[PATCH v4 00/10] preallocate filter

[PATCH v4 00/10] preallocate filter

[Vladimir Sementsov-Ogievskiy]

Hi all!

Here is a filter, which does preallocation on write.

In Virtuozzo we have to deal with some custom distributed storage
solution, where allocation is relatively expensive operation. We have to
workaround it in Qemu, so here is a new filter.

v4:
01-04: add r-bs
05: add coroutine_fn tag
06: use QEMU_LOCK_GUARD and fix reqs_lock leak
07: grammar
08-10: add r-b

I decided to not resend patches 11-12, for which I don't know
how they can be applied universally. I think I'll keep them
downstream only for now, and probably drop in future if we
can insert filter in libvirt.

Vladimir Sementsov-Ogievskiy (10):
  block: simplify comment to BDRV_REQ_SERIALISING
  block/io.c: drop assertion on double waiting for request serialisation
  block/io: split out bdrv_find_conflicting_request
  block/io: bdrv_wait_serialising_requests_locked: drop extra bs arg
  block: bdrv_mark_request_serialising: split non-waiting function
  block: introduce BDRV_REQ_NO_WAIT flag
  block: introduce preallocate filter
  iotests.py: add verify_o_direct helper
  iotests.py: add filter_img_check
  iotests: add 298 to test new preallocate filter driver

 docs/system/qemu-block-drivers.rst.inc |  26 +++
 qapi/block-core.json                   |  20 +-
 include/block/block.h                  |  20 +-
 include/block/block_int.h              |   3 +-
 block/file-posix.c                     |   2 +-
 block/io.c                             | 130 ++++++-----
 block/preallocate.c                    | 291 +++++++++++++++++++++++++
 block/Makefile.objs                    |   1 +
 tests/qemu-iotests/298                 |  50 +++++
 tests/qemu-iotests/298.out             |   6 +
 tests/qemu-iotests/group               |   1 +
 tests/qemu-iotests/iotests.py          |  10 +
 12 files changed, 492 insertions(+), 68 deletions(-)
 create mode 100644 block/preallocate.c
 create mode 100644 tests/qemu-iotests/298
 create mode 100644 tests/qemu-iotests/298.out

-- 
2.21.3

[PATCH v4 01/10] block: simplify comment to BDRV_REQ_SERIALISING

[Vladimir Sementsov-Ogievskiy]

1. BDRV_REQ_NO_SERIALISING doesn't exist already, don't mention it.

2. We are going to add one more user of BDRV_REQ_SERIALISING, so
   comment about backup becomes a bit confusing here. The use case in
   backup is documented in block/backup.c, so let's just drop
   duplication here.

3. The fact that BDRV_REQ_SERIALISING is only for write requests is
   omitted. Add a note.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 include/block/block.h | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index 6e36154061..b8f4e86e8d 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -53,16 +53,7 @@ typedef enum {
      * content. */
     BDRV_REQ_WRITE_UNCHANGED    = 0x40,
 
-    /*
-     * BDRV_REQ_SERIALISING forces request serialisation for writes.
-     * It is used to ensure that writes to the backing file of a backup process
-     * target cannot race with a read of the backup target that defers to the
-     * backing file.
-     *
-     * Note, that BDRV_REQ_SERIALISING is _not_ opposite in meaning to
-     * BDRV_REQ_NO_SERIALISING. A more descriptive name for the latter might be
-     * _DO_NOT_WAIT_FOR_SERIALISING, except that is too long.
-     */
+    /* Forces request serialisation. Use only with write requests. */
     BDRV_REQ_SERIALISING        = 0x80,
 
     /* Execute the request only if the operation can be offloaded or otherwise
-- 
2.21.3

[PATCH v4 02/10] block/io.c: drop assertion on double waiting for request serialisation

[Vladimir Sementsov-Ogievskiy]

The comments states, that on misaligned request we should have already
been waiting. But for bdrv_padding_rmw_read, we called
bdrv_mark_request_serialising with align = request_alignment, and now
we serialise with align = cluster_size. So we may have to wait again
with larger alignment.

Note, that the only user of BDRV_REQ_SERIALISING is backup which issues
cluster-aligned requests, so seems the assertion should not fire for
now. But it's wrong anyway.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
---
 block/io.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/block/io.c b/block/io.c
index ad3a51ed53..b18680a842 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1881,7 +1881,6 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
                           BdrvTrackedRequest *req, int flags)
 {
     BlockDriverState *bs = child->bs;
-    bool waited;
     int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
 
     if (bs->read_only) {
@@ -1893,15 +1892,7 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
     assert(!(flags & ~BDRV_REQ_MASK));
 
     if (flags & BDRV_REQ_SERIALISING) {
-        waited = bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
-        /*
-         * For a misaligned request we should have already waited earlier,
-         * because we come after bdrv_padding_rmw_read which must be called
-         * with the request already marked as serialising.
-         */
-        assert(!waited ||
-               (req->offset == req->overlap_offset &&
-                req->bytes == req->overlap_bytes));
+        bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
     } else {
         bdrv_wait_serialising_requests(req);
     }
-- 
2.21.3

[PATCH v4 03/10] block/io: split out bdrv_find_conflicting_request

[Vladimir Sementsov-Ogievskiy]

To be reused in separate.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/io.c | 71 +++++++++++++++++++++++++++++++-----------------------
 1 file changed, 41 insertions(+), 30 deletions(-)

diff --git a/block/io.c b/block/io.c
index b18680a842..5b96715058 100644
--- a/block/io.c
+++ b/block/io.c
@@ -727,43 +727,54 @@ static bool tracked_request_overlaps(BdrvTrackedRequest *req,
     return true;
 }
 
+/* Called with self->bs->reqs_lock held */
+static BdrvTrackedRequest *
+bdrv_find_conflicting_request(BdrvTrackedRequest *self)
+{
+    BdrvTrackedRequest *req;
+
+    QLIST_FOREACH(req, &self->bs->tracked_requests, list) {
+        if (req == self || (!req->serialising && !self->serialising)) {
+            continue;
+        }
+        if (tracked_request_overlaps(req, self->overlap_offset,
+                                     self->overlap_bytes))
+        {
+            /*
+             * Hitting this means there was a reentrant request, for
+             * example, a block driver issuing nested requests.  This must
+             * never happen since it means deadlock.
+             */
+            assert(qemu_coroutine_self() != req->co);
+
+            /*
+             * If the request is already (indirectly) waiting for us, or
+             * will wait for us as soon as it wakes up, then just go on
+             * (instead of producing a deadlock in the former case).
+             */
+            if (!req->waiting_for) {
+                return req;
+            }
+        }
+    }
+
+    return NULL;
+}
+
 static bool coroutine_fn
 bdrv_wait_serialising_requests_locked(BlockDriverState *bs,
                                       BdrvTrackedRequest *self)
 {
     BdrvTrackedRequest *req;
-    bool retry;
     bool waited = false;
 
-    do {
-        retry = false;
-        QLIST_FOREACH(req, &bs->tracked_requests, list) {
-            if (req == self || (!req->serialising && !self->serialising)) {
-                continue;
-            }
-            if (tracked_request_overlaps(req, self->overlap_offset,
-                                         self->overlap_bytes))
-            {
-                /* Hitting this means there was a reentrant request, for
-                 * example, a block driver issuing nested requests.  This must
-                 * never happen since it means deadlock.
-                 */
-                assert(qemu_coroutine_self() != req->co);
-
-                /* If the request is already (indirectly) waiting for us, or
-                 * will wait for us as soon as it wakes up, then just go on
-                 * (instead of producing a deadlock in the former case). */
-                if (!req->waiting_for) {
-                    self->waiting_for = req;
-                    qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
-                    self->waiting_for = NULL;
-                    retry = true;
-                    waited = true;
-                    break;
-                }
-            }
-        }
-    } while (retry);
+    while ((req = bdrv_find_conflicting_request(self))) {
+        self->waiting_for = req;
+        qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
+        self->waiting_for = NULL;
+        waited = true;
+    }
+
     return waited;
 }
 
-- 
2.21.3

[PATCH v4 04/10] block/io: bdrv_wait_serialising_requests_locked: drop extra bs arg

[Vladimir Sementsov-Ogievskiy]

bs is linked in req, so no needs to pass it separately. Most of
tracked-requests API doesn't have bs argument. Actually, after this
patch only tracked_request_begin has it, but it's for purpose.

While being here, also add a comment about what "_locked" is.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/io.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/io.c b/block/io.c
index 5b96715058..36bbe4b9b1 100644
--- a/block/io.c
+++ b/block/io.c
@@ -761,16 +761,16 @@ bdrv_find_conflicting_request(BdrvTrackedRequest *self)
     return NULL;
 }
 
+/* Called with self->bs->reqs_lock held */
 static bool coroutine_fn
-bdrv_wait_serialising_requests_locked(BlockDriverState *bs,
-                                      BdrvTrackedRequest *self)
+bdrv_wait_serialising_requests_locked(BdrvTrackedRequest *self)
 {
     BdrvTrackedRequest *req;
     bool waited = false;
 
     while ((req = bdrv_find_conflicting_request(self))) {
         self->waiting_for = req;
-        qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
+        qemu_co_queue_wait(&req->wait_queue, &self->bs->reqs_lock);
         self->waiting_for = NULL;
         waited = true;
     }
@@ -794,7 +794,7 @@ bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
 
     req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
     req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
-    waited = bdrv_wait_serialising_requests_locked(bs, req);
+    waited = bdrv_wait_serialising_requests_locked(req);
     qemu_co_mutex_unlock(&bs->reqs_lock);
     return waited;
 }
@@ -876,7 +876,7 @@ static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self
     }
 
     qemu_co_mutex_lock(&bs->reqs_lock);
-    waited = bdrv_wait_serialising_requests_locked(bs, self);
+    waited = bdrv_wait_serialising_requests_locked(self);
     qemu_co_mutex_unlock(&bs->reqs_lock);
 
     return waited;
-- 
2.21.3

[PATCH v4 05/10] block: bdrv_mark_request_serialising: split non-waiting function

[Vladimir Sementsov-Ogievskiy]

We'll need a separate function, which will only "mark" request
serialising with specified align but not wait for conflicting
requests. So, it will be like old bdrv_mark_request_serialising(),
before merging bdrv_wait_serialising_requests_locked() into it.

To reduce the possible mess, let's do the following:

Public function that does both marking and waiting will be called
bdrv_make_request_serialising, and private function which will only
"mark" will be called tracked_request_set_serialising().

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block_int.h |  3 ++-
 block/file-posix.c        |  2 +-
 block/io.c                | 35 +++++++++++++++++++++++------------
 3 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 38dec0275b..4d56a1b141 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1039,7 +1039,8 @@ extern unsigned int bdrv_drain_all_count;
 void bdrv_apply_subtree_drain(BdrvChild *child, BlockDriverState *new_parent);
 void bdrv_unapply_subtree_drain(BdrvChild *child, BlockDriverState *old_parent);
 
-bool coroutine_fn bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align);
+bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
+                                                uint64_t align);
 BdrvTrackedRequest *coroutine_fn bdrv_co_get_self_request(BlockDriverState *bs);
 
 int get_tmp_filename(char *filename, int size);
diff --git a/block/file-posix.c b/block/file-posix.c
index 9a00d4190a..560d1c0a94 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2957,7 +2957,7 @@ raw_do_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int bytes,
         req->bytes = end - req->offset;
         req->overlap_bytes = req->bytes;
 
-        bdrv_mark_request_serialising(req, bs->bl.request_alignment);
+        bdrv_make_request_serialising(req, bs->bl.request_alignment);
     }
 #endif
 
diff --git a/block/io.c b/block/io.c
index 36bbe4b9b1..dd28befb08 100644
--- a/block/io.c
+++ b/block/io.c
@@ -778,15 +778,14 @@ bdrv_wait_serialising_requests_locked(BdrvTrackedRequest *self)
     return waited;
 }
 
-bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
+/* Called with req->bs->reqs_lock held */
+static void tracked_request_set_serialising(BdrvTrackedRequest *req,
+                                            uint64_t align)
 {
-    BlockDriverState *bs = req->bs;
     int64_t overlap_offset = req->offset & ~(align - 1);
     uint64_t overlap_bytes = ROUND_UP(req->offset + req->bytes, align)
                                - overlap_offset;
-    bool waited;
 
-    qemu_co_mutex_lock(&bs->reqs_lock);
     if (!req->serialising) {
         atomic_inc(&req->bs->serialising_in_flight);
         req->serialising = true;
@@ -794,9 +793,6 @@ bool bdrv_mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
 
     req->overlap_offset = MIN(req->overlap_offset, overlap_offset);
     req->overlap_bytes = MAX(req->overlap_bytes, overlap_bytes);
-    waited = bdrv_wait_serialising_requests_locked(req);
-    qemu_co_mutex_unlock(&bs->reqs_lock);
-    return waited;
 }
 
 /**
@@ -882,6 +878,21 @@ static bool coroutine_fn bdrv_wait_serialising_requests(BdrvTrackedRequest *self
     return waited;
 }
 
+bool coroutine_fn bdrv_make_request_serialising(BdrvTrackedRequest *req,
+                                                uint64_t align)
+{
+    bool waited;
+
+    qemu_co_mutex_lock(&req->bs->reqs_lock);
+
+    tracked_request_set_serialising(req, align);
+    waited = bdrv_wait_serialising_requests_locked(req);
+
+    qemu_co_mutex_unlock(&req->bs->reqs_lock);
+
+    return waited;
+}
+
 static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
                                    size_t size)
 {
@@ -1492,7 +1503,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
          * with each other for the same cluster.  For example, in copy-on-read
          * it ensures that the CoR read and write operations are atomic and
          * guest writes cannot interleave between them. */
-        bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
+        bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
     } else {
         bdrv_wait_serialising_requests(req);
     }
@@ -1903,7 +1914,7 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
     assert(!(flags & ~BDRV_REQ_MASK));
 
     if (flags & BDRV_REQ_SERIALISING) {
-        bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
+        bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
     } else {
         bdrv_wait_serialising_requests(req);
     }
@@ -2069,7 +2080,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
 
     padding = bdrv_init_padding(bs, offset, bytes, &pad);
     if (padding) {
-        bdrv_mark_request_serialising(req, align);
+        bdrv_make_request_serialising(req, align);
 
         bdrv_padding_rmw_read(child, req, &pad, true);
 
@@ -2183,7 +2194,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
     }
 
     if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
-        bdrv_mark_request_serialising(&req, align);
+        bdrv_make_request_serialising(&req, align);
         bdrv_padding_rmw_read(child, &req, &pad, false);
     }
 
@@ -3347,7 +3358,7 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
      * new area, we need to make sure that no write requests are made to it
      * concurrently or they might be overwritten by preallocation. */
     if (new_bytes) {
-        bdrv_mark_request_serialising(&req, 1);
+        bdrv_make_request_serialising(&req, 1);
     }
     if (bs->read_only) {
         error_setg(errp, "Image is read-only");
-- 
2.21.3

[PATCH v4 06/10] block: introduce BDRV_REQ_NO_WAIT flag

[Vladimir Sementsov-Ogievskiy]

Add flag to make serialising request no wait: if there are conflicting
requests, just return error immediately. It's will be used in upcoming
preallocate filter.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block.h |  9 ++++++++-
 block/io.c            | 11 ++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/block/block.h b/include/block/block.h
index b8f4e86e8d..877fda06a4 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -67,8 +67,15 @@ typedef enum {
      * written to qiov parameter which may be NULL.
      */
     BDRV_REQ_PREFETCH  = 0x200,
+
+    /*
+     * If we need to wait for other requests, just fail immediately. Used
+     * only together with BDRV_REQ_SERIALISING.
+     */
+    BDRV_REQ_NO_WAIT = 0x400,
+
     /* Mask of valid flags */
-    BDRV_REQ_MASK               = 0x3ff,
+    BDRV_REQ_MASK               = 0x7ff,
 } BdrvRequestFlags;
 
 typedef struct BlockSizes {
diff --git a/block/io.c b/block/io.c
index dd28befb08..c93b1e98a3 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1912,9 +1912,18 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
     assert(!(bs->open_flags & BDRV_O_INACTIVE));
     assert((bs->open_flags & BDRV_O_NO_IO) == 0);
     assert(!(flags & ~BDRV_REQ_MASK));
+    assert(!((flags & BDRV_REQ_NO_WAIT) && !(flags & BDRV_REQ_SERIALISING)));
 
     if (flags & BDRV_REQ_SERIALISING) {
-        bdrv_make_request_serialising(req, bdrv_get_cluster_size(bs));
+        QEMU_LOCK_GUARD(&bs->reqs_lock);
+
+        tracked_request_set_serialising(req, bdrv_get_cluster_size(bs));
+
+        if ((flags & BDRV_REQ_NO_WAIT) && bdrv_find_conflicting_request(req)) {
+            return -EBUSY;
+        }
+
+        bdrv_wait_serialising_requests_locked(req);
     } else {
         bdrv_wait_serialising_requests(req);
     }
-- 
2.21.3

[PATCH v4 07/10] block: introduce preallocate filter

[Vladimir Sementsov-Ogievskiy]

It's intended to be inserted between format and protocol nodes to
preallocate additional space (expanding protocol file) on writes
crossing EOF. It improves performance for file-systems with slow
allocation.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 docs/system/qemu-block-drivers.rst.inc |  26 +++
 qapi/block-core.json                   |  20 +-
 block/preallocate.c                    | 291 +++++++++++++++++++++++++
 block/Makefile.objs                    |   1 +
 4 files changed, 337 insertions(+), 1 deletion(-)
 create mode 100644 block/preallocate.c

diff --git a/docs/system/qemu-block-drivers.rst.inc b/docs/system/qemu-block-drivers.rst.inc
index b052a6d14e..5e8a35c571 100644
--- a/docs/system/qemu-block-drivers.rst.inc
+++ b/docs/system/qemu-block-drivers.rst.inc
@@ -952,3 +952,29 @@ on host and see if there are locks held by the QEMU process on the image file.
 More than one byte could be locked by the QEMU instance, each byte of which
 reflects a particular permission that is acquired or protected by the running
 block driver.
+
+Filter drivers
+~~~~~~~~~~~~~~
+
+QEMU supports several filter drivers, which don't store any data, but do some
+additional tasks, hooking io requests.
+
+.. program:: filter-drivers
+.. option:: preallocate
+
+  Preallocate filter driver is intended to be inserted between format
+  and protocol nodes and does preallocation of some additional space
+  (expanding the protocol file) on write. It may be used for
+  file-systems with slow allocation.
+
+  Supported options:
+
+  .. program:: preallocate
+  .. option:: prealloc-align
+
+    On preallocation, align file length to this number, default 1M.
+
+  .. program:: preallocate
+  .. option:: prealloc-size
+
+    How much to preallocate, default 128M.
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 197bdc1c36..b40448063b 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2805,7 +2805,7 @@
             'cloop', 'compress', 'copy-on-read', 'dmg', 'file', 'ftp', 'ftps',
             'gluster', 'host_cdrom', 'host_device', 'http', 'https', 'iscsi',
             'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
-            'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
+            'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
             { 'name': 'replication', 'if': 'defined(CONFIG_REPLICATION)' },
             'sheepdog',
             'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
@@ -3074,6 +3074,23 @@
   'data': { 'aes': 'QCryptoBlockOptionsQCow',
             'luks': 'QCryptoBlockOptionsLUKS'} }
 
+##
+# @BlockdevOptionsPreallocate:
+#
+# Filter driver intended to be inserted between format and protocol node
+# and do preallocation in protocol node on write.
+#
+# @prealloc-align: on preallocation, align file length to this number,
+#                 default 1048576 (1M)
+#
+# @prealloc-size: how much to preallocate, default 134217728 (128M)
+#
+# Since: 5.2
+##
+{ 'struct': 'BlockdevOptionsPreallocate',
+  'base': 'BlockdevOptionsGenericFormat',
+  'data': { '*prealloc-align': 'int', '*prealloc-size': 'int' } }
+
 ##
 # @BlockdevOptionsQcow2:
 #
@@ -3979,6 +3996,7 @@
       'null-co':    'BlockdevOptionsNull',
       'nvme':       'BlockdevOptionsNVMe',
       'parallels':  'BlockdevOptionsGenericFormat',
+      'preallocate':'BlockdevOptionsPreallocate',
       'qcow2':      'BlockdevOptionsQcow2',
       'qcow':       'BlockdevOptionsQcow',
       'qed':        'BlockdevOptionsGenericCOWFormat',
diff --git a/block/preallocate.c b/block/preallocate.c
new file mode 100644
index 0000000000..bdf54dbd2f
--- /dev/null
+++ b/block/preallocate.c
@@ -0,0 +1,291 @@
+/*
+ * preallocate filter driver
+ *
+ * The driver performs preallocate operation: it is injected above
+ * some node, and before each write over EOF it does additional preallocating
+ * write-zeroes request.
+ *
+ * Copyright (c) 2020 Virtuozzo International GmbH.
+ *
+ * Author:
+ *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+
+#include "qapi/error.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/units.h"
+#include "block/block_int.h"
+
+
+typedef struct BDRVPreallocateState {
+    int64_t prealloc_size;
+    int64_t prealloc_align;
+
+    /*
+     * Filter is started as not-active, so it doesn't do any preallocations nor
+     * requires BLK_PERM_RESIZE on its child. This is needed to create filter
+     * above another node-child and then do bdrv_replace_node to insert the
+     * filter.
+     *
+     * Filter becomes active the first time it detects that its parents have
+     * BLK_PERM_RESIZE on it.
+     *
+     * Filter becomes active forever: it doesn't lose active status if parents
+     * lose BLK_PERM_RESIZE, otherwise we'll not be able to shrink the file on
+     * filter close.
+     */
+    bool active;
+
+    /*
+     * Track real data end, to crop preallocation on close  data_end may be
+     * negative, which means that actual status is unknown (nothing cropped in
+     * this case)
+     */
+    int64_t data_end;
+} BDRVPreallocateState;
+
+#define PREALLOCATE_OPT_PREALLOC_ALIGN "prealloc-align"
+#define PREALLOCATE_OPT_PREALLOC_SIZE "prealloc-size"
+static QemuOptsList runtime_opts = {
+    .name = "preallocate",
+    .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
+    .desc = {
+        {
+            .name = PREALLOCATE_OPT_PREALLOC_ALIGN,
+            .type = QEMU_OPT_SIZE,
+            .help = "on preallocation, align file length to this number, "
+                "default 1M",
+        },
+        {
+            .name = PREALLOCATE_OPT_PREALLOC_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "how much to preallocate, default 128M",
+        },
+        { /* end of list */ }
+    },
+};
+
+static int preallocate_open(BlockDriverState *bs, QDict *options, int flags,
+                            Error **errp)
+{
+    QemuOpts *opts;
+    BDRVPreallocateState *s = bs->opaque;
+
+    /*
+     * Parameters are hardcoded now. May need to add corresponding options in
+     * future.
+     */
+    opts = qemu_opts_create(&runtime_opts, NULL, 0, &error_abort);
+    qemu_opts_absorb_qdict(opts, options, &error_abort);
+    s->prealloc_align =
+        qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_ALIGN, 1 * MiB);
+    s->prealloc_size =
+        qemu_opt_get_size(opts, PREALLOCATE_OPT_PREALLOC_SIZE, 128 * MiB);
+    qemu_opts_del(opts);
+
+    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
+                               BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY,
+                               false, errp);
+    if (!bs->file) {
+        return -EINVAL;
+    }
+
+    s->data_end = bdrv_getlength(bs->file->bs);
+    if (s->data_end < 0) {
+        return s->data_end;
+    }
+
+    bs->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
+        (BDRV_REQ_FUA & bs->file->bs->supported_write_flags);
+
+    bs->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
+        ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
+            bs->file->bs->supported_zero_flags);
+
+    return 0;
+}
+
+static void preallocate_close(BlockDriverState *bs)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    if (s->active && s->data_end >= 0 &&
+        bdrv_getlength(bs->file->bs) > s->data_end)
+    {
+        bdrv_truncate(bs->file, s->data_end, true, PREALLOC_MODE_OFF, 0, NULL);
+    }
+}
+
+static void preallocate_child_perm(BlockDriverState *bs, BdrvChild *c,
+                                   BdrvChildRole role,
+                                   BlockReopenQueue *reopen_queue,
+                                   uint64_t perm, uint64_t shared,
+                                   uint64_t *nperm, uint64_t *nshared)
+{
+    BDRVPreallocateState *s = bs->opaque;
+
+    bdrv_default_perms(bs, c, role, reopen_queue, perm, shared, nperm, nshared);
+
+    s->active = s->active || (perm & BLK_PERM_RESIZE);
+
+    if (s->active) {
+        /* Force RESIZE permission, to be able to crop file on close() */
+        *nperm |= BLK_PERM_RESIZE;
+    }
+}
+
+static coroutine_fn int preallocate_co_preadv_part(
+        BlockDriverState *bs, uint64_t offset, uint64_t bytes,
+        QEMUIOVector *qiov, size_t qiov_offset, int flags)
+{
+    return bdrv_co_preadv_part(bs->file, offset, bytes, qiov, qiov_offset,
+                               flags);
+}
+
+static int coroutine_fn preallocate_co_pdiscard(BlockDriverState *bs,
+                                               int64_t offset, int bytes)
+{
+    return bdrv_co_pdiscard(bs->file, offset, bytes);
+}
+
+static bool coroutine_fn do_preallocate(BlockDriverState *bs, int64_t offset,
+                                       int64_t bytes, bool write_zero)
+{
+    BDRVPreallocateState *s = bs->opaque;
+    int64_t len, start, end;
+
+    if (!s->active) {
+        return false;
+    }
+
+    if (s->data_end >= 0) {
+        s->data_end = MAX(s->data_end,
+                          QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE));
+    }
+
+    len = bdrv_getlength(bs->file->bs);
+    if (len < 0) {
+        return false;
+    }
+
+    if (s->data_end < 0) {
+        s->data_end = MAX(len,
+                          QEMU_ALIGN_UP(offset + bytes, BDRV_SECTOR_SIZE));
+    }
+
+    if (offset + bytes <= len) {
+        return false;
+    }
+
+    start = write_zero ? MIN(offset, len) : len;
+    end = QEMU_ALIGN_UP(offset + bytes + s->prealloc_size, s->prealloc_align);
+
+    return !bdrv_co_pwrite_zeroes(bs->file, start, end - start,
+            BDRV_REQ_NO_FALLBACK | BDRV_REQ_SERIALISING | BDRV_REQ_NO_WAIT);
+}
+
+static int coroutine_fn preallocate_co_pwrite_zeroes(BlockDriverState *bs,
+        int64_t offset, int bytes, BdrvRequestFlags flags)
+{
+    if (do_preallocate(bs, offset, bytes, true)) {
+        return 0;
+    }
+
+    return bdrv_co_pwrite_zeroes(bs->file, offset, bytes, flags);
+}
+
+static coroutine_fn int preallocate_co_pwritev_part(BlockDriverState *bs,
+                                                    uint64_t offset,
+                                                    uint64_t bytes,
+                                                    QEMUIOVector *qiov,
+                                                    size_t qiov_offset,
+                                                    int flags)
+{
+    do_preallocate(bs, offset, bytes, false);
+
+    return bdrv_co_pwritev_part(bs->file, offset, bytes, qiov, qiov_offset,
+                                flags);
+}
+
+static int coroutine_fn
+preallocate_co_truncate(BlockDriverState *bs, int64_t offset,
+                        bool exact, PreallocMode prealloc,
+                        BdrvRequestFlags flags, Error **errp)
+{
+    BDRVPreallocateState *s = bs->opaque;
+    int ret = bdrv_co_truncate(bs->file, offset, exact, prealloc, flags, errp);
+
+    /* s->data_end may become negative here, which means unknown data end */
+    s->data_end = bdrv_getlength(bs->file->bs);
+
+    return ret;
+}
+
+static int coroutine_fn preallocate_co_flush(BlockDriverState *bs)
+{
+    return bdrv_co_flush(bs->file->bs);
+}
+
+static int64_t preallocate_getlength(BlockDriverState *bs)
+{
+    /*
+     * We probably can return s->data_end here, but seems safer to return real
+     * file length, not trying to hide the preallocation.
+     *
+     * Still, don't miss the chance to restore s->data_end if it is broken.
+     */
+    BDRVPreallocateState *s = bs->opaque;
+    int64_t ret = bdrv_getlength(bs->file->bs);
+
+    if (s->data_end < 0) {
+        s->data_end = ret;
+    }
+
+    return ret;
+}
+
+BlockDriver bdrv_preallocate_filter = {
+    .format_name = "preallocate",
+    .instance_size = sizeof(BDRVPreallocateState),
+
+    .bdrv_getlength = preallocate_getlength,
+    .bdrv_open = preallocate_open,
+    .bdrv_close = preallocate_close,
+
+    .bdrv_co_preadv_part = preallocate_co_preadv_part,
+    .bdrv_co_pwritev_part = preallocate_co_pwritev_part,
+    .bdrv_co_pwrite_zeroes = preallocate_co_pwrite_zeroes,
+    .bdrv_co_pdiscard = preallocate_co_pdiscard,
+    .bdrv_co_flush = preallocate_co_flush,
+    .bdrv_co_truncate = preallocate_co_truncate,
+
+    .bdrv_co_block_status = bdrv_co_block_status_from_file,
+
+    .bdrv_child_perm = preallocate_child_perm,
+
+    .has_variable_length = true,
+    .is_filter = true,
+};
+
+static void bdrv_preallocate_init(void)
+{
+    bdrv_register(&bdrv_preallocate_filter);
+}
+
+block_init(bdrv_preallocate_init);
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 19c6f371c9..f8e6f16522 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -44,6 +44,7 @@ block-obj-y += crypto.o
 block-obj-y += aio_task.o
 block-obj-y += backup-top.o
 block-obj-y += filter-compress.o
+block-obj-y += preallocate.o
 common-obj-y += monitor/
 block-obj-y += monitor/
 
-- 
2.21.3

[PATCH v4 08/10] iotests.py: add verify_o_direct helper

[Vladimir Sementsov-Ogievskiy]

Add python notrun-helper similar to _check_o_direct for bash tests.
To be used in the following commit.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/iotests.py | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 717b5b652c..369e9918b4 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -1083,6 +1083,12 @@ def _verify_aio_mode(supported_aio_modes: Sequence[str] = ()) -> None:
     if supported_aio_modes and (aiomode not in supported_aio_modes):
         notrun('not suitable for this aio mode: %s' % aiomode)
 
+def verify_o_direct() -> None:
+    with FilePath('test_o_direct') as f:
+        qemu_img_create('-f', 'raw', f, '1M')
+        if 'O_DIRECT' in qemu_io('-f', 'raw', '-t', 'none', '-c', 'quit', f):
+            notrun(f'file system at {test_dir} does not support O_DIRECT')
+
 def supports_quorum():
     return 'quorum' in qemu_img_pipe('--help')
 
-- 
2.21.3

[PATCH v4 09/10] iotests.py: add filter_img_check

[Vladimir Sementsov-Ogievskiy]

Add analog of bash _filter_qemu_img_check to python framework.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/iotests.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 369e9918b4..ef3da4ee61 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -402,6 +402,10 @@ def filter_img_info(output, filename):
         lines.append(line)
     return '\n'.join(lines)
 
+def filter_img_check(msg):
+    msg = re.sub(r'.*allocated.*fragmented.*compressed clusters', '', msg)
+    return re.sub(r'Image end offset: [0-9]+', '', msg).strip()
+
 def filter_imgfmt(msg):
     return msg.replace(imgfmt, 'IMGFMT')
 
-- 
2.21.3

[PATCH v4 10/10] iotests: add 298 to test new preallocate filter driver

[Vladimir Sementsov-Ogievskiy]

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 tests/qemu-iotests/298     | 50 ++++++++++++++++++++++++++++++++++++++
 tests/qemu-iotests/298.out |  6 +++++
 tests/qemu-iotests/group   |  1 +
 3 files changed, 57 insertions(+)
 create mode 100644 tests/qemu-iotests/298
 create mode 100644 tests/qemu-iotests/298.out

diff --git a/tests/qemu-iotests/298 b/tests/qemu-iotests/298
new file mode 100644
index 0000000000..4f2087352a
--- /dev/null
+++ b/tests/qemu-iotests/298
@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+#
+# Test for preallocate filter
+#
+# Copyright (c) 2020 Virtuozzo International GmbH.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+import os
+import iotests
+from iotests import log
+
+iotests.script_initialize(supported_fmts=['qcow2'])
+iotests.verify_o_direct()
+
+size = 10 * 1024 * 1024
+disk = iotests.file_path('disk')
+
+iotests.qemu_img_create('-f', iotests.imgfmt, disk, str(size))
+
+opts = f'driver={iotests.imgfmt},' \
+    f'file.driver=preallocate,file.file.filename={disk}'
+p = iotests.QemuIoInteractive('--image-opts', '-t', 'none', opts)
+
+log(p.cmd('write 0 1M'), filters=[iotests.filter_qemu_io])
+p.cmd('flush')
+
+if os.path.getsize(disk) > 100 * 1024 * 1024:
+    log('file in progress is big, preallocation works')
+
+p.close()
+
+if os.path.getsize(disk) < 10 * 1024 * 1024:
+    log('file is small after close')
+
+# Check that there are no leaks.
+log(iotests.qemu_img_pipe('check', '-f', 'qcow2', disk),
+    filters=[iotests.filter_img_check])
diff --git a/tests/qemu-iotests/298.out b/tests/qemu-iotests/298.out
new file mode 100644
index 0000000000..baf8f8425c
--- /dev/null
+++ b/tests/qemu-iotests/298.out
@@ -0,0 +1,6 @@
+wrote 1048576/1048576 bytes at offset 0
+1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+file in progress is big, preallocation works
+file is small after close
+No errors were found on the image.
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 7f76066640..cdcde2fe48 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -306,6 +306,7 @@
 295 rw
 296 rw
 297 meta
+298 auto quick
 299 auto quick
 301 backing quick
 302 quick
-- 
2.21.3

Re: [PATCH v4 00/10] preallocate filter

[no-reply]

Patchew URL: https://patchew.org/QEMU/20200820183950.13109-1-vsementsov@virtuozzo.com/



Hi,

This series failed the docker-quick@centos7 build test. Please find the testing commands and
their output below. If you have Docker installed, you can probably reproduce it
locally.

=== TEST SCRIPT BEGIN ===
#!/bin/bash
make docker-image-centos7 V=1 NETWORK=1
time make docker-test-quick@centos7 SHOW_ENV=1 J=14 NETWORK=1
=== TEST SCRIPT END ===

  TEST    check-unit: tests/test-char
Unexpected error in object_property_try_add() at /tmp/qemu-test/src/qom/object.c:1181:
attempt to add duplicate property 'serial-id' to object (type 'container')
ERROR test-char - too few tests run (expected 38, got 9)
make: *** [check-unit] Error 1
make: *** Waiting for unfinished jobs....
  TEST    iotest-qcow2: 018
  TEST    iotest-qcow2: 019
---
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['sudo', '-n', 'docker', 'run', '--label', 'com.qemu.instance.uuid=a80f0516394e4d83b19a19e329899c17', '-u', '1003', '--security-opt', 'seccomp=unconfined', '--rm', '-e', 'TARGET_LIST=', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=14', '-e', 'DEBUG=', '-e', 'SHOW_ENV=1', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/home/patchew2/.cache/qemu-docker-ccache:/var/tmp/ccache:z', '-v', '/var/tmp/patchew-tester-tmp-n_a2v5bj/src/docker-src.2020-08-20-15.00.31.12987:/var/tmp/qemu:z,ro', 'qemu/centos7', '/var/tmp/qemu/run', 'test-quick']' returned non-zero exit status 2.
filter=--filter=label=com.qemu.instance.uuid=a80f0516394e4d83b19a19e329899c17
make[1]: *** [docker-run] Error 1
make[1]: Leaving directory `/var/tmp/patchew-tester-tmp-n_a2v5bj/src'
make: *** [docker-run-test-quick@centos7] Error 2

real    16m13.105s
user    0m8.886s


The full log is available at
http://patchew.org/logs/20200820183950.13109-1-vsementsov@virtuozzo.com/testing.docker-quick@centos7/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

Re: [PATCH v4 00/10] preallocate filter

[Vladimir Sementsov-Ogievskiy]

20.08.2020 22:16, no-reply@patchew.org wrote:
> Patchew URL: https://patchew.org/QEMU/20200820183950.13109-1-vsementsov@virtuozzo.com/
> 
> 
> 
> Hi,
> 
> This series failed the docker-quick@centos7 build test. Please find the testing commands and
> their output below. If you have Docker installed, you can probably reproduce it
> locally.
> 
> === TEST SCRIPT BEGIN ===
> #!/bin/bash
> make docker-image-centos7 V=1 NETWORK=1
> time make docker-test-quick@centos7 SHOW_ENV=1 J=14 NETWORK=1
> === TEST SCRIPT END ===
> 
>    TEST    check-unit: tests/test-char
> Unexpected error in object_property_try_add() at /tmp/qemu-test/src/qom/object.c:1181:
> attempt to add duplicate property 'serial-id' to object (type 'container')
> ERROR test-char - too few tests run (expected 38, got 9)
> make: *** [check-unit] Error 1
> make: *** Waiting for unfinished jobs....
>    TEST    iotest-qcow2: 018
>    TEST    iotest-qcow2: 019
> ---
>      raise CalledProcessError(retcode, cmd)
> subprocess.CalledProcessError: Command '['sudo', '-n', 'docker', 'run', '--label', 'com.qemu.instance.uuid=a80f0516394e4d83b19a19e329899c17', '-u', '1003', '--security-opt', 'seccomp=unconfined', '--rm', '-e', 'TARGET_LIST=', '-e', 'EXTRA_CONFIGURE_OPTS=', '-e', 'V=', '-e', 'J=14', '-e', 'DEBUG=', '-e', 'SHOW_ENV=1', '-e', 'CCACHE_DIR=/var/tmp/ccache', '-v', '/home/patchew2/.cache/qemu-docker-ccache:/var/tmp/ccache:z', '-v', '/var/tmp/patchew-tester-tmp-n_a2v5bj/src/docker-src.2020-08-20-15.00.31.12987:/var/tmp/qemu:z,ro', 'qemu/centos7', '/var/tmp/qemu/run', 'test-quick']' returned non-zero exit status 2.
> filter=--filter=label=com.qemu.instance.uuid=a80f0516394e4d83b19a19e329899c17
> make[1]: *** [docker-run] Error 1
> make[1]: Leaving directory `/var/tmp/patchew-tester-tmp-n_a2v5bj/src'
> make: *** [docker-run-test-quick@centos7] Error 2
> 
> real    16m13.105s
> user    0m8.886s
> 
> 
> The full log is available at
> http://patchew.org/logs/20200820183950.13109-1-vsementsov@virtuozzo.com/testing.docker-quick@centos7/?type=message.
> ---
> Email generated automatically by Patchew [https://patchew.org/].
> Please send your feedback to patchew-devel@redhat.com
> 


Seems something unrelated

-- 
Best regards,
Vladimir

Re: [PATCH v4 08/10] iotests.py: add verify_o_direct helper

[Nir Soffer]

On Thu, Aug 20, 2020 at 9:49 PM Vladimir Sementsov-Ogievskiy
<vsementsov@virtuozzo.com> wrote:
>
> Add python notrun-helper similar to _check_o_direct for bash tests.
> To be used in the following commit.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  tests/qemu-iotests/iotests.py | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
> index 717b5b652c..369e9918b4 100644
> --- a/tests/qemu-iotests/iotests.py
> +++ b/tests/qemu-iotests/iotests.py
> @@ -1083,6 +1083,12 @@ def _verify_aio_mode(supported_aio_modes: Sequence[str] = ()) -> None:
>      if supported_aio_modes and (aiomode not in supported_aio_modes):
>          notrun('not suitable for this aio mode: %s' % aiomode)
>
> +def verify_o_direct() -> None:
> +    with FilePath('test_o_direct') as f:
> +        qemu_img_create('-f', 'raw', f, '1M')
> +        if 'O_DIRECT' in qemu_io('-f', 'raw', '-t', 'none', '-c', 'quit', f):
> +            notrun(f'file system at {test_dir} does not support O_DIRECT')

Why not:

    with FilePath('test_o_direct') as f:
        try:
            fd = os.open(f, os.O_DIRECT | os.O_CREAT | os.O_RDWR)
        except OSError as e:
            if e.errno != errno.EINVAL:
                raise
            notrun(...)
        else:
           os.close(fd)

More verbose, but the intent is more clear, and we do not depend on the output
of qemu-io which is not a public API. For example if someone improves qemu-io
to fail with:

    Direct I/O is not supported

It would break the tests using this helper.

Nir

> +
>  def supports_quorum():
>      return 'quorum' in qemu_img_pipe('--help')
>
> --
> 2.21.3
>
>

Re: [PATCH v4 08/10] iotests.py: add verify_o_direct helper

[Vladimir Sementsov-Ogievskiy]

21.08.2020 00:00, Nir Soffer wrote:
> On Thu, Aug 20, 2020 at 9:49 PM Vladimir Sementsov-Ogievskiy
> <vsementsov@virtuozzo.com> wrote:
>>
>> Add python notrun-helper similar to _check_o_direct for bash tests.
>> To be used in the following commit.
>>
>> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>> ---
>>   tests/qemu-iotests/iotests.py | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
>> index 717b5b652c..369e9918b4 100644
>> --- a/tests/qemu-iotests/iotests.py
>> +++ b/tests/qemu-iotests/iotests.py
>> @@ -1083,6 +1083,12 @@ def _verify_aio_mode(supported_aio_modes: Sequence[str] = ()) -> None:
>>       if supported_aio_modes and (aiomode not in supported_aio_modes):
>>           notrun('not suitable for this aio mode: %s' % aiomode)
>>
>> +def verify_o_direct() -> None:
>> +    with FilePath('test_o_direct') as f:
>> +        qemu_img_create('-f', 'raw', f, '1M')
>> +        if 'O_DIRECT' in qemu_io('-f', 'raw', '-t', 'none', '-c', 'quit', f):
>> +            notrun(f'file system at {test_dir} does not support O_DIRECT')
> 
> Why not:
> 
>      with FilePath('test_o_direct') as f:
>          try:
>              fd = os.open(f, os.O_DIRECT | os.O_CREAT | os.O_RDWR)
>          except OSError as e:
>              if e.errno != errno.EINVAL:
>                  raise
>              notrun(...)
>          else:
>             os.close(fd)
> 
> More verbose, but the intent is more clear, and we do not depend on the output
> of qemu-io which is not a public API. For example if someone improves qemu-io
> to fail with:
> 
>      Direct I/O is not supported
> 
> It would break the tests using this helper.
> 

Agree, that's better. Will use it, thanks!

> 
>> +
>>   def supports_quorum():
>>       return 'quorum' in qemu_img_pipe('--help')
>>
>> --
>> 2.21.3
>>
>>
> 


-- 
Best regards,
Vladimir