Merge pull request #27954 from vespa-engine/balder/add-better-error-detection

Provide more information when failing to mmap files

1 files changed, 10 insertions, 6 deletions

diff --git a/vespalib/src/vespa/vespalib/util/mmap_file_allocator.cpp b/vespalib/src/vespa/vespalib/util/mmap_file_allocator.cpp
index 2c0d0f4339d..51a639a3c4e 100644
--- a/vespalib/src/vespa/vespalib/util/mmap_file_allocator.cpp
+++ b/vespalib/src/vespa/vespalib/util/mmap_file_allocator.cpp
@@ -2,12 +2,16 @@
 
 #include "mmap_file_allocator.h"
 #include "round_up_to_page_size.h"
+#include "exceptions.h"
+#include "stringfmt.h"
 #include <vespa/vespalib/stllike/hash_map.hpp>
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <cassert>
 #include <filesystem>
 
+using vespalib::make_string_short::fmt;
+
 namespace vespalib::alloc {
 
 MmapFileAllocator::MmapFileAllocator(const vespalib::string& dir_name)
@@ -50,12 +54,12 @@ MmapFileAllocator::alloc(size_t sz) const
     }
     sz = round_up_to_page_size(sz);
     uint64_t offset = alloc_area(sz);
-    void *buf = mmap(nullptr, sz,
-                     PROT_READ | PROT_WRITE,
-                     MAP_SHARED,
-                     _file.getFileDescriptor(),
-                     offset);
-    assert(buf != MAP_FAILED);
+    void *buf = mmap(nullptr, sz, PROT_READ | PROT_WRITE, MAP_SHARED, _file.getFileDescriptor(), offset);
+    if (buf == MAP_FAILED) {
+        throw IoException(fmt("Failed mmap(nullptr, %zu, PROT_READ | PROT_WRITE, MAP_SHARED, %s(fd=%d), %lu). Reason given by OS = '%s'",
+                              sz, _file.getFilename().c_str(), _file.getFileDescriptor(), offset, getLastErrorString().c_str()),
+                          IoException::getErrorType(errno), VESPA_STRLOC);
+    }
     assert(buf != nullptr);
     // Register allocation
     auto ins_res = _allocations.insert(std::make_pair(buf, SizeAndOffset(sz, offset)));