[Libguestfs] [nbdkit PATCH 1/4] filters: Drop useless .open callbacks

[Eric Blake]

The cache filter .open has never done any useful work; since its
introduction in c10d126f, it appears to exist purely as copy-and-paste
from the cow filter (differing only in whether the readonly parameter
is massaged before passing on to next).

The error filter .open used to track a per-connection handle, but for
testing purposes, it was changed to use only global state in commit
b33ccbb8.

Drop these two .open callbacks in favor of using nbdkit's default
behavior, with no semantic change.  All other filters with an .open
callback either massage parameters passed to next, create a
per-connection handle, or both.

Signed-off-by: Eric Blake <eblake at redhat.com>
---
 filters/cache/cache.c | 10 ----------
 filters/error/error.c | 10 ----------
 2 files changed, 20 deletions(-)

diff --git a/filters/cache/cache.c b/filters/cache/cache.c
index b3fef42..19ce555 100644
--- a/filters/cache/cache.c
+++ b/filters/cache/cache.c
@@ -186,15 +186,6 @@ cache_config_complete (nbdkit_next_config_complete *next, void *nxdata)
   return next (nxdata);
 }

-static void *
-cache_open (nbdkit_next_open *next, void *nxdata, int readonly)
-{
-  if (next (nxdata, readonly) == -1)
-    return NULL;
-
-  return NBDKIT_HANDLE_NOT_NEEDED;
-}
-
 /* Get the file size and ensure the cache is the correct size. */
 static int64_t
 cache_get_size (struct nbdkit_next_ops *next_ops, void *nxdata,
@@ -476,7 +467,6 @@ static struct nbdkit_filter filter = {
   .unload            = cache_unload,
   .config            = cache_config,
   .config_complete   = cache_config_complete,
-  .open              = cache_open,
   .prepare           = cache_prepare,
   .get_size          = cache_get_size,
   .pread             = cache_pread,
diff --git a/filters/error/error.c b/filters/error/error.c
index add7566..8932292 100644
--- a/filters/error/error.c
+++ b/filters/error/error.c
@@ -252,15 +252,6 @@ error_config (nbdkit_next_config *next, void *nxdata,
   "error-pread*, error-pwrite*, error-trim*, error-zero*, error-extents*\n" \
   "                               Apply settings only to read/write/etc"

-static void *
-error_open (nbdkit_next_open *next, void *nxdata, int readonly)
-{
-  if (next (nxdata, readonly) == -1)
-    return NULL;
-
-  return NBDKIT_HANDLE_NOT_NEEDED;
-}
-
 /* This function injects a random error. */
 static bool
 random_error (const struct error_settings *error_settings,
@@ -366,7 +357,6 @@ static struct nbdkit_filter filter = {
   .unload            = error_unload,
   .config            = error_config,
   .config_help       = error_config_help,
-  .open              = error_open,
   .pread             = error_pread,
   .pwrite            = error_pwrite,
   .trim              = error_trim,
-- 
2.20.1