copyfile-146.250.1.tar.gz

diff --git a/copyfile.c b/copyfile.c
index 885bd4d2193db286662f07a3a382a4eb76693da9..99e6d42b10ad2ea43d14c20d3d677c7d9c085f10 100644 (file)
--- a/copyfile.c
+++ b/copyfile.c
@@ -2424,14 +2424,27 @@ static int copyfile_data(copyfile_state_t s)
        /* If supported, do preallocation for Xsan / HFS / apfs volumes */
 #ifdef F_PREALLOCATE
        {
-               fstore_t fst;
-
-               fst.fst_flags = 0;
-               fst.fst_posmode = F_PEOFPOSMODE;
-               fst.fst_offset = 0;
-               fst.fst_length = s->sb.st_size;
-               /* Ignore errors; this is merely advisory. */
-               (void)fcntl(s->dst_fd, F_PREALLOCATE, &fst);
+               off_t dst_bytes_allocated = 0;
+               struct stat dst_sb;
+
+               if (fstat(s->dst_fd, &dst_sb) == 0) {
+                       // The destination may already have
+                       // preallocated space we can use.
+                       dst_bytes_allocated = dst_sb.st_blocks * S_BLKSIZE;
+               }
+
+               if (dst_bytes_allocated < s->sb.st_size) {
+                       fstore_t fst;
+
+                       fst.fst_flags = 0;
+                       fst.fst_posmode = F_PEOFPOSMODE;
+                       fst.fst_offset = 0;
+                       fst.fst_length = s->sb.st_size - dst_bytes_allocated;
+
+                       copyfile_debug(3, "preallocating %lld bytes on destination", fst.fst_length);
+                       /* Ignore errors; this is merely advisory. */
+                       (void)fcntl(s->dst_fd, F_PREALLOCATE, &fst);
+               }
        }
 #endif