[PATCH v2] block/file-posix: optimize append write

[Sam Li <faithilikerun@gmail.com>]

When the file-posix driver emulates append write, it holds the lock
whenever accessing wp, which limits the IO queue depth to one.

The write IO flow can be optimized to allow concurrent writes. The lock
is held in two cases:
1. Assumed that the write IO succeeds, update the wp before issuing the
write.
2. If the write IO fails, report that zone and use the reported value
as the current wp.

Signed-off-by: Sam Li <faithilikerun@gmail.com>
---
 block/file-posix.c | 57 ++++++++++++++++++++++++++++++----------------
 1 file changed, 38 insertions(+), 19 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 90fa54352c..a65a23cb2c 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2482,18 +2482,46 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, int64_t *offset_ptr,
     BDRVRawState *s = bs->opaque;
     RawPosixAIOData acb;
     int ret;
-    uint64_t offset = *offset_ptr;
+    uint64_t end_offset, end_zone, offset = *offset_ptr;
+    uint64_t *wp;
 
     if (fd_open(bs) < 0)
         return -EIO;
 #if defined(CONFIG_BLKZONED)
     if ((type & (QEMU_AIO_WRITE | QEMU_AIO_ZONE_APPEND)) &&
         bs->bl.zoned != BLK_Z_NONE) {
-        qemu_co_mutex_lock(&bs->wps->colock);
-        if (type & QEMU_AIO_ZONE_APPEND) {
-            int index = offset / bs->bl.zone_size;
-            offset = bs->wps->wp[index];
+        BlockZoneWps *wps = bs->wps;
+        int index = offset / bs->bl.zone_size;
+
+        qemu_co_mutex_lock(&wps->colock);
+        wp = &wps->wp[index];
+        if (!BDRV_ZT_IS_CONV(*wp)) {
+            if (type & QEMU_AIO_WRITE && offset != *wp) {
+                error_report("write offset 0x%" PRIx64 " is not equal to the wp"
+                             " of zone[%d] 0x%" PRIx64 "", offset, index, *wp);
+                qemu_co_mutex_unlock(&wps->colock);
+                return -EINVAL;
+            }
+
+            if (type & QEMU_AIO_ZONE_APPEND) {
+                offset = *wp;
+                *offset_ptr = offset;
+            }
+
+            end_offset = offset + bytes;
+            end_zone = (index + 1) * bs->bl.zone_size;
+            if (end_offset > end_zone) {
+                error_report("write exceeds zone boundary with end_offset "
+                             "%" PRIu64 ", end_zone %" PRIu64 "",
+                             end_offset, end_zone);
+                qemu_co_mutex_unlock(&wps->colock);
+                return -EINVAL;
+            }
+
+            /* Advance the wp */
+            *wp = end_offset;
         }
+        qemu_co_mutex_unlock(&bs->wps->colock);
     }
 #endif
 
@@ -2540,28 +2568,19 @@ out:
 #if defined(CONFIG_BLKZONED)
     if ((type & (QEMU_AIO_WRITE | QEMU_AIO_ZONE_APPEND)) &&
         bs->bl.zoned != BLK_Z_NONE) {
-        BlockZoneWps *wps = bs->wps;
         if (ret == 0) {
-            uint64_t *wp = &wps->wp[offset / bs->bl.zone_size];
-            if (!BDRV_ZT_IS_CONV(*wp)) {
-                if (type & QEMU_AIO_ZONE_APPEND) {
-                    *offset_ptr = *wp;
-                    trace_zbd_zone_append_complete(bs, *offset_ptr
-                        >> BDRV_SECTOR_BITS);
-                }
-                /* Advance the wp if needed */
-                if (offset + bytes > *wp) {
-                    *wp = offset + bytes;
-                }
+            if (type & QEMU_AIO_ZONE_APPEND) {
+                trace_zbd_zone_append_complete(bs, *offset_ptr
+                    >> BDRV_SECTOR_BITS);
             }
         } else {
+            qemu_co_mutex_lock(&bs->wps->colock);
             /*
              * write and append write are not allowed to cross zone boundaries
              */
             update_zones_wp(bs, s->fd, offset, 1);
+            qemu_co_mutex_unlock(&bs->wps->colock);
         }
-
-        qemu_co_mutex_unlock(&wps->colock);
     }
 #endif
     return ret;
-- 
2.34.1