[Libguestfs] [PATCH nbdkit 3/3] server: filters: Remove struct b_h.

This was previously used as ‘nxdata’ and stored a tuple of ’b->next’ and the real filter handle. However after recent changes we don't need it. We can use ‘b->next’ as nxdata, and the handle is passed to us by the calling functions. Inspired by Eric Blakes observations in this email: https://www.redhat.com/archives/libguestfs/2020-February/msg00092.html --- server/filters.c | 217 ++++++++++++++++------------------------------- 1 file changed, 73 insertions(+), 144 deletions(-) diff --git a/server/filters.c b/server/filters.c index c916217c..92b0ceb3 100644 --- a/server/filters.c +++ b/server/filters.c @@ -49,16 +49,6 @@ 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) @@ -186,20 +176,19 @@ filter_config_complete (struct backend *b) static int next_preconnect (void *nxdata, int readonly) { - struct b_h *b_h = nxdata; - return b_h->b->preconnect (b_h->b, readonly); + struct backend *b_next = nxdata; + return b_next->preconnect (b_next, readonly); } static int filter_preconnect (struct backend *b, int readonly) { struct backend_filter *f = container_of (b, struct backend_filter, backend); - struct b_h nxdata = { .b = b->next }; debug ("%s: preconnect", b->name); if (f->filter.preconnect) - return f->filter.preconnect (next_preconnect, &nxdata, readonly); + return f->filter.preconnect (next_preconnect, b->next, readonly); else return b->next->preconnect (b->next, readonly); } @@ -216,201 +205,181 @@ plugin_magic_config_key (struct backend *b) static int next_open (void *nxdata, int readonly) { - struct b_h *b_h = nxdata; + struct backend *b_next = nxdata; - return backend_open (b_h->b, readonly); + return backend_open (b_next, readonly); } static void * filter_open (struct backend *b, int readonly) { struct backend_filter *f = container_of (b, struct backend_filter, backend); - struct b_h *nxdata = malloc (sizeof *nxdata); - - if (!nxdata) { - nbdkit_error ("malloc: %m"); - return NULL; - } - - nxdata->b = b->next; - nxdata->handle = NULL; + void *handle; /* Most filters will call next_open first, resulting in * inner-to-outer ordering. */ if (f->filter.open) - nxdata->handle = f->filter.open (next_open, nxdata, readonly); + handle = f->filter.open (next_open, b->next, readonly); else if (backend_open (b->next, readonly) == -1) - nxdata->handle = NULL; + handle = NULL; else - nxdata->handle = NBDKIT_HANDLE_NOT_NEEDED; - if (nxdata->handle == NULL) { - free (nxdata); - return NULL; - } - return nxdata; + handle = NBDKIT_HANDLE_NOT_NEEDED; + return handle; } 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) { - assert (nxdata->b == b->next); - f->filter.close (nxdata->handle); - free (nxdata); - } + if (handle && f->filter.close) + f->filter.close (handle); } /* The next_functions structure contains pointers to backend - * 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’). + * 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. */ static int next_reopen (void *nxdata, int readonly) { - struct b_h *b_h = nxdata; - return backend_reopen (b_h->b, readonly); + struct backend *b_next = nxdata; + return backend_reopen (b_next, readonly); } static int64_t next_get_size (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_get_size (b_h->b); + struct backend *b_next = nxdata; + return backend_get_size (b_next); } static int next_can_write (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_write (b_h->b); + struct backend *b_next = nxdata; + return backend_can_write (b_next); } static int next_can_flush (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_flush (b_h->b); + struct backend *b_next = nxdata; + return backend_can_flush (b_next); } static int next_is_rotational (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_is_rotational (b_h->b); + struct backend *b_next = nxdata; + return backend_is_rotational (b_next); } static int next_can_trim (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_trim (b_h->b); + struct backend *b_next = nxdata; + return backend_can_trim (b_next); } static int next_can_zero (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_zero (b_h->b); + struct backend *b_next = nxdata; + return backend_can_zero (b_next); } static int next_can_fast_zero (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_fast_zero (b_h->b); + struct backend *b_next = nxdata; + return backend_can_fast_zero (b_next); } static int next_can_extents (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_extents (b_h->b); + struct backend *b_next = nxdata; + return backend_can_extents (b_next); } static int next_can_fua (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_fua (b_h->b); + struct backend *b_next = nxdata; + return backend_can_fua (b_next); } static int next_can_multi_conn (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_multi_conn (b_h->b); + struct backend *b_next = nxdata; + return backend_can_multi_conn (b_next); } static int next_can_cache (void *nxdata) { - struct b_h *b_h = nxdata; - return backend_can_cache (b_h->b); + struct backend *b_next = nxdata; + return backend_can_cache (b_next); } static int next_pread (void *nxdata, void *buf, uint32_t count, uint64_t offset, uint32_t flags, int *err) { - struct b_h *b_h = nxdata; - return backend_pread (b_h->b, buf, count, offset, flags, - err); + struct backend *b_next = nxdata; + return backend_pread (b_next, 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 b_h *b_h = nxdata; - return backend_pwrite (b_h->b, buf, count, offset, flags, - err); + struct backend *b_next = nxdata; + return backend_pwrite (b_next, buf, count, offset, flags, err); } static int next_flush (void *nxdata, uint32_t flags, int *err) { - struct b_h *b_h = nxdata; - return backend_flush (b_h->b, flags, err); + struct backend *b_next = nxdata; + return backend_flush (b_next, flags, err); } static int next_trim (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, int *err) { - struct b_h *b_h = nxdata; - return backend_trim (b_h->b, count, offset, flags, err); + struct backend *b_next = nxdata; + return backend_trim (b_next, count, offset, flags, err); } static int next_zero (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, int *err) { - struct b_h *b_h = nxdata; - return backend_zero (b_h->b, count, offset, flags, err); + struct backend *b_next = nxdata; + return backend_zero (b_next, 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 b_h *b_h = nxdata; - return backend_extents (b_h->b, count, offset, flags, - extents, err); + struct backend *b_next = nxdata; + return backend_extents (b_next, count, offset, flags, extents, err); } static int next_cache (void *nxdata, uint32_t count, uint64_t offset, uint32_t flags, int *err) { - struct b_h *b_h = nxdata; - return backend_cache (b_h->b, count, offset, flags, err); + struct backend *b_next = nxdata; + return backend_cache (b_next, count, offset, flags, err); } static struct nbdkit_next_ops next_ops = { @@ -439,11 +408,9 @@ 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, nxdata, nxdata->handle, readonly) == -1) + f->filter.prepare (&next_ops, b->next, handle, readonly) == -1) return -1; return 0; @@ -453,11 +420,9 @@ 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, nxdata, nxdata->handle) == -1) + f->filter.finalize (&next_ops, b->next, handle) == -1) return -1; return 0; } @@ -466,11 +431,9 @@ 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, nxdata, nxdata->handle); + return f->filter.get_size (&next_ops, b->next, handle); else return backend_get_size (b->next); } @@ -479,11 +442,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_write (&next_ops, b->next, handle); else return backend_can_write (b->next); } @@ -492,11 +453,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_flush (&next_ops, b->next, handle); else return backend_can_flush (b->next); } @@ -505,11 +464,9 @@ 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, nxdata, nxdata->handle); + return f->filter.is_rotational (&next_ops, b->next, handle); else return backend_is_rotational (b->next); } @@ -518,11 +475,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_trim (&next_ops, b->next, handle); else return backend_can_trim (b->next); } @@ -531,11 +486,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_zero (&next_ops, b->next, handle); else return backend_can_zero (b->next); } @@ -544,11 +497,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_fast_zero (&next_ops, b->next, handle); else return backend_can_fast_zero (b->next); } @@ -557,11 +508,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_extents (&next_ops, b->next, handle); else return backend_can_extents (b->next); } @@ -570,11 +519,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_fua (&next_ops, b->next, handle); else return backend_can_fua (b->next); } @@ -583,11 +530,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_multi_conn (&next_ops, b->next, handle); else return backend_can_multi_conn (b->next); } @@ -596,11 +541,9 @@ 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, nxdata, nxdata->handle); + return f->filter.can_cache (&next_ops, b->next, handle); else return backend_can_cache (b->next); } @@ -611,11 +554,9 @@ 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, nxdata, nxdata->handle, + return f->filter.pread (&next_ops, b->next, handle, buf, count, offset, flags, err); else return backend_pread (b->next, buf, count, offset, flags, err); @@ -627,11 +568,9 @@ 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, nxdata, nxdata->handle, + return f->filter.pwrite (&next_ops, b->next, handle, buf, count, offset, flags, err); else return backend_pwrite (b->next, buf, count, offset, flags, err); @@ -642,11 +581,9 @@ 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, nxdata, nxdata->handle, flags, err); + return f->filter.flush (&next_ops, b->next, handle, flags, err); else return backend_flush (b->next, flags, err); } @@ -657,11 +594,9 @@ 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, nxdata, nxdata->handle, count, offset, + return f->filter.trim (&next_ops, b->next, handle, count, offset, flags, err); else return backend_trim (b->next, count, offset, flags, err); @@ -672,11 +607,9 @@ 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, nxdata, nxdata->handle, + return f->filter.zero (&next_ops, b->next, handle, count, offset, flags, err); else return backend_zero (b->next, count, offset, flags, err); @@ -688,11 +621,9 @@ 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, nxdata, nxdata->handle, + return f->filter.extents (&next_ops, b->next, handle, count, offset, flags, extents, err); else @@ -706,11 +637,9 @@ 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, nxdata, nxdata->handle, + return f->filter.cache (&next_ops, b->next, handle, count, offset, flags, err); else return backend_cache (b->next, count, offset, flags, err); -- 2.25.0