[PATCH V4 06/19] physmem: preserve ram blocks for cpr

[Steve Sistare]

Save the memfd for ramblocks in CPR state, along with a name that
uniquely identifies it.  The block's idstr is not yet set, so it
cannot be used for this purpose.  Find the saved memfd in new QEMU when
creating a block.  If the block size is larger in new QEMU, extend the
block using fallocate, and the extra space will be useable after a guest
reset.

Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
 system/physmem.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/system/physmem.c b/system/physmem.c
index 0bcb2cc..aa095a3 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -70,6 +70,7 @@
 
 #include "qemu/pmem.h"
 
+#include "migration/cpr.h"
 #include "migration/vmstate.h"
 
 #include "qemu/range.h"
@@ -1661,6 +1662,19 @@ void qemu_ram_unset_idstr(RAMBlock *block)
     }
 }
 
+static char *cpr_name(RAMBlock *block)
+{
+    MemoryRegion *mr = block->mr;
+    const char *mr_name = memory_region_name(mr);
+    g_autofree char *id = mr->dev ? qdev_get_dev_path(mr->dev) : NULL;
+
+    if (id) {
+        return g_strdup_printf("%s/%s", id, mr_name);
+    } else {
+        return g_strdup(mr_name);
+    }
+}
+
 size_t qemu_ram_pagesize(RAMBlock *rb)
 {
     return rb->page_size;
@@ -2080,8 +2094,18 @@ static bool qemu_ram_alloc_shared(RAMBlock *new_block, 
Error **errp)
 {
     size_t max_length = new_block->max_length;
     MemoryRegion *mr = new_block->mr;
-    const char *name = memory_region_name(mr);
-    int fd;
+    g_autofree char *name = cpr_name(new_block);
+    int fd = cpr_find_fd(name, 0);
+
+    if (fd >= 0) {
+        if (lseek(fd, 0, SEEK_END) < max_length && ftruncate(fd, max_length)) {
+            error_setg_errno(errp, errno,
+                             "cannot grow ram block %s fd %d to %ld bytes",
+                             name, fd, max_length);
+            goto err;
+        }
+        goto have_fd;
+    }
 
     if (qemu_memfd_available()) {
         fd = qemu_memfd_create(name, max_length + mr->align, 0, 0, 0, errp);
@@ -2111,7 +2135,9 @@ static bool qemu_ram_alloc_shared(RAMBlock *new_block, 
Error **errp)
             return true;
         }
     }
+    cpr_save_fd(name, 0, fd);
 
+have_fd:
     new_block->mr->align = QEMU_VMALLOC_ALIGN;
     new_block->host = file_ram_alloc(new_block, max_length, fd, false, 0, 
errp);
 
@@ -2122,6 +2148,8 @@ static bool qemu_ram_alloc_shared(RAMBlock *new_block, 
Error **errp)
         return true;
     }
 
+err:
+    cpr_delete_fd(name, 0);
     close(fd);
     return false;
 }
@@ -2234,6 +2262,8 @@ static void reclaim_ramblock(RAMBlock *block)
 
 void qemu_ram_free(RAMBlock *block)
 {
+    g_autofree char *name = NULL;
+
     if (!block) {
         return;
     }
@@ -2244,6 +2274,8 @@ void qemu_ram_free(RAMBlock *block)
     }
 
     qemu_mutex_lock_ramlist();
+    name = cpr_name(block);
+    cpr_delete_fd(name, 0);
     QLIST_REMOVE_RCU(block, next);
     ram_list.mru_block = NULL;
     /* Write list before version */
-- 
1.8.3.1