.

Suggested-by: Vladimir Sementsov-Ogievskiy 
Signed-off-by: Andrey Shinkevich 
---
 block/io.c| 12 ++--
 include/block/block_int.h |  4 
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 54f0968..78ddf13 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1392,6 +1392,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild 
*child,
 if (flags & BDRV_REQ_COPY_ON_READ) {
 int64_t pnum;
 
+/* The flag BDRV_REQ_COPY_ON_READ has reached its addressee */
+flags &= ~BDRV_REQ_COPY_ON_READ;
+
 ret = bdrv_is_allocated(bs, offset, bytes, &pnum);
 if (ret < 0) {
 goto out;
@@ -1413,9 +1416,13 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild 
*child,
 goto out;
 }
 
+if (flags & ~bs->supported_read_flags) {
+abort();
+}
+
 max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
 if (bytes <= max_bytes && bytes <= max_transfer) {
-ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, 0);
+ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, flags);
 goto out;
 }
 
@@ -1428,7 +1435,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild 
*child,
 
 ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,
  num, qiov,
- qiov_offset + bytes - bytes_remaining, 0);
+ qiov_offset + bytes - bytes_remaining,
+ flags);
 max_bytes -= num;
 } else {
 num = bytes_remaining;
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f782737..474174c 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -873,6 +873,10 @@ struct BlockDriverState {
 /* I/O Limits */
 BlockLimits bl;
 
+/*
+ * Flags honored during pread
+ */
+unsigned int supported_read_flags;
 /* Flags honored during pwrite (so far: BDRV_REQ_FUA,
  * BDRV_REQ_WRITE_UNCHANGED).
  * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those
-- 
1.8.3.1

Re: [PATCH v12 10/14] block: include supported_read_flags into BDS structure

[Vladimir Sementsov-Ogievskiy]

22.10.2020 21:13, Andrey Shinkevich wrote:

Add the new member supported_read_flags to the BlockDriverState
structure. It will control the flags set for copy-on-read operations.
Make the block generic layer evaluate supported read flags before they
go to a block driver.

Suggested-by: Vladimir Sementsov-Ogievskiy 
Signed-off-by: Andrey Shinkevich 
---
  block/io.c| 12 ++--
  include/block/block_int.h |  4 
  2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/block/io.c b/block/io.c
index 54f0968..78ddf13 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1392,6 +1392,9 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild 
*child,
  if (flags & BDRV_REQ_COPY_ON_READ) {
  int64_t pnum;
  
+/* The flag BDRV_REQ_COPY_ON_READ has reached its addressee */

+flags &= ~BDRV_REQ_COPY_ON_READ;
+
  ret = bdrv_is_allocated(bs, offset, bytes, &pnum);
  if (ret < 0) {
  goto out;
@@ -1413,9 +1416,13 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild 
*child,
  goto out;
  }
  
+if (flags & ~bs->supported_read_flags) {

+abort();
+}
+


So, you decided to be strict with all read-flags passed to driver, not only 
PREFETCH.. It makes sense.



  max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
  if (bytes <= max_bytes && bytes <= max_transfer) {
-ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, 0);
+ret = bdrv_driver_preadv(bs, offset, bytes, qiov, qiov_offset, flags);
  goto out;
  }
  
@@ -1428,7 +1435,8 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
  
  ret = bdrv_driver_preadv(bs, offset + bytes - bytes_remaining,

   num, qiov,
- qiov_offset + bytes - bytes_remaining, 0);
+ qiov_offset + bytes - bytes_remaining,
+ flags);
  max_bytes -= num;
  } else {
  num = bytes_remaining;
diff --git a/include/block/block_int.h b/include/block/block_int.h
index f782737..474174c 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -873,6 +873,10 @@ struct BlockDriverState {
  /* I/O Limits */
  BlockLimits bl;
  
+/*

+ * Flags honored during pread
+ */
+unsigned int supported_read_flags;
  /* Flags honored during pwrite (so far: BDRV_REQ_FUA,
   * BDRV_REQ_WRITE_UNCHANGED).
   * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those




Reviewed-by: Vladimir Sementsov-Ogievskiy 

--
Best regards,
Vladimir