[Libguestfs] [nbdkit PATCH v2 3/6] Revert "server: filters: Remove struct b_h."
Eric Blake
eblake at redhat.com
Thu Feb 25 20:59:44 UTC 2021
This reverts commit fdbebe389f15bebbda8bf20c81043013396b66f5.
This has no semantic impact, but will allow the next patch to expand
the contents of b_h with one more field needed to make it possible to
implement a multi-conn filter. The reversion is a bit more complex
than undoing the original because of new callbacks added in the
meantime, but it is still fairly mechanical.
---
server/filters.c | 221 +++++++++++++++++++++++++++++++----------------
1 file changed, 146 insertions(+), 75 deletions(-)
diff --git a/server/filters.c b/server/filters.c
index f4dbfea7..3e79ef5e 100644
--- a/server/filters.c
+++ b/server/filters.c
@@ -49,6 +49,16 @@ struct backend_filter {
struct nbdkit_filter filter;
};
+/* Literally a backend and the filter's handle.
+ *
+ * This is the implementation of our handle in .open, and serves as
+ * a stable ‘void *nxdata’ in the filter API.
+ */
+struct b_h {
+ struct backend *b;
+ void *handle;
+};
+
/* Note this frees the whole chain. */
static void
filter_free (struct backend *b)
@@ -288,9 +298,8 @@ filter_default_export (struct backend *b, int readonly, int is_tls)
static int
next_open (void *nxdata, int readonly, const char *exportname)
{
- struct backend *b_next = nxdata;
-
- return backend_open (b_next, readonly, exportname);
+ struct b_h *b_h = nxdata;
+ return backend_open (b_h->b, readonly, exportname);
}
static void *
@@ -298,180 +307,200 @@ filter_open (struct backend *b, int readonly, const char *exportname,
int is_tls)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
- void *handle;
+ struct b_h *nxdata = calloc (1, sizeof *nxdata);
+
+ if (!nxdata) {
+ nbdkit_error ("malloc: %m");
+ return NULL;
+ }
+
+ nxdata->b = b->next;
/* Most filters will call next_open first, resulting in
* inner-to-outer ordering.
*/
if (f->filter.open)
- handle = f->filter.open (next_open, b->next, readonly, exportname,
- is_tls);
+ nxdata->handle = f->filter.open (next_open, nxdata, readonly, exportname,
+ is_tls);
else if (backend_open (b->next, readonly, exportname) == -1)
- handle = NULL;
+ nxdata->handle = NULL;
else
- handle = NBDKIT_HANDLE_NOT_NEEDED;
- return handle;
+ nxdata->handle = NBDKIT_HANDLE_NOT_NEEDED;
+ if (nxdata->handle == NULL) {
+ free (nxdata);
+ return NULL;
+ }
+
+ return nxdata;
}
static void
filter_close (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
- if (handle && f->filter.close)
- f->filter.close (handle);
+ if (handle && f->filter.close) {
+ assert (nxdata->b == b->next);
+ f->filter.close (nxdata->handle);
+ }
+ free (nxdata);
}
/* The next_functions structure contains pointers to backend
- * functions. These are only needed for type safety (nxdata is void
- * pointer, backend_* functions expect a struct backend * parameter).
- * nxdata is a pointer to the next backend in the linked list.
+ * functions. However because these functions are all expecting a
+ * backend and a handle, we cannot call them directly, but must
+ * write some next_* functions that unpack the two parameters from a
+ * single ‘void *nxdata’ struct pointer (‘b_h’).
*/
static int
next_reopen (void *nxdata, int readonly, const char *exportname)
{
- struct backend *b_next = nxdata;
- return backend_reopen (b_next, readonly, exportname);
+ struct b_h *b_h = nxdata;
+ return backend_reopen (b_h->b, readonly, exportname);
}
static int64_t
next_get_size (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_get_size (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_get_size (b_h->b);
}
static const char *
next_export_description (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_export_description (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_export_description (b_h->b);
}
static int
next_can_write (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_write (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_write (b_h->b);
}
static int
next_can_flush (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_flush (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_flush (b_h->b);
}
static int
next_is_rotational (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_is_rotational (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_is_rotational (b_h->b);
}
static int
next_can_trim (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_trim (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_trim (b_h->b);
}
static int
next_can_zero (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_zero (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_zero (b_h->b);
}
static int
next_can_fast_zero (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_fast_zero (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_fast_zero (b_h->b);
}
static int
next_can_extents (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_extents (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_extents (b_h->b);
}
static int
next_can_fua (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_fua (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_fua (b_h->b);
}
static int
next_can_multi_conn (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_multi_conn (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_multi_conn (b_h->b);
}
static int
next_can_cache (void *nxdata)
{
- struct backend *b_next = nxdata;
- return backend_can_cache (b_next);
+ struct b_h *b_h = nxdata;
+ return backend_can_cache (b_h->b);
}
static int
next_pread (void *nxdata, void *buf, uint32_t count, uint64_t offset,
uint32_t flags, int *err)
{
- struct backend *b_next = nxdata;
- return backend_pread (b_next, buf, count, offset, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_pread (b_h->b, buf, count, offset, flags,
+ err);
}
static int
next_pwrite (void *nxdata, const void *buf, uint32_t count, uint64_t offset,
uint32_t flags, int *err)
{
- struct backend *b_next = nxdata;
- return backend_pwrite (b_next, buf, count, offset, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_pwrite (b_h->b, buf, count, offset, flags,
+ err);
}
static int
next_flush (void *nxdata, uint32_t flags, int *err)
{
- struct backend *b_next = nxdata;
- return backend_flush (b_next, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_flush (b_h->b, flags, err);
}
static int
next_trim (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags,
int *err)
{
- struct backend *b_next = nxdata;
- return backend_trim (b_next, count, offset, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_trim (b_h->b, count, offset, flags, err);
}
static int
next_zero (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags,
int *err)
{
- struct backend *b_next = nxdata;
- return backend_zero (b_next, count, offset, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_zero (b_h->b, count, offset, flags, err);
}
static int
next_extents (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags,
struct nbdkit_extents *extents, int *err)
{
- struct backend *b_next = nxdata;
- return backend_extents (b_next, count, offset, flags, extents, err);
+ struct b_h *b_h = nxdata;
+ return backend_extents (b_h->b, count, offset, flags,
+ extents, err);
}
static int
next_cache (void *nxdata, uint32_t count, uint64_t offset,
uint32_t flags, int *err)
{
- struct backend *b_next = nxdata;
- return backend_cache (b_next, count, offset, flags, err);
+ struct b_h *b_h = nxdata;
+ return backend_cache (b_h->b, count, offset, flags, err);
}
static struct nbdkit_next_ops next_ops = {
@@ -501,9 +530,11 @@ static int
filter_prepare (struct backend *b, void *handle, int readonly)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.prepare &&
- f->filter.prepare (&next_ops, b->next, handle, readonly) == -1)
+ f->filter.prepare (&next_ops, nxdata, nxdata->handle, readonly) == -1)
return -1;
return 0;
@@ -513,9 +544,11 @@ static int
filter_finalize (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.finalize &&
- f->filter.finalize (&next_ops, b->next, handle) == -1)
+ f->filter.finalize (&next_ops, nxdata, nxdata->handle) == -1)
return -1;
return 0;
}
@@ -524,9 +557,11 @@ static const char *
filter_export_description (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.export_description)
- return f->filter.export_description (&next_ops, b->next, handle);
+ return f->filter.export_description (&next_ops, nxdata, nxdata->handle);
else
return backend_export_description (b->next);
}
@@ -535,9 +570,11 @@ static int64_t
filter_get_size (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.get_size)
- return f->filter.get_size (&next_ops, b->next, handle);
+ return f->filter.get_size (&next_ops, nxdata, nxdata->handle);
else
return backend_get_size (b->next);
}
@@ -546,9 +583,11 @@ static int
filter_can_write (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_write)
- return f->filter.can_write (&next_ops, b->next, handle);
+ return f->filter.can_write (&next_ops, nxdata, nxdata->handle);
else
return backend_can_write (b->next);
}
@@ -557,9 +596,11 @@ static int
filter_can_flush (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_flush)
- return f->filter.can_flush (&next_ops, b->next, handle);
+ return f->filter.can_flush (&next_ops, nxdata, nxdata->handle);
else
return backend_can_flush (b->next);
}
@@ -568,9 +609,11 @@ static int
filter_is_rotational (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.is_rotational)
- return f->filter.is_rotational (&next_ops, b->next, handle);
+ return f->filter.is_rotational (&next_ops, nxdata, nxdata->handle);
else
return backend_is_rotational (b->next);
}
@@ -579,9 +622,11 @@ static int
filter_can_trim (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_trim)
- return f->filter.can_trim (&next_ops, b->next, handle);
+ return f->filter.can_trim (&next_ops, nxdata, nxdata->handle);
else
return backend_can_trim (b->next);
}
@@ -590,9 +635,11 @@ static int
filter_can_zero (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_zero)
- return f->filter.can_zero (&next_ops, b->next, handle);
+ return f->filter.can_zero (&next_ops, nxdata, nxdata->handle);
else
return backend_can_zero (b->next);
}
@@ -601,9 +648,11 @@ static int
filter_can_fast_zero (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_fast_zero)
- return f->filter.can_fast_zero (&next_ops, b->next, handle);
+ return f->filter.can_fast_zero (&next_ops, nxdata, nxdata->handle);
else
return backend_can_fast_zero (b->next);
}
@@ -612,9 +661,11 @@ static int
filter_can_extents (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_extents)
- return f->filter.can_extents (&next_ops, b->next, handle);
+ return f->filter.can_extents (&next_ops, nxdata, nxdata->handle);
else
return backend_can_extents (b->next);
}
@@ -623,9 +674,11 @@ static int
filter_can_fua (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_fua)
- return f->filter.can_fua (&next_ops, b->next, handle);
+ return f->filter.can_fua (&next_ops, nxdata, nxdata->handle);
else
return backend_can_fua (b->next);
}
@@ -634,9 +687,11 @@ static int
filter_can_multi_conn (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_multi_conn)
- return f->filter.can_multi_conn (&next_ops, b->next, handle);
+ return f->filter.can_multi_conn (&next_ops, nxdata, nxdata->handle);
else
return backend_can_multi_conn (b->next);
}
@@ -645,9 +700,11 @@ static int
filter_can_cache (struct backend *b, void *handle)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.can_cache)
- return f->filter.can_cache (&next_ops, b->next, handle);
+ return f->filter.can_cache (&next_ops, nxdata, nxdata->handle);
else
return backend_can_cache (b->next);
}
@@ -658,9 +715,11 @@ filter_pread (struct backend *b, void *handle,
uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.pread)
- return f->filter.pread (&next_ops, b->next, handle,
+ return f->filter.pread (&next_ops, nxdata, nxdata->handle,
buf, count, offset, flags, err);
else
return backend_pread (b->next, buf, count, offset, flags, err);
@@ -672,9 +731,11 @@ filter_pwrite (struct backend *b, void *handle,
uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.pwrite)
- return f->filter.pwrite (&next_ops, b->next, handle,
+ return f->filter.pwrite (&next_ops, nxdata, nxdata->handle,
buf, count, offset, flags, err);
else
return backend_pwrite (b->next, buf, count, offset, flags, err);
@@ -685,9 +746,11 @@ filter_flush (struct backend *b, void *handle,
uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.flush)
- return f->filter.flush (&next_ops, b->next, handle, flags, err);
+ return f->filter.flush (&next_ops, nxdata, nxdata->handle, flags, err);
else
return backend_flush (b->next, flags, err);
}
@@ -698,9 +761,11 @@ filter_trim (struct backend *b, void *handle,
uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.trim)
- return f->filter.trim (&next_ops, b->next, handle, count, offset,
+ return f->filter.trim (&next_ops, nxdata, nxdata->handle, count, offset,
flags, err);
else
return backend_trim (b->next, count, offset, flags, err);
@@ -711,9 +776,11 @@ filter_zero (struct backend *b, void *handle,
uint32_t count, uint64_t offset, uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.zero)
- return f->filter.zero (&next_ops, b->next, handle,
+ return f->filter.zero (&next_ops, nxdata, nxdata->handle,
count, offset, flags, err);
else
return backend_zero (b->next, count, offset, flags, err);
@@ -725,9 +792,11 @@ filter_extents (struct backend *b, void *handle,
struct nbdkit_extents *extents, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.extents)
- return f->filter.extents (&next_ops, b->next, handle,
+ return f->filter.extents (&next_ops, nxdata, nxdata->handle,
count, offset, flags,
extents, err);
else
@@ -741,9 +810,11 @@ filter_cache (struct backend *b, void *handle,
uint32_t flags, int *err)
{
struct backend_filter *f = container_of (b, struct backend_filter, backend);
+ struct b_h *nxdata = handle;
+ assert (nxdata->b == b->next);
if (f->filter.cache)
- return f->filter.cache (&next_ops, b->next, handle,
+ return f->filter.cache (&next_ops, nxdata, nxdata->handle,
count, offset, flags, err);
else
return backend_cache (b->next, count, offset, flags, err);
--
2.30.1
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