.

wcfs/internal/wcfs.cpp

@@ -445,6 +445,8 @@ error _Conn::resync(zodb::Tid at) {
 error _Mapping::_remmapblk(int64_t blk, zodb::Tid at) {
     // XXX err context? blk #<blk> @<at>
     _Mapping *mmap = this;
+    xerr::Contextf E("conn @%s: f<%s>: remmapblk #%ld @%s",
+            v(mmap->fileh->wconn->at), v(mmap->fileh->foid), blk, v(at)); // XXX +wcfs path?
 
     ASSERT(mmap->blk_start <= blk && blk < mmap->blk_stop());
     FileH f = mmap->fileh;
@@ -461,7 +463,7 @@ error _Mapping::_remmapblk(int64_t blk, zodb::Tid at) {
         tie(fsfile, err) = f->wconn->_wc->_open(
                 fmt::sprintf("@%s/bigfile/%s", v(at), v(f->foid)));
         if (err != nil)
-            return err;
+            return E(err);
         fclose = true;
     }
     defer([&]() {
@@ -472,22 +474,22 @@ error _Mapping::_remmapblk(int64_t blk, zodb::Tid at) {
     struct stat st;
     err = fsfile->stat(&st);
     if (err != nil)
-        return err;
+        return E(err);
     if ((size_t)st.st_blksize != f->blksize)
-        return fmt::errorf("wcfs bug: blksize changed: %zd -> %ld", f->blksize, st.st_blksize);
+        return E(fmt::errorf("wcfs bug: blksize changed: %zd -> %ld", f->blksize, st.st_blksize));
 
     // block is beyond file size - mmap with zeros - else access to memory
     // after file.size will raise SIGBUS. (assumes head/f size ↑=)
     if ((blk+1)*f->blksize > (size_t)st.st_size) {
         err = mmap_zero_into_ro(blkmem, 1*f->blksize);
         if (err != nil)
-            return err;
+            return E(err);
     }
     // block is inside file - mmap file data
     else {
         err = mmap_into_ro(blkmem, 1*f->blksize, fsfile, blk*f->blksize);
         if (err != nil)
-            return err;
+            return E(err);
     }
 
     return nil;