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ptp2: cleanup of find_child() and [folder|file]_list_func() functions
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Those 3 functions were calling ptp_list_folder to update the object cache
and then iterating over the object cache to find the children of some
specific handle, thereby calling ptp_object_want() which could potentially
remove objects from the list they were iterating over. This was explicitly
marked as "DANGEROUS", which it was.

This patch introduces a return parameter to ptp_list_folder, to let the
caller know, which handles it found. This does two things: a) it is a
potential performance improvement and b) the caller can iterate over a
fixed list of handles, instead of a potentially changing list of objects.
This also did away with the 'retry' logic that tried to deal with this
situation.

I further removed the special fetching of the root folder entries from
the camera_init function and other places and I removed the code
duplication between file_list_func and folder_list_func.
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@axxel
axxel committed Oct 22, 2024
1 parent 16f1b7d commit ffff8f0
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Showing 3 changed files with 101 additions and 194 deletions.
239 changes: 70 additions & 169 deletions camlibs/ptp2/library.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7969,34 +7969,24 @@ find_child (PTPParams *params, const char *path, uint32_t storage, uint32_t hand
const char *slash = strchr (path, '/');
size_t filename_len = slash ? (size_t)(slash - path) : strlen(path);

ret = ptp_list_folder (params, storage, handle);
PTPObjectHandles handles = {0};
ret = ptp_list_folder (params, storage, handle, &handles);
if (ret != PTP_RC_OK)
return PTP_HANDLER_SPECIAL;

for_each (PTPObject*, ob, params->objects) {
uint32_t oid = ob->oid;

ret = PTP_RC_OK;
if ((ob->flags & (PTPOBJECT_PARENTOBJECT_LOADED|PTPOBJECT_STORAGEID_LOADED)) != (PTPOBJECT_PARENTOBJECT_LOADED|PTPOBJECT_STORAGEID_LOADED))
ret = ptp_object_want (params, oid, PTPOBJECT_PARENTOBJECT_LOADED|PTPOBJECT_STORAGEID_LOADED, &ob);
if (ret != PTP_RC_OK) {
/* NOTE: the "i" array entry might now be invalid, as object_want can remove objects from the list */
GP_LOG_D("failed getting info of oid 0x%08x?", oid);
/* could happen if file gets removed between */
for_each (uint32_t*, poid, handles) {
PTPObject *ob;
if (PTP_RC_OK != ptp_object_want (params, *poid, PTPOBJECT_PARENTOBJECT_LOADED, &ob)) // refresh
continue; /* object might have been deleted but ObjectRemoved event not handled, yet */
if (ob->oi.ParentObject != handle)
continue;
}
if ((ob->oi.StorageID==storage) && (ob->oi.ParentObject==handle)) {
ret = ptp_object_want (params, oid, PTPOBJECT_OBJECTINFO_LOADED, &ob);
if (ret != PTP_RC_OK) {
GP_LOG_D("failed getting info of oid 0x%08x?", oid);
/* could happen if file gets removed between */
/* FIXME: should remove, but then we irritate our list */
continue;
}
if (!strncmp (ob->oi.Filename, path, filename_len)) {
if (retob) *retob = ob;
return oid;
}

if (PTP_RC_OK != ptp_object_want (params, *poid, PTPOBJECT_OBJECTINFO_LOADED, &ob)) // refresh
continue; /* object might have been deleted but ObjectRemoved event not handled, yet */
if (!strncmp (ob->oi.Filename, path, filename_len)) {
if (retob)
*retob = ob;
return *poid;
}
}
/* else not found */
Expand All @@ -8008,11 +7998,8 @@ folder_to_handle(PTPParams *params, const char *folder, uint32_t storage, uint32
{
GP_LOG_D("(folder='%s', storage=0x%08x, parent=0x%08x)", folder, storage, parent);
if (retob) *retob = NULL;
if (!strlen(folder) || !strcmp(folder, "/")) {
/* was initially read, no need to reread */
/* ptp_list_folder (params, storage, 0); */
if (!strlen(folder) || !strcmp(folder, "/"))
return PTP_HANDLER_ROOT;
}

if (folder[0] == '/')
folder++;
Expand Down Expand Up @@ -8050,113 +8037,99 @@ find_storage_and_handle_from_path(PTPParams *params, const char *folder, uint32_
}

static int
file_list_func (CameraFilesystem *fs, const char *folder, CameraList *list,
void *data, GPContext *context)
generic_list_func (PTPParams *params, const char *folder, int is_directory, CameraList *list)
{
Camera *camera = (Camera *)data;
PTPParams *params = &camera->pl->params;
uint32_t parent, storage=0x0000000;
unsigned int i, hasgetstorageids;
SET_CONTEXT_P(params, context);
unsigned int lastobjects_len = params->objects.len, redoneonce = 0;

GP_LOG_D ("file_list_func(%s)", folder);

/* There should be NO files in root folder */
if (!strcmp(folder, "/"))
return (GP_OK);
/* Look for objects that are either files or directories.
* Currently we specify *any* PTP association as directory.
*/

if (!strcmp(folder, "/special")) {
for_each (special_file*, psf, special_files)
CR (gp_list_append (list, psf->name, NULL));
return (GP_OK);
}
uint32_t storage, parent;

CR (find_storage_and_handle_from_path(params, folder, &storage, &parent));

C_PTP_REP (ptp_list_folder (params, storage, parent));
GP_LOG_D ("after list folder");

hasgetstorageids = ptp_operation_issupported(params,PTP_OC_GetStorageIDs);
/* list this directory */
PTPObjectHandles handles = {0};
C_PTP (ptp_list_folder (params, storage, parent, &handles));
GP_LOG_D ("ptp_list_folder(storage=0x%08x, handle=0x%08x) found %d object handles", storage, parent, handles.len);

retry:
for (i = 0; i < params->objects.len; i++) {
for_each (uint32_t*, phandle, handles) {
PTPObject *ob;
uint16_t ret;
uint32_t handle;

/* not our parent -> next */
C_PTP_REP (ptp_object_want (params, params->objects.val[i].oid, PTPOBJECT_PARENTOBJECT_LOADED|PTPOBJECT_STORAGEID_LOADED, &ob));

/* DANGER DANGER: i is now invalid as objects might have been inserted in the list! */

if (ob->oi.ParentObject!=parent)
continue;
if (PTP_RC_OK != ptp_object_want (params, *phandle, PTPOBJECT_PARENTOBJECT_LOADED, &ob)) { // refresh
GP_LOG_D ("could not find object 0x%08x, possibly deleted on camera", *phandle);
continue; /* object might have been deleted but ObjectRemoved event not handled, yet */
}

/* not on our storage devices -> next */
if ((hasgetstorageids && (ob->oi.StorageID != storage)))
/* If a filtered ptp_getobjecthandles in ptp_list_folder is not supported by the device,
* we might end up having handles for all objects in 'handles', therefore we check the parent */
if ((ob->oi.ParentObject != parent))
continue;

handle = ob->oid; /* ob might change or even become invalid in the function below */
ret = ptp_object_want (params, handle, PTPOBJECT_OBJECTINFO_LOADED, &ob);
if (ret != PTP_RC_OK) {
/* we might raced another delete or ongoing addition, seen on a D810 */
if (ret == PTP_RC_InvalidObjectHandle) {
GP_LOG_D ("Handle %08x was in list, but not/no longer found via getobjectinfo.\n", handle);
/* remove it for now, we will readd it later if we see it again. */
ptp_remove_object_from_cache(params, handle);
continue;
if (!(ob->flags & PTPOBJECT_OBJECTINFO_LOADED))
if (PTP_RC_OK != ptp_object_want (params, *phandle, PTPOBJECT_OBJECTINFO_LOADED, &ob)) { // refresh
GP_LOG_D ("could not find object 0x%08x, possibly deleted on camera", *phandle);
continue; /* object might have been deleted but ObjectRemoved event not handled, yet */
}
C_PTP_REP (ret);
}
/* Is a directory -> next */
if (ob->oi.ObjectFormat == PTP_OFC_Association)
continue;

log_objectinfo(params, &ob->oi);
/* only looking for directories or files */
if (is_directory != (ob->oi.ObjectFormat == PTP_OFC_Association))
continue;

if (!ob->oi.Filename)
continue;

if (1) {
/* GP_LOG_D ("adding 0x%08x to folder", ob->oid); */

#if 0 /* TODO: Axel disabled this for its performance panalty and questionable value. */
/* HP Photosmart 850, the camera tends to duplicate filename in the list.
* Original patch by [email protected] */
/* search backwards, likely gets hits faster. */
/* FIXME Marcus: This is also O(n^2) ... bad for large directories. */
if (GP_OK == gp_list_find_by_name(list, NULL, ob->oi.Filename)) {
GP_LOG_E (
"Duplicate filename '%s' in folder '%s'. Ignoring nth entry.\n",
"Duplicate entry '%s' in folder '%s'. Ignoring nth entry.\n",
ob->oi.Filename, folder);
continue;
}
}
#endif
CR(gp_list_append (list, ob->oi.Filename, NULL));
}

/* Did we change the object tree list during our traversal? if yes, redo the scan. */
if (params->objects.len != lastobjects_len) {
if (redoneonce++) {
GP_LOG_E("list changed again on second pass, returning anyway");
return GP_OK;
}
lastobjects_len = params->objects.len;
gp_list_reset(list);
goto retry;
}
GP_LOG_D ("returning list with %d %s entries", gp_list_count(list), is_directory ? "directory" : "file");

return GP_OK;
}

static int
file_list_func (CameraFilesystem *fs, const char *folder, CameraList *list,
void *data, GPContext *context)
{
PTPParams *params = &((Camera *)data)->pl->params;

SET_CONTEXT_P(params, context);
GP_LOG_D ("file_list_func(%s)", folder);

/* There should be NO files in root folder */
if (!strcmp(folder, "/"))
return (GP_OK);

if (!strcmp(folder, "/special")) {
for_each (special_file*, psf, special_files)
CR (gp_list_append (list, psf->name, NULL));
return (GP_OK);
}

return generic_list_func(params, folder, FALSE, list);
}

static int
folder_list_func (CameraFilesystem *fs, const char *folder, CameraList *list,
void *data, GPContext *context)
{
PTPParams *params = &((Camera *)data)->pl->params;
unsigned int i, hasgetstorageids;
uint32_t handler,storage;
unsigned int redoneonce = 0, lastobjects_len = params->objects.len;

SET_CONTEXT_P(params, context);
GP_LOG_D ("folder_list_func(%s)", folder);

/* add storage pseudofolders in root folder */
if (!strcmp(folder, "/")) {
/* use the cached storageids. they should be valid after camera_init */
Expand Down Expand Up @@ -8191,63 +8164,7 @@ folder_list_func (CameraFilesystem *fs, const char *folder, CameraList *list,
return (GP_OK);
}

CR (find_storage_and_handle_from_path(params, folder, &storage, &handler));

/* list this directory */
C_PTP_REP (ptp_list_folder (params, storage, handler));

GP_LOG_D ("after list folder (storage=0x%08x, handler=0x%08x)", storage, handler);

/* Look for objects we can present as directories.
* Currently we specify *any* PTP association as directory.
*/
hasgetstorageids = ptp_operation_issupported(params,PTP_OC_GetStorageIDs);
retry:
for (i = 0; i < params->objects.len; i++) {
PTPObject *ob;
uint16_t ret;
uint32_t handle;

C_PTP_REP (ptp_object_want (params, params->objects.val[i].oid, PTPOBJECT_STORAGEID_LOADED|PTPOBJECT_PARENTOBJECT_LOADED, &ob));

/* DANGER DANGER: i is now invalid as objects might have been inserted in the list! */

if (ob->oi.ParentObject != handler)
continue;
if (hasgetstorageids && (ob->oi.StorageID != storage))
continue;

handle = ob->oid;
ret = ptp_object_want (params, handle, PTPOBJECT_OBJECTINFO_LOADED, &ob);
if (ret != PTP_RC_OK) {
/* we might raced another delete or ongoing addition, seen on a D810 */
if (ret == PTP_RC_InvalidObjectHandle) {
GP_LOG_D ("Handle %08x was in list, but not/no longer found via getobjectinfo.\n", handle);
/* remove it for now, we will readd it later if we see it again. */
ptp_remove_object_from_cache(params, handle);
continue;
}
C_PTP_REP (ret);
}
if (ob->oi.ObjectFormat!=PTP_OFC_Association)
continue;
GP_LOG_D ("adding 0x%x / ob=%p to folder", ob->oid, ob);
if (GP_OK == gp_list_find_by_name(list, NULL, ob->oi.Filename)) {
GP_LOG_E ( "Duplicated foldername '%s' in folder '%s'. should not happen!\n", ob->oi.Filename, folder);
continue;
}
CR (gp_list_append (list, ob->oi.Filename, NULL));
}
if (lastobjects_len != params->objects.len) {
if (redoneonce++) {
GP_LOG_E("list changed again on second pass, returning anyway");
return GP_OK;
}
lastobjects_len = params->objects.len;
gp_list_reset (list);
goto retry;
}
return GP_OK;
return generic_list_func(params, folder, TRUE, list);
}

/* To avoid roundtrips for querying prop desc
Expand Down Expand Up @@ -9992,16 +9909,6 @@ camera_init (Camera *camera, GPContext *context)
gp_port_set_timeout (camera->port, timeout);
}

/* avoid doing this on the Sonys DSLRs in control mode, they hang. :( */

if (params->deviceinfo.VendorExtensionID != PTP_VENDOR_SONY)
ptp_list_folder (params, PTP_HANDLER_SPECIAL, PTP_HANDLER_SPECIAL);

for_each (uint32_t*, psid, params->storageids) {
if ((*psid & 0xffff) && (*psid != 0x80000001))
ptp_list_folder (params, *psid, PTP_HANDLER_SPECIAL);
}

/* moved down here in case the filesystem needs to first be initialized as the Olympus app does */
if (params->deviceinfo.VendorExtensionID == PTP_VENDOR_GP_OLYMPUS_OMD) {

Expand All @@ -10012,12 +9919,6 @@ camera_init (Camera *camera, GPContext *context)
free_array (&params->storageids);
C_PTP (ptp_getstorageids(params, &params->storageids));

/* refetch root */
for_each (uint32_t*, psid, params->storageids) {
if ((*psid & 0xffff) && (*psid != 0x80000001))
ptp_list_folder (params, *psid, PTP_HANDLER_SPECIAL);
}

/*
if(params->storageids.len > 0) { // Olympus app gets storage info for first item, so emulating here
PTPStorageInfo storageinfo;
Expand Down
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