[Libguestfs] [PATCH] fuse: provide a stub "flush" implementation (RHBZ#660687).

[Pino Toscano]

It seems that FUSE can invoke flush to make sure the pending changes
(e.g. to the attributes) of a file are set. Since a missing flush
implementation is handled as if it were returning ENOSYS, this can cause
issues later.

To overcome this, just provide a stub implementation which does nothing,
since we have nothing to do and don't want to have FUSE error out.

Furthermore, uncomment the timestamp checks in test-fuse.sh, since now
they should be working fine.
---
 fuse/test-fuse.sh | 23 +++++++++++------------
 src/fuse.c        | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/fuse/test-fuse.sh b/fuse/test-fuse.sh
index f1e03d0..30b3c31 100755
--- a/fuse/test-fuse.sh
+++ b/fuse/test-fuse.sh
@@ -220,18 +220,17 @@ if truncate --help >/dev/null 2>&1; then
     rm -f truncated
 fi
 
-# Disabled because of RHBZ#660687 on Debian.
-# stage Checking utimens and timestamps
-# for ts in 12345 1234567 987654321; do
-#     # NB: It's not possible to set the ctime with touch.
-#     touch -a -d @$ts timestamp
-#     [ "$(stat -c %X timestamp)" -eq $ts ]
-#     touch -m -d @$ts timestamp
-#     [ "$(stat -c %Y timestamp)" -eq $ts ]
-#     touch    -d @$ts timestamp
-#     [ "$(stat -c %X timestamp)" -eq $ts ]
-#     [ "$(stat -c %Y timestamp)" -eq $ts ]
-# done
+stage Checking utimens and timestamps
+for ts in 12345 1234567 987654321; do
+    # NB: It's not possible to set the ctime with touch.
+    touch -a -d @$ts timestamp
+    [ "$(stat -c %X timestamp)" -eq $ts ]
+    touch -m -d @$ts timestamp
+    [ "$(stat -c %Y timestamp)" -eq $ts ]
+    touch    -d @$ts timestamp
+    [ "$(stat -c %X timestamp)" -eq $ts ]
+    [ "$(stat -c %Y timestamp)" -eq $ts ]
+done
 
 stage Checking writes
 cp hello.txt copy.txt
diff --git a/src/fuse.c b/src/fuse.c
index 967a744..748b933 100644
--- a/src/fuse.c
+++ b/src/fuse.c
@@ -876,6 +876,20 @@ mount_local_removexattr(const char *path, const char *name)
   return 0;
 }
 
+static int
+mount_local_flush(const char *path, struct fuse_file_info *fi)
+{
+  DECL_G ();
+  DEBUG_CALL ("%s", path);
+
+  /* Just a stub. This method is called whenever FUSE wants to flush the
+   * pending changes (f.ex. to attributes) to a file.  Since we don't have
+   * anything to do and don't want FUSE to think something went badly,
+   * just return 0.
+   */
+  return 0;
+}
+
 static struct fuse_operations mount_local_operations = {
   .getattr	= mount_local_getattr,
   .access	= mount_local_access,
@@ -902,6 +916,7 @@ static struct fuse_operations mount_local_operations = {
   .getxattr	= mount_local_getxattr,
   .listxattr	= mount_local_listxattr,
   .removexattr	= mount_local_removexattr,
+  .flush        = mount_local_flush,
 };
 
 int
-- 
1.8.3.1