diff --git a/src/osd_ops.h b/src/osd_ops.h
index 9f232c75..8055bbfc 100644
--- a/src/osd_ops.h
+++ b/src/osd_ops.h
@@ -191,7 +191,7 @@ struct __attribute__((__packed__)) osd_op_rw_t
     uint64_t inode;
     // offset
     uint64_t offset;
-    // length
+    // length. 0 means to read all bitmaps of the specified range, but no data.
     uint32_t len;
     // flags (for future)
     uint32_t flags;
diff --git a/src/osd_primary.cpp b/src/osd_primary.cpp
index 95d947c3..2ceeacee 100644
--- a/src/osd_primary.cpp
+++ b/src/osd_primary.cpp
@@ -186,10 +186,22 @@ void osd_t::continue_primary_read(osd_op_t *cur_op)
     cur_op->reply.rw.bitmap_len = 0;
     {
         auto & pg = pgs.at({ .pool_id = INODE_POOL(op_data->oid.inode), .pg_num = op_data->pg_num });
-        for (int role = 0; role < op_data->pg_data_size; role++)
+        if (cur_op->req.rw.len == 0)
         {
-            op_data->stripes[role].read_start = op_data->stripes[role].req_start;
-            op_data->stripes[role].read_end = op_data->stripes[role].req_end;
+            // len=0 => bitmap read
+            for (int role = 0; role < op_data->pg_data_size; role++)
+            {
+                op_data->stripes[role].read_start = 0;
+                op_data->stripes[role].read_end = UINT32_MAX;
+            }
+        }
+        else
+        {
+            for (int role = 0; role < op_data->pg_data_size; role++)
+            {
+                op_data->stripes[role].read_start = op_data->stripes[role].req_start;
+                op_data->stripes[role].read_end = op_data->stripes[role].req_end;
+            }
         }
         // Determine version
         auto vo_it = pg.ver_override.find(op_data->oid);
diff --git a/src/osd_primary_subops.cpp b/src/osd_primary_subops.cpp
index 5b6ab48d..da8520a0 100644
--- a/src/osd_primary_subops.cpp
+++ b/src/osd_primary_subops.cpp
@@ -151,6 +151,13 @@ int osd_t::submit_primary_subop_batch(int submit_type, inode_t inode, uint64_t o
         {
             int stripe_num = rep ? 0 : role;
             osd_op_t *subop = op_data->subops + i;
+            uint32_t subop_len = wr
+                ? stripes[stripe_num].write_end - stripes[stripe_num].write_start
+                : stripes[stripe_num].read_end - stripes[stripe_num].read_start;
+            if (!wr && stripes[stripe_num].read_end == UINT32_MAX)
+            {
+                subop_len = 0;
+            }
             if (role_osd_num == this->osd_num)
             {
                 clock_gettime(CLOCK_REALTIME, &subop->tv_begin);
@@ -169,7 +176,7 @@ int osd_t::submit_primary_subop_batch(int submit_type, inode_t inode, uint64_t o
                     },
                     .version = op_version,
                     .offset = wr ? stripes[stripe_num].write_start : stripes[stripe_num].read_start,
-                    .len = wr ? stripes[stripe_num].write_end - stripes[stripe_num].write_start : stripes[stripe_num].read_end - stripes[stripe_num].read_start,
+                    .len = subop_len,
                     .buf = wr ? stripes[stripe_num].write_buf : stripes[stripe_num].read_buf,
                     .bitmap = stripes[stripe_num].bmp_buf,
                 });
@@ -199,7 +206,7 @@ int osd_t::submit_primary_subop_batch(int submit_type, inode_t inode, uint64_t o
                     },
                     .version = op_version,
                     .offset = wr ? stripes[stripe_num].write_start : stripes[stripe_num].read_start,
-                    .len = wr ? stripes[stripe_num].write_end - stripes[stripe_num].write_start : stripes[stripe_num].read_end - stripes[stripe_num].read_start,
+                    .len = subop_len,
                     .attr_len = wr ? clean_entry_bitmap_size : 0,
                 };
 #ifdef OSD_DEBUG
@@ -218,9 +225,9 @@ int osd_t::submit_primary_subop_batch(int submit_type, inode_t inode, uint64_t o
                 }
                 else
                 {
-                    if (stripes[stripe_num].read_end > stripes[stripe_num].read_start)
+                    if (subop_len > 0)
                     {
-                        subop->iov.push_back(stripes[stripe_num].read_buf, stripes[stripe_num].read_end - stripes[stripe_num].read_start);
+                        subop->iov.push_back(stripes[stripe_num].read_buf, subop_len);
                     }
                 }
                 subop->callback = [cur_op, this](osd_op_t *subop)
diff --git a/src/osd_rmw.cpp b/src/osd_rmw.cpp
index 593ff95c..aedc3a6b 100644
--- a/src/osd_rmw.cpp
+++ b/src/osd_rmw.cpp
@@ -28,7 +28,9 @@ static inline void extend_read(uint32_t start, uint32_t end, osd_rmw_stripe_t &
     }
     else
     {
-        if (stripe.read_end < end)
+        if (stripe.read_end < end && end != UINT32_MAX ||
+            // UINT32_MAX means that stripe only needs bitmap, end != 0 => needs also data
+            stripe.read_end == UINT32_MAX && end != 0)
             stripe.read_end = end;
         if (stripe.read_start > start)
             stripe.read_start = start;
@@ -105,24 +107,30 @@ void reconstruct_stripes_xor(osd_rmw_stripe_t *stripes, int pg_size, uint32_t bi
                     }
                     else if (prev >= 0)
                     {
-                        assert(stripes[role].read_start >= stripes[prev].read_start &&
-                            stripes[role].read_start >= stripes[other].read_start);
-                        memxor(
-                            (uint8_t*)stripes[prev].read_buf + (stripes[role].read_start - stripes[prev].read_start),
-                            (uint8_t*)stripes[other].read_buf + (stripes[role].read_start - stripes[other].read_start),
-                            stripes[role].read_buf, stripes[role].read_end - stripes[role].read_start
-                        );
+                        if (stripes[role].read_end != UINT32_MAX)
+                        {
+                            assert(stripes[role].read_start >= stripes[prev].read_start &&
+                                stripes[role].read_start >= stripes[other].read_start);
+                            memxor(
+                                (uint8_t*)stripes[prev].read_buf + (stripes[role].read_start - stripes[prev].read_start),
+                                (uint8_t*)stripes[other].read_buf + (stripes[role].read_start - stripes[other].read_start),
+                                stripes[role].read_buf, stripes[role].read_end - stripes[role].read_start
+                            );
+                        }
                         memxor(stripes[prev].bmp_buf, stripes[other].bmp_buf, stripes[role].bmp_buf, bitmap_size);
                         prev = -1;
                     }
                     else
                     {
-                        assert(stripes[role].read_start >= stripes[other].read_start);
-                        memxor(
-                            stripes[role].read_buf,
-                            (uint8_t*)stripes[other].read_buf + (stripes[role].read_start - stripes[other].read_start),
-                            stripes[role].read_buf, stripes[role].read_end - stripes[role].read_start
-                        );
+                        if (stripes[role].read_end != UINT32_MAX)
+                        {
+                            assert(stripes[role].read_start >= stripes[other].read_start);
+                            memxor(
+                                stripes[role].read_buf,
+                                (uint8_t*)stripes[other].read_buf + (stripes[role].read_start - stripes[other].read_start),
+                                stripes[role].read_buf, stripes[role].read_end - stripes[role].read_start
+                            );
+                        }
                         memxor(stripes[role].bmp_buf, stripes[other].bmp_buf, stripes[role].bmp_buf, bitmap_size);
                     }
                 }
@@ -356,20 +364,23 @@ void reconstruct_stripes_ec(osd_rmw_stripe_t *stripes, int pg_size, int pg_minsi
     uint64_t read_start = 0, read_end = 0;
     auto recover_seq = [&]()
     {
-        int orig = 0;
-        for (int other = 0; other < pg_size && orig < pg_minsize; other++)
+        if (read_end != UINT32_MAX)
         {
-            if (stripes[other].read_end != 0 && !stripes[other].missing)
+            int orig = 0;
+            for (int other = 0; other < pg_size && orig < pg_minsize; other++)
             {
-                assert(stripes[other].read_start <= read_start);
-                assert(stripes[other].read_end >= read_end);
-                data_ptrs[orig++] = (uint8_t*)stripes[other].read_buf + (read_start - stripes[other].read_start);
+                if (stripes[other].read_end != 0 && !stripes[other].missing)
+                {
+                    assert(stripes[other].read_start <= read_start);
+                    assert(stripes[other].read_end >= read_end);
+                    data_ptrs[orig++] = (uint8_t*)stripes[other].read_buf + (read_start - stripes[other].read_start);
+                }
             }
+            ec_encode_data(
+                read_end-read_start, pg_minsize, wanted, dectable + wanted_base*32*pg_minsize,
+                data_ptrs, data_ptrs + pg_minsize
+            );
         }
-        ec_encode_data(
-            read_end-read_start, pg_minsize, wanted, dectable + wanted_base*32*pg_minsize,
-            data_ptrs, data_ptrs + pg_minsize
-        );
         wanted_base += wanted;
         wanted = 0;
     };
@@ -438,7 +449,8 @@ void reconstruct_stripes_ec(osd_rmw_stripe_t *stripes, int pg_size, int pg_minsi
         if (stripes[role].read_end != 0 && stripes[role].missing)
         {
             recovered = true;
-            if (stripes[role].read_end > stripes[role].read_start)
+            if (stripes[role].read_end > stripes[role].read_start &&
+                stripes[role].read_end != UINT32_MAX)
             {
                 for (int other = 0; other < pg_size; other++)
                 {
@@ -557,7 +569,8 @@ void* alloc_read_buffer(osd_rmw_stripe_t *stripes, int read_pg_size, uint64_t ad
     uint64_t buf_size = add_size;
     for (int role = 0; role < read_pg_size; role++)
     {
-        if (stripes[role].read_end != 0)
+        if (stripes[role].read_end != 0 &&
+            stripes[role].read_end != UINT32_MAX)
         {
             buf_size += stripes[role].read_end - stripes[role].read_start;
         }
@@ -567,7 +580,8 @@ void* alloc_read_buffer(osd_rmw_stripe_t *stripes, int read_pg_size, uint64_t ad
     uint64_t buf_pos = add_size;
     for (int role = 0; role < read_pg_size; role++)
     {
-        if (stripes[role].read_end != 0)
+        if (stripes[role].read_end != 0 &&
+            stripes[role].read_end != UINT32_MAX)
         {
             stripes[role].read_buf = (uint8_t*)buf + buf_pos;
             buf_pos += stripes[role].read_end - stripes[role].read_start;
diff --git a/src/osd_rmw.h b/src/osd_rmw.h
index e185113b..672584c8 100644
--- a/src/osd_rmw.h
+++ b/src/osd_rmw.h
@@ -23,6 +23,7 @@ struct osd_rmw_stripe_t
     void *read_buf, *write_buf;
     void *bmp_buf;
     uint32_t req_start, req_end;
+    // read_end=UINT32_MAX means to only read bitmap, but not data
     uint32_t read_start, read_end;
     uint32_t write_start, write_end;
     bool missing;