From eblake at redhat.com  Fri May  9 20:40:18 2025
From: eblake at redhat.com (Eric Blake)
Date: Fri,  9 May 2025 15:40:18 -0500
Subject: [GEDI] [PATCH v4 01/13] block: Expand block status mode from bool
	to flags
In-Reply-To: <20250509204341.3553601-15-eblake@redhat.com>
References: <20250509204341.3553601-15-eblake@redhat.com>
Message-ID: <20250509204341.3553601-16-eblake@redhat.com>

This patch is purely mechanical, changing bool want_zero into an
unsigned int for bitwise-or of flags.  As of this patch, all
implementations are unchanged (the old want_zero==true is now
mode==BDRV_WANT_PRECISE which is a superset of BDRV_WANT_ZERO); but
the callers in io.c that used to pass want_zero==false are now
prepared for future driver changes that can now distinguish bewteen
BDRV_WANT_ZERO vs. BDRV_WANT_ALLOCATED.  The next patch will actually
change the file-posix driver along those lines, now that we have
more-specific hints.

As for the background why this patch is useful: right now, the
file-posix driver recognizes that if allocation is being queried, the
entire image can be reported as allocated (there is no backing file to
refer to) - but this throws away information on whether the entire
image reads as zero (trivially true if lseek(SEEK_HOLE) at offset 0
returns -ENXIO, a bit more complicated to prove if the raw file was
created with 'qemu-img create' since we intentionally allocate a small
chunk of all-zero data to help with alignment probing).  Later patches
will add a generic algorithm for seeing if an entire file reads as
zeroes.

Signed-off-by: Eric Blake <eblake at redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 block/coroutines.h               |  4 +--
 include/block/block-common.h     | 11 +++++++
 include/block/block_int-common.h | 27 +++++++++--------
 include/block/block_int-io.h     |  4 +--
 block/io.c                       | 51 ++++++++++++++++----------------
 block/blkdebug.c                 |  6 ++--
 block/copy-before-write.c        |  4 +--
 block/file-posix.c               |  4 +--
 block/gluster.c                  |  4 +--
 block/iscsi.c                    |  6 ++--
 block/nbd.c                      |  4 +--
 block/null.c                     |  6 ++--
 block/parallels.c                |  6 ++--
 block/qcow.c                     |  2 +-
 block/qcow2.c                    |  6 ++--
 block/qed.c                      |  6 ++--
 block/quorum.c                   |  4 +--
 block/raw-format.c               |  4 +--
 block/rbd.c                      |  6 ++--
 block/snapshot-access.c          |  4 +--
 block/vdi.c                      |  4 +--
 block/vmdk.c                     |  2 +-
 block/vpc.c                      |  2 +-
 block/vvfat.c                    |  6 ++--
 tests/unit/test-block-iothread.c |  2 +-
 25 files changed, 99 insertions(+), 86 deletions(-)

diff --git a/block/coroutines.h b/block/coroutines.h
index 79e5efbf752..892646bb7aa 100644
--- a/block/coroutines.h
+++ b/block/coroutines.h
@@ -47,7 +47,7 @@ int coroutine_fn GRAPH_RDLOCK
 bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   BlockDriverState *base,
                                   bool include_base,
-                                  bool want_zero,
+                                  unsigned int mode,
                                   int64_t offset,
                                   int64_t bytes,
                                   int64_t *pnum,
@@ -78,7 +78,7 @@ int co_wrapper_mixed_bdrv_rdlock
 bdrv_common_block_status_above(BlockDriverState *bs,
                                BlockDriverState *base,
                                bool include_base,
-                               bool want_zero,
+                               unsigned int mode,
                                int64_t offset,
                                int64_t bytes,
                                int64_t *pnum,
diff --git a/include/block/block-common.h b/include/block/block-common.h
index 0b831ef87b1..c8c626daeaa 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -333,6 +333,17 @@ typedef enum {
 #define BDRV_BLOCK_RECURSE      0x40
 #define BDRV_BLOCK_COMPRESSED   0x80

+/*
+ * Block status hints: the bitwise-or of these flags emphasize what
+ * the caller hopes to learn, and some drivers may be able to give
+ * faster answers by doing less work when the hint permits.
+ */
+#define BDRV_WANT_ZERO          BDRV_BLOCK_ZERO
+#define BDRV_WANT_OFFSET_VALID  BDRV_BLOCK_OFFSET_VALID
+#define BDRV_WANT_ALLOCATED     BDRV_BLOCK_ALLOCATED
+#define BDRV_WANT_PRECISE       (BDRV_WANT_ZERO | BDRV_WANT_OFFSET_VALID | \
+                                 BDRV_WANT_OFFSET_VALID)
+
 typedef QTAILQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;

 typedef struct BDRVReopenState {
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 0d8187f6567..2982dd31180 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -604,15 +604,16 @@ struct BlockDriver {
      * according to the current layer, and should only need to set
      * BDRV_BLOCK_DATA, BDRV_BLOCK_ZERO, BDRV_BLOCK_OFFSET_VALID,
      * and/or BDRV_BLOCK_RAW; if the current layer defers to a backing
-     * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  See
-     * block.h for the overall meaning of the bits.  As a hint, the
-     * flag want_zero is true if the caller cares more about precise
-     * mappings (favor accurate _OFFSET_VALID/_ZERO) or false for
-     * overall allocation (favor larger *pnum, perhaps by reporting
-     * _DATA instead of _ZERO).  The block layer guarantees input
-     * clamped to bdrv_getlength() and aligned to request_alignment,
-     * as well as non-NULL pnum, map, and file; in turn, the driver
-     * must return an error or set pnum to an aligned non-zero value.
+     * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  The
+     * caller will synthesize BDRV_BLOCK_ALLOCATED based on the
+     * non-zero results.  See block.h for the overall meaning of the
+     * bits.  As a hint, the flags in @mode may include a bitwise-or
+     * of BDRV_WANT_ALLOCATED, BDRV_WANT_OFFSET_VALID, or
+     * BDRV_WANT_ZERO based on what the caller is looking for in the
+     * results.  The block layer guarantees input clamped to
+     * bdrv_getlength() and aligned to request_alignment, as well as
+     * non-NULL pnum, map, and file; in turn, the driver must return
+     * an error or set pnum to an aligned non-zero value.
      *
      * Note that @bytes is just a hint on how big of a region the
      * caller wants to inspect.  It is not a limit on *pnum.
@@ -624,8 +625,8 @@ struct BlockDriver {
      * to clamping *pnum for return to its caller.
      */
     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_block_status)(
-        BlockDriverState *bs,
-        bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
+        BlockDriverState *bs, unsigned int mode,
+        int64_t offset, int64_t bytes, int64_t *pnum,
         int64_t *map, BlockDriverState **file);

     /*
@@ -649,8 +650,8 @@ struct BlockDriver {
         QEMUIOVector *qiov, size_t qiov_offset);

     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_snapshot_block_status)(
-        BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-        int64_t *pnum, int64_t *map, BlockDriverState **file);
+        BlockDriverState *bs, unsigned int mode, int64_t offset,
+        int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file);

     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_pdiscard_snapshot)(
         BlockDriverState *bs, int64_t offset, int64_t bytes);
diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index 4a7cf2b4fdc..4f94eb3c5a2 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -38,8 +38,8 @@
 int coroutine_fn GRAPH_RDLOCK bdrv_co_preadv_snapshot(BdrvChild *child,
     int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset);
 int coroutine_fn GRAPH_RDLOCK bdrv_co_snapshot_block_status(
-    BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-    int64_t *pnum, int64_t *map, BlockDriverState **file);
+    BlockDriverState *bs, unsigned int mode, int64_t offset,
+    int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file);
 int coroutine_fn GRAPH_RDLOCK bdrv_co_pdiscard_snapshot(BlockDriverState *bs,
     int64_t offset, int64_t bytes);

diff --git a/block/io.c b/block/io.c
index 6d98b0abb98..b5b143cd1b0 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2364,10 +2364,8 @@ int bdrv_flush_all(void)
  * Drivers not implementing the functionality are assumed to not support
  * backing files, hence all their sectors are reported as allocated.
  *
- * If 'want_zero' is true, the caller is querying for mapping
- * purposes, with a focus on valid BDRV_BLOCK_OFFSET_VALID, _DATA, and
- * _ZERO where possible; otherwise, the result favors larger 'pnum',
- * with a focus on accurate BDRV_BLOCK_ALLOCATED.
+ * 'mode' serves as a hint as to which results are favored; see the
+ * BDRV_WANT_* macros for details.
  *
  * If 'offset' is beyond the end of the disk image the return value is
  * BDRV_BLOCK_EOF and 'pnum' is set to 0.
@@ -2387,7 +2385,7 @@ int bdrv_flush_all(void)
  * set to the host mapping and BDS corresponding to the guest offset.
  */
 static int coroutine_fn GRAPH_RDLOCK
-bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
+bdrv_co_do_block_status(BlockDriverState *bs, unsigned int mode,
                         int64_t offset, int64_t bytes,
                         int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
@@ -2476,7 +2474,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
             local_file = bs;
             local_map = aligned_offset;
         } else {
-            ret = bs->drv->bdrv_co_block_status(bs, want_zero, aligned_offset,
+            ret = bs->drv->bdrv_co_block_status(bs, mode, aligned_offset,
                                                 aligned_bytes, pnum, &local_map,
                                                 &local_file);

@@ -2488,10 +2486,10 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
              * the cache requires an RCU update, so double check here to avoid
              * such an update if possible.
              *
-             * Check want_zero, because we only want to update the cache when we
+             * Check mode, because we only want to update the cache when we
              * have accurate information about what is zero and what is data.
              */
-            if (want_zero &&
+            if (mode == BDRV_WANT_PRECISE &&
                 ret == (BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID) &&
                 QLIST_EMPTY(&bs->children))
             {
@@ -2548,7 +2546,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,

     if (ret & BDRV_BLOCK_RAW) {
         assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
-        ret = bdrv_co_do_block_status(local_file, want_zero, local_map,
+        ret = bdrv_co_do_block_status(local_file, mode, local_map,
                                       *pnum, pnum, &local_map, &local_file);
         goto out;
     }
@@ -2560,7 +2558,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,

         if (!cow_bs) {
             ret |= BDRV_BLOCK_ZERO;
-        } else if (want_zero) {
+        } else if (mode == BDRV_WANT_PRECISE) {
             int64_t size2 = bdrv_co_getlength(cow_bs);

             if (size2 >= 0 && offset >= size2) {
@@ -2569,14 +2567,14 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
         }
     }

-    if (want_zero && ret & BDRV_BLOCK_RECURSE &&
+    if (mode == BDRV_WANT_PRECISE && ret & BDRV_BLOCK_RECURSE &&
         local_file && local_file != bs &&
         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
         (ret & BDRV_BLOCK_OFFSET_VALID)) {
         int64_t file_pnum;
         int ret2;

-        ret2 = bdrv_co_do_block_status(local_file, want_zero, local_map,
+        ret2 = bdrv_co_do_block_status(local_file, mode, local_map,
                                        *pnum, &file_pnum, NULL, NULL);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
@@ -2627,7 +2625,7 @@ int coroutine_fn
 bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   BlockDriverState *base,
                                   bool include_base,
-                                  bool want_zero,
+                                  unsigned int mode,
                                   int64_t offset,
                                   int64_t bytes,
                                   int64_t *pnum,
@@ -2654,7 +2652,7 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
         return 0;
     }

-    ret = bdrv_co_do_block_status(bs, want_zero, offset, bytes, pnum,
+    ret = bdrv_co_do_block_status(bs, mode, offset, bytes, pnum,
                                   map, file);
     ++*depth;
     if (ret < 0 || *pnum == 0 || ret & BDRV_BLOCK_ALLOCATED || bs == base) {
@@ -2671,7 +2669,7 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
     for (p = bdrv_filter_or_cow_bs(bs); include_base || p != base;
          p = bdrv_filter_or_cow_bs(p))
     {
-        ret = bdrv_co_do_block_status(p, want_zero, offset, bytes, pnum,
+        ret = bdrv_co_do_block_status(p, mode, offset, bytes, pnum,
                                       map, file);
         ++*depth;
         if (ret < 0) {
@@ -2734,7 +2732,8 @@ int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
                                             BlockDriverState **file)
 {
     IO_CODE();
-    return bdrv_co_common_block_status_above(bs, base, false, true, offset,
+    return bdrv_co_common_block_status_above(bs, base, false,
+                                             BDRV_WANT_PRECISE, offset,
                                              bytes, pnum, map, file, NULL);
 }

@@ -2765,8 +2764,9 @@ int coroutine_fn bdrv_co_is_zero_fast(BlockDriverState *bs, int64_t offset,
         return 1;
     }

-    ret = bdrv_co_common_block_status_above(bs, NULL, false, false, offset,
-                                            bytes, &pnum, NULL, NULL, NULL);
+    ret = bdrv_co_common_block_status_above(bs, NULL, false, BDRV_WANT_ZERO,
+                                            offset, bytes, &pnum, NULL, NULL,
+                                            NULL);

     if (ret < 0) {
         return ret;
@@ -2782,9 +2782,9 @@ int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t offset,
     int64_t dummy;
     IO_CODE();

-    ret = bdrv_co_common_block_status_above(bs, bs, true, false, offset,
-                                            bytes, pnum ? pnum : &dummy, NULL,
-                                            NULL, NULL);
+    ret = bdrv_co_common_block_status_above(bs, bs, true, BDRV_WANT_ALLOCATED,
+                                            offset, bytes, pnum ? pnum : &dummy,
+                                            NULL, NULL, NULL);
     if (ret < 0) {
         return ret;
     }
@@ -2817,7 +2817,8 @@ int coroutine_fn bdrv_co_is_allocated_above(BlockDriverState *bs,
     int ret;
     IO_CODE();

-    ret = bdrv_co_common_block_status_above(bs, base, include_base, false,
+    ret = bdrv_co_common_block_status_above(bs, base, include_base,
+                                            BDRV_WANT_ALLOCATED,
                                             offset, bytes, pnum, NULL, NULL,
                                             &depth);
     if (ret < 0) {
@@ -3698,8 +3699,8 @@ bdrv_co_preadv_snapshot(BdrvChild *child, int64_t offset, int64_t bytes,
 }

 int coroutine_fn
-bdrv_co_snapshot_block_status(BlockDriverState *bs,
-                              bool want_zero, int64_t offset, int64_t bytes,
+bdrv_co_snapshot_block_status(BlockDriverState *bs, unsigned int mode,
+                              int64_t offset, int64_t bytes,
                               int64_t *pnum, int64_t *map,
                               BlockDriverState **file)
 {
@@ -3717,7 +3718,7 @@ bdrv_co_snapshot_block_status(BlockDriverState *bs,
     }

     bdrv_inc_in_flight(bs);
-    ret = drv->bdrv_co_snapshot_block_status(bs, want_zero, offset, bytes,
+    ret = drv->bdrv_co_snapshot_block_status(bs, mode, offset, bytes,
                                              pnum, map, file);
     bdrv_dec_in_flight(bs);

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 1c1967f8e0a..c54aee0c84b 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -751,9 +751,9 @@ blkdebug_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
 }

 static int coroutine_fn GRAPH_RDLOCK
-blkdebug_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                         int64_t bytes, int64_t *pnum, int64_t *map,
-                         BlockDriverState **file)
+blkdebug_co_block_status(BlockDriverState *bs, unsigned int mode,
+                         int64_t offset, int64_t bytes, int64_t *pnum,
+                         int64_t *map, BlockDriverState **file)
 {
     int err;

diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index fd470f5f926..2badb3a8856 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -291,8 +291,8 @@ cbw_co_preadv_snapshot(BlockDriverState *bs, int64_t offset, int64_t bytes,
 }

 static int coroutine_fn GRAPH_RDLOCK
-cbw_co_snapshot_block_status(BlockDriverState *bs,
-                             bool want_zero, int64_t offset, int64_t bytes,
+cbw_co_snapshot_block_status(BlockDriverState *bs, unsigned int mode,
+                             int64_t offset, int64_t bytes,
                              int64_t *pnum, int64_t *map,
                              BlockDriverState **file)
 {
diff --git a/block/file-posix.c b/block/file-posix.c
index ef52ed9169e..805a1a2949b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -3273,7 +3273,7 @@ static int find_allocation(BlockDriverState *bs, off_t start,
  * well exceed it.
  */
 static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
-                                            bool want_zero,
+                                            unsigned int mode,
                                             int64_t offset,
                                             int64_t bytes, int64_t *pnum,
                                             int64_t *map,
@@ -3289,7 +3289,7 @@ static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (!want_zero) {
+    if (mode != BDRV_WANT_PRECISE) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/gluster.c b/block/gluster.c
index 8712aa606a4..1a2ef53e9b0 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1461,7 +1461,7 @@ exit:
  * (Based on raw_co_block_status() from file-posix.c.)
  */
 static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
-                                                     bool want_zero,
+                                                     unsigned int mode,
                                                      int64_t offset,
                                                      int64_t bytes,
                                                      int64_t *pnum,
@@ -1478,7 +1478,7 @@ static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (!want_zero) {
+    if (mode != BDRV_WANT_PRECISE) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/iscsi.c b/block/iscsi.c
index 2f0f4dac097..15b96ee8800 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -694,9 +694,9 @@ out_unlock:


 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,
+                                              unsigned int mode,
+                                              int64_t offset, int64_t bytes,
+                                              int64_t *pnum, int64_t *map,
                                               BlockDriverState **file)
 {
     IscsiLun *iscsilun = bs->opaque;
diff --git a/block/nbd.c b/block/nbd.c
index 887841bc813..d5a2b21c6d1 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1397,8 +1397,8 @@ nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
 }

 static int coroutine_fn GRAPH_RDLOCK nbd_client_co_block_status(
-        BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-        int64_t *pnum, int64_t *map, BlockDriverState **file)
+        BlockDriverState *bs, unsigned int mode, int64_t offset,
+        int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
     int ret, request_ret;
     NBDExtent64 extent = { 0 };
diff --git a/block/null.c b/block/null.c
index dc0b1fdbd9b..4e448d593d7 100644
--- a/block/null.c
+++ b/block/null.c
@@ -227,9 +227,9 @@ static int null_reopen_prepare(BDRVReopenState *reopen_state,
 }

 static int coroutine_fn null_co_block_status(BlockDriverState *bs,
-                                             bool want_zero, int64_t offset,
-                                             int64_t bytes, int64_t *pnum,
-                                             int64_t *map,
+                                             unsigned int mode,
+                                             int64_t offset, int64_t bytes,
+                                             int64_t *pnum, int64_t *map,
                                              BlockDriverState **file)
 {
     BDRVNullState *s = bs->opaque;
diff --git a/block/parallels.c b/block/parallels.c
index 347ca127f34..3a375e2a8ab 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -416,9 +416,9 @@ parallels_co_flush_to_os(BlockDriverState *bs)
 }

 static int coroutine_fn GRAPH_RDLOCK
-parallels_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                          int64_t bytes, int64_t *pnum, int64_t *map,
-                          BlockDriverState **file)
+parallels_co_block_status(BlockDriverState *bs, unsigned int mode,
+                          int64_t offset, int64_t bytes, int64_t *pnum,
+                          int64_t *map, BlockDriverState **file)
 {
     BDRVParallelsState *s = bs->opaque;
     int count;
diff --git a/block/qcow.c b/block/qcow.c
index da8ad4d2430..8a3e7591a92 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -530,7 +530,7 @@ get_cluster_offset(BlockDriverState *bs, uint64_t offset, int allocate,
 }

 static int coroutine_fn GRAPH_RDLOCK
-qcow_co_block_status(BlockDriverState *bs, bool want_zero,
+qcow_co_block_status(BlockDriverState *bs, unsigned int mode,
                      int64_t offset, int64_t bytes, int64_t *pnum,
                      int64_t *map, BlockDriverState **file)
 {
diff --git a/block/qcow2.c b/block/qcow2.c
index 7774e7f0909..66fba89b414 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2141,9 +2141,9 @@ static void qcow2_join_options(QDict *options, QDict *old_options)
 }

 static int coroutine_fn GRAPH_RDLOCK
-qcow2_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                      int64_t count, int64_t *pnum, int64_t *map,
-                      BlockDriverState **file)
+qcow2_co_block_status(BlockDriverState *bs, unsigned int mode,
+                      int64_t offset, int64_t count, int64_t *pnum,
+                      int64_t *map, BlockDriverState **file)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t host_offset;
diff --git a/block/qed.c b/block/qed.c
index ac24449ffb3..4a36fb39294 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -833,9 +833,9 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-bdrv_qed_co_block_status(BlockDriverState *bs, bool want_zero, int64_t pos,
-                         int64_t bytes, int64_t *pnum, int64_t *map,
-                         BlockDriverState **file)
+bdrv_qed_co_block_status(BlockDriverState *bs, unsigned int mode,
+                         int64_t pos, int64_t bytes, int64_t *pnum,
+                         int64_t *map, BlockDriverState **file)
 {
     BDRVQEDState *s = bs->opaque;
     size_t len = MIN(bytes, SIZE_MAX);
diff --git a/block/quorum.c b/block/quorum.c
index 30747a6df93..ed8ce801ee3 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -1226,7 +1226,7 @@ static void quorum_child_perm(BlockDriverState *bs, BdrvChild *c,
  * region contains zeroes, and BDRV_BLOCK_DATA otherwise.
  */
 static int coroutine_fn GRAPH_RDLOCK
-quorum_co_block_status(BlockDriverState *bs, bool want_zero,
+quorum_co_block_status(BlockDriverState *bs, unsigned int mode,
                        int64_t offset, int64_t count,
                        int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
@@ -1238,7 +1238,7 @@ quorum_co_block_status(BlockDriverState *bs, bool want_zero,
     for (i = 0; i < s->num_children; i++) {
         int64_t bytes;
         ret = bdrv_co_common_block_status_above(s->children[i]->bs, NULL, false,
-                                                want_zero, offset, count,
+                                                mode, offset, count,
                                                 &bytes, NULL, NULL, NULL);
         if (ret < 0) {
             quorum_report_bad(QUORUM_OP_TYPE_READ, offset, count,
diff --git a/block/raw-format.c b/block/raw-format.c
index e08526e2eca..df16ac1ea25 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -283,8 +283,8 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-raw_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                    int64_t bytes, int64_t *pnum, int64_t *map,
+raw_co_block_status(BlockDriverState *bs, unsigned int mode,
+                    int64_t offset, int64_t bytes, int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
 {
     BDRVRawState *s = bs->opaque;
diff --git a/block/rbd.c b/block/rbd.c
index 7446e66659e..951cd63f9ae 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1503,9 +1503,9 @@ static int qemu_rbd_diff_iterate_cb(uint64_t offs, size_t len,
 }

 static int coroutine_fn qemu_rbd_co_block_status(BlockDriverState *bs,
-                                                 bool want_zero, int64_t offset,
-                                                 int64_t bytes, int64_t *pnum,
-                                                 int64_t *map,
+                                                 unsigned int mode,
+                                                 int64_t offset, int64_t bytes,
+                                                 int64_t *pnum, int64_t *map,
                                                  BlockDriverState **file)
 {
     BDRVRBDState *s = bs->opaque;
diff --git a/block/snapshot-access.c b/block/snapshot-access.c
index 71ac83c01f0..17ed2402db8 100644
--- a/block/snapshot-access.c
+++ b/block/snapshot-access.c
@@ -41,11 +41,11 @@ snapshot_access_co_preadv_part(BlockDriverState *bs,

 static int coroutine_fn GRAPH_RDLOCK
 snapshot_access_co_block_status(BlockDriverState *bs,
-                                bool want_zero, int64_t offset,
+                                unsigned int mode, int64_t offset,
                                 int64_t bytes, int64_t *pnum,
                                 int64_t *map, BlockDriverState **file)
 {
-    return bdrv_co_snapshot_block_status(bs->file->bs, want_zero, offset,
+    return bdrv_co_snapshot_block_status(bs->file->bs, mode, offset,
                                          bytes, pnum, map, file);
 }

diff --git a/block/vdi.c b/block/vdi.c
index a2da6ecab01..3ddc62a5690 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -523,8 +523,8 @@ static int vdi_reopen_prepare(BDRVReopenState *state,
 }

 static int coroutine_fn GRAPH_RDLOCK
-vdi_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                    int64_t bytes, int64_t *pnum, int64_t *map,
+vdi_co_block_status(BlockDriverState *bs, unsigned int mode,
+                    int64_t offset, int64_t bytes, int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
 {
     BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
diff --git a/block/vmdk.c b/block/vmdk.c
index 2adec499122..9c7ab037e14 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1777,7 +1777,7 @@ static inline uint64_t vmdk_find_offset_in_cluster(VmdkExtent *extent,
 }

 static int coroutine_fn GRAPH_RDLOCK
-vmdk_co_block_status(BlockDriverState *bs, bool want_zero,
+vmdk_co_block_status(BlockDriverState *bs, unsigned int mode,
                      int64_t offset, int64_t bytes, int64_t *pnum,
                      int64_t *map, BlockDriverState **file)
 {
diff --git a/block/vpc.c b/block/vpc.c
index 0309e319f60..801ff5793f8 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -726,7 +726,7 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-vpc_co_block_status(BlockDriverState *bs, bool want_zero,
+vpc_co_block_status(BlockDriverState *bs, unsigned int mode,
                     int64_t offset, int64_t bytes,
                     int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
diff --git a/block/vvfat.c b/block/vvfat.c
index 91d69b3cc83..814796d9185 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -3134,9 +3134,9 @@ vvfat_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
 }

 static int coroutine_fn vvfat_co_block_status(BlockDriverState *bs,
-                                              bool want_zero, int64_t offset,
-                                              int64_t bytes, int64_t *n,
-                                              int64_t *map,
+                                              unsigned int mode,
+                                              int64_t offset, int64_t bytes,
+                                              int64_t *n, int64_t *map,
                                               BlockDriverState **file)
 {
     *n = bytes;
diff --git a/tests/unit/test-block-iothread.c b/tests/unit/test-block-iothread.c
index 2b358eaaa82..e26b3be5939 100644
--- a/tests/unit/test-block-iothread.c
+++ b/tests/unit/test-block-iothread.c
@@ -63,7 +63,7 @@ bdrv_test_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
 }

 static int coroutine_fn bdrv_test_co_block_status(BlockDriverState *bs,
-                                                  bool want_zero,
+                                                  unsigned int mode,
                                                   int64_t offset, int64_t count,
                                                   int64_t *pnum, int64_t *map,
                                                   BlockDriverState **file)
-- 
2.49.0


From eblake at redhat.com  Fri May  9 20:40:19 2025
From: eblake at redhat.com (Eric Blake)
Date: Fri,  9 May 2025 15:40:19 -0500
Subject: [GEDI] [PATCH v4 02/13] file-posix,
	gluster: Handle zero block status hint better
In-Reply-To: <20250509204341.3553601-15-eblake@redhat.com>
References: <20250509204341.3553601-15-eblake@redhat.com>
Message-ID: <20250509204341.3553601-17-eblake@redhat.com>

Although the previous patch to change 'bool want_zero' into a bitmask
made no semantic change, it is now time to differentiate.  When the
caller specifically wants to know what parts of the file read as zero,
we need to use lseek and actually reporting holes, rather than
short-circuiting and advertising full allocation.

This change will be utilized in later patches to let mirroring
optimize for the case when the destination already reads as zeroes.

Signed-off-by: Eric Blake <eblake at redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
---
 block/file-posix.c | 3 ++-
 block/gluster.c    | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 805a1a2949b..ec95b748696 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -3289,7 +3289,8 @@ static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (mode != BDRV_WANT_PRECISE) {
+    if (!(mode & BDRV_WANT_ZERO)) {
+        /* There is no backing file - all bytes are allocated in this file.  */
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/gluster.c b/block/gluster.c
index 1a2ef53e9b0..89abd40f313 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1478,7 +1478,7 @@ static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (mode != BDRV_WANT_PRECISE) {
+    if (!(mode & BDRV_WANT_ZERO)) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
-- 
2.49.0


From eblake at redhat.com  Thu May 15 02:28:44 2025
From: eblake at redhat.com (Eric Blake)
Date: Wed, 14 May 2025 21:28:44 -0500
Subject: [GEDI] [PULL 01/14] block: Expand block status mode from bool to
	flags
In-Reply-To: <20250515022904.575509-16-eblake@redhat.com>
References: <20250515022904.575509-16-eblake@redhat.com>
Message-ID: <20250515022904.575509-17-eblake@redhat.com>

This patch is purely mechanical, changing bool want_zero into an
unsigned int for bitwise-or of flags.  As of this patch, all
implementations are unchanged (the old want_zero==true is now
mode==BDRV_WANT_PRECISE which is a superset of BDRV_WANT_ZERO); but
the callers in io.c that used to pass want_zero==false are now
prepared for future driver changes that can now distinguish bewteen
BDRV_WANT_ZERO vs. BDRV_WANT_ALLOCATED.  The next patch will actually
change the file-posix driver along those lines, now that we have
more-specific hints.

As for the background why this patch is useful: right now, the
file-posix driver recognizes that if allocation is being queried, the
entire image can be reported as allocated (there is no backing file to
refer to) - but this throws away information on whether the entire
image reads as zero (trivially true if lseek(SEEK_HOLE) at offset 0
returns -ENXIO, a bit more complicated to prove if the raw file was
created with 'qemu-img create' since we intentionally allocate a small
chunk of all-zero data to help with alignment probing).  Later patches
will add a generic algorithm for seeing if an entire file reads as
zeroes.

Signed-off-by: Eric Blake <eblake at redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
Message-ID: <20250509204341.3553601-16-eblake at redhat.com>
---
 block/coroutines.h               |  4 +--
 include/block/block-common.h     | 11 +++++++
 include/block/block_int-common.h | 27 +++++++++--------
 include/block/block_int-io.h     |  4 +--
 block/io.c                       | 51 ++++++++++++++++----------------
 block/blkdebug.c                 |  6 ++--
 block/copy-before-write.c        |  4 +--
 block/file-posix.c               |  4 +--
 block/gluster.c                  |  4 +--
 block/iscsi.c                    |  6 ++--
 block/nbd.c                      |  4 +--
 block/null.c                     |  6 ++--
 block/parallels.c                |  6 ++--
 block/qcow.c                     |  2 +-
 block/qcow2.c                    |  6 ++--
 block/qed.c                      |  6 ++--
 block/quorum.c                   |  4 +--
 block/raw-format.c               |  4 +--
 block/rbd.c                      |  6 ++--
 block/snapshot-access.c          |  4 +--
 block/vdi.c                      |  4 +--
 block/vmdk.c                     |  2 +-
 block/vpc.c                      |  2 +-
 block/vvfat.c                    |  6 ++--
 tests/unit/test-block-iothread.c |  2 +-
 25 files changed, 99 insertions(+), 86 deletions(-)

diff --git a/block/coroutines.h b/block/coroutines.h
index 79e5efbf752..892646bb7aa 100644
--- a/block/coroutines.h
+++ b/block/coroutines.h
@@ -47,7 +47,7 @@ int coroutine_fn GRAPH_RDLOCK
 bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   BlockDriverState *base,
                                   bool include_base,
-                                  bool want_zero,
+                                  unsigned int mode,
                                   int64_t offset,
                                   int64_t bytes,
                                   int64_t *pnum,
@@ -78,7 +78,7 @@ int co_wrapper_mixed_bdrv_rdlock
 bdrv_common_block_status_above(BlockDriverState *bs,
                                BlockDriverState *base,
                                bool include_base,
-                               bool want_zero,
+                               unsigned int mode,
                                int64_t offset,
                                int64_t bytes,
                                int64_t *pnum,
diff --git a/include/block/block-common.h b/include/block/block-common.h
index 0b831ef87b1..c8c626daeaa 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -333,6 +333,17 @@ typedef enum {
 #define BDRV_BLOCK_RECURSE      0x40
 #define BDRV_BLOCK_COMPRESSED   0x80

+/*
+ * Block status hints: the bitwise-or of these flags emphasize what
+ * the caller hopes to learn, and some drivers may be able to give
+ * faster answers by doing less work when the hint permits.
+ */
+#define BDRV_WANT_ZERO          BDRV_BLOCK_ZERO
+#define BDRV_WANT_OFFSET_VALID  BDRV_BLOCK_OFFSET_VALID
+#define BDRV_WANT_ALLOCATED     BDRV_BLOCK_ALLOCATED
+#define BDRV_WANT_PRECISE       (BDRV_WANT_ZERO | BDRV_WANT_OFFSET_VALID | \
+                                 BDRV_WANT_OFFSET_VALID)
+
 typedef QTAILQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;

 typedef struct BDRVReopenState {
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 0d8187f6567..2982dd31180 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -604,15 +604,16 @@ struct BlockDriver {
      * according to the current layer, and should only need to set
      * BDRV_BLOCK_DATA, BDRV_BLOCK_ZERO, BDRV_BLOCK_OFFSET_VALID,
      * and/or BDRV_BLOCK_RAW; if the current layer defers to a backing
-     * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  See
-     * block.h for the overall meaning of the bits.  As a hint, the
-     * flag want_zero is true if the caller cares more about precise
-     * mappings (favor accurate _OFFSET_VALID/_ZERO) or false for
-     * overall allocation (favor larger *pnum, perhaps by reporting
-     * _DATA instead of _ZERO).  The block layer guarantees input
-     * clamped to bdrv_getlength() and aligned to request_alignment,
-     * as well as non-NULL pnum, map, and file; in turn, the driver
-     * must return an error or set pnum to an aligned non-zero value.
+     * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  The
+     * caller will synthesize BDRV_BLOCK_ALLOCATED based on the
+     * non-zero results.  See block.h for the overall meaning of the
+     * bits.  As a hint, the flags in @mode may include a bitwise-or
+     * of BDRV_WANT_ALLOCATED, BDRV_WANT_OFFSET_VALID, or
+     * BDRV_WANT_ZERO based on what the caller is looking for in the
+     * results.  The block layer guarantees input clamped to
+     * bdrv_getlength() and aligned to request_alignment, as well as
+     * non-NULL pnum, map, and file; in turn, the driver must return
+     * an error or set pnum to an aligned non-zero value.
      *
      * Note that @bytes is just a hint on how big of a region the
      * caller wants to inspect.  It is not a limit on *pnum.
@@ -624,8 +625,8 @@ struct BlockDriver {
      * to clamping *pnum for return to its caller.
      */
     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_block_status)(
-        BlockDriverState *bs,
-        bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
+        BlockDriverState *bs, unsigned int mode,
+        int64_t offset, int64_t bytes, int64_t *pnum,
         int64_t *map, BlockDriverState **file);

     /*
@@ -649,8 +650,8 @@ struct BlockDriver {
         QEMUIOVector *qiov, size_t qiov_offset);

     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_snapshot_block_status)(
-        BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-        int64_t *pnum, int64_t *map, BlockDriverState **file);
+        BlockDriverState *bs, unsigned int mode, int64_t offset,
+        int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file);

     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_pdiscard_snapshot)(
         BlockDriverState *bs, int64_t offset, int64_t bytes);
diff --git a/include/block/block_int-io.h b/include/block/block_int-io.h
index 4a7cf2b4fdc..4f94eb3c5a2 100644
--- a/include/block/block_int-io.h
+++ b/include/block/block_int-io.h
@@ -38,8 +38,8 @@
 int coroutine_fn GRAPH_RDLOCK bdrv_co_preadv_snapshot(BdrvChild *child,
     int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset);
 int coroutine_fn GRAPH_RDLOCK bdrv_co_snapshot_block_status(
-    BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-    int64_t *pnum, int64_t *map, BlockDriverState **file);
+    BlockDriverState *bs, unsigned int mode, int64_t offset,
+    int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file);
 int coroutine_fn GRAPH_RDLOCK bdrv_co_pdiscard_snapshot(BlockDriverState *bs,
     int64_t offset, int64_t bytes);

diff --git a/block/io.c b/block/io.c
index 6d98b0abb98..b5b143cd1b0 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2364,10 +2364,8 @@ int bdrv_flush_all(void)
  * Drivers not implementing the functionality are assumed to not support
  * backing files, hence all their sectors are reported as allocated.
  *
- * If 'want_zero' is true, the caller is querying for mapping
- * purposes, with a focus on valid BDRV_BLOCK_OFFSET_VALID, _DATA, and
- * _ZERO where possible; otherwise, the result favors larger 'pnum',
- * with a focus on accurate BDRV_BLOCK_ALLOCATED.
+ * 'mode' serves as a hint as to which results are favored; see the
+ * BDRV_WANT_* macros for details.
  *
  * If 'offset' is beyond the end of the disk image the return value is
  * BDRV_BLOCK_EOF and 'pnum' is set to 0.
@@ -2387,7 +2385,7 @@ int bdrv_flush_all(void)
  * set to the host mapping and BDS corresponding to the guest offset.
  */
 static int coroutine_fn GRAPH_RDLOCK
-bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
+bdrv_co_do_block_status(BlockDriverState *bs, unsigned int mode,
                         int64_t offset, int64_t bytes,
                         int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
@@ -2476,7 +2474,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
             local_file = bs;
             local_map = aligned_offset;
         } else {
-            ret = bs->drv->bdrv_co_block_status(bs, want_zero, aligned_offset,
+            ret = bs->drv->bdrv_co_block_status(bs, mode, aligned_offset,
                                                 aligned_bytes, pnum, &local_map,
                                                 &local_file);

@@ -2488,10 +2486,10 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
              * the cache requires an RCU update, so double check here to avoid
              * such an update if possible.
              *
-             * Check want_zero, because we only want to update the cache when we
+             * Check mode, because we only want to update the cache when we
              * have accurate information about what is zero and what is data.
              */
-            if (want_zero &&
+            if (mode == BDRV_WANT_PRECISE &&
                 ret == (BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID) &&
                 QLIST_EMPTY(&bs->children))
             {
@@ -2548,7 +2546,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,

     if (ret & BDRV_BLOCK_RAW) {
         assert(ret & BDRV_BLOCK_OFFSET_VALID && local_file);
-        ret = bdrv_co_do_block_status(local_file, want_zero, local_map,
+        ret = bdrv_co_do_block_status(local_file, mode, local_map,
                                       *pnum, pnum, &local_map, &local_file);
         goto out;
     }
@@ -2560,7 +2558,7 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,

         if (!cow_bs) {
             ret |= BDRV_BLOCK_ZERO;
-        } else if (want_zero) {
+        } else if (mode == BDRV_WANT_PRECISE) {
             int64_t size2 = bdrv_co_getlength(cow_bs);

             if (size2 >= 0 && offset >= size2) {
@@ -2569,14 +2567,14 @@ bdrv_co_do_block_status(BlockDriverState *bs, bool want_zero,
         }
     }

-    if (want_zero && ret & BDRV_BLOCK_RECURSE &&
+    if (mode == BDRV_WANT_PRECISE && ret & BDRV_BLOCK_RECURSE &&
         local_file && local_file != bs &&
         (ret & BDRV_BLOCK_DATA) && !(ret & BDRV_BLOCK_ZERO) &&
         (ret & BDRV_BLOCK_OFFSET_VALID)) {
         int64_t file_pnum;
         int ret2;

-        ret2 = bdrv_co_do_block_status(local_file, want_zero, local_map,
+        ret2 = bdrv_co_do_block_status(local_file, mode, local_map,
                                        *pnum, &file_pnum, NULL, NULL);
         if (ret2 >= 0) {
             /* Ignore errors.  This is just providing extra information, it
@@ -2627,7 +2625,7 @@ int coroutine_fn
 bdrv_co_common_block_status_above(BlockDriverState *bs,
                                   BlockDriverState *base,
                                   bool include_base,
-                                  bool want_zero,
+                                  unsigned int mode,
                                   int64_t offset,
                                   int64_t bytes,
                                   int64_t *pnum,
@@ -2654,7 +2652,7 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
         return 0;
     }

-    ret = bdrv_co_do_block_status(bs, want_zero, offset, bytes, pnum,
+    ret = bdrv_co_do_block_status(bs, mode, offset, bytes, pnum,
                                   map, file);
     ++*depth;
     if (ret < 0 || *pnum == 0 || ret & BDRV_BLOCK_ALLOCATED || bs == base) {
@@ -2671,7 +2669,7 @@ bdrv_co_common_block_status_above(BlockDriverState *bs,
     for (p = bdrv_filter_or_cow_bs(bs); include_base || p != base;
          p = bdrv_filter_or_cow_bs(p))
     {
-        ret = bdrv_co_do_block_status(p, want_zero, offset, bytes, pnum,
+        ret = bdrv_co_do_block_status(p, mode, offset, bytes, pnum,
                                       map, file);
         ++*depth;
         if (ret < 0) {
@@ -2734,7 +2732,8 @@ int coroutine_fn bdrv_co_block_status_above(BlockDriverState *bs,
                                             BlockDriverState **file)
 {
     IO_CODE();
-    return bdrv_co_common_block_status_above(bs, base, false, true, offset,
+    return bdrv_co_common_block_status_above(bs, base, false,
+                                             BDRV_WANT_PRECISE, offset,
                                              bytes, pnum, map, file, NULL);
 }

@@ -2765,8 +2764,9 @@ int coroutine_fn bdrv_co_is_zero_fast(BlockDriverState *bs, int64_t offset,
         return 1;
     }

-    ret = bdrv_co_common_block_status_above(bs, NULL, false, false, offset,
-                                            bytes, &pnum, NULL, NULL, NULL);
+    ret = bdrv_co_common_block_status_above(bs, NULL, false, BDRV_WANT_ZERO,
+                                            offset, bytes, &pnum, NULL, NULL,
+                                            NULL);

     if (ret < 0) {
         return ret;
@@ -2782,9 +2782,9 @@ int coroutine_fn bdrv_co_is_allocated(BlockDriverState *bs, int64_t offset,
     int64_t dummy;
     IO_CODE();

-    ret = bdrv_co_common_block_status_above(bs, bs, true, false, offset,
-                                            bytes, pnum ? pnum : &dummy, NULL,
-                                            NULL, NULL);
+    ret = bdrv_co_common_block_status_above(bs, bs, true, BDRV_WANT_ALLOCATED,
+                                            offset, bytes, pnum ? pnum : &dummy,
+                                            NULL, NULL, NULL);
     if (ret < 0) {
         return ret;
     }
@@ -2817,7 +2817,8 @@ int coroutine_fn bdrv_co_is_allocated_above(BlockDriverState *bs,
     int ret;
     IO_CODE();

-    ret = bdrv_co_common_block_status_above(bs, base, include_base, false,
+    ret = bdrv_co_common_block_status_above(bs, base, include_base,
+                                            BDRV_WANT_ALLOCATED,
                                             offset, bytes, pnum, NULL, NULL,
                                             &depth);
     if (ret < 0) {
@@ -3698,8 +3699,8 @@ bdrv_co_preadv_snapshot(BdrvChild *child, int64_t offset, int64_t bytes,
 }

 int coroutine_fn
-bdrv_co_snapshot_block_status(BlockDriverState *bs,
-                              bool want_zero, int64_t offset, int64_t bytes,
+bdrv_co_snapshot_block_status(BlockDriverState *bs, unsigned int mode,
+                              int64_t offset, int64_t bytes,
                               int64_t *pnum, int64_t *map,
                               BlockDriverState **file)
 {
@@ -3717,7 +3718,7 @@ bdrv_co_snapshot_block_status(BlockDriverState *bs,
     }

     bdrv_inc_in_flight(bs);
-    ret = drv->bdrv_co_snapshot_block_status(bs, want_zero, offset, bytes,
+    ret = drv->bdrv_co_snapshot_block_status(bs, mode, offset, bytes,
                                              pnum, map, file);
     bdrv_dec_in_flight(bs);

diff --git a/block/blkdebug.c b/block/blkdebug.c
index 1c1967f8e0a..c54aee0c84b 100644
--- a/block/blkdebug.c
+++ b/block/blkdebug.c
@@ -751,9 +751,9 @@ blkdebug_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
 }

 static int coroutine_fn GRAPH_RDLOCK
-blkdebug_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                         int64_t bytes, int64_t *pnum, int64_t *map,
-                         BlockDriverState **file)
+blkdebug_co_block_status(BlockDriverState *bs, unsigned int mode,
+                         int64_t offset, int64_t bytes, int64_t *pnum,
+                         int64_t *map, BlockDriverState **file)
 {
     int err;

diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index 00af0b18ac4..36d5d3ed9b0 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -291,8 +291,8 @@ cbw_co_preadv_snapshot(BlockDriverState *bs, int64_t offset, int64_t bytes,
 }

 static int coroutine_fn GRAPH_RDLOCK
-cbw_co_snapshot_block_status(BlockDriverState *bs,
-                             bool want_zero, int64_t offset, int64_t bytes,
+cbw_co_snapshot_block_status(BlockDriverState *bs, unsigned int mode,
+                             int64_t offset, int64_t bytes,
                              int64_t *pnum, int64_t *map,
                              BlockDriverState **file)
 {
diff --git a/block/file-posix.c b/block/file-posix.c
index ef52ed9169e..805a1a2949b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -3273,7 +3273,7 @@ static int find_allocation(BlockDriverState *bs, off_t start,
  * well exceed it.
  */
 static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
-                                            bool want_zero,
+                                            unsigned int mode,
                                             int64_t offset,
                                             int64_t bytes, int64_t *pnum,
                                             int64_t *map,
@@ -3289,7 +3289,7 @@ static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (!want_zero) {
+    if (mode != BDRV_WANT_PRECISE) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/gluster.c b/block/gluster.c
index 8712aa606a4..1a2ef53e9b0 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1461,7 +1461,7 @@ exit:
  * (Based on raw_co_block_status() from file-posix.c.)
  */
 static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
-                                                     bool want_zero,
+                                                     unsigned int mode,
                                                      int64_t offset,
                                                      int64_t bytes,
                                                      int64_t *pnum,
@@ -1478,7 +1478,7 @@ static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (!want_zero) {
+    if (mode != BDRV_WANT_PRECISE) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/iscsi.c b/block/iscsi.c
index 2f0f4dac097..15b96ee8800 100644
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -694,9 +694,9 @@ out_unlock:


 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,
+                                              unsigned int mode,
+                                              int64_t offset, int64_t bytes,
+                                              int64_t *pnum, int64_t *map,
                                               BlockDriverState **file)
 {
     IscsiLun *iscsilun = bs->opaque;
diff --git a/block/nbd.c b/block/nbd.c
index 887841bc813..d5a2b21c6d1 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1397,8 +1397,8 @@ nbd_client_co_pdiscard(BlockDriverState *bs, int64_t offset, int64_t bytes)
 }

 static int coroutine_fn GRAPH_RDLOCK nbd_client_co_block_status(
-        BlockDriverState *bs, bool want_zero, int64_t offset, int64_t bytes,
-        int64_t *pnum, int64_t *map, BlockDriverState **file)
+        BlockDriverState *bs, unsigned int mode, int64_t offset,
+        int64_t bytes, int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
     int ret, request_ret;
     NBDExtent64 extent = { 0 };
diff --git a/block/null.c b/block/null.c
index dc0b1fdbd9b..4e448d593d7 100644
--- a/block/null.c
+++ b/block/null.c
@@ -227,9 +227,9 @@ static int null_reopen_prepare(BDRVReopenState *reopen_state,
 }

 static int coroutine_fn null_co_block_status(BlockDriverState *bs,
-                                             bool want_zero, int64_t offset,
-                                             int64_t bytes, int64_t *pnum,
-                                             int64_t *map,
+                                             unsigned int mode,
+                                             int64_t offset, int64_t bytes,
+                                             int64_t *pnum, int64_t *map,
                                              BlockDriverState **file)
 {
     BDRVNullState *s = bs->opaque;
diff --git a/block/parallels.c b/block/parallels.c
index 347ca127f34..3a375e2a8ab 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -416,9 +416,9 @@ parallels_co_flush_to_os(BlockDriverState *bs)
 }

 static int coroutine_fn GRAPH_RDLOCK
-parallels_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                          int64_t bytes, int64_t *pnum, int64_t *map,
-                          BlockDriverState **file)
+parallels_co_block_status(BlockDriverState *bs, unsigned int mode,
+                          int64_t offset, int64_t bytes, int64_t *pnum,
+                          int64_t *map, BlockDriverState **file)
 {
     BDRVParallelsState *s = bs->opaque;
     int count;
diff --git a/block/qcow.c b/block/qcow.c
index da8ad4d2430..8a3e7591a92 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -530,7 +530,7 @@ get_cluster_offset(BlockDriverState *bs, uint64_t offset, int allocate,
 }

 static int coroutine_fn GRAPH_RDLOCK
-qcow_co_block_status(BlockDriverState *bs, bool want_zero,
+qcow_co_block_status(BlockDriverState *bs, unsigned int mode,
                      int64_t offset, int64_t bytes, int64_t *pnum,
                      int64_t *map, BlockDriverState **file)
 {
diff --git a/block/qcow2.c b/block/qcow2.c
index 7774e7f0909..66fba89b414 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2141,9 +2141,9 @@ static void qcow2_join_options(QDict *options, QDict *old_options)
 }

 static int coroutine_fn GRAPH_RDLOCK
-qcow2_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                      int64_t count, int64_t *pnum, int64_t *map,
-                      BlockDriverState **file)
+qcow2_co_block_status(BlockDriverState *bs, unsigned int mode,
+                      int64_t offset, int64_t count, int64_t *pnum,
+                      int64_t *map, BlockDriverState **file)
 {
     BDRVQcow2State *s = bs->opaque;
     uint64_t host_offset;
diff --git a/block/qed.c b/block/qed.c
index ac24449ffb3..4a36fb39294 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -833,9 +833,9 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-bdrv_qed_co_block_status(BlockDriverState *bs, bool want_zero, int64_t pos,
-                         int64_t bytes, int64_t *pnum, int64_t *map,
-                         BlockDriverState **file)
+bdrv_qed_co_block_status(BlockDriverState *bs, unsigned int mode,
+                         int64_t pos, int64_t bytes, int64_t *pnum,
+                         int64_t *map, BlockDriverState **file)
 {
     BDRVQEDState *s = bs->opaque;
     size_t len = MIN(bytes, SIZE_MAX);
diff --git a/block/quorum.c b/block/quorum.c
index 30747a6df93..ed8ce801ee3 100644
--- a/block/quorum.c
+++ b/block/quorum.c
@@ -1226,7 +1226,7 @@ static void quorum_child_perm(BlockDriverState *bs, BdrvChild *c,
  * region contains zeroes, and BDRV_BLOCK_DATA otherwise.
  */
 static int coroutine_fn GRAPH_RDLOCK
-quorum_co_block_status(BlockDriverState *bs, bool want_zero,
+quorum_co_block_status(BlockDriverState *bs, unsigned int mode,
                        int64_t offset, int64_t count,
                        int64_t *pnum, int64_t *map, BlockDriverState **file)
 {
@@ -1238,7 +1238,7 @@ quorum_co_block_status(BlockDriverState *bs, bool want_zero,
     for (i = 0; i < s->num_children; i++) {
         int64_t bytes;
         ret = bdrv_co_common_block_status_above(s->children[i]->bs, NULL, false,
-                                                want_zero, offset, count,
+                                                mode, offset, count,
                                                 &bytes, NULL, NULL, NULL);
         if (ret < 0) {
             quorum_report_bad(QUORUM_OP_TYPE_READ, offset, count,
diff --git a/block/raw-format.c b/block/raw-format.c
index e08526e2eca..df16ac1ea25 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -283,8 +283,8 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-raw_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                    int64_t bytes, int64_t *pnum, int64_t *map,
+raw_co_block_status(BlockDriverState *bs, unsigned int mode,
+                    int64_t offset, int64_t bytes, int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
 {
     BDRVRawState *s = bs->opaque;
diff --git a/block/rbd.c b/block/rbd.c
index 7446e66659e..951cd63f9ae 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1503,9 +1503,9 @@ static int qemu_rbd_diff_iterate_cb(uint64_t offs, size_t len,
 }

 static int coroutine_fn qemu_rbd_co_block_status(BlockDriverState *bs,
-                                                 bool want_zero, int64_t offset,
-                                                 int64_t bytes, int64_t *pnum,
-                                                 int64_t *map,
+                                                 unsigned int mode,
+                                                 int64_t offset, int64_t bytes,
+                                                 int64_t *pnum, int64_t *map,
                                                  BlockDriverState **file)
 {
     BDRVRBDState *s = bs->opaque;
diff --git a/block/snapshot-access.c b/block/snapshot-access.c
index 71ac83c01f0..17ed2402db8 100644
--- a/block/snapshot-access.c
+++ b/block/snapshot-access.c
@@ -41,11 +41,11 @@ snapshot_access_co_preadv_part(BlockDriverState *bs,

 static int coroutine_fn GRAPH_RDLOCK
 snapshot_access_co_block_status(BlockDriverState *bs,
-                                bool want_zero, int64_t offset,
+                                unsigned int mode, int64_t offset,
                                 int64_t bytes, int64_t *pnum,
                                 int64_t *map, BlockDriverState **file)
 {
-    return bdrv_co_snapshot_block_status(bs->file->bs, want_zero, offset,
+    return bdrv_co_snapshot_block_status(bs->file->bs, mode, offset,
                                          bytes, pnum, map, file);
 }

diff --git a/block/vdi.c b/block/vdi.c
index a2da6ecab01..3ddc62a5690 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -523,8 +523,8 @@ static int vdi_reopen_prepare(BDRVReopenState *state,
 }

 static int coroutine_fn GRAPH_RDLOCK
-vdi_co_block_status(BlockDriverState *bs, bool want_zero, int64_t offset,
-                    int64_t bytes, int64_t *pnum, int64_t *map,
+vdi_co_block_status(BlockDriverState *bs, unsigned int mode,
+                    int64_t offset, int64_t bytes, int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
 {
     BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
diff --git a/block/vmdk.c b/block/vmdk.c
index 2adec499122..9c7ab037e14 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1777,7 +1777,7 @@ static inline uint64_t vmdk_find_offset_in_cluster(VmdkExtent *extent,
 }

 static int coroutine_fn GRAPH_RDLOCK
-vmdk_co_block_status(BlockDriverState *bs, bool want_zero,
+vmdk_co_block_status(BlockDriverState *bs, unsigned int mode,
                      int64_t offset, int64_t bytes, int64_t *pnum,
                      int64_t *map, BlockDriverState **file)
 {
diff --git a/block/vpc.c b/block/vpc.c
index 0309e319f60..801ff5793f8 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -726,7 +726,7 @@ fail:
 }

 static int coroutine_fn GRAPH_RDLOCK
-vpc_co_block_status(BlockDriverState *bs, bool want_zero,
+vpc_co_block_status(BlockDriverState *bs, unsigned int mode,
                     int64_t offset, int64_t bytes,
                     int64_t *pnum, int64_t *map,
                     BlockDriverState **file)
diff --git a/block/vvfat.c b/block/vvfat.c
index 91d69b3cc83..814796d9185 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -3134,9 +3134,9 @@ vvfat_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
 }

 static int coroutine_fn vvfat_co_block_status(BlockDriverState *bs,
-                                              bool want_zero, int64_t offset,
-                                              int64_t bytes, int64_t *n,
-                                              int64_t *map,
+                                              unsigned int mode,
+                                              int64_t offset, int64_t bytes,
+                                              int64_t *n, int64_t *map,
                                               BlockDriverState **file)
 {
     *n = bytes;
diff --git a/tests/unit/test-block-iothread.c b/tests/unit/test-block-iothread.c
index 2b358eaaa82..e26b3be5939 100644
--- a/tests/unit/test-block-iothread.c
+++ b/tests/unit/test-block-iothread.c
@@ -63,7 +63,7 @@ bdrv_test_co_truncate(BlockDriverState *bs, int64_t offset, bool exact,
 }

 static int coroutine_fn bdrv_test_co_block_status(BlockDriverState *bs,
-                                                  bool want_zero,
+                                                  unsigned int mode,
                                                   int64_t offset, int64_t count,
                                                   int64_t *pnum, int64_t *map,
                                                   BlockDriverState **file)
-- 
2.49.0


From eblake at redhat.com  Thu May 15 02:28:45 2025
From: eblake at redhat.com (Eric Blake)
Date: Wed, 14 May 2025 21:28:45 -0500
Subject: [GEDI] [PULL 02/14] file-posix,
	gluster: Handle zero block status hint better
In-Reply-To: <20250515022904.575509-16-eblake@redhat.com>
References: <20250515022904.575509-16-eblake@redhat.com>
Message-ID: <20250515022904.575509-18-eblake@redhat.com>

Although the previous patch to change 'bool want_zero' into a bitmask
made no semantic change, it is now time to differentiate.  When the
caller specifically wants to know what parts of the file read as zero,
we need to use lseek and actually reporting holes, rather than
short-circuiting and advertising full allocation.

This change will be utilized in later patches to let mirroring
optimize for the case when the destination already reads as zeroes.

Signed-off-by: Eric Blake <eblake at redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
Message-ID: <20250509204341.3553601-17-eblake at redhat.com>
---
 block/file-posix.c | 3 ++-
 block/gluster.c    | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 805a1a2949b..ec95b748696 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -3289,7 +3289,8 @@ static int coroutine_fn raw_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (mode != BDRV_WANT_PRECISE) {
+    if (!(mode & BDRV_WANT_ZERO)) {
+        /* There is no backing file - all bytes are allocated in this file.  */
         *pnum = bytes;
         *map = offset;
         *file = bs;
diff --git a/block/gluster.c b/block/gluster.c
index 1a2ef53e9b0..89abd40f313 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1478,7 +1478,7 @@ static int coroutine_fn qemu_gluster_co_block_status(BlockDriverState *bs,
         return ret;
     }

-    if (mode != BDRV_WANT_PRECISE) {
+    if (!(mode & BDRV_WANT_ZERO)) {
         *pnum = bytes;
         *map = offset;
         *file = bs;
-- 
2.49.0