Merge remote-tracking branch 'remotes/cody/tags/block-pull-request' into staging

# gpg: Signature made Wed 29 Jun 2016 04:09:26 BST
# gpg:                using RSA key 0xBDBE7B27C0DE3057
# gpg: Good signature from "Jeffrey Cody <jcody@redhat.com>"
# gpg:                 aka "Jeffrey Cody <jeff@codyprime.org>"
# gpg:                 aka "Jeffrey Cody <codyprime@gmail.com>"
# Primary key fingerprint: 9957 4B4D 3474 90E7 9D98  D624 BDBE 7B27 C0DE 3057

* remotes/cody/tags/block-pull-request:
  mirror: fix misleading comments
  blockjob: assert(cb) when create job
  iotests: add small-granularity mirror test
  mirror: limit niov to IOV_MAX elements, again
  mirror: clarify mirror_do_read return code
  block/gluster: add support for selecting debug logging level
  mirror: fix trace_mirror_yield_in_flight usage in mirror_iteration()
  block/nfs: add support for libnfs pagecache
  block/nfs: refuse readahead if cache.direct is on
  block/gluster: add support for SEEK_DATA/SEEK_HOLE

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

7 files changed, 317 insertions, 18 deletions

diff --git a/block/backup.c b/block/backup.c
index 581269b29a..f87f8d539b 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -489,7 +489,6 @@ void backup_start(BlockDriverState *bs, BlockDriverState *target,
 
     assert(bs);
     assert(target);
-    assert(cb);
 
     if (bs == target) {
         error_setg(errp, "Source and target cannot be the same");
diff --git a/block/gluster.c b/block/gluster.c
index d361d8e847..16f7778a50 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -24,6 +24,8 @@ typedef struct GlusterAIOCB {
 typedef struct BDRVGlusterState {
     struct glfs *glfs;
     struct glfs_fd *fd;
+    bool supports_seek_data;
+    int debug_level;
 } BDRVGlusterState;
 
 typedef struct GlusterConf {
@@ -32,6 +34,7 @@ typedef struct GlusterConf {
     char *volname;
     char *image;
     char *transport;
+    int debug_level;
 } GlusterConf;
 
 static void qemu_gluster_gconf_free(GlusterConf *gconf)
@@ -194,11 +197,7 @@ static struct glfs *qemu_gluster_init(GlusterConf *gconf, const char *filename,
         goto out;
     }
 
-    /*
-     * TODO: Use GF_LOG_ERROR instead of hard code value of 4 here when
-     * GlusterFS makes GF_LOG_* macros available to libgfapi users.
-     */
-    ret = glfs_set_logging(glfs, "-", 4);
+    ret = glfs_set_logging(glfs, "-", gconf->debug_level);
     if (ret < 0) {
         goto out;
     }
@@ -256,16 +255,26 @@ static void gluster_finish_aiocb(struct glfs_fd *fd, ssize_t ret, void *arg)
     qemu_bh_schedule(acb->bh);
 }
 
+#define GLUSTER_OPT_FILENAME "filename"
+#define GLUSTER_OPT_DEBUG "debug"
+#define GLUSTER_DEBUG_DEFAULT 4
+#define GLUSTER_DEBUG_MAX 9
+
 /* TODO Convert to fine grained options */
 static QemuOptsList runtime_opts = {
     .name = "gluster",
     .head = QTAILQ_HEAD_INITIALIZER(runtime_opts.head),
     .desc = {
         {
-            .name = "filename",
+            .name = GLUSTER_OPT_FILENAME,
             .type = QEMU_OPT_STRING,
             .help = "URL to the gluster image",
         },
+        {
+            .name = GLUSTER_OPT_DEBUG,
+            .type = QEMU_OPT_NUMBER,
+            .help = "Gluster log level, valid range is 0-9",
+        },
         { /* end of list */ }
     },
 };
@@ -287,6 +296,28 @@ static void qemu_gluster_parse_flags(int bdrv_flags, int *open_flags)
     }
 }
 
+/*
+ * Do SEEK_DATA/HOLE to detect if it is functional. Older broken versions of
+ * gfapi incorrectly return the current offset when SEEK_DATA/HOLE is used.
+ * - Corrected versions return -1 and set errno to EINVAL.
+ * - Versions that support SEEK_DATA/HOLE correctly, will return -1 and set
+ *   errno to ENXIO when SEEK_DATA is called with a position of EOF.
+ */
+static bool qemu_gluster_test_seek(struct glfs_fd *fd)
+{
+    off_t ret, eof;
+
+    eof = glfs_lseek(fd, 0, SEEK_END);
+    if (eof < 0) {
+        /* this should never occur */
+        return false;
+    }
+
+    /* this should always fail with ENXIO if SEEK_DATA is supported */
+    ret = glfs_lseek(fd, eof, SEEK_DATA);
+    return (ret < 0) && (errno == ENXIO);
+}
+
 static int qemu_gluster_open(BlockDriverState *bs,  QDict *options,
                              int bdrv_flags, Error **errp)
 {
@@ -306,8 +337,17 @@ static int qemu_gluster_open(BlockDriverState *bs,  QDict *options,
         goto out;
     }
 
-    filename = qemu_opt_get(opts, "filename");
+    filename = qemu_opt_get(opts, GLUSTER_OPT_FILENAME);
 
+    s->debug_level = qemu_opt_get_number(opts, GLUSTER_OPT_DEBUG,
+                                         GLUSTER_DEBUG_DEFAULT);
+    if (s->debug_level < 0) {
+        s->debug_level = 0;
+    } else if (s->debug_level > GLUSTER_DEBUG_MAX) {
+        s->debug_level = GLUSTER_DEBUG_MAX;
+    }
+
+    gconf->debug_level = s->debug_level;
     s->glfs = qemu_gluster_init(gconf, filename, errp);
     if (!s->glfs) {
         ret = -errno;
@@ -338,6 +378,8 @@ static int qemu_gluster_open(BlockDriverState *bs,  QDict *options,
         ret = -errno;
     }
 
+    s->supports_seek_data = qemu_gluster_test_seek(s->fd);
+
 out:
     qemu_opts_del(opts);
     qemu_gluster_gconf_free(gconf);
@@ -363,6 +405,7 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
                                        BlockReopenQueue *queue, Error **errp)
 {
     int ret = 0;
+    BDRVGlusterState *s;
     BDRVGlusterReopenState *reop_s;
     GlusterConf *gconf = NULL;
     int open_flags = 0;
@@ -370,6 +413,8 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
     assert(state != NULL);
     assert(state->bs != NULL);
 
+    s = state->bs->opaque;
+
     state->opaque = g_new0(BDRVGlusterReopenState, 1);
     reop_s = state->opaque;
 
@@ -377,6 +422,7 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
 
     gconf = g_new0(GlusterConf, 1);
 
+    gconf->debug_level = s->debug_level;
     reop_s->glfs = qemu_gluster_init(gconf, state->bs->filename, errp);
     if (reop_s->glfs == NULL) {
         ret = -errno;
@@ -510,6 +556,14 @@ static int qemu_gluster_create(const char *filename,
     char *tmp = NULL;
     GlusterConf *gconf = g_new0(GlusterConf, 1);
 
+    gconf->debug_level = qemu_opt_get_number_del(opts, GLUSTER_OPT_DEBUG,
+                                                 GLUSTER_DEBUG_DEFAULT);
+    if (gconf->debug_level < 0) {
+        gconf->debug_level = 0;
+    } else if (gconf->debug_level > GLUSTER_DEBUG_MAX) {
+        gconf->debug_level = GLUSTER_DEBUG_MAX;
+    }
+
     glfs = qemu_gluster_init(gconf, filename, errp);
     if (!glfs) {
         ret = -errno;
@@ -727,6 +781,159 @@ static int qemu_gluster_has_zero_init(BlockDriverState *bs)
     return 0;
 }
 
+/*
+ * Find allocation range in @bs around offset @start.
+ * May change underlying file descriptor's file offset.
+ * If @start is not in a hole, store @start in @data, and the
+ * beginning of the next hole in @hole, and return 0.
+ * If @start is in a non-trailing hole, store @start in @hole and the
+ * beginning of the next non-hole in @data, and return 0.
+ * If @start is in a trailing hole or beyond EOF, return -ENXIO.
+ * If we can't find out, return a negative errno other than -ENXIO.
+ *
+ * (Shamefully copied from raw-posix.c, only miniscule adaptions.)
+ */
+static int find_allocation(BlockDriverState *bs, off_t start,
+                           off_t *data, off_t *hole)
+{
+    BDRVGlusterState *s = bs->opaque;
+    off_t offs;
+
+    if (!s->supports_seek_data) {
+        return -ENOTSUP;
+    }
+
+    /*
+     * SEEK_DATA cases:
+     * D1. offs == start: start is in data
+     * D2. offs > start: start is in a hole, next data at offs
+     * D3. offs < 0, errno = ENXIO: either start is in a trailing hole
+     *                              or start is beyond EOF
+     *     If the latter happens, the file has been truncated behind
+     *     our back since we opened it.  All bets are off then.
+     *     Treating like a trailing hole is simplest.
+     * D4. offs < 0, errno != ENXIO: we learned nothing
+     */
+    offs = glfs_lseek(s->fd, start, SEEK_DATA);
+    if (offs < 0) {
+        return -errno;          /* D3 or D4 */
+    }
+    assert(offs >= start);
+
+    if (offs > start) {
+        /* D2: in hole, next data at offs */
+        *hole = start;
+        *data = offs;
+        return 0;
+    }
+
+    /* D1: in data, end not yet known */
+
+    /*
+     * SEEK_HOLE cases:
+     * H1. offs == start: start is in a hole
+     *     If this happens here, a hole has been dug behind our back
+     *     since the previous lseek().
+     * H2. offs > start: either start is in data, next hole at offs,
+     *                   or start is in trailing hole, EOF at offs
+     *     Linux treats trailing holes like any other hole: offs ==
+     *     start.  Solaris seeks to EOF instead: offs > start (blech).
+     *     If that happens here, a hole has been dug behind our back
+     *     since the previous lseek().
+     * H3. offs < 0, errno = ENXIO: start is beyond EOF
+     *     If this happens, the file has been truncated behind our
+     *     back since we opened it.  Treat it like a trailing hole.
+     * H4. offs < 0, errno != ENXIO: we learned nothing
+     *     Pretend we know nothing at all, i.e. "forget" about D1.
+     */
+    offs = glfs_lseek(s->fd, start, SEEK_HOLE);
+    if (offs < 0) {
+        return -errno;          /* D1 and (H3 or H4) */
+    }
+    assert(offs >= start);
+
+    if (offs > start) {
+        /*
+         * D1 and H2: either in data, next hole at offs, or it was in
+         * data but is now in a trailing hole.  In the latter case,
+         * all bets are off.  Treating it as if it there was data all
+         * the way to EOF is safe, so simply do that.
+         */
+        *data = start;
+        *hole = offs;
+        return 0;
+    }
+
+    /* D1 and H1 */
+    return -EBUSY;
+}
+
+/*
+ * Returns the allocation status of the specified sectors.
+ *
+ * If 'sector_num' is beyond the end of the disk image the return value is 0
+ * and 'pnum' is set to 0.
+ *
+ * 'pnum' is set to the number of sectors (including and immediately following
+ * the specified sector) that are known to be in the same
+ * allocated/unallocated state.
+ *
+ * 'nb_sectors' is the max value 'pnum' should be set to.  If nb_sectors goes
+ * beyond the end of the disk image it will be clamped.
+ *
+ * (Based on raw_co_get_block_status() from raw-posix.c.)
+ */
+static int64_t coroutine_fn qemu_gluster_co_get_block_status(
+        BlockDriverState *bs, int64_t sector_num, int nb_sectors, int *pnum,
+        BlockDriverState **file)
+{
+    BDRVGlusterState *s = bs->opaque;
+    off_t start, data = 0, hole = 0;
+    int64_t total_size;
+    int ret = -EINVAL;
+
+    if (!s->fd) {
+        return ret;
+    }
+
+    start = sector_num * BDRV_SECTOR_SIZE;
+    total_size = bdrv_getlength(bs);
+    if (total_size < 0) {
+        return total_size;
+    } else if (start >= total_size) {
+        *pnum = 0;
+        return 0;
+    } else if (start + nb_sectors * BDRV_SECTOR_SIZE > total_size) {
+        nb_sectors = DIV_ROUND_UP(total_size - start, BDRV_SECTOR_SIZE);
+    }
+
+    ret = find_allocation(bs, start, &data, &hole);
+    if (ret == -ENXIO) {
+        /* Trailing hole */
+        *pnum = nb_sectors;
+        ret = BDRV_BLOCK_ZERO;
+    } else if (ret < 0) {
+        /* No info available, so pretend there are no holes */
+        *pnum = nb_sectors;
+        ret = BDRV_BLOCK_DATA;
+    } else if (data == start) {
+        /* On a data extent, compute sectors to the end of the extent,
+         * possibly including a partial sector at EOF. */
+        *pnum = MIN(nb_sectors, DIV_ROUND_UP(hole - start, BDRV_SECTOR_SIZE));
+        ret = BDRV_BLOCK_DATA;
+    } else {
+        /* On a hole, compute sectors to the beginning of the next extent.  */
+        assert(hole == start);
+        *pnum = MIN(nb_sectors, (data - start) / BDRV_SECTOR_SIZE);
+        ret = BDRV_BLOCK_ZERO;
+    }
+
+    *file = bs;
+
+    return ret | BDRV_BLOCK_OFFSET_VALID | start;
+}
+
+
 static QemuOptsList qemu_gluster_create_opts = {
     .name = "qemu-gluster-create-opts",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_gluster_create_opts.head),
@@ -741,6 +948,11 @@ static QemuOptsList qemu_gluster_create_opts = {
             .type = QEMU_OPT_STRING,
             .help = "Preallocation mode (allowed values: off, full)"
         },
+        {
+            .name = GLUSTER_OPT_DEBUG,
+            .type = QEMU_OPT_NUMBER,
+            .help = "Gluster log level, valid range is 0-9",
+        },
         { /* end of list */ }
     }
 };
@@ -769,6 +981,7 @@ static BlockDriver bdrv_gluster = {
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
 #endif
+    .bdrv_co_get_block_status     = qemu_gluster_co_get_block_status,
     .create_opts                  = &qemu_gluster_create_opts,
 };
 
@@ -796,6 +1009,7 @@ static BlockDriver bdrv_gluster_tcp = {
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
 #endif
+    .bdrv_co_get_block_status     = qemu_gluster_co_get_block_status,
     .create_opts                  = &qemu_gluster_create_opts,
 };
 
@@ -823,6 +1037,7 @@ static BlockDriver bdrv_gluster_unix = {
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
 #endif
+    .bdrv_co_get_block_status     = qemu_gluster_co_get_block_status,
     .create_opts                  = &qemu_gluster_create_opts,
 };
 
@@ -850,6 +1065,7 @@ static BlockDriver bdrv_gluster_rdma = {
 #ifdef CONFIG_GLUSTERFS_ZEROFILL
     .bdrv_co_pwrite_zeroes        = qemu_gluster_co_pwrite_zeroes,
 #endif
+    .bdrv_co_get_block_status     = qemu_gluster_co_get_block_status,
     .create_opts                  = &qemu_gluster_create_opts,
 };
 
diff --git a/block/mirror.c b/block/mirror.c
index a04ed9c7a4..8d96049555 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -218,7 +218,9 @@ static inline void mirror_wait_for_io(MirrorBlockJob *s)
 }
 
 /* Submit async read while handling COW.
- * Returns: nb_sectors if no alignment is necessary, or
+ * Returns: The number of sectors copied after and including sector_num,
+ *          excluding any sectors copied prior to sector_num due to alignment.
+ *          This will be nb_sectors if no alignment is necessary, or
  *          (new_end - sector_num) if tail is rounded up or down due to
  *          alignment or buffer limit.
  */
@@ -227,14 +229,18 @@ static int mirror_do_read(MirrorBlockJob *s, int64_t sector_num,
 {
     BlockBackend *source = s->common.blk;
     int sectors_per_chunk, nb_chunks;
-    int ret = nb_sectors;
+    int ret;
     MirrorOp *op;
+    int max_sectors;
 
     sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
+    max_sectors = sectors_per_chunk * s->max_iov;
 
     /* We can only handle as much as buf_size at a time. */
     nb_sectors = MIN(s->buf_size >> BDRV_SECTOR_BITS, nb_sectors);
+    nb_sectors = MIN(max_sectors, nb_sectors);
     assert(nb_sectors);
+    ret = nb_sectors;
 
     if (s->cow_bitmap) {
         ret += mirror_cow_align(s, &sector_num, &nb_sectors);
@@ -327,7 +333,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
 
     first_chunk = sector_num / sectors_per_chunk;
     while (test_bit(first_chunk, s->in_flight_bitmap)) {
-        trace_mirror_yield_in_flight(s, first_chunk, s->in_flight);
+        trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
         mirror_wait_for_io(s);
     }
 
@@ -769,7 +775,7 @@ static void mirror_complete(BlockJob *job, Error **errp)
         }
     }
 
-    /* check the target bs is not blocked and block all operations on it */
+    /* block all operations on to_replace bs */
     if (s->replaces) {
         AioContext *replace_aio_context;
 
diff --git a/block/nfs.c b/block/nfs.c
index 9f51cc3f10..15d6832c4c 100644
--- a/block/nfs.c
+++ b/block/nfs.c
@@ -1,7 +1,7 @@
 /*
  * QEMU Block driver for native access to files on NFS shares
  *
- * Copyright (c) 2014 Peter Lieven <pl@kamp.de>
+ * Copyright (c) 2014-2016 Peter Lieven <pl@kamp.de>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -38,6 +38,7 @@
 #include <nfsc/libnfs.h>
 
 #define QEMU_NFS_MAX_READAHEAD_SIZE 1048576
+#define QEMU_NFS_MAX_PAGECACHE_SIZE (8388608 / NFS_BLKSIZE)
 #define QEMU_NFS_MAX_DEBUG_LEVEL 2
 
 typedef struct NFSClient {
@@ -47,6 +48,7 @@ typedef struct NFSClient {
     bool has_zero_init;
     AioContext *aio_context;
     blkcnt_t st_blocks;
+    bool cache_used;
 } NFSClient;
 
 typedef struct NFSRPC {
@@ -278,7 +280,7 @@ static void nfs_file_close(BlockDriverState *bs)
 }
 
 static int64_t nfs_client_open(NFSClient *client, const char *filename,
-                               int flags, Error **errp)
+                               int flags, Error **errp, int open_flags)
 {
     int ret = -EINVAL, i;
     struct stat st;
@@ -330,12 +332,38 @@ static int64_t nfs_client_open(NFSClient *client, const char *filename,
             nfs_set_tcp_syncnt(client->context, val);
 #ifdef LIBNFS_FEATURE_READAHEAD
         } else if (!strcmp(qp->p[i].name, "readahead")) {
+            if (open_flags & BDRV_O_NOCACHE) {
+                error_setg(errp, "Cannot enable NFS readahead "
+                                 "if cache.direct = on");
+                goto fail;
+            }
             if (val > QEMU_NFS_MAX_READAHEAD_SIZE) {
                 error_report("NFS Warning: Truncating NFS readahead"
                              " size to %d", QEMU_NFS_MAX_READAHEAD_SIZE);
                 val = QEMU_NFS_MAX_READAHEAD_SIZE;
             }
             nfs_set_readahead(client->context, val);
+#ifdef LIBNFS_FEATURE_PAGECACHE
+            nfs_set_pagecache_ttl(client->context, 0);
+#endif
+            client->cache_used = true;
+#endif
+#ifdef LIBNFS_FEATURE_PAGECACHE
+            nfs_set_pagecache_ttl(client->context, 0);
+        } else if (!strcmp(qp->p[i].name, "pagecache")) {
+            if (open_flags & BDRV_O_NOCACHE) {
+                error_setg(errp, "Cannot enable NFS pagecache "
+                                 "if cache.direct = on");
+                goto fail;
+            }
+            if (val > QEMU_NFS_MAX_PAGECACHE_SIZE) {
+                error_report("NFS Warning: Truncating NFS pagecache"
+                             " size to %d pages", QEMU_NFS_MAX_PAGECACHE_SIZE);
+                val = QEMU_NFS_MAX_PAGECACHE_SIZE;
+            }
+            nfs_set_pagecache(client->context, val);
+            nfs_set_pagecache_ttl(client->context, 0);
+            client->cache_used = true;
 #endif
 #ifdef LIBNFS_FEATURE_DEBUG
         } else if (!strcmp(qp->p[i].name, "debug")) {
@@ -418,7 +446,7 @@ static int nfs_file_open(BlockDriverState *bs, QDict *options, int flags,
     }
     ret = nfs_client_open(client, qemu_opt_get(opts, "filename"),
                           (flags & BDRV_O_RDWR) ? O_RDWR : O_RDONLY,
-                          errp);
+                          errp, bs->open_flags);
     if (ret < 0) {
         goto out;
     }
@@ -454,7 +482,7 @@ static int nfs_file_create(const char *url, QemuOpts *opts, Error **errp)
     total_size = ROUND_UP(qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0),
                           BDRV_SECTOR_SIZE);
 
-    ret = nfs_client_open(client, url, O_CREAT, errp);
+    ret = nfs_client_open(client, url, O_CREAT, errp, 0);
     if (ret < 0) {
         goto out;
     }
@@ -516,6 +544,12 @@ static int nfs_reopen_prepare(BDRVReopenState *state,
         return -EACCES;
     }
 
+    if ((state->flags & BDRV_O_NOCACHE) && client->cache_used) {
+        error_setg(errp, "Cannot disable cache if libnfs readahead or"
+                         " pagecache is enabled");
+        return -EINVAL;
+    }
+
     /* Update cache for read-only reopens */
     if (!(state->flags & BDRV_O_RDWR)) {
         ret = nfs_fstat(client->context, client->fh, &st);
@@ -530,6 +564,15 @@ static int nfs_reopen_prepare(BDRVReopenState *state,
     return 0;
 }
 
+#ifdef LIBNFS_FEATURE_PAGECACHE
+static void nfs_invalidate_cache(BlockDriverState *bs,
+                                 Error **errp)
+{
+    NFSClient *client = bs->opaque;
+    nfs_pagecache_invalidate(client->context, client->fh);
+}
+#endif
+
 static BlockDriver bdrv_nfs = {
     .format_name                    = "nfs",
     .protocol_name                  = "nfs",
@@ -553,6 +596,10 @@ static BlockDriver bdrv_nfs = {
 
     .bdrv_detach_aio_context        = nfs_detach_aio_context,
     .bdrv_attach_aio_context        = nfs_attach_aio_context,
+
+#ifdef LIBNFS_FEATURE_PAGECACHE
+    .bdrv_invalidate_cache          = nfs_invalidate_cache,
+#endif
 };
 
 static void nfs_block_init(void)
diff --git a/blockjob.c b/blockjob.c
index 90c4e262b0..205da9df4e 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -110,6 +110,7 @@ void *block_job_create(const BlockJobDriver *driver, BlockDriverState *bs,
     BlockBackend *blk;
     BlockJob *job;
 
+    assert(cb);
     if (bs->job) {
         error_setg(errp, QERR_DEVICE_IN_USE, bdrv_get_device_name(bs));
         return NULL;
diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
index ed1d9d464c..cbf5e0ba5c 100755
--- a/tests/qemu-iotests/041
+++ b/tests/qemu-iotests/041
@@ -727,6 +727,36 @@ class TestUnbackedSource(iotests.QMPTestCase):
         self.complete_and_wait()
         self.assert_no_active_block_jobs()
 
+class TestGranularity(iotests.QMPTestCase):
+    image_len = 10 * 1024 * 1024 # MB
+
+    def setUp(self):
+        qemu_img('create', '-f', iotests.imgfmt, test_img,
+                 str(TestGranularity.image_len))
+        qemu_io('-c', 'write 0 %d' % (self.image_len),
+                test_img)
+        self.vm = iotests.VM().add_drive(test_img)
+        self.vm.launch()
+
+    def tearDown(self):
+        self.vm.shutdown()
+        self.assertTrue(iotests.compare_images(test_img, target_img),
+                        'target image does not match source after mirroring')
+        os.remove(test_img)
+        os.remove(target_img)
+
+    def test_granularity(self):
+        self.assert_no_active_block_jobs()
+        result = self.vm.qmp('drive-mirror', device='drive0',
+                             sync='full', target=target_img,
+                             mode='absolute-paths', granularity=8192)
+        self.assert_qmp(result, 'return', {})
+        event = self.vm.get_qmp_event(wait=60.0)
+        # Failures will manifest as COMPLETED/ERROR.
+        self.assert_qmp(event, 'event', 'BLOCK_JOB_READY')
+        self.complete_and_wait(drive='drive0', wait_ready=False)
+        self.assert_no_active_block_jobs()
+
 class TestRepairQuorum(iotests.QMPTestCase):
     """ This class test quorum file repair using drive-mirror.
         It's mostly a fork of TestSingleDrive """
diff --git a/tests/qemu-iotests/041.out b/tests/qemu-iotests/041.out
index b0cadc8245..b67d0504a6 100644
--- a/tests/qemu-iotests/041.out
+++ b/tests/qemu-iotests/041.out
@@ -1,5 +1,5 @@
-...........................................................................
+............................................................................
 ----------------------------------------------------------------------
-Ran 75 tests
+Ran 76 tests
 
 OK