similar to: [libnbd PATCH] lib: Reduce number of read/block_status callbacks

The freeing feature can now be done by associating a free callback with a closure's user_data, so having the valid_flag is no longer necessary and it can be completely removed. This mostly reverts commit 2d9b98e96772e282d51dafac07f16387dadc8afa. --- TODO | 2 - docs/libnbd.pod | 64 ++-------------- examples/glib-main-loop.c |

Mechanical change: Wherever we call any closure with the LIBNBD_CALLBACK_FREE function, we also call nbd_internal_free_callback with the closure's user_data. This allows calls to associate a free callback with any closure via its user_data pointer. --- generator/states-reply-simple.c | 1 + generator/states-reply-structured.c | 24 ++++++++++++++++++------ generator/states-reply.c

For example nbd_set_debug takes a callback function. Previously this was defined explicitly inside the function parameters. This commit defines a new public typedef: typedef int (*nbd_debug_callback) (unsigned valid_flag, void *user_data, const char *context, const char *msg); and then uses the typedef like this: extern int nbd_set_debug_callback

Change the way that we deal with freeing closures in language bindings: * The valid_flag is removed (mostly reverting commit 2d9b98e96772e282d51dafac07f16387dadc8afa). * An extra ‘free’ parameter is added to all callback structures. This is called by the library whenever the closure won't be called again (so the user_data can be freed). This is analogous to valid_flag ==

On 7/24/19 7:17 AM, Richard W.M. Jones wrote: > Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures

The definition of functions that take a callback is changed so that the callback and user_data are combined into a single structure, eg: int64_t nbd_aio_pread (struct nbd_handle *h, void *buf, size_t count, uint64_t offset, - int (*completion_callback) (/*..*/), void *user_data, + nbd_completion_callback completion_callback, uint32_t flags); Several

On 8/13/19 5:36 PM, Richard W.M. Jones wrote: > Change the way that we deal with freeing closures in language > bindings: > > * The valid_flag is removed (mostly reverting > commit 2d9b98e96772e282d51dafac07f16387dadc8afa). > > * An extra ‘free’ parameter is added to all callback structures. This > is called by the library whenever the closure won't be called

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

On 7/25/19 8:07 AM, Richard W.M. Jones wrote: > Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

Some callers of nbd_aio_pread_structured_callback or nbd_aio_block_status_callback share the same opaque pointer to both calls, with the intent to only free the pointer on the completion callback. Although our documentation does not explicitly specify the order in which callbacks are made, allowing the callback(FREE) to occur prior to the read(FREE) puts a burden on the client to not dereference

On Wed, Jul 24, 2019 at 12:21:37PM -0500, Eric Blake wrote: > On 7/24/19 7:17 AM, Richard W.M. Jones wrote: > > Previously closures had a crude flag which tells if they are > > persistent or transient. Transient closures (flag = false) last for > > the lifetime of the currently called libnbd function. Persistent > > closures had an indefinite lifetime which could last

On 7/22/19 6:50 AM, Richard W.M. Jones wrote: > On Mon, Jul 22, 2019 at 10:08:25AM +0100, Richard W.M. Jones wrote: >> On Sat, Jul 20, 2019 at 07:38:45AM +0100, Richard W.M. Jones wrote: >>> More thoughts on callbacks, etc. following on from: >>> https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00184 >>> >>> Closure lifetimes

On 7/24/19 11:54 AM, Richard W.M. Jones wrote: > Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures

On 7/25/19 10:43 AM, Eric Blake wrote: >> +++ b/generator/states-reply-structured.c >> @@ -298,7 +298,7 @@ >> * current error rather than any earlier one. If the callback fails >> * without setting errno, then use the server's error below. >> */ >> - if (cmd->cb.fn.read (cmd->cb.fn_user_data, >> + if

On Wed, Aug 14, 2019 at 05:38:31PM -0500, Eric Blake wrote: > When we introduced valid_flags, there was an incentive to do as few > callbacks as possible, favoring cb(VALID|FREE) calls over the sequence > cb(VALID);cb(FREE). To make it work, we set .callback=NULL after an > early free, so that the later check during retirement didn't free > again. > > But now that our

On 7/24/19 7:17 AM, Richard W.M. Jones wrote: > Previously closures had a crude flag which tells if they are > persistent or transient. Transient closures (flag = false) last for > the lifetime of the currently called libnbd function. Persistent > closures had an indefinite lifetime which could last for as long as > the handle. In language bindings handling persistent closures

On Mon, Jul 22, 2019 at 10:08:25AM +0100, Richard W.M. Jones wrote: > On Sat, Jul 20, 2019 at 07:38:45AM +0100, Richard W.M. Jones wrote: > > More thoughts on callbacks, etc. following on from: > > https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00184 > > > > Closure lifetimes > > ----------------- Here's a possibly better idea which still

When we introduced valid_flags, there was an incentive to do as few callbacks as possible, favoring cb(VALID|FREE) calls over the sequence cb(VALID);cb(FREE). To make it work, we set .callback=NULL after an early free, so that the later check during retirement didn't free again. But now that our .free callback is distinct from our other callbacks, there is no longer an advantage to bundling