system/physmem: take into account fd_offset for file fallocate

Punching a hole in a file with fallocate needs to take into account the
fd_offset value for a correct file location.

Fixes: 4b870dc ("hostmem-file: add offset option")

Signed-off-by: William Roche <william.roche@oracle.com>

system/physmem.c

@@ -3689,18 +3689,20 @@ int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length)
             }
 
             ret = fallocate(rb->fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
-                            start, length);
+                            start + rb->fd_offset, length);
             if (ret) {
                 ret = -errno;
                 error_report("%s: Failed to fallocate %s:%" PRIx64 " +%zx (%d)",
-                             __func__, rb->idstr, start, length, ret);
+                             __func__, rb->idstr, start + rb->fd_offset, length,
+                             ret);
                 goto err;
             }
 #else
             ret = -ENOSYS;
             error_report("%s: fallocate not available/file"
                          "%s:%" PRIx64 " +%zx (%d)",
-                         __func__, rb->idstr, start, length, ret);
+                         __func__, rb->idstr, start + rb->fd_offset, length,
+                         ret);
             goto err;
 #endif
         }
@@ -3748,17 +3750,17 @@ int ram_block_discard_guest_memfd_range(RAMBlock *rb, uint64_t start,
 
 #ifdef CONFIG_FALLOCATE_PUNCH_HOLE
     ret = fallocate(rb->guest_memfd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
-                    start, length);
+                    start + rb->offset, length);
 
     if (ret) {
         ret = -errno;
         error_report("%s: Failed to fallocate %s:%" PRIx64 " +%zx (%d)",
-                     __func__, rb->idstr, start, length, ret);
+                     __func__, rb->idstr, start + rb->fd_offset, length, ret);
     }
 #else
     ret = -ENOSYS;
     error_report("%s: fallocate not available %s:%" PRIx64 " +%zx (%d)",
-                 __func__, rb->idstr, start, length, ret);
+                 __func__, rb->idstr, start + rb->fd_offset, length, ret);
 #endif
 
     return ret;