diff mbox series

[3/7] block: Make bdrv_{pread,pwrite}() return 0 on success

Message ID 20220512233849.2219275-4-afaria@redhat.com (mailing list archive)
State New, archived
Headers show
Series Implement bdrv_{pread, pwrite, pwrite_sync, pwrite_zeroes}() using generated_co_wrapper | expand

Commit Message

Alberto Faria May 12, 2022, 11:38 p.m. UTC 
They currently return the value of their 'bytes' parameter on success.

Make them return 0 instead, for consistency with other I/O functions and
in preparation to implement them using generated_co_wrapper. This also
makes it clear that short reads/writes are not possible.

The few callers that rely on the previous behavior are adjusted
accordingly by hand.

Signed-off-by: Alberto Faria <afaria@redhat.com>
---
 block/cloop.c                    |  2 +-
 block/crypto.c                   |  4 ++--
 block/dmg.c                      | 10 +++++-----
 block/io.c                       | 10 ++--------
 block/qcow.c                     |  2 +-
 block/qcow2.c                    |  4 ++--
 block/qed.c                      |  7 +------
 block/vhdx-log.c                 |  3 +++
 block/vmdk.c                     |  5 ++---
 tests/unit/test-block-iothread.c |  4 ++--
 10 files changed, 21 insertions(+), 30 deletions(-)

Comments

Paolo Bonzini May 13, 2022, 8:22 a.m. UTC | #1 
On 5/13/22 01:38, Alberto Faria wrote:
> 
> @@ -113,7 +113,7 @@ static ssize_t qcow2_crypto_hdr_read_func(QCryptoBlock *block, size_t offset,
>          error_setg_errno(errp, -ret, "Could not read encryption header");
>          return -1;
>      }
> -    return ret;
> +    return buflen;
>  }
>  
>  
> @@ -174,7 +174,7 @@ static ssize_t qcow2_crypto_hdr_write_func(QCryptoBlock *block, size_t offset,
>          error_setg_errno(errp, -ret, "Could not read encryption header");
>          return -1;
>      }
> -    return ret;
> +    return buflen;
>  }
>  
>  static QDict*

As a follow-up you could change the calling convention of readfunc and 
writefunc in crypto/block-luks.c and crypto/block-qcow.c.

More in general, crypto/block-luks.c and crypto/block-qcow.c should be 
annotated for coroutine_fn.  Let's put it on the todo list.

> @@ -88,6 +88,7 @@ static int vhdx_log_peek_hdr(BlockDriverState *bs, VHDXLogEntries *log,
>      if (ret < 0) {
>          goto exit;
>      }
> +    ret = sizeof(VHDXLogEntryHeader);
>      vhdx_log_entry_hdr_le_import(hdr);
>  
>  exit:

The callers only check the return code of vhdx_log_peek_hdr, 
vhdx_log_read_sectors, vhdx_log_write_sectors with ret < 0.  But looking 
at the callers:

- vhdx_log_read_desc propagates ret directly from a successful 
vhdx_log_read_sectors, but its callers don't care about which 
nonnegative result is returned

- vhdx_validate_log_entry might occasionally return ret directly from a 
successful vhdx_log_read_desc or vhdx_log_read_sectors, but 
vhdx_log_search, the caller of vhdx_validate_log_entry, also doesn't 
care about which nonnegative result is returned

- vhdx_log_flush only returns a successful return value from bdrv_flush

- vhdx_log_write propagates ret directly from a successful 
vhdx_log_write_sectors, but vhdx_log_write_and_flush only returns a 
successful return value from vhdx_log_flush

So (perhaps as a separate patch?) you can remove the three assignments 
of ret.


A possible cleanup is missing in vdi_co_pwritev:

>         ret = bdrv_pwrite(bs->file, offset * SECTOR_SIZE, base,
>                           n_sectors * SECTOR_SIZE);
>     }
> 
>     return ret < 0 ? ret : 0;

ret is returned by either bdrv_pwrite or bdrv_co_writev, so it can be 
simplified to just "return ret".


As an aside, while reviewing I noticed this in qcow2_mark_dirty:

     ret = bdrv_pwrite(bs->file, offsetof(QCowHeader, 
incompatible_features),
                       &val, sizeof(val));
     if (ret < 0) {
         return ret;
     }
     ret = bdrv_flush(bs->file->bs);
     if (ret < 0) {
         return ret;
     }

I'm not sure if there are other occurrencies, perhaps you can try using 
Coccinelle to find them and change them to a bdrv_pwrite_sync.

But anyway:

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Paolo
Alberto Faria May 13, 2022, 2:56 p.m. UTC | #2 
On Fri, May 13, 2022 at 9:22 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
> The callers only check the return code of vhdx_log_peek_hdr,
> vhdx_log_read_sectors, vhdx_log_write_sectors with ret < 0.  But looking
> at the callers:
>
> - vhdx_log_read_desc propagates ret directly from a successful
> vhdx_log_read_sectors, but its callers don't care about which
> nonnegative result is returned
>
> - vhdx_validate_log_entry might occasionally return ret directly from a
> successful vhdx_log_read_desc or vhdx_log_read_sectors, but
> vhdx_log_search, the caller of vhdx_validate_log_entry, also doesn't
> care about which nonnegative result is returned
>
> - vhdx_log_flush only returns a successful return value from bdrv_flush
>
> - vhdx_log_write propagates ret directly from a successful
> vhdx_log_write_sectors, but vhdx_log_write_and_flush only returns a
> successful return value from vhdx_log_flush
>
> So (perhaps as a separate patch?) you can remove the three assignments
> of ret.

Thanks, I'll fix this. I think I'll just fold it in, but let me know
if it really should be split into a separate patch.

> As an aside, while reviewing I noticed this in qcow2_mark_dirty:
>
>      ret = bdrv_pwrite(bs->file, offsetof(QCowHeader,
> incompatible_features),
>                        &val, sizeof(val));
>      if (ret < 0) {
>          return ret;
>      }
>      ret = bdrv_flush(bs->file->bs);
>      if (ret < 0) {
>          return ret;
>      }
>
> I'm not sure if there are other occurrencies, perhaps you can try using
> Coccinelle to find them and change them to a bdrv_pwrite_sync.

Looks like this is the only occurrence. I'll add a patch to convert it
to bdrv_pwrite_sync().

Alberto
diff mbox series

Patch

diff --git a/block/cloop.c b/block/cloop.c
index 9a2334495e..40b146e714 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -222,7 +222,7 @@  static inline int cloop_read_block(BlockDriverState *bs, int block_num)
 
         ret = bdrv_pread(bs->file, s->offsets[block_num], bytes,
                          s->compressed_block, 0);
-        if (ret != bytes) {
+        if (ret < 0) {
             return -1;
         }
 
diff --git a/block/crypto.c b/block/crypto.c
index deec7fae2f..e7f5c4e31a 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -70,7 +70,7 @@  static ssize_t block_crypto_read_func(QCryptoBlock *block,
         error_setg_errno(errp, -ret, "Could not read encryption header");
         return ret;
     }
-    return ret;
+    return buflen;
 }
 
 static ssize_t block_crypto_write_func(QCryptoBlock *block,
@@ -88,7 +88,7 @@  static ssize_t block_crypto_write_func(QCryptoBlock *block,
         error_setg_errno(errp, -ret, "Could not write encryption header");
         return ret;
     }
-    return ret;
+    return buflen;
 }
 
 
diff --git a/block/dmg.c b/block/dmg.c
index 5a460c3eb1..98db18d82a 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -390,7 +390,7 @@  static int dmg_read_plist_xml(BlockDriverState *bs, DmgHeaderState *ds,
     buffer = g_malloc(info_length + 1);
     buffer[info_length] = '\0';
     ret = bdrv_pread(bs->file, info_begin, info_length, buffer, 0);
-    if (ret != info_length) {
+    if (ret < 0) {
         ret = -EINVAL;
         goto fail;
     }
@@ -611,7 +611,7 @@  static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -637,7 +637,7 @@  static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -658,7 +658,7 @@  static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
              * inflated. */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->compressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
 
@@ -674,7 +674,7 @@  static inline int dmg_read_chunk(BlockDriverState *bs, uint64_t sector_num)
         case UDRW: /* copy */
             ret = bdrv_pread(bs->file, s->offsets[chunk], s->lengths[chunk],
                              s->uncompressed_chunk, 0);
-            if (ret != s->lengths[chunk]) {
+            if (ret < 0) {
                 return -1;
             }
             break;
diff --git a/block/io.c b/block/io.c
index 2ed963d9e0..78a289192e 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1115,7 +1115,6 @@  int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags)
 int bdrv_pread(BdrvChild *child, int64_t offset, int64_t bytes, void *buf,
                BdrvRequestFlags flags)
 {
-    int ret;
     QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
     IO_CODE();
 
@@ -1123,9 +1122,7 @@  int bdrv_pread(BdrvChild *child, int64_t offset, int64_t bytes, void *buf,
         return -EINVAL;
     }
 
-    ret = bdrv_preadv(child, offset, bytes, &qiov, flags);
-
-    return ret < 0 ? ret : bytes;
+    return bdrv_preadv(child, offset, bytes, &qiov, flags);
 }
 
 /* Return no. of bytes on success or < 0 on error. Important errors are:
@@ -1137,7 +1134,6 @@  int bdrv_pread(BdrvChild *child, int64_t offset, int64_t bytes, void *buf,
 int bdrv_pwrite(BdrvChild *child, int64_t offset, int64_t bytes,
                 const void *buf, BdrvRequestFlags flags)
 {
-    int ret;
     QEMUIOVector qiov = QEMU_IOVEC_INIT_BUF(qiov, buf, bytes);
     IO_CODE();
 
@@ -1145,9 +1141,7 @@  int bdrv_pwrite(BdrvChild *child, int64_t offset, int64_t bytes,
         return -EINVAL;
     }
 
-    ret = bdrv_pwritev(child, offset, bytes, &qiov, flags);
-
-    return ret < 0 ? ret : bytes;
+    return bdrv_pwritev(child, offset, bytes, &qiov, flags);
 }
 
 /*
diff --git a/block/qcow.c b/block/qcow.c
index c94524b814..c646d6b16d 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -597,7 +597,7 @@  static int decompress_cluster(BlockDriverState *bs, uint64_t cluster_offset)
         csize &= (s->cluster_size - 1);
         BLKDBG_EVENT(bs->file, BLKDBG_READ_COMPRESSED);
         ret = bdrv_pread(bs->file, coffset, csize, s->cluster_data, 0);
-        if (ret != csize)
+        if (ret < 0)
             return -1;
         if (decompress_buffer(s->cluster_cache, s->cluster_size,
                               s->cluster_data, csize) < 0) {
diff --git a/block/qcow2.c b/block/qcow2.c
index 5493e6b847..d5a1e8bc43 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -113,7 +113,7 @@  static ssize_t qcow2_crypto_hdr_read_func(QCryptoBlock *block, size_t offset,
         error_setg_errno(errp, -ret, "Could not read encryption header");
         return -1;
     }
-    return ret;
+    return buflen;
 }
 
 
@@ -174,7 +174,7 @@  static ssize_t qcow2_crypto_hdr_write_func(QCryptoBlock *block, size_t offset,
         error_setg_errno(errp, -ret, "Could not read encryption header");
         return -1;
     }
-    return ret;
+    return buflen;
 }
 
 static QDict*
diff --git a/block/qed.c b/block/qed.c
index ba93e99570..55da91eb72 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -87,14 +87,9 @@  static void qed_header_cpu_to_le(const QEDHeader *cpu, QEDHeader *le)
 int qed_write_header_sync(BDRVQEDState *s)
 {
     QEDHeader le;
-    int ret;
 
     qed_header_cpu_to_le(&s->header, &le);
-    ret = bdrv_pwrite(s->bs->file, 0, sizeof(le), &le, 0);
-    if (ret != sizeof(le)) {
-        return ret;
-    }
-    return 0;
+    return bdrv_pwrite(s->bs->file, 0, sizeof(le), &le, 0);
 }
 
 /**
diff --git a/block/vhdx-log.c b/block/vhdx-log.c
index 572582b87b..33a7786631 100644
--- a/block/vhdx-log.c
+++ b/block/vhdx-log.c
@@ -88,6 +88,7 @@  static int vhdx_log_peek_hdr(BlockDriverState *bs, VHDXLogEntries *log,
     if (ret < 0) {
         goto exit;
     }
+    ret = sizeof(VHDXLogEntryHeader);
     vhdx_log_entry_hdr_le_import(hdr);
 
 exit:
@@ -148,6 +149,7 @@  static int vhdx_log_read_sectors(BlockDriverState *bs, VHDXLogEntries *log,
         if (ret < 0) {
             goto exit;
         }
+        ret = VHDX_LOG_SECTOR_SIZE;
         read = vhdx_log_inc_idx(read, log->length);
 
         *sectors_read = *sectors_read + 1;
@@ -199,6 +201,7 @@  static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log,
         if (ret < 0) {
             goto exit;
         }
+        ret = VHDX_LOG_SECTOR_SIZE;
         buffer_tmp += VHDX_LOG_SECTOR_SIZE;
 
         log->write = write;
diff --git a/block/vmdk.c b/block/vmdk.c
index aacea1095f..332565c80f 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -473,7 +473,6 @@  static int vmdk_parent_open(BlockDriverState *bs)
     if (ret < 0) {
         goto out;
     }
-    ret = 0;
 
     p_name = strstr(desc, "parentFileNameHint");
     if (p_name != NULL) {
@@ -905,7 +904,7 @@  static char *vmdk_read_desc(BdrvChild *file, uint64_t desc_offset, Error **errp)
         g_free(buf);
         return NULL;
     }
-    buf[ret] = 0;
+    buf[size] = 0;
 
     return buf;
 }
@@ -1630,7 +1629,7 @@  static int get_cluster_offset(BlockDriverState *bs,
                 l2_size_bytes,
                 l2_table,
                 0
-            ) != l2_size_bytes) {
+            ) < 0) {
         return VMDK_ERROR;
     }
 
diff --git a/tests/unit/test-block-iothread.c b/tests/unit/test-block-iothread.c
index 49fb1ef1ea..a5c163af7e 100644
--- a/tests/unit/test-block-iothread.c
+++ b/tests/unit/test-block-iothread.c
@@ -89,7 +89,7 @@  static void test_sync_op_pread(BdrvChild *c)
 
     /* Success */
     ret = bdrv_pread(c, 0, sizeof(buf), buf, 0);
-    g_assert_cmpint(ret, ==, 512);
+    g_assert_cmpint(ret, ==, 0);
 
     /* Early error: Negative offset */
     ret = bdrv_pread(c, -2, sizeof(buf), buf, 0);
@@ -103,7 +103,7 @@  static void test_sync_op_pwrite(BdrvChild *c)
 
     /* Success */
     ret = bdrv_pwrite(c, 0, sizeof(buf), buf, 0);
-    g_assert_cmpint(ret, ==, 512);
+    g_assert_cmpint(ret, ==, 0);
 
     /* Early error: Negative offset */
     ret = bdrv_pwrite(c, -2, sizeof(buf), buf, 0);