userlandfs: implement get_fs_info using ioctl

This avoids introducing an entirely custom hook in FUSE.
It uses the ioctl hook in an unconventional way (calling it with no
valid fuse_file_info) but this can be fixed if a filesystem requires it
(by opening a file handle on /, doing the ioctl, then closing again).

An updated version of fusesmb-haiku is available and confirmed working:
https://github.com/haikuarchives/fusesmb-haiku

Change-Id: If1268113874363fa035e5340be75e9f5198216d6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5199
Reviewed-by: Adrien Destugues <[email protected]>
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/userlandfs/fuse/fuse.h

@@ -37,11 +37,6 @@
 extern "C" {
 #endif
 
-#ifdef HAS_FUSE_HAIKU_EXTENSIONS
-struct fs_info;
-extern int gHasHaikuFuseExtensions;
-#endif
-
 
 /* ----------------------------------------------------------- *
  * Basic FUSE API					       *
@@ -459,10 +454,6 @@ struct fuse_operations {
 	 */
 	int (*bmap) (const char *, size_t blocksize, uint64_t *idx);
 
-#ifdef HAS_FUSE_HAIKU_EXTENSIONS
-	int (*get_fs_info) (struct fs_info*);
-#endif
-
 	/**
 	 * Flag indicating that the filesystem can accept a NULL path
 	 * as the first argument for the following operations:
@@ -903,10 +894,6 @@ void fuse_fs_destroy(struct fuse_fs *fs);
 
 int fuse_notify_poll(struct fuse_pollhandle *ph);
 
-#ifdef HAS_FUSE_HAIKU_EXTENSIONS
-int fuse_fs_get_fs_info(struct fuse_fs* fs, struct fs_info* info);
-#endif
-
 /**
  * Create a new fuse filesystem object
  *

headers/private/userlandfs/fuse/fuse_common.h

@@ -113,6 +113,12 @@ struct fuse_file_info {
 #define FUSE_CAP_FLOCK_LOCKS	(1 << 10)
 #define FUSE_CAP_IOCTL_DIR	(1 << 11)
 
+/* Indicate support for Haiku-specific extensions in struct fuse_operations and fuse_ll_ops */
+#define FUSE_CAP_HAIKU_FUSE_EXTENSIONS	(1 << 31)
+
+#define FUSE_HAIKU_GET_DRIVE_INFO (((uint32_t)'H' << 24) | ((uint32_t)'G' << 16) \
+	| ((uint32_t)'D' << 8) | (uint32_t)'I')
+
 /**
  * Ioctl flags
  *

src/add-ons/kernel/file_systems/userlandfs/server/fuse/FUSEFileSystem.cpp

@@ -376,6 +376,8 @@ fNodeCapabilities.Dump();
 	fConnectionInfo.async_read = false;
 	fConnectionInfo.max_write = 64 * 1024;
 	fConnectionInfo.max_readahead = 64 * 1024;
+	fConnectionInfo.capable = FUSE_CAP_ATOMIC_O_TRUNC | FUSE_CAP_BIG_WRITES | FUSE_CAP_IOCTL_DIR
+		| FUSE_CAP_HAIKU_FUSE_EXTENSIONS;
 
 	fuse_fs_init(fFS, &fConnectionInfo);
 

src/add-ons/kernel/file_systems/userlandfs/server/fuse/FUSEFileSystem.h

@@ -41,6 +41,12 @@ public:
 
 			const fuse_config&	GetFUSEConfig() const	{ return fFUSEConfig; }
 
+			bool				HasHaikuFuseExtensions() const
+									{
+										return (fConnectionInfo.want
+											& FUSE_CAP_HAIKU_FUSE_EXTENSIONS) != 0;
+									}
+
 	virtual	status_t			CreateVolume(Volume** _volume, dev_t id);
 	virtual	status_t			DeleteVolume(Volume* volume);
 

src/add-ons/kernel/file_systems/userlandfs/server/fuse/FUSEVolume.cpp

@@ -882,8 +882,9 @@ FUSEVolume::Sync()
 status_t
 FUSEVolume::ReadFSInfo(fs_info* info)
 {
-	if (gHasHaikuFuseExtensions == 1 && fFS->ops.get_fs_info != NULL) {
-		int fuseError = fuse_fs_get_fs_info(fFS, info);
+	if (_FileSystem()->HasHaikuFuseExtensions() && fFS->ops.ioctl != NULL) {
+		int fuseError = fuse_fs_ioctl(fFS, "/", FUSE_HAIKU_GET_DRIVE_INFO, info, NULL,
+			sizeof(fs_info), NULL);
 		if (fuseError != 0)
 			return fuseError;
 		return B_OK;

src/add-ons/kernel/file_systems/userlandfs/server/fuse/fuse_fs.cpp

@@ -342,6 +342,16 @@ fuse_fs_bmap(struct fuse_fs* fs, const char* path, size_t blocksize,
 }
 
 
+int fuse_fs_ioctl(struct fuse_fs *fs, const char *path, int cmd, void *arg,
+	struct fuse_file_info *fi, unsigned int flags, void *data)
+{
+	if (fs->ops.ioctl == NULL)
+		return ENOSYS;
+
+	return fs->ops.ioctl(path, cmd, arg, fi, flags, data);
+}
+
+
 void
 fuse_fs_init(struct fuse_fs* fs, struct fuse_conn_info* conn)
 {
@@ -381,11 +391,3 @@ fuse_fs_new(const struct fuse_operations* ops, size_t opSize, void* userData)
 	return fs;
 }
 
-
-int
-fuse_fs_get_fs_info(struct fuse_fs* fs, struct fs_info* info)
-{
-	if (fs->ops.get_fs_info == NULL)
-		return ENOSYS;
-	return fs->ops.get_fs_info(info);
-}

src/add-ons/kernel/file_systems/userlandfs/server/fuse/fuse_main.cpp

@@ -17,11 +17,6 @@
 #include "../RequestThread.h"
 
 
-int gHasHaikuFuseExtensions = 0;
-	// This global can be set to 1 by a Haiku-aware FUSE add-on to signal
-	// that it implements the Haiku-specific functions in struct
-	// fuse_operations (those which are guarded by HAS_FUSE_HAIKU_EXTENSIONS).
-
 int
 fuse_main_real(int argc, char* argv[], const struct fuse_operations* op,
 	size_t opSize, void* userData)