[Libguestfs] [PATCH] v2v: rework free space check in guest mountpoints

[Pino Toscano]

- move the space needed by mountpoint mapping to an own function,
  outside of the checking loop
- remove the minimum limit of 100M on partitions, since existing
  partitions that we check (e.g. /boot) may be smaller than that
- in case /boot is not on a separate mountpoint, enforce the space check
  on the root mountpoint instead, since it is where /boot is in that
  case
---
 v2v/v2v.ml | 55 ++++++++++++++++++++++++++++---------------------------
 1 file changed, 28 insertions(+), 27 deletions(-)

diff --git a/v2v/v2v.ml b/v2v/v2v.ml
index b4c41e188..24b38458f 100644
--- a/v2v/v2v.ml
+++ b/v2v/v2v.ml
@@ -415,34 +415,35 @@ and print_mpstat chan { mp_dev = dev; mp_path = path;
  *)
 and check_guest_free_space mpstats =
   message (f_"Checking for sufficient free disk space in the guest");
+
+  (* Check whether /boot has its own mount point. *)
+  let has_boot = List.exists (fun { mp_path } -> mp_path = "/boot") mpstats in
+
+  let needed_bytes_for_mp = function
+    | "/boot"
+    | "/" when not has_boot ->
+      (* We usually regenerate the initramfs, which has a
+       * typical size of 20-30MB.  Hence:
+       *)
+      50_000_000L
+    | "/" ->
+      (* We may install some packages, and they would usually go
+       * on the root filesystem.
+       *)
+      20_000_000L
+    | _ ->
+      (* For everything else, just make sure there is some free space. *)
+      10_000_000L
+  in
+
   List.iter (
-    fun { mp_path = mp;
-          mp_statvfs = { G.bfree; blocks; bsize } } ->
-      (* Ignore small filesystems. *)
-      let total_size = blocks *^ bsize in
-      if total_size > 100_000_000L then (
-        (* bfree = free blocks for root user *)
-        let free_bytes = bfree *^ bsize in
-        let needed_bytes =
-          match mp with
-          | "/" ->
-            (* We may install some packages, and they would usually go
-             * on the root filesystem.
-             *)
-            20_000_000L
-          | "/boot" ->
-            (* We usually regenerate the initramfs, which has a
-             * typical size of 20-30MB.  Hence:
-             *)
-            50_000_000L
-          | _ ->
-            (* For everything else, just make sure there is some free space. *)
-            10_000_000L in
-
-        if free_bytes < needed_bytes then
-          error (f_"not enough free space for conversion on filesystem ‘%s’.  %Ld bytes free < %Ld bytes needed")
-            mp free_bytes needed_bytes
-      )
+    fun { mp_path; mp_statvfs = { G.bfree; bsize } } ->
+      (* bfree = free blocks for root user *)
+      let free_bytes = bfree *^ bsize in
+      let needed_bytes = needed_bytes_for_mp mp_path in
+      if free_bytes < needed_bytes then
+        error (f_"not enough free space for conversion on filesystem ‘%s’.  %Ld bytes free < %Ld bytes needed")
+          mp_path free_bytes needed_bytes
   ) mpstats
 
 (* Perform the fstrim. *)
-- 
2.13.6