* Extracted file_map API out of the file cache - it's now an optional service

that can be used by file systems.
* Changed the way the file cache works: instead of reading/writing to the
  underlying device directly, it can now be used for any data source, ie.
  also network file systems.
* As a result, the former pages_io() moved to the VFS layer, and can now be
  called by a file system via {read|write}_file_io_vec_pages() (naming
  suggestions are always welcomed :-)). It now gets an FD, and uses that to
  communicate with the device (via its fs_{read|write}_pages() hooks).
* The file_cache_{read|write}() functions must now be called without holding
  an I/O relevant file system lock. That allows the file cache to prepare the
  pages without colliding with the page writer, IOW the "mayBlock" flag can
  go into the attic again (yay!).
* This also results in a much better performance when the system does I/O and
  is low on memory, as the page writer can now finally write back some pages,
  and that even without maxing out the CPU :)
* The API changes put slightly more burden on the fs_{read|write}_pages()
  hooks, but in combination with the file_map it's still pretty straight
  forward. It just will have to dispatch the call to the underlying device
  directly, usually it will just call its fs_{read|write}_pages() hooks
  via the above mentioned calls.
* Ported BFS and FAT to the new API, the latter has not been tested, though.
* Also ported the API changes to the fs_shell. I also completely removed its
  file cache level page handling - the downside is that device access is no
  longer cached (ie. depends on the host OS now), the upside is that the code
  is greatly simplified.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@22886 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/vfs.h

@@ -94,11 +94,9 @@ void vfs_acquire_vnode(struct vnode *vnode);
 status_t vfs_get_cookie_from_fd(int fd, void **_cookie);
 bool vfs_can_page(struct vnode *vnode, void *cookie);
 status_t vfs_read_pages(struct vnode *vnode, void *cookie, off_t pos,
-			const iovec *vecs, size_t count, size_t *_numBytes, bool mayBlock,
-			bool fsReenter);
+			const iovec *vecs, size_t count, size_t *_numBytes, bool fsReenter);
 status_t vfs_write_pages(struct vnode *vnode, void *cookie, off_t pos,
-			const iovec *vecs, size_t count, size_t *_numBytes, bool mayBlock,
-			bool fsReenter);
+			const iovec *vecs, size_t count, size_t *_numBytes, bool fsReenter);
 status_t vfs_get_vnode_cache(struct vnode *vnode, struct vm_cache **_cache,
 			bool allocate);
 status_t vfs_get_file_map(struct vnode *vnode, off_t offset, size_t size,

headers/private/kernel/vm_types.h

@@ -223,11 +223,9 @@ typedef struct vm_store_ops {
 	status_t (*commit)(struct vm_store *backingStore, off_t size);
 	bool (*has_page)(struct vm_store *backingStore, off_t offset);
 	status_t (*read)(struct vm_store *backingStore, off_t offset,
-		const iovec *vecs, size_t count, size_t *_numBytes, bool mayBlock,
-		bool fsReenter);
+		const iovec *vecs, size_t count, size_t *_numBytes, bool fsReenter);
 	status_t (*write)(struct vm_store *backingStore, off_t offset,
-		const iovec *vecs, size_t count, size_t *_numBytes, bool mayBlock,
-		bool fsReenter);
+		const iovec *vecs, size_t count, size_t *_numBytes, bool fsReenter);
 	status_t (*fault)(struct vm_store *backingStore,
 		struct vm_address_space *aspace, off_t offset);
 	status_t (*acquire_unreferenced_ref)(struct vm_store *backingStore);