file-posix: add tracking of the zone write pointers

Since Linux doesn't have a user API to issue zone append operations to
zoned devices from user space, the file-posix driver is modified to add
zone append emulation using regular writes. To do this, the file-posix
driver tracks the wp location of all zones of the device. It uses an
array of uint64_t. The most significant bit of each wp location indicates
if the zone type is conventional zones.

The zones wp can be changed due to the following operations issued:
- zone reset: change the wp to the start offset of that zone
- zone finish: change to the end location of that zone
- write to a zone
- zone append

Signed-off-by: Sam Li <faithilikerun@gmail.com>
Message-id: 20230508051510.177850-2-faithilikerun@gmail.com
[Fix errno propagation from handle_aiocb_zone_mgmt()
--Stefan]
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/file-posix.c

@@ -1323,9 +1323,93 @@ static int hdev_get_max_segments(int fd, struct stat *st)
 }
 
 #if defined(CONFIG_BLKZONED)
+/*
+ * If the reset_all flag is true, then the wps of zone whose state is
+ * not readonly or offline should be all reset to the start sector.
+ * Else, take the real wp of the device.
+ */
+static int get_zones_wp(BlockDriverState *bs, int fd, int64_t offset,
+                        unsigned int nrz, bool reset_all)
+{
+    struct blk_zone *blkz;
+    size_t rep_size;
+    uint64_t sector = offset >> BDRV_SECTOR_BITS;
+    BlockZoneWps *wps = bs->wps;
+    unsigned int j = offset / bs->bl.zone_size;
+    unsigned int n = 0, i = 0;
+    int ret;
+    rep_size = sizeof(struct blk_zone_report) + nrz * sizeof(struct blk_zone);
+    g_autofree struct blk_zone_report *rep = NULL;
+
+    rep = g_malloc(rep_size);
+    blkz = (struct blk_zone *)(rep + 1);
+    while (n < nrz) {
+        memset(rep, 0, rep_size);
+        rep->sector = sector;
+        rep->nr_zones = nrz - n;
+
+        do {
+            ret = ioctl(fd, BLKREPORTZONE, rep);
+        } while (ret != 0 && errno == EINTR);
+        if (ret != 0) {
+            error_report("%d: ioctl BLKREPORTZONE at %" PRId64 " failed %d",
+                    fd, offset, errno);
+            return -errno;
+        }
+
+        if (!rep->nr_zones) {
+            break;
+        }
+
+        for (i = 0; i < rep->nr_zones; ++i, ++n, ++j) {
+            /*
+             * The wp tracking cares only about sequential writes required and
+             * sequential write preferred zones so that the wp can advance to
+             * the right location.
+             * Use the most significant bit of the wp location to indicate the
+             * zone type: 0 for SWR/SWP zones and 1 for conventional zones.
+             */
+            if (blkz[i].type == BLK_ZONE_TYPE_CONVENTIONAL) {
+                wps->wp[j] |= 1ULL << 63;
+            } else {
+                switch(blkz[i].cond) {
+                case BLK_ZONE_COND_FULL:
+                case BLK_ZONE_COND_READONLY:
+                    /* Zone not writable */
+                    wps->wp[j] = (blkz[i].start + blkz[i].len) << BDRV_SECTOR_BITS;
+                    break;
+                case BLK_ZONE_COND_OFFLINE:
+                    /* Zone not writable nor readable */
+                    wps->wp[j] = (blkz[i].start) << BDRV_SECTOR_BITS;
+                    break;
+                default:
+                    if (reset_all) {
+                        wps->wp[j] = blkz[i].start << BDRV_SECTOR_BITS;
+                    } else {
+                        wps->wp[j] = blkz[i].wp << BDRV_SECTOR_BITS;
+                    }
+                    break;
+                }
+            }
+        }
+        sector = blkz[i - 1].start + blkz[i - 1].len;
+    }
+
+    return 0;
+}
+
+static void update_zones_wp(BlockDriverState *bs, int fd, int64_t offset,
+                            unsigned int nrz)
+{
+    if (get_zones_wp(bs, fd, offset, nrz, 0) < 0) {
+        error_report("update zone wp failed");
+    }
+}
+
 static void raw_refresh_zoned_limits(BlockDriverState *bs, struct stat *st,
                                      Error **errp)
 {
+    BDRVRawState *s = bs->opaque;
     BlockZoneModel zoned;
     int ret;
 
@@ -1376,6 +1460,23 @@ static void raw_refresh_zoned_limits(BlockDriverState *bs, struct stat *st,
     if (ret > 0) {
         bs->bl.max_append_sectors = ret >> BDRV_SECTOR_BITS;
     }
+
+    ret = get_sysfs_long_val(st, "physical_block_size");
+    if (ret >= 0) {
+        bs->bl.write_granularity = ret;
+    }
+
+    /* The refresh_limits() function can be called multiple times. */
+    g_free(bs->wps);
+    bs->wps = g_malloc(sizeof(BlockZoneWps) +
+            sizeof(int64_t) * bs->bl.nr_zones);
+    ret = get_zones_wp(bs, s->fd, 0, bs->bl.nr_zones, 0);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "report wps failed");
+        bs->wps = NULL;
+        return;
+    }
+    qemu_co_mutex_init(&bs->wps->colock);
 }
 #else /* !defined(CONFIG_BLKZONED) */
 static void raw_refresh_zoned_limits(BlockDriverState *bs, struct stat *st,
@@ -2061,7 +2162,7 @@ static int handle_aiocb_zone_mgmt(void *opaque)
         ret = ioctl(fd, aiocb->zone_mgmt.op, &range);
     } while (ret != 0 && errno == EINTR);
 
-    return ret;
+    return ret < 0 ? -errno : ret;
 }
 #endif
 
@@ -2347,9 +2448,15 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
 {
     BDRVRawState *s = bs->opaque;
     RawPosixAIOData acb;
+    int ret;
 
     if (fd_open(bs) < 0)
         return -EIO;
+#if defined(CONFIG_BLKZONED)
+    if (type & QEMU_AIO_WRITE && bs->wps) {
+        qemu_co_mutex_lock(&bs->wps->colock);
+    }
+#endif
 
     /*
      * When using O_DIRECT, the request must be aligned to be able to use
@@ -2362,12 +2469,15 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
 #ifdef CONFIG_LINUX_IO_URING
     } else if (s->use_linux_io_uring) {
         assert(qiov->size == bytes);
-        return luring_co_submit(bs, s->fd, offset, qiov, type);
+        ret = luring_co_submit(bs, s->fd, offset, qiov, type);
+        goto out;
 #endif
 #ifdef CONFIG_LINUX_AIO
     } else if (s->use_linux_aio) {
         assert(qiov->size == bytes);
-        return laio_co_submit(s->fd, offset, qiov, type, s->aio_max_batch);
+        ret = laio_co_submit(s->fd, offset, qiov, type,
+                              s->aio_max_batch);
+        goto out;
 #endif
     }
 
@@ -2384,7 +2494,35 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, uint64_t offset,
     };
 
     assert(qiov->size == bytes);
-    return raw_thread_pool_submit(handle_aiocb_rw, &acb);
+    ret = raw_thread_pool_submit(handle_aiocb_rw, &acb);
+    goto out; /* Avoid the compiler err of unused label */
+
+out:
+#if defined(CONFIG_BLKZONED)
+{
+    BlockZoneWps *wps = bs->wps;
+    if (ret == 0) {
+        if (type & QEMU_AIO_WRITE && wps && bs->bl.zone_size) {
+            uint64_t *wp = &wps->wp[offset / bs->bl.zone_size];
+            if (!BDRV_ZT_IS_CONV(*wp)) {
+                /* Advance the wp if needed */
+                if (offset + bytes > *wp) {
+                    *wp = offset + bytes;
+                }
+            }
+        }
+    } else {
+        if (type & QEMU_AIO_WRITE) {
+            update_zones_wp(bs, s->fd, 0, 1);
+        }
+    }
+
+    if (type & QEMU_AIO_WRITE && wps) {
+        qemu_co_mutex_unlock(&wps->colock);
+    }
+}
+#endif
+    return ret;
 }
 
 static int coroutine_fn raw_co_preadv(BlockDriverState *bs, int64_t offset,
@@ -2487,6 +2625,9 @@ static void raw_close(BlockDriverState *bs)
     BDRVRawState *s = bs->opaque;
 
     if (s->fd >= 0) {
+#if defined(CONFIG_BLKZONED)
+        g_free(bs->wps);
+#endif
         qemu_close(s->fd);
         s->fd = -1;
     }
@@ -3284,6 +3425,7 @@ static int coroutine_fn raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
     const char *op_name;
     unsigned long zo;
     int ret;
+    BlockZoneWps *wps = bs->wps;
     int64_t capacity = bs->total_sectors << BDRV_SECTOR_BITS;
 
     zone_size = bs->bl.zone_size;
@@ -3301,6 +3443,14 @@ static int coroutine_fn raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
         return -EINVAL;
     }
 
+    uint32_t i = offset / bs->bl.zone_size;
+    uint32_t nrz = len / bs->bl.zone_size;
+    uint64_t *wp = &wps->wp[i];
+    if (BDRV_ZT_IS_CONV(*wp) && len != capacity) {
+        error_report("zone mgmt operations are not allowed for conventional zones");
+        return -EIO;
+    }
+
     switch (op) {
     case BLK_ZO_OPEN:
         op_name = "BLKOPENZONE";
@@ -3338,7 +3488,27 @@ static int coroutine_fn raw_co_zone_mgmt(BlockDriverState *bs, BlockZoneOp op,
                         len >> BDRV_SECTOR_BITS);
     ret = raw_thread_pool_submit(handle_aiocb_zone_mgmt, &acb);
     if (ret != 0) {
+        update_zones_wp(bs, s->fd, offset, i);
         error_report("ioctl %s failed %d", op_name, ret);
+        return ret;
+    }
+
+    if (zo == BLKRESETZONE && len == capacity) {
+        ret = get_zones_wp(bs, s->fd, 0, bs->bl.nr_zones, 1);
+        if (ret < 0) {
+            error_report("reporting single wp failed");
+            return ret;
+        }
+    } else if (zo == BLKRESETZONE) {
+        for (unsigned int j = 0; j < nrz; ++j) {
+            wp[j] = offset + j * zone_size;
+        }
+    } else if (zo == BLKFINISHZONE) {
+        for (unsigned int j = 0; j < nrz; ++j) {
+            /* The zoned device allows the last zone smaller that the
+             * zone size. */
+            wp[j] = MIN(offset + (j + 1) * zone_size, offset + len);
+        }
     }
 
     return ret;

include/block/block-common.h

@@ -118,6 +118,14 @@ typedef struct BlockZoneDescriptor {
     BlockZoneState state;
 } BlockZoneDescriptor;
 
+/*
+ * Track write pointers of a zone in bytes.
+ */
+typedef struct BlockZoneWps {
+    CoMutex colock;
+    uint64_t wp[];
+} BlockZoneWps;
+
 typedef struct BlockDriverInfo {
     /* in bytes, 0 if irrelevant */
     int cluster_size;
@@ -240,6 +248,12 @@ typedef enum {
 #define BDRV_SECTOR_BITS   9
 #define BDRV_SECTOR_SIZE   (1ULL << BDRV_SECTOR_BITS)
 
+/*
+ * Get the first most significant bit of wp. If it is zero, then
+ * the zone type is SWR.
+ */
+#define BDRV_ZT_IS_CONV(wp)    (wp & (1ULL << 63))
+
 #define BDRV_REQUEST_MAX_SECTORS MIN_CONST(SIZE_MAX >> BDRV_SECTOR_BITS, \
                                            INT_MAX >> BDRV_SECTOR_BITS)
 #define BDRV_REQUEST_MAX_BYTES (BDRV_REQUEST_MAX_SECTORS << BDRV_SECTOR_BITS)

include/block/block_int-common.h

@@ -891,6 +891,8 @@ typedef struct BlockLimits {
 
     /* maximum number of active zones */
     uint32_t max_active_zones;
+
+    uint32_t write_granularity;
 } BlockLimits;
 
 typedef struct BdrvOpBlocker BdrvOpBlocker;
@@ -1252,6 +1254,9 @@ struct BlockDriverState {
     CoMutex bsc_modify_lock;
     /* Always non-NULL, but must only be dereferenced under an RCU read guard */
     BdrvBlockStatusCache *block_status_cache;
+
+    /* array of write pointers' location of each zone in the zoned device. */
+    BlockZoneWps *wps;
 };
 
 struct BlockBackendRootState {