From: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
Introduce NBDExtentArray class, to handle extents list creation in more
controlled way and with fewer OUT parameters in functions.
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@xxxxxxxxxxxxx>
Reviewed-by: Eric Blake <eblake@xxxxxxxxxx>
Message-id: 20200205112041.6003-9-vsementsov@xxxxxxxxxxxxx
Signed-off-by: John Snow <jsnow@xxxxxxxxxx>
---
nbd/server.c | 210 +++++++++++++++++++++++++++++----------------------
1 file changed, 118 insertions(+), 92 deletions(-)
diff --git a/nbd/server.c b/nbd/server.c
index 3106aaf3b4..f90bb33a75 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1909,27 +1909,98 @@ static int coroutine_fn nbd_co_send_sparse_read(NBDClient *client,
return ret;
}
+typedef struct NBDExtentArray {
+ NBDExtent *extents;
+ unsigned int nb_alloc;
+ unsigned int count;
+ uint64_t total_length;
+ bool can_add;
+ bool converted_to_be;
+} NBDExtentArray;
+
+static NBDExtentArray *nbd_extent_array_new(unsigned int nb_alloc)
+{
+ NBDExtentArray *ea = g_new0(NBDExtentArray, 1);
+
+ ea->nb_alloc = nb_alloc;
+ ea->extents = g_new(NBDExtent, nb_alloc);
+ ea->can_add = true;
+
+ return ea;
+}
+
+static void nbd_extent_array_free(NBDExtentArray *ea)
+{
+ g_free(ea->extents);
+ g_free(ea);
+}
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(NBDExtentArray, nbd_extent_array_free);
+
+/* Further modifications of the array after conversion are abandoned */
+static void nbd_extent_array_convert_to_be(NBDExtentArray *ea)
+{
+ int i;
+
+ assert(!ea->converted_to_be);
+ ea->can_add = false;
+ ea->converted_to_be = true;
+
+ for (i = 0; i < ea->count; i++) {
+ ea->extents[i].flags = cpu_to_be32(ea->extents[i].flags);
+ ea->extents[i].length = cpu_to_be32(ea->extents[i].length);
+ }
+}
+
/*
- * Populate @extents from block status. Update @bytes to be the actual
- * length encoded (which may be smaller than the original), and update
- * @nb_extents to the number of extents used.
- *
- * Returns zero on success and -errno on bdrv_block_status_above failure.
+ * Add extent to NBDExtentArray. If extent can't be added (no available space),
+ * return -1.
+ * For safety, when returning -1 for the first time, .can_add is set to false,
+ * further call to nbd_extent_array_add() will crash.
+ * (to avoid the situation, when after failing to add an extent (returned -1),
+ * user miss this failure and add another extent, which is successfully added
+ * (array is full, but new extent may be squashed into the last one), then we
+ * have invalid array with skipped extent)
*/
+static int nbd_extent_array_add(NBDExtentArray *ea,
+ uint32_t length, uint32_t flags)
+{
+ assert(ea->can_add);
+
+ if (!length) {
+ return 0;
+ }
+
+ /* Extend previous extent if flags are the same */
+ if (ea->count > 0 && flags == ea->extents[ea->count - 1].flags) {
+ uint64_t sum = (uint64_t)length + ea->extents[ea->count - 1].length;
+
+ if (sum <= UINT32_MAX) {
+ ea->extents[ea->count - 1].length = sum;
+ ea->total_length += length;
+ return 0;
+ }
+ }
+
+ if (ea->count >= ea->nb_alloc) {
+ ea->can_add = false;
+ return -1;
+ }
+
+ ea->total_length += length;
+ ea->extents[ea->count] = (NBDExtent) {.length = length, .flags = flags};
+ ea->count++;
+
+ return 0;
+}
+
static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
- uint64_t *bytes, NBDExtent *extents,
- unsigned int *nb_extents)
+ uint64_t bytes, NBDExtentArray *ea)
{
- uint64_t remaining_bytes = *bytes;
- NBDExtent *extent = extents, *extents_end = extents + *nb_extents;
- bool first_extent = true;
-
- assert(*nb_extents);
- while (remaining_bytes) {
+ while (bytes) {
uint32_t flags;
int64_t num;
- int ret = bdrv_block_status_above(bs, NULL, offset, remaining_bytes,
- &num, NULL, NULL);
+ int ret = bdrv_block_status_above(bs, NULL, offset, bytes, &num,
+ NULL, NULL);
if (ret < 0) {
return ret;
@@ -1938,60 +2009,37 @@ static int blockstatus_to_extents(BlockDriverState *bs, uint64_t offset,
flags = (ret & BDRV_BLOCK_ALLOCATED ? 0 : NBD_STATE_HOLE) |
(ret & BDRV_BLOCK_ZERO ? NBD_STATE_ZERO : 0);
- if (first_extent) {
- extent->flags = flags;
- extent->length = num;
- first_extent = false;
- } else if (flags == extent->flags) {
- /* extend current extent */
- extent->length += num;
- } else {
- if (extent + 1 == extents_end) {
- break;
- }
-
- /* start new extent */
- extent++;
- extent->flags = flags;
- extent->length = num;
+ if (nbd_extent_array_add(ea, num, flags) < 0) {
+ return 0;
}
+
offset += num;
- remaining_bytes -= num;
+ bytes -= num;
}
- extents_end = extent + 1;
-
- for (extent = extents; extent < extents_end; extent++) {
- extent->flags = cpu_to_be32(extent->flags);
- extent->length = cpu_to_be32(extent->length);
- }
-
- *bytes -= remaining_bytes;
- *nb_extents = extents_end - extents;
-
return 0;
}
-/* nbd_co_send_extents
+/*
+ * nbd_co_send_extents
*
- * @length is only for tracing purposes (and may be smaller or larger
- * than the client's original request). @last controls whether
- * NBD_REPLY_FLAG_DONE is sent. @extents should already be in
- * big-endian format.
+ * @ea is converted to BE by the function
+ * @last controls whether NBD_REPLY_FLAG_DONE is sent.
*/
static int nbd_co_send_extents(NBDClient *client, uint64_t handle,
- NBDExtent *extents, unsigned int nb_extents,
- uint64_t length, bool last,
- uint32_t context_id, Error **errp)
+ NBDExtentArray *ea,
+ bool last, uint32_t context_id, Error **errp)
{
NBDStructuredMeta chunk;
-
struct iovec iov[] = {
{.iov_base = &chunk, .iov_len = sizeof(chunk)},
- {.iov_base = extents, .iov_len = nb_extents * sizeof(extents[0])}
+ {.iov_base = ea->extents, .iov_len = ea->count * sizeof(ea->extents[0])}
};
- trace_nbd_co_send_extents(handle, nb_extents, context_id, length, last);
+ nbd_extent_array_convert_to_be(ea);
+
+ trace_nbd_co_send_extents(handle, ea->count, context_id, ea->total_length,
+ last);
set_be_chunk(&chunk.h, last ? NBD_REPLY_FLAG_DONE : 0,
NBD_REPLY_TYPE_BLOCK_STATUS,
handle, sizeof(chunk) - sizeof(chunk.h) + iov[1].iov_len);
@@ -2009,39 +2057,27 @@ static int nbd_co_send_block_status(NBDClient *client, uint64_t handle,
{
int ret;
unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
- NBDExtent *extents = g_new(NBDExtent, nb_extents);
- uint64_t final_length = length;
+ g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
- ret = blockstatus_to_extents(bs, offset, &final_length, extents,
- &nb_extents);
+ ret = blockstatus_to_extents(bs, offset, length, ea);
if (ret < 0) {
- g_free(extents);
return nbd_co_send_structured_error(
client, handle, -ret, "can't get block status", errp);
}
- ret = nbd_co_send_extents(client, handle, extents, nb_extents,
- final_length, last, context_id, errp);
-
- g_free(extents);
-
- return ret;
+ return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
}
/*
- * Populate @extents from a dirty bitmap. Unless @dont_fragment, the
- * final extent may exceed the original @length. Store in @length the
- * byte length encoded (which may be smaller or larger than the
- * original), and return the number of extents used.
+ * Populate @ea from a dirty bitmap. Unless @dont_fragment, the
+ * final extent may exceed the original @length.
*/
-static unsigned int bitmap_to_extents(BdrvDirtyBitmap *bitmap, uint64_t offset,
- uint64_t *length, NBDExtent *extents,
- unsigned int nb_extents,
- bool dont_fragment)
+static void bitmap_to_extents(BdrvDirtyBitmap *bitmap,
+ uint64_t offset, uint64_t length,
+ NBDExtentArray *ea, bool dont_fragment)
{
uint64_t begin = offset, end = offset;
- uint64_t overall_end = offset + *length;
- unsigned int i = 0;
+ uint64_t overall_end = offset + length;
BdrvDirtyBitmapIter *it;
bool dirty;
@@ -2050,8 +2086,7 @@ static unsigned int bitmap_to_extents(BdrvDirtyBitmap *bitmap, uint64_t offset,
it = bdrv_dirty_iter_new(bitmap);
dirty = bdrv_dirty_bitmap_get_locked(bitmap, offset);
- assert(begin < overall_end && nb_extents);
- while (begin < overall_end && i < nb_extents) {
+ while (begin < overall_end) {
bool next_dirty = !dirty;
if (dirty) {
@@ -2071,9 +2106,10 @@ static unsigned int bitmap_to_extents(BdrvDirtyBitmap *bitmap, uint64_t offset,
end = overall_end;
}
- extents[i].length = cpu_to_be32(end - begin);
- extents[i].flags = cpu_to_be32(dirty ? NBD_STATE_DIRTY : 0);
- i++;
+ if (nbd_extent_array_add(ea, end - begin,
+ dirty ? NBD_STATE_DIRTY : 0) < 0) {
+ break;
+ }
begin = end;
dirty = next_dirty;
}
@@ -2083,8 +2119,6 @@ static unsigned int bitmap_to_extents(BdrvDirtyBitmap *bitmap, uint64_t offset,
bdrv_dirty_bitmap_unlock(bitmap);
assert(offset < end);
- *length = end - offset;
- return i;
}
static int nbd_co_send_bitmap(NBDClient *client, uint64_t handle,
@@ -2092,20 +2126,12 @@ static int nbd_co_send_bitmap(NBDClient *client, uint64_t handle,
uint32_t length, bool dont_fragment, bool last,
uint32_t context_id, Error **errp)
{
- int ret;
unsigned int nb_extents = dont_fragment ? 1 : NBD_MAX_BLOCK_STATUS_EXTENTS;
- NBDExtent *extents = g_new(NBDExtent, nb_extents);
- uint64_t final_length = length;
+ g_autoptr(NBDExtentArray) ea = nbd_extent_array_new(nb_extents);
- nb_extents = bitmap_to_extents(bitmap, offset, &final_length, extents,
- nb_extents, dont_fragment);
+ bitmap_to_extents(bitmap, offset, length, ea, dont_fragment);
- ret = nbd_co_send_extents(client, handle, extents, nb_extents,
- final_length, last, context_id, errp);
-
- g_free(extents);
-
- return ret;
+ return nbd_co_send_extents(client, handle, ea, last, context_id, errp);
}
/* nbd_co_receive_request
--
2.21.1
