[PATCH RFC 10/21] ramblock: Add ramblock_file_map()

[Peter Xu]

Add a helper to do mmap() for a ramblock based on the cached informations.

A trivial thing to mention is we need to move ramblock->fd setup to be
earlier, before the ramblock_file_map() call, because it'll need to
reference the fd being mapped.  However that should not be a problem at
all, majorly because the fd won't be freed if successful, and if it failed
the fd will be freeed (or to be explicit, close()ed) by the caller.

Export it - prepare to be used outside this file.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/exec/ram_addr.h |  1 +
 softmmu/physmem.c       | 25 +++++++++++++++++--------
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 0bf9cfc659..56db25009a 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -98,6 +98,7 @@ bool ramblock_is_pmem(RAMBlock *rb);
 
 long qemu_minrampagesize(void);
 long qemu_maxrampagesize(void);
+void *ramblock_file_map(RAMBlock *block);
 
 /**
  * qemu_ram_alloc_from_file,
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 6096eac286..cdda7eaea5 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1532,17 +1532,31 @@ static int file_ram_open(const char *path,
     return fd;
 }
 
+/* Do the mmap() for a ramblock based on information already setup */
+void *ramblock_file_map(RAMBlock *block)
+{
+    uint32_t qemu_map_flags;
+
+    qemu_map_flags = (block->flags & RAM_READONLY) ? QEMU_MAP_READONLY : 0;
+    qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0;
+    qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0;
+    qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE : 0;
+
+    return qemu_ram_mmap(block->fd, block->mmap_length, block->mr->align,
+                         qemu_map_flags, block->file_offset);
+}
+
 static void *file_ram_alloc(RAMBlock *block,
                             int fd,
                             bool truncate,
                             off_t offset,
                             Error **errp)
 {
-    uint32_t qemu_map_flags;
     void *area;
 
     /* Remember the offset just in case we'll need to map the range again */
     block->file_offset = offset;
+    block->fd = fd;
     block->page_size = qemu_fd_getpagesize(fd);
     if (block->mr->align % block->page_size) {
         error_setg(errp, "alignment 0x%" PRIx64
@@ -1588,19 +1602,14 @@ static void *file_ram_alloc(RAMBlock *block,
         perror("ftruncate");
     }
 
-    qemu_map_flags = (block->flags & RAM_READONLY) ? QEMU_MAP_READONLY : 0;
-    qemu_map_flags |= (block->flags & RAM_SHARED) ? QEMU_MAP_SHARED : 0;
-    qemu_map_flags |= (block->flags & RAM_PMEM) ? QEMU_MAP_SYNC : 0;
-    qemu_map_flags |= (block->flags & RAM_NORESERVE) ? QEMU_MAP_NORESERVE : 0;
-    area = qemu_ram_mmap(fd, block->mmap_length, block->mr->align,
-                         qemu_map_flags, offset);
+    area = ramblock_file_map(block);
+
     if (area == MAP_FAILED) {
         error_setg_errno(errp, errno,
                          "unable to map backing store for guest RAM");
         return NULL;
     }
 
-    block->fd = fd;
     return area;
 }
 #endif
-- 
2.37.3